Category: Research article
article id 1405, category Research article
Tropical forest canopy cover estimation using satellite imagery and airborne lidar reference data. Silva Fennica vol. 49 no. 5 article id 1405. https://doi.org/10.14214/sf.1405
Highlights: The fusion of airborne lidar data and satellite images enables accurate canopy cover mapping; The zero-and-one inflated beta regression is demonstrated in large area estimation; Forest/non-forest classification should be done directly, for example by using logistic regression.
The fusion of optical satellite imagery, strips of lidar data and field plots is a promising approach for the inventory of tropical forests. Airborne lidars also enable an accurate direct estimation of the forest canopy cover (CC), and thus a sample of lidar strips can be used as reference data for creating CC maps which are based on satellite images. In this study, our objective was to validate CC maps obtained from an ALOS AVNIR-2 satellite image wall-to-wall, against a lidar-based CC map of a tropical forest area located in Laos. The reference CC values which were needed for model training were obtained from a sample of four lidar strips. Zero-and-one inflated beta regression (ZOINBR) models were applied to link the spectral vegetation indices derived from the ALOS image with the lidar-based CC estimates. In addition, we compared ZOINBR and logistic regression models in the forest area estimation by using >20% CC as a forest definition. Using a total of 409 217 30 × 30 m population units as validation, our model showed a strong correlation between lidar-based CC and spectral satellite features (root mean square error = 12.8%, R2 = 0.82). In the forest area estimation, a direct classification using logistic regression provided better accuracy than the estimation of CC values as an intermediate step (kappa = 0.61 vs. 0.53). It is important to obtain sufficient training data from both ends of the CC range. The forest area estimation should be done before the CC estimation, rather than vice versa.
article id 1403, category Research article
Impact of site-preparation on soil-surface CO2 fluxes and litter decomposition in a clear-cut in Sweden. Silva Fennica vol. 49 no. 5 article id 1403. https://doi.org/10.14214/sf.1403
Highlights: Disturbances of the soil did not lead to higher CO2 emissions from the soil; Heavy mixing of the soil lead to lower CO2 emissions from the soil; Buried needles and coarse roots decomposed faster than those on the surface; Abundance of δ15N decreased in needles and roots after site preparation.
Boreal forest soil contains significant amounts of organic carbon. Soil disturbance, caused for example by site preparation or stump extraction, may increase decomposition and thus lead to higher CO2 emissions, contributing to global warming. The aim of this study was to quantify responses of soil-surface CO2 fluxes (Rs) and litter (needle and root) decomposition rates following various kinds of soil disturbance commonly caused by mechanical site preparation and stump harvest. For this purpose four treatments were applied in a clear-cut site in central Sweden: i) removal of the humus layer and top 2 cm of mineral soil, ii) placement of a humus layer and 2 cm of mineral soil upside down on top of undisturbed soil, forming a double humus layer buried under mineral soil, iii) heavy mixing of the humus layer and mineral soil, and iv) no disturbance (control). Rs measurements were acquired with a portable respiration system during two growing seasons. To assess the treatments’ effects on litter decomposition rates, needles or coarse roots (Ø = 6 mm) were incubated in litterbags at positions they would be located after the treatments (buried, or on top of the soil). The results indicate that site preparation-simulating treatments have no effect or may significantly reduce, rather than increase, CO2 emissions during the following two years. They also show that buried litter decomposes more rapidly than litter on the surface, but in other respects the treatments have little effect on litter decomposition rates.
article id 1395, category Research article
Income and time dependence of forest product demand elasticities and implications for forecasting. Silva Fennica vol. 49 no. 5 article id 1395. https://doi.org/10.14214/sf.1395
Highlights: Elasticities of demand with gross domestic product and prices were stable over time and income level for sawnwood and particleboard only; Other product elasticities differed with income and time, leading in conjunction with a sector model to higher projected world demand and prices than obtained by ignoring differences between countries and over time.
In view of improving multi-country forest sector models, this study investigated to what extent the price and income elasticity of demand for forest products had changed in the past two decades, and how much they depended on the countries income level. For each of seven major product groups annual observations were divided between high-income (top 20% in gross domestic product per capita) and low-income, and between recent (2004–2013) and older (1992–2003) observations. The results indicated that for sawnwood and particleboard the data could be pooled across all countries and years. For the other commodity groups (veneer & plywood, fiberboard, newsprint, printing & writing paper, other paper & paperboard), there were statistically significant differences in gross domestic product or price elasticity between high and low-income levels or old and recent observations. Efficient elasticities were obtained by pooling the maximum number of observations while respecting the statistically significant differences. The resulting GDP elasticities were the same, or very close, across income levels for all products. The price elasticities differed by income level only for newsprint and for veneer and plywood. International forest sector projections to 2065 obtained with these elasticities compared with those based on pooling all data across time and income levels gave less than 3% difference for world consumption of sawnwood, particleboard, fiberboard, and newsprint, but 19% higher consumption for veneer and plywood, 31% for printing and writing paper, and 18% for other paper and paperboard. The world price was 1% to 11% higher for end products and 3% to 22% higher for raw materials and intermediate products.
article id 1394, category Research article
Finnish wood harvesting contractors’ risks in Russia. Silva Fennica vol. 49 no. 5 article id 1394. https://doi.org/10.14214/sf.1394
Highlights: Disagreements on wood measurement and payment delays were the most important economic risks; Dependency on a few clients created risk for unfavourable agreements and work interruptions; Fires in site huts caused the risk of personal injury; Inadequate professional skills were serious economic and work interruption risks; Unhealthy competition, the functioning of the authorities, and infrastructure were important external risk factors.
Finnish wood harvesting contractors have been working in Russia since the 1990s and new entrepreneurs are still interested in starting operations there, even though Russia is not an easy business environment. This study identifies the most significant risks in contracting in Russia. Risks were identified through expert evaluation and a risk analysis was conducted by using a risk matrix. Possible preventative measures were assessed for the identified risks. Some risks were found to be common in Russia and Finland, for example a limited number of clients, dependency on a few clients, and weak negotiating positions. A stable amount of work, i.e. the availability of stands for harvesting, was also a challenge on the both sides of border. Typical problems in Russia were breaches of contract, especially disagreements on wood measurement and payment delays, potentially causing serious economic losses. Specific to Russia were problems related to machine service and spare parts, as well as security issues. The professional skills of machine operators, as well as changing work motivation were risks in Russia. Cultural differences lead to more challenging supervision and management of staff. Among the external factors, the most challenging in Russia were unhealthy competition in the marketplace and non-transparent and the unpredictable procedures of the authorities. In Russia problems caused by seasonality are amplified by the sparse road network and longer downtime. The revealed specific features of the Russian business environment can help Finnish wood harvesting companies to plan a risk management process for operations in Russia.
article id 1382, category Research article
Performance of a small and a medium sized professional chippers and the impact of storage time on Scots pine (Pinus sylvestris) stem wood chips characteristics. Silva Fennica vol. 49 no. 5 article id 1382. https://doi.org/10.14214/sf.1382
Highlights: The storage time of pulpwood had no significant effect on particle size distribution in any chip size classes; The study confirms the knowledge that chipping time consumption is inversely proportional to engine power and grapple load size in feeding; The use of an narrower 80 mm × 80 mm sieve on Scots pine material does not seem to offer any benefit compared to a 100 mm × 100 mm sieve from the perspective of chip quality.
The primary aim of this study was to clarify the chipping productivity and fuel consumption of tractor-powered and truck-mounted drum chippers when chipping pine pulpwood at a terminal. The secondary aim was to evaluate the impact of wood storage time on the chemical and physical technical specifications of wood chips by chipping pulpwood from eight different storage time groups, using Scots pine (Pinus sylvestris) pulpwood stems logged between 2 and 21 months previously at the terminal with the above-mentioned chippers. Thirdly, the impact of sieve mesh size on the particle size distribution of wood chips from different age groups was compared by using an 80 mm × 80 mm sieve for a tractor-powered chipper and a 100 mm × 100 mm sieve for a truck-mounted chipper. With both chippers, the chipping productivity grew as a function of grapple load weight. The average chipping productivity of the tractor-powered chipper unit was 19 508 kg (dry mass) per effective hour (E0h), and for the truck-mounted chipper the average productivity was 31 184 kg E0h–1. The tractor-powered drum chipper’s fuel consumption was 3.1 litres and for the truck-mounted chipper 3.3 litres per chipped 1000 kg (dry mass). The amount of extractives or volatiles did not demonstrate any statistically significant differences between storage time groups. The particle size distributions with both chippers were quite uniform, and the storage time of pulpwood did not have a significant effect on the particle size distribution in any chip size classes. One reason for this might be that the basic density of chipped wood was homogenous and there was no statistical difference between different storage times. The use of new sharp knives is likely to have affected chip quality, as witnessed by the absence of oversized particles and the moderate presence of fines. The use of narrower 80 mm × 80 mm sieves on Scots pine material does not seem to offer any benefit compared to 100 mm × 100 mm from the chip quality point of view.
article id 1377, category Research article
Distribution, characteristics and potential of biomass-dense thinning forests in Sweden. Silva Fennica vol. 49 no. 5 article id 1377. https://doi.org/10.14214/sf.1377
Highlights: Biomass-dense thinning forests (BDTF) cover 2.1–9.8 M ha in Sweden, which represents 9–44% of the country’s productive forest land area, depending on the constraints applied; 65% of BDTF area is found in northern Sweden; Analyses revealed a yearly harvesting potential of at least 4.3 M OD t of undelimbed whole trees (3.0 M OD t of delimbed stemwood including tops).
Understanding the characteristics of unutilized biomass resources, such as small-diameter trees from biomass-dense thinning forests (BDTF) (non-commercially-thinned forests), can provide important information for developing a bio-based economy. The aim of this study was to describe the areal distribution, characteristics (biomass of growing stock, tree height, etc.) and harvesting potential of BDTF in Sweden. A national forest inventory plot dataset was imported into a geographical information system and plots containing BDTF were selected by applying increasingly stringent constraints. Results show that, depending on the constraints applied, BDTF covers 9–44% (2.1–9.8 M ha) of the productive forest land area, and contains 7–34% of the total growing stock (119–564 M OD t), with an average biomass density of 57 OD t ha–1. Of the total BDTF area, 65% is located in northern Sweden and 2% corresponds to set-aside farmlands. Comparisons with a study from 2008 indicate that BDTF area has increased by at least 4% (about 102 000 ha), in line with general trends for Sweden and Europe. Analyses revealed that the technical harvesting potential of delimbed stemwood (over bark, including tops) from BDTF ranges from 3.0 to 6.1 M OD t yr–1 (7.5 to 15.1 M m3 yr–1), while the potential of whole-tree harvesting ranges from 4.3 to 8.7 M OD t yr–1 (10.2 to 20.6 M m3 yr–1) depending on the scenario considered. However, further technological developments of the harvest and supply systems are needed to utilize the full potential of BDTF.
article id 1348, category Research article
Unmanned aerial system imagery and photogrammetric canopy height data in area-based estimation of forest variables. Silva Fennica vol. 49 no. 5 article id 1348. https://doi.org/10.14214/sf.1348
Highlights: Orthoimage mosaic and 3D canopy height model were derived from UAV-borne colour-infrared digital camera imagery and ALS-based terrain model; Features extracted from orthomosaic and canopy height data were used for estimating forest variables; The accuracy of forest estimates was similar to that of the combination of ALS and digital aerial imagery.
In this paper we examine the feasibility of data from unmanned aerial vehicle (UAV)-borne aerial imagery in stand-level forest inventory. As airborne sensor platforms, UAVs offer advantages cost and flexibility over traditional manned aircraft in forest remote sensing applications in small areas, but they lack range and endurance in larger areas. On the other hand, advances in the processing of digital stereo photography make it possible to produce three-dimensional (3D) forest canopy data on the basis of images acquired using simple lightweight digital camera sensors. In this study, an aerial image orthomosaic and 3D photogrammetric canopy height data were derived from the images acquired by a UAV-borne camera sensor. Laser-based digital terrain model was applied for estimating ground elevation. Features extracted from orthoimages and 3D canopy height data were used to estimate forest variables of sample plots. K-nearest neighbor method was used in the estimation, and a genetic algorithm was applied for selecting an appropriate set of features for the estimation task. Among the selected features, 3D canopy features were given the greatest weight in the estimation supplemented by textural image features. Spectral aerial photograph features were given very low weight in the selected feature set. The accuracy of the forest estimates based on a combination of photogrammetric 3D data and orthoimagery from UAV-borne aerial imaging was at a similar level to those based on airborne laser scanning data and aerial imagery acquired using purpose-built aerial camera from the same study area.
article id 1347, category Research article
Impact of maximum opening area constraints on profitability and biomass availability in forestry – a large, real world case. Silva Fennica vol. 49 no. 5 article id 1347. https://doi.org/10.14214/sf.1347
Highlights: We solved a large and real world near city forestry problem; The inclusion of maximum open area constraints caused 7.0% loss in NPV; Solution value at maximum deviated 0.01% from the true optimum value; The annual energy supply of 20–30 GWh estimated from harvest residues could provide a small, but stable supply of energy to the municipality.
The nature areas surrounding the capital of Norway (Oslomarka), comprising 1 700 km2 of forest land, are the recreational home turf for a population of 1.2 mill. people. These areas are highly valuable, not only for recreational purposes and biodiversity, but also for commercial activities. To assess the impacts of the challenges that Oslo municipality forest face in their management, we developed four optimization problems with different levels of management constraints. The constraints consider control of harvest level, guarantee of minimum old-growth forest area and maximum open area after final harvest. For the latter, to date, no appropriate analyses quantifying the impact of such a constraint on economy and biomass production have been carried out in Norway. The problem solved is large due to both the number of stands and number of treatment schedules. However, the model applied demonstrated its relevance for solving large problems involving maximum opening areas. The inclusion of maximum open area constraints caused 7.0% loss in NPV compared to the business as usual case with controlled harvest volume and minimum old-growth area. The estimated supply of 20-30 GWh annual energy from harvest residues could provide a small, but stable supply of energy to the municipality.
article id 1342, category Research article
Assessing chipper productivity and operator effects in forest biomass operations. Silva Fennica vol. 49 no. 5 article id 1342. https://doi.org/10.14214/sf.1342
Highlights: A model is constructed to assess the productivity in chipping of wood biomass at roadside; The data includes 172 trials and 67 operators in Italy; The operator effect was included in a mixed model approach; The R2 were 0.76 (fixed part) and 0.88 (incl. operator effects).
The present research focuses on the productivity of energy wood chipping operations at several sites in Italy. The aim was to assess the productivity and specifically the effect attributed to the operator in the chipping of wood biomass. The research included 172 trials involving 67 operators across the country that were analysed using a mixed model approach, in order to assess productivity, and to isolate the operator effect from other potential variables. The model was constructed using different predictors aiming to explain the variability due to the machines and the raw-materials. The final model included the average piece weight of raw material chipped as well as the power of the machine. The coefficients of determination (R2) were 0.76 for the fixed part of the model, and 0.88 when the effects due to the operators were included. The operators’ performance compared to their peers was established, and it was compared to a subjective classification based on the operator’s previous experience. The results of this study can help to the planning and logistics of raw material supply for bioenergy, as well as to a more effective training of future forest operators.
article id 1340, category Research article
Near Infrared Spectroscopy as non-destructive method for sorting viable, petrified and empty seeds of Larix sibirica. Silva Fennica vol. 49 no. 5 article id 1340. https://doi.org/10.14214/sf.1340
Highlights: Near Infrared spectroscopy discriminates filled-viable, empty and petrified seeds of Larix sibirica with 98%, 82% and 87% accuracy, respectively based on spectral differences attributed to moisture and storage reserves; The classification accuracy reached 100% when sorting seeds into viable and non-viable class; The results demonstrate that NIR spectroscopy has great potential as non-destructive sorting technique to upgrade seed lot quality.
Larix sibirica Ledeb. is one of the promising timber species for planting in the boreal ecosystem; but poor seed lot quality is the major hurdle for production of sufficient quantity of planting stocks. Here, we evaluated the potential of Near Infrared (NIR) Spectroscopy for sorting viable and non-viable seeds, as the conventional sorting technique is inefficient. NIR reflectance spectra were collected from single seeds, and discriminant models were developed with Orthogonal Projections to Latent Structure – Discriminant Analysis (OPLS-DA). The computed model predicted the class membership of filled-viable, empty and petrified seeds in the test set with 98%, 82% and 87% accuracy, respectively. When two-class OPLS-DA model was fitted to discriminate viable and non-viable (empty and petrified seeds combined), the predicted class membership of test set samples was 100% for both classes. The origins of spectral differences between non-viable (petrified and empty) and viable seeds were attributed to differences in seed moisture content and storage reserves. In conclusion, the result provides evidence that NIR spectroscopy is a powerful non-destructive method for sorting non-viable seeds of Larix sibirica; thus efforts should be made to develop on-line sorting system for large-scale seed handling.
article id 1334, category Research article
Single seed Near Infrared Spectroscopy discriminates viable and non-viable seeds of Juniperus polycarpos. Silva Fennica vol. 49 no. 5 article id 1334. https://doi.org/10.14214/sf.1334
Highlights: Near Infrared (NIR) Spectroscopy discriminates viable and non-viable (empty, insect-attacked and shriveled) seeds of J. polycarpos with 98% and 100% accuracy, respectively; The origins of spectral differences between non-viable and viable seeds were attributed to differences in seed coat chemical composition and storage reserves; The results demonstrate that NIR spectroscopy has great potential as seed sorting technology to ensure precision sowing.
A large quantity of non-viable (empty, insect-attacked and shriveled) seeds of Juniperus polycarpos (K. Koch) is often encountered during seed collection, which should be removed from the seed lots to ensure precision sowing in the nursery or out in the field. The aims of this study were to evaluate different modelling approaches and to examine the sensitivity of the change in detection system (Silicon-detector in the shorter vis-a-vis InGsAs-detector in the longer NIR regions) for discriminating non-viable seeds from viable seeds by Near Infrared (NIR) spectroscopy. NIR reflectance spectra were collected from single seeds, and discriminant models were developed by Partial Least Squares – Discriminant Analysis (PLS-DA) and Orthogonal Projection to Latent Structures – Discriminant Analysis (OPLS-DA) using the entire or selected NIR regions. Both modelling approaches resulted in 98% and 100% classification accuracy for viable and non-viable seeds in the test set, respectively. However, OPLS-DA models were superb in terms of model parsimony and information quality. Modelling in the shorter and longer wavelength region also resulted in similar classification accuracy, suggesting that prediction of class membership is insensitive to change in the detection system. The origins of spectral differences between non-viable and viable seeds were attributed to differences in seed coat chemical composition, mainly terpenoids that were dominant in non-viable seeds and storage reserves in viable seeds. In conclusion, the results demonstrate that NIR spectroscopy has great potential as seed sorting technology to upgrade seed lot quality that ensures precision sowing.
article id 1328, category Research article
Ophiostomatoid fungi and their roles in Quercus robur die-back in Tellermann forest, Russia. Silva Fennica vol. 49 no. 5 article id 1328. https://doi.org/10.14214/sf.1328
Highlights: Dominant ophiostomatoid fungi associated with Q. robur in the post-outbreak region of oak die-back were investigated; Ophiostoma quercus was the most commonly encountered fungus; This is the first report of O. grandicarpum from Russia; The results of preliminary pathogenicity experiments demonstrate that fungi investigated in this study are unlikely to play causal role in oak die-back
Several eastern European countries have reported outbreaks of oak die-back during the 1980’s. Species of Ophiostoma Syd. were isolated from diseased trees and have been suggested to be the possible causal agents of the die-back, but this view have generally not been accepted. In order to monitor the post-outbreak region of oak die-back and to consider the possible role of Ophiostoma spp. in the syndrome, research has been conducted in the Tellerman forest, Voronezh region, Russia between 2005 and 2011. Our study resulted in the isolation of ophiostomatoid fungi from Quercus robur L. trees displaying external signs of desiccation. Fungi were identified based on morphological characteristics and DNA sequence comparisons. Three species of Ophiostoma were identified including O. grandicarpum (Kowalski & Butin) Rulamort, a species closely related to O. abietinum Marm. & Butin, O. fusiforme Aghayeva & M.J. Wingf. and O. lunatum Aghayeva & M.J. Wingf. representing a poorly understood species complex, and most commonly O. quercus (Georgev.) Nannf. Pathogenicity of these fungi was tested using artificial inoculations on Q. robur trees. The fungi were shown to be non-pathogenic and unlikely to play any role in oak die-back. These fungi are most likely only components in a complex of abiotic, biotic and anthropogenic factors that have contributed to a die-back of Quercus spp. in Russia.
article id 1312, category Research article
Effect of stump size and timing of stump harvesting on ground disturbance and root breakage diameter. Silva Fennica vol. 49 no. 5 article id 1312. https://doi.org/10.14214/sf.1312
Highlights: The ground disturbance and root breakage diameter during conventional stump harvesting on mineral soil were quantified; A function for estimating the disturbed area based on stump size was constructed; Many fine roots were found to be harvested; The total ground disturbance at the site after stump harvesting was similar to that caused by soil scarification.
Stump wood is a possible alternative to fossil fuel. Its harvesting, however, disturbs the ground and this has not yet been quantified at stump level. Such disturbance is likely to be dependent on stump size, type of soil and timing of stump harvesting. Therefore, we measured ground disturbance and root breakage diameter at two Norway spruce sites with sandy glacial till soil. The sites were harvested with a fork type head, 6 and 18 months after clear cutting. Measurements were made within 2 weeks of harvest. No difference was found between the two sites. The mean area of disturbed ground was 6.06 (std 3.14) m2 per stump and increased exponentially with stump size. A regression function modelling the relationship was constructed. Unexpectedly, many fine roots where extracted in the harvest. The arithmetic and basal area weighted mean root breakage diameter was 4.6 (std 2.2) and 29.5 (std 17.9) mm, respectively. There seems to be a limited increase in root breakage diameter with increased stump size. The small root breakage diameter is associated with reduced fuel quality and greater nutrient removal. It appears that much of the ground disturbance is associated with the creation of ruts rather than stump harvest per se. Stump harvesting disturbs a larger percentage of the area of a harvested site than mounding. Postponing stump harvest by one year did not decrease the ground disturbance or increase the root breakage diameter. To achieve less disturbance and larger root breakage diameter, probably new stump harvesting technology is required.
article id 1310, category Research article
Gap closure process by lateral extension growth of canopy trees and its effect on woody species regeneration in a temperate secondary forest, Northeast China. Silva Fennica vol. 49 no. 5 article id 1310. https://doi.org/10.14214/sf.1310
Highlights: Gap closure process by lateral extension growth can be described by quadratic functions; Large gaps (514–621 m2) had higher closure rates but lower closure percentages compared with middle (174–321 m2) and small gaps (68–125 m2); Gaps promoted woody species regeneration in early stage; Large and middle gaps would provide opportunities for filling regeneration, but regeneration in small gaps may eventually fail.
Gap formation and its effects on regeneration have been reported as being important in forest development, but seldom studies concentrated on the gap closure process by lateral extension growth of canopy trees surrounding gaps. We monitored the closure process of 12 artificial gaps for 7 years with three size classes: small (from 68 m2 to 125 m2), middle (from 174 m2 to 321 m2), and large (from 514 m2 to 621 m2); and investigated the regeneration twice in a temperate secondary forest, Northeast China. The closure process can be described through quadratic functions, which showed the closure rates slowed down with gap ages. Large gaps had a higher closure rate (39 m2 a–1) than middle gaps (25 m2 a–1) and small gaps (11 m2 a–1). According to the quadratic equations, the lateral growth could last 11, 13 and 16 years for small, middle and large gaps with a remaining size of 12, 69 and 223 m2, respectively. As expected, regeneration exhibited the highest seedling density and volume in large gaps. There was no significant difference in regeneration density between middle gaps, small gaps and forest understory in the final investigation; but the volume of regenerated woody species increased significantly from small gaps to large gaps compared with forest understory. These results may provide references on the choice of appropriate gap sizes to promote the regeneration in temperate secondary forests.
article id 1408, category Research article
Quantifying changes of the coniferous forest line in Finnish Lapland during 1983–2009. Silva Fennica vol. 49 no. 4 article id 1408. https://doi.org/10.14214/sf.1408
Highlights: Volume of the growing stock of spruce and pine has increased in forests and in timber lines during the past 26 years; Spruce stem numbers increased on average, while pine stem numbers remained stable and location-specific variation was observed; Presuming that the ongoing trend of increasing temperature will remain, the enhanced forest regeneration and growth may result in extension of forests in the future.
The boreal timber- and tree-line forests grow in harsh environmental conditions in their outermost distribution limit. Here even small environmental changes may cause dramatic changes in the distribution of tree species. We examined changes of the forest lines of Norway spruce (Picea abies (L.) H. Karst.) and Scots pine (Pinus sylvestris L.) in Finnish Lapland five times during 1983–2009. We monitored the number of stems and the volume of the growing stock in thirteen different locations in forest-line areas. The linear temporal trends and the variations of these response variables were used as indicators of a possible change during the study period. Spruce showed a significant increase both in the volume of the growing stock (up to 40% increase) and in the total stem number (up to 100% increase). A significant increase in the volume of the growing stock was observed in the pine data as well (up to 70% increase), whereas the stem number stagnated or even decreased. The results suggest that spruce needs favourable conditions to have an abundant regeneration, but after the establishment the seedlings seem to be more resistant against biotic and abiotic disturbances than pine seedlings. The increasing stand volume might result in a climate-related northward and upward extension of forests in the future. However, our results show that responses in the boreal forest line are species and location specific and a more favourable climate does not necessarily lead to an advance of the coniferous forest line.
article id 1391, category Research article
Relation of tree-ring width and earlywood vessel size of alien Quercus rubra L. with climatic factors in Latvia. Silva Fennica vol. 49 no. 4 article id 1391. https://doi.org/10.14214/sf.1391
Highlights: Climate-growth relationships of red oak from three sites in Latvia were studied; Tree-ring width was mainly affected by temperature and precipitation in late summer; Vessel size was correlated with temperature parameters in autumn–spring; Sets of climatic factors significant for growth of red oak differed between sites; Changes in climate-growth relationships occurred during 20th century.
The effect of climatic factors on wood anatomy of the alien red oak (Quercus rubra L.) growing in three experimental plantations in Latvia was assessed by classical dendrochronological techniques. Two tree-ring proxies – tree-ring width (TRW) and mean area of earlywood vessel lumen (VLA) – were studied on 33 trees. Annual variation of TRW amongst trees was similar (mean r = 0.46), but there was more individuality in VLA (mean r = 0.26); nevertheless, chronologies of both proxies had rather synchronous variation amongst the sites. Annual variation of TRW was affected by factors related to water deficit in late summer, as suggested by the negative effect of temperature and positive effect of precipitation that have intensified during the 20th century, likely due to warming. Although weather conditions during the dormant period did not directly affect TRW, temperature during the autumn-spring period has been the main climatic determinant of VLA likely via influence on overwintering and hence vigour of tree. This suggests that conductive properties of wood and hence the susceptibility to water deficit have been affected by weather conditions before the formation of tree rings. During the 20th century, sensitivity of VLA has shifted from temperature in winter to temperature in autumn likely due to climate change. Still, the positive effect of these factors suggests that warming of climate would increase VLA and hence the risk of embolism and xylem disfunction. Therefore, the importance of availability of water for growth of red oak in Latvia is increasing.
article id 1354, category Research article
Multiannual hydrological responses in Scots pine radial growth within raised bogs in southern Sweden. Silva Fennica vol. 49 no. 4 article id 1354. https://doi.org/10.14214/sf.1354
Highlights: Annual growth of Scots pine (Pinus sylvestris L.) at Boreal raised bogs was found to reflect a synthesis of climate controlled moisture variability over the preceding one to four year period; Excessive soil moisture is a growth limiting factor for trees at raised bogs; River discharge data reflect hydrological conditions in peat bogs better than precipitation data.
To explore interactions between climate and peatland hydrology, Scots pine (Pinus sylvestris L.) growing at four raised bogs in southern Sweden were subject to a dendroclimatological study. Radial tree growth reflecting climate and water table fluctuations over multiannual periods was detected as significant negative correlations between tree-ring width (TRW) chronologies and the preceding one to four years total precipitation or river discharge. Systematically stronger negative correlations were obtained when river discharge instead of precipitation was compared to radial tree growth. This indicates that river discharge reflect moisture variability of peat bogs better than what precipitation data does. Meanwhile, monthly precipitation and radial tree growth did not show any clear correlation, whereas spring and early summer temperatures had a positive influence on the tree growth. Our study shows that growth variability of bog pines in the Boreal zone reflect hydrological responses related to a synthesis of climate controlled moisture variability over several year periods.
article id 1326, category Research article
Analysis of the performance of different implementations of a heuristic method to optimize forest harvest scheduling. Silva Fennica vol. 49 no. 4 article id 1326. https://doi.org/10.14214/sf.1326
Highlights: The number of treatment schedules available for each stand has an impact on the optimal configuration of opt-moves (i.e. number stands where the treatment schedule is changed in an iteration); Considering a large number of treatment schedules per stand, the one-opt move implementation is preferred, yet when considering a low number of decision choices the two-opt moves option performs better.
Finding an optimal solution of forest management scheduling problems with even flow constraints while addressing spatial concerns is not an easy task. Solving these combinatorial problems exactly with mixed-integer programming (MIP) methods may be infeasible or else involve excessive computational costs. This has prompted the use of heuristics. In this paper we analyze the performance of different implementations of the Simulated Annealing (SA) heuristic algorithm for solving three typical harvest scheduling problems. Typically SA consists of searching a better solution by changing one decision choice in each iteration. In forest planning this means that one treatment schedule in a single stand is changed in each iteration (i.e. one-opt move). We present a comparison of the performance of the typical implementation of SA with the new implementation where up to three decision choices are changed simultaneously in each iteration (i.e. treatment schedules are changed in more than one stand). This may allow avoiding local optimal. In addition, the impact of SA - parameters (i.e. cooling schedule and initial temperature) are tested. We compare our heuristic results with a MIP formulation. The study case is tested in a real forest with 1000 stands and a total of 213116 decision choices. The study shows that when the combinatorial problem is very large, changing simultaneously the treatment schedule in more than one stand does not improve the performance of SA. Contrarily, if we reduce the size of the problem (i.e. reduce considerably the number of alternatives per stand) the two-opt moves approach performs better.
article id 1283, category Research article
Genetic patterns in range-edge populations of Vaccinium species from the central Balkans: implications on conservation prospects and sustainable usage. Silva Fennica vol. 49 no. 4 article id 1283. https://doi.org/10.14214/sf.1283
Highlights: We studied fragmentary distributed range-edge populations of Vaccinium myrtillus, Vaccinium uliginosum and Vaccinium vitis-idaea from the Balkans using RAPDs; Low genetic diversities and high genetic differentiation were found in all species; The prevalence of clonal individuals was not observed; Past interspecific hybridization among V. vitis-idaea and the other two species was detected; Guidelines for conservation and sustainable usage were provided.
Vaccinium myrtillus L., Vaccinium uliginosum L. and Vaccinium vitis-idaea L. are perennial, cold-adapted clonal shrubs distributed throughout Europe, northern Asia and North America. Due to their usage in food (berries) and pharmaceutical industry (berries and leaves), their natural populations are exposed to anthropogenic and other impacts that affect their genetic make-up. We analyzed 14 fragmentary distributed and small-sized peripheral populations of these species from the Balkans, which represents the southeastern-European marginal area of their wide European distributions, using RAPD molecular markers. The contemporary genetic patterns in all three species within the Balkans were generally similar, and in comparison to previous reports on populations of these species found in northward Europe, where they have a more continuous distribution, the levels of genetic diversity were more or less halved, genetic differentiation was several times higher, gene flow exceptionally low, and the expected prevalence of clonal individuals was lacking. The population dynamics of all three species within the Balkans was complex and distinct, and was characterized by a past admixture of individuals from discrete populations of the same species and interspecific hybridisation not only between V. myrtillus and V. vitis-idaea but also between V. uliginosum and V. vitis-idaea, the latter not being reported to date. Conservation measures suitable for preservation of presumably genetically distinct portions of the Balkans’ gene pools of studied species have been suggested, while the utility of interspecific hybrids in breeding programs and/ or in food/pharmaceutical industry is yet to be assessed.
article id 1265, category Research article
Soil and soil-water chemistry below different amounts of logging residues at two harvested forest sites in Sweden. Silva Fennica vol. 49 no. 4 article id 1265. https://doi.org/10.14214/sf.1265
Highlights: Soil-water chemistry, ground vegetation cover and water flux were affected by the amounts of logging residues stored on the ground after harvest; A strong response on soil-water chemistry was recorded at only one of the two sites; At the site showing a weak response, less residue remained after seven years in the treatments giving the most pronounced effects.
Logging residues (LR), i.e. tops, branches, and needles, are increasingly being harvested for energy production in Fennoscandia. These residues are temporarily piled on site awaiting transport. This study was undertaken to investigate effects on the soil and soil-water chemistry below different amounts of LR at two recently harvested coniferous sites in Sweden. Seven treatments were included and the studied amounts of LR ranged from no LR left on the ground to four times the estimated LR amount of the harvested stands. Two treatments included eight times the estimated LR amount of the harvested stands but here the LR were removed after 7 or 20 weeks. Soil-water samples were collected during the first six or seven growing seasons. Effects of treatment were detected in the soil water for 11 chemical variables at the northern site, and for the NO3- and Cl- concentrations at the southern site. The strongest response was generally found in the treatment with four times the estimated LR amount, for which the highest concentrations were recorded in most cases. In the first three seasons, the water flux through the LR decreased with an increasing amount of residue. Effects on the exchangeable store of Ca2+ in the mor layer and the upper 20 cm of the mineral soil was detected at both sites. At the northern site, the weight of the remaining LR, ground vegetation and all other material above the mor layer in the treatments with two and four times the estimated LR amount was roughly twice the corresponding weights at the southern site seven years after treatment. Although strong effects on the soil-solution chemistry were detected at one of the study sites, in the treatments corresponding to two and four times the estimated logging residue amount, the effect on the leaching from an entire regeneration area is likely to be relatively small given the percentage of the area hosting these logging residue amounts (ca. 20% after stem-only harvesting and 9% after fuel-adapted felling).
article id 1243, category Research article
Effects of pruning and stand density on cone and pollen production in an experimental Pinus sylvestris seed orchard. Silva Fennica vol. 49 no. 4 article id 1243. https://doi.org/10.14214/sf.1243
Highlights: Pollen production of Pinus sylvestris began at the same age for all studied stand density and pruning height combinations but increased more rapidly at higher densities; Treatments with dense spacing increased seed production earlier; Many combinations of stand density and target height gave comparable levels of seed production, yielding a wide range of viable management options.
Seed orchards are the link between tree breeding and reforestation. This paper presents data on cone, seed and pollen production and seed quality gathered over 21 years in a Pinus sylvestris (L.) experimental seed orchard containing plots with 14 different combinations of stand density and targeted pruning height. The treatments’ stand densities ranged from 267 to 4000 stems ha-1, and the target graft heights ranged from 2 to 6 meters. Pollen production began at the same orchard age for all studied combinations of stand density and target height but the level of pollen production per hectare increased more rapidly in treatments with higher stand densities. In treatments with dense spacing, cone and seed production initially increased more rapidly than in treatments with wider spacing, thereby providing an earlier return on investment and a shorter seed production lag time. However, the levels of cone and seed production in such treatments over the entire study period were not appreciably different to those achieved in treatments with wider spacing and higher target height. The treatments did not differ substantially with respect to seed quality. These results show that comparable levels of seed production can be obtained with different combinations of stand density and target height, giving seed orchard owners and managers a wide range of viable management options.
article id 1236, category Research article
Homogenous genetic structure in populations of Taxus baccata with varied proportions of male and female individuals. Silva Fennica vol. 49 no. 4 article id 1236. https://doi.org/10.14214/sf.1236
Highlights: Polish populations of Taxus baccata showed a high level of genetic diversity within populations and moderate genetic differentiation between them after nSSR marker testing; No significant differences in the genetic variation between T. baccata male and female individuals were observed, and microsatellite loci neutrality was verified; Determining the sex ratio in T. baccata populations is not essential to develop a clear understanding of genetic differentiation and diversity within and between populations of this species.
English yew (Taxus baccata L.) is a strictly outcrossing and dioecious species whose populations are small and isolated. It is known that sex ratios may vary in natural populations due to local environmental conditions or stochastic events. However, unbalanced sex ratios may have negative impacts on genetic diversity through enhanced genetic drift and inbreeding. The present study represents one of the first attempts to compare the genetic variation at microsatellite loci within and between populations with different gender proportions. Our results indicated that there were no significant correlations between sex ratio and the extent of genetic variation in different populations. All populations exhibited high levels of genetic diversity. Additionally, the genetic structure was characterized separately in male and female individuals. Statistical analyses of the set estimators describing the genetic structure of male and female individuals of T. baccata revealed no significant differences between the two groups. Molecular analysis verified that microsatellite nuclear loci neutrality developed for T. baccata, as there were no significant differences in the genetic variation between males and females and no evidence for any outlier loci using coalescent and hierarchical Bayesian simulations. The results demonstrate that ignoring biased sex ratios in T. baccata populations had no effect on the assessment of genetic differentiation and genetic diversity within and between populations of this species. These results are discussed with regards to the practical application of molecular markers in conservation programs.
article id 1155, category Research article
Divergent response of tree-ring width and maximum latewood density of Abies faxoniana to warming trends at the timberline of the western Qinling Mountains and northeastern Tibetan Plateau, China. Silva Fennica vol. 49 no. 4 article id 1155. https://doi.org/10.14214/sf.1155
Highlights: We describe new tree-ring width and maximum latewood density chronologies of Faxon fir; Temperature is the most important limiting factor for the radial growth of Faxon fir; The tree-ring width series captured the warming trends and allowed detecting the recent warming in a long-term context, while the maximum latewood density series showed no upward trend.
Tree-ring width (TRW) and maximum latewood density (MXD) data of Faxon fir (Abies faxoniana Rehd. et Wils.) were analyzed for five timberline sites in the western Qinling Mountains and northeastern Tibetan Plateau, to investigate their relationships to climate change, especially twentieth century warming. The cross-correlations among TRW chronologies at the low-frequency band were higher, while the higher correlations among MXD chronologies were found at the high-frequency band. Response analysis showed that the tree-ring formation of fir trees was significantly and positively affected by temperature variations, while it was also negatively affected by precipitation. The TRW series captured the warming trends and allowed detecting the recent warming in a long-term context, while the MXD series showed no upward trend. We also found the temperature sensitivity of the TRW series is unstable over space and time. The divergent response between TRW and MXD might be caused by the seasonal variations of warming trends.
article id 1337, category Research article
Spruce regeneration on woody microsites in a subalpine forest in the western Carpathians. Silva Fennica vol. 49 no. 3 article id 1337. https://doi.org/10.14214/sf.1337
Highlights: The occurrence probability of Picea abies seedlings on fallen deadwood was found to increase with diameter and decay stage of deadwood and with the volume of living trees, and to decrease with the density of living trees, sapling density, and land slope. It was also higher on stumps with greater diameter and in plots with higher sapling density, but decreased with increasing stump height.
The density of Picea abies [L.] Karst. regeneration on different microsites, the quantity and quality of woody microsites, and seedling occurrence probability on stumps and fallen deadwood were studied in a subalpine forest that has been under protection for approximately 30–40 years (Gorce Mountains in the western Carpathians). Thirty percent of seedlings and 29% of saplings grew on stumps and fallen deadwood, while the remaining regeneration occurred on soil surface and mounds created by uprooted trees. The occurrence probability of Picea seedlings on fallen deadwood increased with deadwood diameter and decay stage and with the volume of living trees, and decreased with increased density of living trees, sapling density, and land slope. Furthermore, seedlings were more likely to grow on stumps with a greater diameter and in plots with higher sapling density, but less likely to grow on higher stumps. Stumps and fallen deadwood covered about 4% of the forest floor, but the material that is most important for promoting regeneration (strongly decomposed logs and those of a diameter exceeding 30 cm) took up only about 22 m2 ha-1. We have concluded that in a subalpine forest that has been protected for 30–40 years regeneration processes take place mostly on soil surface and stumps. The role of fallen deadwood increases over time as a greater number of suitable logs (in terms of size and decay stage) become available.
article id 1302, category Research article
Effects of precommercial thinning strategies on stand structure and growth in a mixed even-aged stand of Scots pine, Norway spruce and birch in southern Sweden. Silva Fennica vol. 49 no. 3 article id 1302. https://doi.org/10.14214/sf.1302
Highlights: Precommercial thinning (PCT) was a useful tool to influence the stand structure in accordance to silvicultural goals; PCT had a great impact on tree species composition; The seemingly great potential to influence the structure of a heterogeneous, mixed stand was restrained by natural settings and unconditional considerations at PCT (e.g. tree vitality, stem quality, regular spacing).
Four different management strategies were applied to a young mixed stand of Scots pine (Pinus sylvestris L.), Norway spruce (Pices abies (L.) Karst.) and birch (Betula pendula Roth and Betula pubescens Ehrh.) in southern Sweden. All strategies included an initial precommercial thinning to ca. 2400 stems ha–1. The different aims were: (i) a conifer-dominated stand with focus on high productivity; (ii) a conifer-dominated stand with high quality timber; (iii) keeping a stem-wise species mixture; (iv) a mosaic-wise species mixture. Stem selection according to the different strategies were simulated with a starting point from plots with a 5 m radius. All strategies were applied to all of the plots. A growth simulator was used to simulate the stand development up to final felling. This study illustrates the possibilities for influencing the structure of a mixed stand through precommercial thinning. The study also illustrates the long-term effects on stand structure and volume yield by consequently applying a management strategy from precommercial thinning until final felling. Precommercial thinning was found to be a useful tool to influence the stand structure in accordance to the aims set. However, the opportunities for influencing the stand by precommercial thinning were restricted by natural settings and unconditional considerations (e.g. tree vitality, stem quality, regular spacing), beyond what could be judged from stand average data. The stem volume production during a rotation was 6% lower for (iii) and (iv) compared to (i) and (ii), mainly due to a greater proportion of birch in the former strategies.
article id 1301, category Research article
Fertilization increased growth of Scots pine and financial performance of forest management in a drained peatland in Finland. Silva Fennica vol. 49 no. 3 article id 1301. https://doi.org/10.14214/sf.1301
Highlights: All fertilizers containing phosphorus and potassium improved the P and K status and the stem growth of Scots pine still 26 years from application; Wood ash, containing more nutrients than other fertilizers, gave the strongest stand growth response and the highest net present value; Ash fertilizer treatment outperformed other fertilizer treatments and control in net present value, regardless of the applied discount rate, 3%, 4% or 5%.
The long-term effects of fertilization on the needle nutrient concentrations, growth and financial performance of a Scots pine (Pinus sylvestris L.) stand was examined in a thick-peated drained peatland forest located in Central Finland. At the trial establishment in 1985, the trees were suffering from P and K deficiencies, but their N status was good. The fertilizer treatments were Control, PK (rock phosphate + potassium chloride), ApaBio (apatite phosphorus + biotite) and wood ash, applied both with and without N and replicated six times. All treatments containing phosphorus and potassium increased foliar P and K concentrations above the deficiency limits up to the end of the study period of 26 years. The effect of the fertilization on stand volume growth of Scots pine was strong and continued still at the end of the study period. The trees on ApaBio and PK plots grew nearly two-fold and those on Ash plots over two-fold compared with the control plots. In a thinning made at the end of the study period the total logging removal on fertilized plots was 1.5–2.2 times greater and included more saw logs than on the control plots. Ash fertilizer treatment outperformed other fertilizer treatments as well as the control. With a 5% discounted equivalent annual income (EAI) of Ash fertilizer treatment was statistically significantly (p=0.009) almost three times higher than that of control. As a conclusion, fertilization (either using PK fertilizers or Ash) in N-rich drained peatlands is a financially feasible method of management.
article id 1295, category Research article
Both nursery and field performance determine suitable nitrogen supply of nursery-grown, exponentially fertilized Chinese pine. Silva Fennica vol. 49 no. 3 article id 1295. https://doi.org/10.14214/sf.1295
Highlights: Increasing exponential fertilization rates in the nursery increased seedling biomass, N content, and N concentration for Chinese pine seedlings; Second year seedling survival illustrated a curvilinear response to seedling fertilization rates rather than a linear one; Considering both nursery responses to fertilization and field performance after two years yielded a recommended nitrogen supply rate of 80 mg N seedling–1.
Optimum fertilization levels are often determined solely from nursery growth responses. However, it is the performance of the seedling on the outplanting site that is the most important. For Pinus species seedlings, little information is known about the field performance of plants cultured with different nutrient rates, especially with exponential fertilization. In this study, Chinese pine (Pinus tabulaeformis Carr.) seedlings grown in 187 ml containers were fertilized exponentially in 6 treatments ranging from 10 to 120 mg N seedling–1 for 25 weeks before outplanting. Dry mass and N content were measured at planting. Survival and field growth were monitored for two growing seasons. In the nursery, our data showed no difference in dry mass among the 40, 80, 100, and 120 mg N seedling–1 fertilizer treatments; collectively, these treatments were significantly greater than at 10 and 20 mg N seedling–1 treatments. Seedling N content was greatest for the 100 and 120 mg N seedling–1 rates. These data suggested that nursery optimum N fertilization rate was no less than 100 mg N seedling–1. Outplanting height and root-collar diameter growth characteristics were not significantly different after two years, whereas maximum mean survival was best for seedlings nursery-fertilized at 80 mg N seedling–1. In consideration of both nursery and field performance metrics, our data suggest that exponentially fertilizing Chinese pine seedlings at 80 mg N seedling–1 maximizes both nursery biomass accumulation and outplanting survival.
article id 1293, category Research article
Comparison of alternative roundwood pricing systems – a simulation approach. Silva Fennica vol. 49 no. 3 article id 1293. https://doi.org/10.14214/sf.1293
Highlights: A discrete event simulation model was developed for studying roundwood pricing systems; For a single buyer, pricing based on residual value appraisal produced (RVA) 4.87 per cent higher wood paying capability and 3.70 per cent higher stumpage price than pricing based on average unit prices; As the number of buyers using RVA increases, the competition increased and the advantage decreased.
In a closed market, roundwood buyers pricing system affect the roundwood flow from the stands to different roundwood users. If a buyer is capable to discriminate higher value stands from low quality stands better than its competitors, the buyer should be able to buy better raw material. In the study, a discrete event simulation was used to examine the effect of residual value appraisal (RVA) -based pricing of roundwood by log dimensions and grades compared to the traditional pricing based on average unit prices (UP) of roundwood assortments on roundwood flow. The core of the simulation model was the data containing 51 pine dominated stands from southern Finland. Sample trees were theoretically bucked by the bucking simulator in order to estimate the volumes, dimensions and grades of the logs and roundwood assortments. The simulation model of roundwood markets included four roundwood buyers, two corporations and two saw milling enterprises. The main finding of the study was that the buyers who use RVA gains an advantage and receives better quality compared to buyers who use UP. As the number of buyers using RVA increases, the competition increased and the advantage decreased.
article id 1267, category Research article
Structural dynamics at boreal forest edges created by a spruce budworm outbreak. Silva Fennica vol. 49 no. 3 article id 1267. https://doi.org/10.14214/sf.1267
Highlights: Insect outbreak edges were 10 m wide with different canopy cover, stem density and tree structural diversity than adjacent ecosystems; Although edge influence on forest structure was weak, forest influence was stronger and extended further, creating an edge zone skewed towards the disturbed area; After thirty years, high-contrast and structurally-diverse transition zones persist on the landscape.
Natural disturbances such as insect outbreaks create boundaries that influence vegetation patterns and ecological processes. To better understand the effects of natural edge creation on relatively intact forests and adjacent disturbed areas, we investigated forest structure on both sides of 30 year-old forest edges created by a spruce budworm (Choristoneura fumiferana Clemens) outbreak in the boreal forest of Cape Breton Highlands National Park, Canada. Our objectives were: 1) to determine edge influence (compared to interior forest) and forest influence (compared to disturbed areas) on vegetation structure, and 2) to gain insight into the structural development of the edges. Canopy cover, tree density, radial growth and deadwood were sampled in 5 m x 20 m plots along 120 m transects across six edges. Randomization tests were used to estimate the magnitude and distance of edge and forest influence. Narrow transition zones approximately 10 m wide characterized the spruce budworm-induced edges. Edge influence did not extend into the forest; however, forest influence on structure was detected up to 40 m from the edge into the disturbed area. We found evidence of the insect outbreak in the form of reduced radial growth during the disturbance across the entire disturbed area-forest gradient, which indicates that spruce budworm activity may not have ceased directly at the edge. Tree mortality caused by the insect outbreak resulted in snags, many of which have transformed into logs since the outbreak collapsed. Spruce budworm outbreak-induced forest edges are narrow but dynamic boundaries separating two distinct vegetation communities in the boreal landscape.
article id 1262, category Research article
The effect of climatic factors on height increment of Scots pine in sites differing by continentality in Latvia. Silva Fennica vol. 49 no. 3 article id 1262. https://doi.org/10.14214/sf.1262
Highlights: Height increment-climate relationships of Scots pine were assessed using dendrochronological techniques; Annual height increment was significantly affected by climatic factors; In western Latvia, temperature in preceding summer mainly affected height increment; In eastern Latvia height increment was affected by previous autumn temperature; During the 20th century, the effect of climatic factors has altered likely dues to climate change.
Height growth of trees is a crucial parameter that influences the composition and productivity of forest stands and quality of timber; however, the relationships between annual height increment (HI) and climatic factors have been poorly studied. In this study, the effect of monthly mean temperature and precipitation sums on the HI of Scots pine in two sites in Latvia have been determined using dendrochronological techniques. Correlation and response function analyses were conducted for entire chronologies of HI and for 50-year intervals within them. Climatic factors significantly affected the HI of Scots pine; however, not only did the suite of significant factors differ between the sites, but the influence of these factors changed during the 20th century. In the site in western Latvia where climate is milder, temperature in the preceding summer was the main climatic determinant of HI. The effect of temperature in the dormant period and spring was significant during the first part of the 20th century, while the effect of temperature in the previous September and November has become significant since the second half of the 20th century. In the site in eastern Latvia where summers are hotter, HI has been affected by both temperature and water deficit related factors in the summer. However, since the later part of the 20th century, the effect of temperature in the previous October has intensified and become the main climatic determinant of HI.
article id 1226, category Research article
Optimal management in Pinus pinea L. stands combining silvicultural schedules for timber and cone production. Silva Fennica vol. 49 no. 3 article id 1226. https://doi.org/10.14214/sf.1226
Highlights: Three management scenarios are proposed to integrate timber and pine nuts; Different silvicultural regimes for each output are addressed jointly; Goal programming is used in order to solve forest management models; In the mixed scenario, the area allocated to pine nuts should be notably greater.
This work aimed to tackle a timber harvest scheduling problem by simultaneously integrating into the analysis two forestry products derived from the same species: the timber and the pine nut. For this purpose, three management scenarios were proposed: two in which each of the productions is maximised separately, and a third mixed where, in each management unit, the product to which the silvicultural effort should be devoted is decided. After defining a set of objectives, and optimising the rotation length, a multi-criteria model based on goal programming was considered since no feasible solutions have been obtained when employing linear programming. The results in our case study show how the feasible solutions reached can be more attractive for the manager. Specifically, the area to be devoted to timber and cone/pine-nut production was computed in a scenario where the optimal silviculture (oriented towards timber or pine nuts) in each stand was selected, and it was concluded that the area allocated to pine nuts should be notably greater. This situation is the opposite of the current management.
article id 1056, category Research article
Seed soak-sorting prior to sowing affects the size and quality of 1.5-year-old containerized Picea abies seedlings. Silva Fennica vol. 49 no. 3 article id 1056. https://doi.org/10.14214/sf.1056
Highlights: After soak-sorting all sunken seeds (bottom fraction) were full and viable, whereas floating seeds contained larvae-filled and immature seed; Seedlings originating from the bottom fraction were greater in height and diameter than control seedlings or those originating from the floating seeds; The proportion of saleable seedlings was four percentage points higher in the bottom fraction than in the other seedlings.
We studied the effect of soak-sorting Norway spruce (Picea abies (L.) H. Karst.) seeds on emergence, development and quality of container seedlings in two commercial seed lots. The seeds, separated by soaking into bottom and surface fractions, were sown in June, and the seedlings were grown during two growing seasons under typical Finnish nursery conditions. The first summer seedlings were grown in a greenhouse and outdoors for the second, full growing season. All sunken seeds were full and viable according to radiography, whereas the floating seeds contained 2% and 13% larvae-filled and 8% and 11% anatomically immature seeds, depending on the seed lot. Seedlings grown from the bottom fraction seed emerged 2.5–3.5 days earlier than seedlings of storage dry (i.e. control) seed. Height, diameter, and shoot and root dry mass of the seedlings were affected by soaking after both the first and second growing seasons. The largest seedlings originated from the bottom fraction. The proportion of saleable seedlings was four percentage points higher in the bottom fraction than in the other seedlings. The effects of soaking found in this study are more notable than as previously reported for Norway spruce seedlings. This suggests that soaking and soak-sorting may be most useful when the growing conditions are stressful, i.e. when seeds are sown in summer rather than 1-year-old seedling crops sown in spring under the climate conditions typical of Finland.
article id 1280, category Research article
The cost competitiveness of conifer stumps in the procurement of forest chips for fuel in Southern and Northern Finland. Silva Fennica vol. 49 no. 2 article id 1280. https://doi.org/10.14214/sf.1280
Highlights: Pre-grinding and integrated screening is a way of guaranteeing fuel quality, but, when the stumps’ ash content is six per cent or below, the procurement costs are higher than with grinding of stumps at the plant. Because of high transportation costs, stump harvesting is the most profitable in Southern Finland, where there is greater availability of stumps than in Northern Finland.
The aim of this study was to evaluate cost competitiveness, at regional level, of various systems for stump transportation and grinding, and to compare the results to the procurement costs of delimbed stems from early thinnings at the stand and regional level. The accumulation and procurement costs of stumps and delimbed stems were estimated within a 100-kilometer radius from two power plants located in Kouvola and in Kajaani. The analyses were performed as simulated treatments in clear cuts and thinnings of young stands, using existing productivity and cost functions, alternative ash percentages for stump wood, and yield calculations based on the forest industry regeneration felling stand data and the sample plots data of the National Forest Inventory of Finland. The results were expressed as Euros per solid cubic meter (€ m–3) and Euros per megawatt hour (€ MWh–1). The results highlight the need to improve stump fuel quality and increase the heating value. The procurement cost of stumps was about 1 € MWh–1 lower in Kouvola compared to Kajaani, when using conceivable ash content of 6% for stumps ground at the plant, and ash content of 1.5% for stumps pre-ground at the roadside landing. The procurement costs of stumps were, on average, 0.55 € MWh–1 lower compared to delimbed stems in Kouvola, and on average 0.6 € MWh–1 higher in Kajaani. Pre-grinding and integrated screening is a feasible way to guarantee the fuel quality expressed as ash content already at roadside landings, but the procurement costs are higher compared to grinding stumps at the plant, when the ash content of ground stumps is 6% or less.
article id 1279, category Research article
Spatial tree community structure in three stands across a forest succession gradient in northern boreal Fennoscandia. Silva Fennica vol. 49 no. 2 article id 1279. https://doi.org/10.14214/sf.1279
Highlights: We studied the tree community spatial structure in three 1.2-ha plots representing naturally developed northern boreal forests of varying ages; Spatial structure showed little differences between the mid-successional, late-successional and old-growth stands; The occurrence of Picea abies relative to Betula spp. indicated a mosaic-like spatial assembly; Mosaics are likely maintained by species-specific replacement, not reciprocal replacement as thought earlier.
Development of species composition during succession is well studied in natural boreal forests, but empirical assessments of how within-stand spatial structure develops in late-successional stages are few. Here, we quantified spatial patterns in three unmanaged stands consisting of Picea abies (L.) Karst. and Betula pubescens Ehrh. and Betula pendula Roth (hereafter Betula spp.) in northern boreal Fennoscandia. We conducted a comprehensive analysis of small-scale spatial point patterns in three fully mapped 1.2-ha sample plots, representing different forest developmental stages: mid-successional, late-successional and old-growth forest. We used several variants of Ripley’s K-function to analyze the spatial point patterns along the successional gradient. Univariate analyses showed that mature trees of both species were either randomly distributed or clumped. P. abies saplings were clumped, and Betula spp. saplings occurred in a random or clumped manner. In the bivariate analyses, saplings were more likely to be found in the surroundings of mature trees of the same species, but occurred independent of the individuals of other tree species. Mature trees showed interspecific repulsion. Only modest differences occurred in the univariate patterns between the three successional stages, but in the bivariate analyses the most evident patterns, i.e. intraspecific attraction and interspecific repulsion, were stronger in the older successional stages. Overall, the studied stands appear structured as species-specific mosaics. These mosaics, along with mixed species composition, seem to be maintained by species self-replacement, which contrasts with findings from earlier studies.
article id 1274, category Research article
Variation in height and survival among northern populations of pedunculate oak (Quercus robur L.): results of a 13-year field study. Silva Fennica vol. 49 no. 2 article id 1274. https://doi.org/10.14214/sf.1274
Highlights: A height-sum function allowed us to compare the combined growth and survival of northernmost stands of pedunculate oak; Individuals from Turku-Katariinanlaakso performed the best, although other families performed more consistently across trials, which should be considered in future conservation and breeding. Surprisingly, trees planted in a trial location beyond the natural northern limit of pedunculate oak showed the best performance.
We analysed the adaptive potential of pedunculate oak (Quercus robur L.) in terms of variation in height and survival in five field trials located in southern and central Finland. The trials were established with Finnish native material from six different seed origins. Thirteen years after planting, the number of living trees was counted and measured for height. Analysis of height and survival revealed a significant effect of origin, i.e., a genetic basis to individual tree performance. Two origins from the Turku region (Ruissalo and Katariinanlaakso) performed the best while trees originating from Parainen (Lenholmen) performed the worst. In order to study the effects due to tree origin, a comparison of families (half-sibling trees, i.e. those sharing the same ‘mother’ tree) was made by combining height and survival through a height-sum equation (i.e., the product of mean survival and height of each family in each trial) and used to calculate family- and origin-level ecovalences. Ecovalence is a metric for performance consistency, and indicates how much each variable contributes to the total variation; the higher the value, the lower the consistency of trees across the trials based on their origin or family. Analysis of consistency showed similar results to growth and survival, with Turku families performing the best and families from Parainen performing the worst. Families in the Katariinanlaakso stand (Turku) generally had more stable ecovalence values and more dispersed height-sums, while Ruissalo (Turku) families had higher mean height-sum but higher variability in ecovalence values. These results suggest that seed origins (i.e., genotypes) can be optimized in terms of their suitability for commercial or ecological forest management.
article id 1266, category Research article
Using thermal time models to predict germination of five provenances of silver birch (Betula pendula Roth) in southern England. Silva Fennica vol. 49 no. 2 article id 1266. https://doi.org/10.14214/sf.1266
Highlights: Using cumulative germination data, thermal time models were developed for Betula pendula; Models indicated varying degrees of dormancy and pre-chill requirements among provenances; Thermal time parameters were used with climatic data to predict germination times under mild and cold winters in southern England; Predictions suggest that pre-chilled French seeds would germinate about six weeks later than the fastest germinating provenance.
Climate predictions indicate that growing conditions may become unfavourable for certain tree species in parts of Britain. Guidelines suggest some planting of seed sources from regions between 2° and 5° south of those currently used as part of a climate change adaptation strategy. However, there has been little research on the benefits and risks associated with the use of planting stock from more southerly seed sources. Seeds of five provenances of the ‘relatively’ dormant Betula pendula were germinated over a range of temperatures both with and without a pre-chill. Subsequently, a thermal time model was used to predict the impact of migrating these provenances to southern England. Results identified geographical differences in germination response; those from higher latitude were more sensitive to pre-chill.
article id 1239, category Research article
Applicability of portable tools in assessing the bearing capacity of forest roads. Silva Fennica vol. 49 no. 2 article id 1239. https://doi.org/10.14214/sf.1239
Highlights: The dynamic cone penetrometer (DCP) and light falling weight deflectometer (LFWD) are useful tools for measuring bearing capacity; The measurement results are not same as with the falling weight deflectometer (FWD), but comparable.
Forest roads provide access to logging sites and enable transportation of timber from forest to mills. Efficient forest management and forest industry are impossible without a proper forest road network. The bearing capacity of forest roads varies significantly by weather conditions and seasons since they are generally made of poor materials and the constructed layers may be mixed with subgrade. A bearing capacity assessment is valuable information when trafficability is uncertain and rutting is obvious. In this study, bearing capacity measurements were carried out using the light falling weight deflectometer (LFWD), the dynamic cone penetrometer (DCP) and the conventional falling weight deflectometer (FWD). The aim was to compare their measurement results in relation to road characteristics and moisture conditions. Data were collected from 35 test road sections in four consecutive springs and during one summer. The test road sections had measurement points both on the wheel path and the centre line. The data show logical correlations between measured quantities, and the study presents reliable regression models between measuring devices. The results indicate that light portable tools, the DCP and the LFWD, can in most cases be used instead of the expensive falling weight deflectometer on forest roads.
article id 1232, category Research article
Search reversion within s-metaheuristics: impacts illustrated with a forest planning problem. Silva Fennica vol. 49 no. 2 article id 1232. https://doi.org/10.14214/sf.1232
Highlights: The interruption of the sequence of events used to explore a solution space and develop a forest plan, and the re-initiation of the search process from a high-quality, known starting point (reversion) seems necessary for some s-metaheuristics; When using a s-metaheuristic, higher quality forest plans may be developed when the reversion interval is around six iterations of the model.
The use of a reversion technique during the search process of s-metaheuristics has received little attention with respect to forest management and planning problems. Reversion involves the interruption of the sequence of events that are used to explore the solution space and the re-initiation of the search process from a high-quality, known starting point. We explored four reversion rates when applied to three different types of s-metaheuristics that have previously shown promise for the forest planning problem explored, threshold accepting, tabu search, and the raindrop method. For two of the s-metaheuristics, we also explored three types of decision choices, a change to the harvest timing of a single management unit (1-opt move), the swapping of two management unit’s harvest timing (2-opt moves), and the swapping of three management unit’s harvest timing (3-opt moves). One hundred independent forest plans were developed for each of the metaheuristic / reversion rate combinations, all beginning with randomly-generated feasible starting solutions. We found that (a) reversion does improve the quality of the solutions generated, and (b) the rate of reversion is an important factor that can affect solution quality.
article id 1218, category Research article
Forest inventory attribute prediction using airborne laser scanning in low-productive forestry-drained boreal peatlands. Silva Fennica vol. 49 no. 2 article id 1218. https://doi.org/10.14214/sf.1218
Highlights: Following current forest inventory practises, stem volume was predicted in low-productive drained peatlands (LPDPs) with a root mean square error (RMSE) of 13.7 m3 ha–1; When 30 reference plots measured from LPDPs were added to the prediction, RMSE was decreased to 10.0 m3 ha–1; Additional reference plots from LPDPs did not affect the forest inventory attribute predictions in productive forests.
Nearly 30% of Finland’s land area is covered by peatlands. In Northern parts of the country there is a significant amount of low-productive drained peatlands (LPDPs) where the average annual stem volume growth is less than 1 m3 ha–1. The re-use of LPDPs has been considered thoroughly since Finnish forest legislation was updated and the forest regeneration prerequisite was removed from LPDPs in January 2014. Currently, forestry is one of the re-use alternatives, thus detailed forest resource information is required for allocating activities. However, current forest inventory practices have not been evaluated for sparse growing stocks (e.g., LPDPs). The purpose of our study was to evaluate the suitability of airborne laser scanning (ALS) for mapping forest inventory attributes in LPDPs. We used ALS data with a density of 0.8 pulses per m2, 558 field-measured reference plots (500 from productive forests and 58 from LPDPs) and k nearest neighbour (k-NN) estimation. Our main aim was to study the sensitivity of predictions to the number of LPDP reference plots used in the k-NN estimation. When the reference data consisted of 500 plots from productive forest stands, the root mean square errors (RMSEs) for the prediction accuracy of Lorey’s height, basal area and stem volume were 1.4 m, 2.7 m2 ha–1 and 13.7 m3 ha–1 in LPDPs, respectively. When 30 additional reference plots were allocated to LPDPs, the respective RMSEs were 1.1 m, 1.7 m2 ha–1 and 10.0 m3 ha–1. Additional reference plot allocation did not affect the predictions in productive forest stands.
article id 1300, category Research article
Post-planting effects of early-season short-day treatment and summer planting on Norway spruce seedlings. Silva Fennica vol. 49 no. 1 article id 1300. https://doi.org/10.14214/sf.1300
Highlights: Summer planting and short-day treatment advanced the bud burst and increased the height of Norway spruce seedlings after planting, compared to autumn and spring planted or untreated seedlings.
Effects of short-day (SD) treatment on bud burst, growth and survival of Norway spruce (Picea abies [L.] Karst.) container seedlings after summer planting were studied in an experiment established in Suonenjoki, Central Finland. One-year-old seedlings were SD-treated for three weeks starting on 18 June, 24 June and 8 July 2004 and then planted on 22 July, 5 August, 6 September 2004 and, as a normal spring planting, on 10 May, 2005. Untreated control seedlings were also planted on these dates. Second flush on the planting year and bud burst the following spring was monitored in planted seedlings, whereas seedling height and survival were determined at the end of growing seasons 2004–2006. We observed a non-significant risk of a second flush if seedlings were SD-treated on 18 June. Also, SD-treated seedlings planted in July or August showed advanced bud burst and increased height the following growing season without significant effects on survival, compared to autumn and spring planted seedlings. Planting in July or early August was associated with a significant increase in the incidence of multiple leaders in later years. Based on our results, to begin a three-week SD treatment in late June or early July and then plant seedlings in late July or early August could be a good practice.
article id 1260, category Research article
Biomass production of coppiced grey alder and the effect of fertilization. Silva Fennica vol. 49 no. 1 article id 1260. https://doi.org/10.14214/sf.1260
Highlights: Fertilisation (wood ash, N, PK) did not affect grey alder biomass production; Leafless above-ground biomass of 17–20 year old stands was 52–57 Mg ha–1; MAI increased with increase of rotation length to the end of the follow-up period of 17–20 years; Coppicing increased stand density manifold.
We studied biomass production of two naturally originated grey alder (Alnus incana (L.) Moench) stands having a mixture of birch and willow located in central Finland. One of the stands was growing on a peatland site (Muhos) and the other on a mineral soil site (Juuka). The stands were clear-cut and fertilization experiments were laid out with several treatments. At Muhos, the treatments included nitrogen fertilisation with different amounts of wood ash and an unfertilized control. At Juuka, the treatments included nitrogen fertilisation either with ash or with PK, and ash and PK treatments alone and an unfertilized control. The sprouts at Muhos were grown for 17 years and at Juuka for 20 years. At Juuka the stand was clear-cut second time at the age of 20 years and grown for 8 years. The stands were measured several times and foliar samples were taken twice during the study period. Clear-cutting increased stem number manifold. The stand density of new coppiced forests after the clear-cutting decreased from 67 000–89 000 stems ha–1 at the age of 3–6 years to 10 000–12 000 stems ha–1 at the age of 17–20 years. On neither site fertilization affected biomass production of alders during the study period. Leafless above-ground biomass was 52–57 Mg ha–1 after 17–20 years. Mean annual leafless above-ground biomass production (MAI) increased with increase of rotation time. At the age of 17–20 years the MAI was 2.8–3.0 Mg ha a–1. At Muhos, ash increased foliar P and Ca concentrations, but decreased those of Mn.
article id 1220, category Research article
On the hidden significance of differing micro-sites on tree-ring based climate reconstructions. Silva Fennica vol. 49 no. 1 article id 1220. https://doi.org/10.14214/sf.1220
Highlights: Pines and spruces show growth level differences in wet and dry micro-sites with higher growth rates in the dry sites; Spruces show a robust climate-growth relationship with June-July temperatures; Application of collective detrending methods can bias long-term trends in climate reconstructions, if relict and recent samples originate from different micro-sites.
Tree-ring chronologies are commonly extended back in time by combining samples from living trees with relict material preserved in man-made structures or natural archives (e.g. lakes). Although spatially close, these natural archives and living-tree-sites often comprise different micro-climates. Inhomogeneous growth conditions among these habitats, which may yield offsets in growth-rates, require caution in data processing. Here we assess species-specific growth dynamics in two micro-habitats and their potential effects on long chronologies by combining tree-ring data from different living-tree-sites with an “artificial” subfossil dataset. Well replicated (n > 80) Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) chronologies from northern Fennoscandia, sampled directly at the lakeshore (wet) and several meters beyond the lakeshore (dry) reveal high coherence of the variance between micro-sites (rspruce = 0.59, rpine = 0.68). Significant differences of the Regional Curves (RC) indicate faster growth of both species at the drier site though. Growth differences are more pronounced between the spruce micro-sites. The combination of recent dry and wet spruce data with artificial relict data results in two long chronologies covering the last 800 years with substantially different trends, although they consist of the same relict material and the micro-site chronologies correlate significantly over the past two centuries. The combination of spruce samples from dry inland micro-sites with subfossil samples originating from the wet lake shore can result in an underestimation of past temperatures prior to the 19th century. Such effects, hidden in the composition of long chronologies (living trees + subfossil samples) can bias long-term trends in climate reconstructions.
article id 1214, category Research article
Enhancing informal interaction and knowledge co-construction among forest owners. Silva Fennica vol. 49 no. 1 article id 1214. https://doi.org/10.14214/sf.1214
Highlights: Forest owners’ own communities could complement the present expert-driven forestry extension; Enhancing informal interaction between forest owners calls for sufficiently homogeneous reference groups and also new communication contexts; New purposes of forest ownership and innovative forest management practices are suggested topics for novel owner communities; Forest professionals may initiate these communities, but the continuity depends on the owners themselves.
It is a common concern that non-resident private forest owners are less able to make informed decisions regarding their forests. Moreover, the present guidance given by forest professionals is not reaching all owners. In this study, we suggest enhancing knowledge exchange among forest owners by increasing their mutual and informal interaction that could inspire them to co-construct new knowledge. The first objective is to identify present emerging activities that constitute knowledge exchange contexts (communities) for Finnish forest owners. The second objective is to discuss the challenges of current Finnish forest extension and their implications when introducing Communities of Practice as a complementary response to existing, yet insufficient, professional-led extension. Data consist of Finnish forest owners’ and forest professionals’ (n = 43) focus group interviews. The qualitative analysis was theoretically oriented followed by data-driven coding and grouping. According to the results, the role of expert-led encounters is strong in Finland and owners’ opportunities for good mutual communication are rare. Informal communities exist mainly in the countryside among neighbouring owners and within families. To enhance knowledge sharing among owners, one needs to identify innovative topics and activities that would inspire owners to commit to their forest property and perform active silviculture. These communities would operate as creative learning environments allowing participation of different levels. When cultivating forest owners’ communities it is important to consider actors’ roles. Forest owners themselves are responsible for the functions and continuity of these communities, although forest professionals could also initiate new and sufficiently homogenous reference groups for the owners.
article id 1191, category Research article
Genetic variation, inheritance patterns and parent–offspring relationships after artificial inoculations with Heterobasidion parviporum and Ceratocystis polonica in Norway spruce seed orchards and progeny tests. Silva Fennica vol. 49 no. 1 article id 1191. https://doi.org/10.14214/sf.1191
Highlights: Genetic variation is demonstrated in response to artificial inoculations with Heterobasidion parviporum and Ceratocystis polonica both between parents and their offspring;Strong relationships are observed between the male parents and their off-spring, less so between the female parents and their offspring.
Inoculations with the two fungi Heterobasidion parviporum and Ceratocystis polonica were made in two series of progeny tests each containing full-sib families planted at two sites and on grafts of the parents in two seed orchards. Significant variation among families in lesion lengths after inoculation was found for both fungi and a predominantly additive inheritance was indicated. The estimates of narrow sense heritability were 0.13 and 0.22 for H. parviporum and C. polonica, respectively. The estimate of the genetic correlation between the lesion lengths of the two fungi was as low as 0.12. Significant variation in lesion lengths was also found among parental clones, and within ramets of the same clone, in the seed orchards. In one of the series a high positive correlation (r = 0.88) was found between the H. parviporum lesion lengths of the male parents and offspring, but not for the female parents and off-spring. The results confirm earlier conclusions that the genetic variation and heritabilities are large enough for practical breeding for resistance.
article id 1141, category Research article
Heartwood, sapwood and bark variation in coppiced Eucalyptus globulus trees in 2nd rotation and comparison with the single-stem 1st rotation. Silva Fennica vol. 49 no. 1 article id 1141. https://doi.org/10.14214/sf.1141
Highlights: Coppiced E. globulus trees in the 2nd rotation have similar heartwood and sapwood development as single-stem trees in the 1st rotation; The initial tree planting density did not influence heartwood development of coppiced E. globulus trees; Heartwood diameter and height can be modelled with tree diameter and height respectively; Sapwood width is approximately constant within and between coppice and single-stem E. globulus trees.
Coppiced Eucalyptus globulus trees with 18 years in a 2nd rotation were analysed in relation to heartwood, sapwood and bark content taking into account the effect of the initial planting density by using a spacing trial. A total of 25 stumps, with a variable number of stems per stump from 1 to 3, were analysed. Comparison was made to the previous 1st rotation single stem trees, also harvested at 18 years. In the 2nd rotation, the stump density did not significantly affect stem height and diameter, in opposition to the 1st rotation where spacing significantly impacted on tree dimensions. The effect of the initial planting density is somewhat lost in the coppiced stand in relation with i.e. the number of stems per stump. Heartwood was present in all the coppiced trees up to 49.9% of the total tree height and heartwood volume amounted to 38.9–51.7% of the total tree volume. Within the tree, heartwood content decreased from the base upwards, representing, on average, 54.1% at the base and decreasing to 5.1% at 15.3 m. The sapwood width remained relatively constant with an average radial width of approximately 2 cm. The average stem bark content of coppiced trees was 17.4% of the total stem volume. The comparison of heartwood and sapwood development in the coppiced trees did not show significant differences to the 1st rotation trees, nor did the initial spacing. Heartwood diameter could be modelled using the tree diameter both for 1st and 2nd rotation trees.
article id 1106, category Research article
Conifer crown profile models from terrestrial laser scanning. Silva Fennica vol. 49 no. 1 article id 1106. https://doi.org/10.14214/sf.1106
Highlights: Crown models are derived from terrestrial laser data for 3 NW USA conifer species; Crown models require only crown length for implementation; Beta and Weibull curves fit to 95th percentile widths describe crown extent; Crown profile curves are species-specific and not interchangeable; Crown shape is not strongly conditioned by tree size or site.
Regional crown profile models were derived for three conifer species of the interior northwestern USA from terrestrial laser scans of eighty-six trees across a range of sizes and growing conditions. Equations were developed to predict crown shape from crown length for Pseudotsuga menziesii, Pinus ponderosa, and Abies lasiocarpa from parametric curves applied to crown-length normalized laser point clouds. The 95th width percentile adequately described each crown’s outer limit; alternate width percentiles produced little profile shape variation. For P. menziesii and P. ponderosa, a scaling parameter-modified beta curve gave the most accurate fit (using cross-validated Mean Absolute Error) to aggregated 95th width percentile points. For A. lasiocarpa, beta and Weibull curves (equivalently modified) produced similar results. For all species, modified beta and Weibull curves fit crown points with less error than conic or cylindrical profiles. Crown profile curves were species-specific; interchanging among species increased error significantly. Laser-derived crown base metrics provided objectivity and consistency, but underestimated field-derived base heights through inclusion of dead branches. Profile curve parameters were not correlated with tree or stand characteristics suggesting that crown shape is not strongly conditioned by size and site factors. However, laser sampling necessarily favored more open growing conditions, potentially under-representing variations in crown shape associated with social position. Overall, Terrrestrial Laser Scanning (TLS) lends itself to detailed measurements of external crown architecture with occlusion-imposed limits to characterization of internal features. Yet, the time and cost of collecting and processing individual tree data precludes use of TLS as a common field sampling tool.
Category: Research note
article id 1415, category Research note
Genetic patterns in Pinus nigra from the central Balkans inferred from plastid and mitochondrial data. Silva Fennica vol. 49 no. 5 article id 1415. https://doi.org/10.14214/sf.1415
Highlights: Seven populations of Pinus nigra from the central Balkans, representing four infraspecific taxa, were analyzed with chloroplast microsatellites and a mitochondrial locus; Molecular data failed to support infraspecific circumscriptions; Levels of genetic diversities/differentiation at both genomes were in the range of those reported in western Mediterranean populations of P. nigra; Iberian/African and Balkans’ populations share one mtDNA polymorphism and differ in three mutations.
Pinus nigra J.F. Arnold, European black pine, is a typical component of Mediterranean and sub-Mediterranean coniferous forests with highly fragmentary distribution. Western Mediterranean populations of this species have been studied genetically to date, while eastern populations from the central Balkans, which are larger and more abundant, are still genetically understudied. We analyzed seven populations of P. nigra representing all infraspecific taxa recognized within the central Balkans (subspecies nigra with varieties nigra and gocensis Đorđević; and subspecies pallasiana (Lamb.) Holmboe with varieties pallasiana and banatica (Endl.) Georgescu et Ionescu), with three chloroplast microsatellites (cpDNA SSRs) and one mitochondrial (mtDNA) locus. Although our molecular data failed to support circumscription of studied infraspecific taxa, we found that genetic patterns at both genomes are in accordance with those found previously in westward populations of this species, that is – exceptionally high levels of genetic diversity (HT = 0.949) and low genetic differentiation (GST = 0.024) at the cpDNA level, and moderate levels of genetic diversity (HT = 0.357) and genetic differentiation (GST = 0.358) at the mtDNA level. Based on genealogical relations of mtDNA types currently present in Balkans’ and Iberian/African populations, we inferred that the ancestral gene pool of P. nigra already harbored polymorphism at position 328 prior to the divergence to two lineages currently present in westward and eastward parts of the species range distribution. Subsequent occurrence of three mutations, which distinguish these two lineages, suggests their long-term isolation.
article id 1330, category Research note
The performance of two Swedish N fertilization functions evaluated on data from Norwegian fertilization experiments. Silva Fennica vol. 49 no. 4 article id 1330. https://doi.org/10.14214/sf.1330
Highlights: The performance of two predictive Swedish fertilization growth response functions was assessed on data from Norwegian fertilization experiments; One function performed well on the full dataset, but overpredicted the growth response in spruce plots and underpredicted in pine plots; The second function performed well in pine stands, but overestimated the growth response in spruce and in total.
This study compares the responses of two Swedish 5-year predictive stand-level functions with the observed responses in 721 fertilization experiment plots in Norway fertilized with nitrogen (N). All plots are single-species consisting of Norway spruce (Picea abies (L.) H. Karst.) or Scots pine (Pinus sylvestris L.) fertilized with ammonium nitrate (AN) or urea. The correlations between the observed and the two predicted responses were 0.34–0.40 for all plots taken together. One response function performed well on average, but underestimated the response in pine plots and overestimated the response in spruce plots. The second function overpredicted the response on the full dataset, in spruce plots and old forest, but performed well in pine plots. Both functions overestimated the growth response in high-productive plots. Higher N deposition in Norway than in Sweden may count for parts of the deviations. Testing of fertilization functions on new datasets is rare, but important part of the evaluation of functions. As the functions are not well fit for predicting the growth response in spruce and high-productive plots in our sample, new functions that include N deposition are welcome.
article id 1320, category Research note
The saprotrophic wood-degrading abilities of Rigidoporus microporus. Silva Fennica vol. 49 no. 4 article id 1320. https://doi.org/10.14214/sf.1320
Highlights: Rigidoporus microporus isolates displayed varying saprotrophic capabilities on wood blocks of Rubber tree (Hevea brasiliensis); Percentage mass loss of (Hevea brasiliensis) wood blocks caused by the pathogenic Rigidoporus microporus was significantly higher than that observed with the endophytic isolate; The endophytic isolate has very poor saprotrophic ability on Hevea brasiliensis wood blocks.
Saprotrophic wood-decaying abilities of Rigidoporus microporus (Polyporales, Basidiomycota) syn. Rigidoporus lignosus and the structural alterations induced in wood blocks of Hevea brasiliensis Muell. Arg were studied. Mass loss of wood blocks was analyzed after 3 and 6 months respectively and the patterns of decay by pathogenic and endophytic isolates of this fungus were investigated using light microscopy. Effects of temperature on growth of the isolates on malt extract agar were also investigated. The R. microporus isolated from a non-H. brasiliensis host caused the highest percentage mass loss (27.2% after 6 months), followed by isolates ED310 (21.1%) and M13 (15.7%), both collected from diseased H. brasiliensis plantations. The isolate initially identified as an endophyte showed very low saprotrophic wood decay capability (4.3% after 6 months). The optimal temperature for growth of the isolates was 30 °C; except for the endophytic isolate which showed highest growth at 25 °C. Wood samples degraded by the R. microporus isolates showed simultaneous attack of wood cell walls, typical of white rot fungi. Results of the study indicate variability in the wood degrading abilities of the isolates and the potential differences in their physiology are discussed. Our findings further support the need for a taxonomical revision of the Rigidoporus genus.
article id 1275, category Research note
Allometric biomass equations for shrub and small tree species in subtropical China. Silva Fennica vol. 49 no. 4 article id 1275. https://doi.org/10.14214/sf.1275
Highlights: Diameter (D) and height (H) are strong predictors in species-specific and multispecies models for the aboveground biomass of subtropical shrubs and small trees; Although wet basic density and crown shape may improve the predictive power of aboveground biomass slightly, the labor intensive measurements for wet basic density and crown shape may be disregarded when a large number of individuals are to be surveyed; Our results extend the generality of D-H models for aboveground biomass for large trees to subtropical shrubs and small trees.
Species-specific allometric equations for shrubs and small trees are relatively scarce, thus limiting the precise quantification of aboveground biomass (AGB) in both shrubby vegetation and forests. Fourteen shrub and small tree species in Eastern China were selected to develop species-specific and multispecies allometric biomass equations. Biometric variables, including the diameter of the longest stem (D), height (H), wet basic density (BD), and crown area and shape were measured for each individual plant. We measured the AGB through a non-destructive method, and validated these measurements using the dry mass of the sampled plant components. The AGB was related to biometric variables using regression analysis. The species-specific allometric models, with D and H as predictors (D-H models) accounted for 70% to 99% of the variation in the AGB of shrubs and small trees. A multispecies allometric D-H model accounted for 71% of the variation in the AGB. Although BD, as an additional predictor, improved the fit of most models, the D-H models were adequate for predicting the AGB for shrubs and small trees in subtropical China without BD data.
article id 1305, category Research note
Antennal response of Prinobius myardi to synthetic tree volatiles. Silva Fennica vol. 49 no. 3 article id 1305. https://doi.org/10.14214/sf.1305
Highlights: Prinobius myardi is a wood borer considered a major threat for Mediterranean oaks, especially Quercus suber and Q. ilex; We performed electroantennographic bioassays to assess olfactory sensitivity of P. myardi to synthetic plant volatiles; P. myardi exhibits a broad sensitivity to common tree volatiles, including those emitted by oaks (α-pinene and β-pinene) or non-host volatiles (1,8-cineole).
Prinobius myardi Mulsant is a wood borer implicated in the decline of Mediterranean oaks, especially Quercus suber L. and Quercus ilex L. Plant volatiles play an important role in plant-insect interactions, and electroantennography (EAG) is an effective tool for exploring the electrophysiological activity of host plant volatiles on insects. To improve our understanding of the olfactory sensitivity of P. myardi, we recorded EAG responses to 20 tree volatiles, and analyzed the dose-dependent response to five doses (10–4:1 to 1:1 v/v) of the three most EAG-active compounds. Antennae of P. myardi responded to 13 chemicals, mainly monoterpenes and green leaf volatiles, with the strongest EAG responses being observed with β-pinene, (+)-α-pinene and 1,8-cineole. Dose–response profiles showed positive dose-dependent responses for all three compounds. Our results suggest a broad sensitivity of P. myardi to common tree volatiles, particularly some host-related compounds and volatiles associated with wounded trees; the olfactory recognition of ratios of these compounds could play a role in host selection by P. myardi.
article id 1321, category Research note
Composition of functional groups of ground vegetation differ between planted stands of non-native Pinus contorta and native Pinus sylvestris and Picea abies in northern Sweden. Silva Fennica vol. 49 no. 2 article id 1321. https://doi.org/10.14214/sf.1321
Highlights: Differences in ground vegetation patterns can be linked to tree species, forest stand age and differences in canopy cover; Vascular plant cover was higher in stands of P. contorta than in stands of both native tree species; The overall differences and similarities between P. contorta and the two native conifers were not consistent over the different age classes.
Intensified forestry increases the interest in replacing native tree species with fast growing non-native species. However, consequences for native biodiversity and ecosystem functioning are poorly understood. We compared cover and composition of major functional groups of ground vegetation between planted stands of non-native Pinus contorta Dougl. var. latifolia Engelm. and native conifers Pinus sylvestris L. and Picea abies (L.) H. Karst. in northern boreal Sweden. We quantified the ground cover of lichens, bryophytes, vascular plants and ground without vegetation (bare ground) in 96 stands covering three different age classes (15, 30 and 85 years old). Our study revealed differences in ground vegetation patterns between non-native and native managed forests, and that these differences are linked to stand age and differences in canopy cover. Total vascular plant cover increased with increasing stand age for all tree species, with P. contorta stands having higher cover than both native conifers. The ground cover of lichens was, although generally low, highest in stands of Pinus sylvestris. P. abies stands had a lower cover of vascular plants, but bare ground was more common compared with P. contorta. Our results suggest that the use of P. contorta as an alternative tree species in Fennoscandian forestry will influence native ground vegetation patterns. This influence is likely to change with time and future research should consider both temporal and landscape-scale effects from shifting tree-species dominance to Pinus contorta and other non-native tree species.
article id 1255, category Research note
Relationships between climatic variables and tree-ring width of European beech and European larch growing outside of their natural distribution area. Silva Fennica vol. 49 no. 1 article id 1255. https://doi.org/10.14214/sf.1255
Highlights: In western Latvia, variation of tree-ring width of European beech and European larch within stands was similar; Dry summers and cold winters caused common event years in tree-rings; Moisture availability at the end of summer was apparently the main limiting factor for tree-ring width; Winter and spring temperature did not have significant and lasting effect on variation of tree-ring width.
Relationships between climatic variables and tree-ring width (TRW) of dominant European larch (Larix decidua Mill.) and European beech (Fagus sylvatica L.) trees growing outside of their natural distribution area in western Latvia were studied. Chronologies of TRW, which covered the periods 1949–2012 and 1911–2012, were produced for beech and larch, respectively. Common signatures in TRW between both species were observed, but their amplitude differed. Correlation analysis showed that variation of TRW of both species was affected by drought related climatic variables. Tree-ring width of beech was affected by temperature in the previous July and August and the effect of spring and autumn temperature was observed. Since the 1980s, the effect of July precipitation has become significant. Summer precipitation was significant for larch in the mid-part of the previous century; however, temperature in the previous September has become a limiting factor since 1970s. The limiting effect of winter and spring temperature apparently lost its significance around the 1950s.
Category: Discussion article
article id 1304, category Discussion article
Challenges in publishing: producing, assuring and communicating quality. Silva Fennica vol. 49 no. 4 article id 1304. https://doi.org/10.14214/sf.1304
This paper is based on a session “How to make forest science available for all? Publishers’, editors’, and authors’ challenges” at the IUFRO XXIV world conference, organized by Pekka Nygren and Eeva Korpilahti from the Finnish Society of Forest Science. The presenters dealt with the topical problems of publishing scientific knowledge from different perspectives. The talks covered the development of journals, publications and submissions, benefits and drawbacks of open access publishing as well as electronic and traditional publishing, and possibilities to promote interesting papers either from the journal’s or from the author’s perspective, and the problems of disseminating the scientific results to the end users. In this paper, a few prevalent viewpoints, inspired by the session, are raised and discussed with some suggestions included.