Category: Research article
article id 10462, category Research article
Comparing the characteristics of boom-corridor and selectively thinned stands of Scots pine and birch. Silva Fennica vol. 55 no. 3 article id 10462. https://doi.org/10.14214/sf.10462
Highlights: After boom-corridor thinning (BCT), the number of stems per hectare was higher than that after selective thinning. The number of future crop trees was at the same level; The removal of the simulated intermediate thinnings and clearcutting in BCT treatments was 10–18% higher than in selective thinning. The saw log volumes were at the same level in both treatments.
Young, dense forest in Finland and Sweden urgently need to receive first thinning. In such stands, conventional selective thinning methods make the harvester work time consuming and, thus, costly. To make small-sized trees economically competitive as raw material for bioenergy and biorefining, new harvesting technologies and/or thinning methods need to be developed. A potential solution is boom-corridor thinning (BCT), rendering effective cutting work. The aim of this study was to describe and compare the stand structure of two Scots pine stands (Pinus sylvestris L.) and one birch-dominated (Betula pendula Roth with natural downy birch, B. pubescens Ehrh.) stand after BCT and selective thinning at the first thinning phase. Furthermore, simulations were conducted to predict the future stand development after the first thinning treatments. The density of the growing stock was 16–46% higher after BCT treatment than after selective thinning because BCT stands included more small and supressed trees with a dbh < 100 mm. However, the numbers of future crop trees with a dbh > 140 mm per hectare were at the same level in both treatments. The stem volume removal per hectare did not differ between treatments. However, simulation of stand development and intermediate thinning and clearcutting revealed that the total removal volume was 10–18% higher in BCT stands compared to selectively thinned ones. The saw log volumes harvested did, however, not differ between treatments. This study shows that BCT generates stands with higher biodiversity compared to conventional thinning as higher levels of biomass removal can be reached throughout stand rotations.
article id 10369, category Research article
Effects of spot mounding and inverting on growth of conifers, exposed mineral soil and natural birch regeneration. Silva Fennica vol. 54 no. 5 article id 10369. https://doi.org/10.14214/sf.10369
Highlights: There were 21% fewer naturally regenerated birches ha–1 in inverted areas (22 951) compared to spot mounded areas (29 086); Spot mounding exposed slightly, but not statistically significantly, larger area of mineral soil than inverting; There was no difference in seedling mortality or growth between the site preparation methods.
In Nordic forests, consistent evidence about better seedling survival rate and increased growth due to site preparation have been obtained in numerous studies. Proper site preparation method can reduce costs of the whole regeneration chain through its effects on survival of planted seedlings, abundance of natural regeneration and competition in early stand development. This study compared the natural regeneration of birches (silver birch (Betula pendula Roth) and downy birch (B. pubescens Ehrh.)), amount of exposed mineral soil, and growth of planted seedlings between spot mounding and inverting site preparation methods. Present study was conducted in eight forest stands established in 2012 or 2015. Even though difference was not statistically significant, inverting exposed less mineral soil than spot mounding and thus reduced the natural regeneration of birch seedlings by 6135 seedlings ha–1 compared to spot mounding. However, the variation between regeneration areas was remarkable. There was no difference in seedling mortality or growth between the site preparation methods. In order to achieve high growth of conifers, moderate amount of exposed mineral soil and thus less naturally regenerated birch, inverting should be favored over spot mounding.
article id 10196, category Research article
Low cost prediction of time consumption for pre-commercial thinning in Finland. Silva Fennica vol. 54 no. 1 article id 10196. https://doi.org/10.14214/sf.10196
Highlights: Time consumption (TC) in pre-commercial thinning (PCT) can be predicted by variables describing site and stands conditions and previous silvicultural management; Applying variables available in forest resources data the field-assessment of worksite difficulty factors is not needed; The TC model could facilitate the predictions of the labour costs of PCT in forest information systems.
The time consumption (TC) of pre-commercial thinning (PCT) varies greatly among sites, stands and forest workers. The TC in PCT is usually estimated by field-assessed work difficulty factors. In this study, a linear mixed model for the TC in PCT was prepared by utilizing forest resources data (FRD). The modelling data included 11 848 and validation data included 3035 worksites with TC information recorded by forest workers within the period of 2008–2018. The worksites represented a range of site and stand conditions across a broad geographical area in Finland. Site and stand characteristics and previous management logically explained the TC in PCT. The more fertile the site, the more working time was needed in PCT. On sites of medium fertility, TC in the initial PCT increased with stand age by 0.5 h ha–1 yr–1. Site wetness increased the TC. PCT in summer was more time consuming than in spring. Small areas were more time consuming to PCT per hectare than larger ones. The between-forest worker variation involved in the TC was as high as 35% of the variation unexplained by the TC model. The coefficient of determination in validation data was 19.3%, RMSE 4.75 h ha–1 and bias –1.6%. The TC model based on FRD was slightly less precise than the one based on field-assessed work difficulty factors (removal quantity and type and terrain difficulty): RMSE 4.9 h ha–1 vs. 4.1 h ha–1 (52% vs. 43%). The TC model could be connected to forest information systems where it would facilitate the predictions of the labour costs of PCT without field-assessing work difficulty factors.
article id 9933, category Research article
Quality of spot mounding performed by continuously advancing mounders. Silva Fennica vol. 52 no. 2 article id 9933. https://doi.org/10.14214/sf.9933
Highlights: The number and quality of mounds varied considerably according to the operating conditions;The main factors reducing the quality of spot mounding were steep terrain, a thick humus layer, fresh logging residues, stoniness and soil texture;With careful selection of timing and conditions for mounding, the quality obtained by continuously advancing mounders can be improved.
Operating conditions affecting the quality of spot mounding by Bracke continuously advancing mounders were investigated on 66 regeneration areas (124 ha) in eastern Finland. The quality of mounds was classified as suitable (good or acceptable after additional compression) or unsuitable for planting. Models were constructed for the number of suitable planting spots obtained per hectare (good and acceptable mounds), the probability of successful mounding (≥1600 planting spots ha–1) and the probability of creating a suitable mound as a function of terrain, site and soil characteristics, as well as slash conditions (removed, fresh or dry logging residues). The average number of mounds created was 1892 ± 290 mounds ha–1, of which 1398 ± 325 mounds ha–1 (74%) were classified as suitable for planting. The quality of spot mounding was reduced by steep terrain, a thick humus layer and fresh logging residues. Stoniness and soil texture also affected the number of planting spots created. Mounding after logging residues had dried increased the number of planting spots by 191 spots ha–1 compared with mounding in the presence of fresh residues. Removing residues did not significantly increase the number of planting spots compared with mounding amongst dry residues. A thick humus layer, very stony soil, steep slopes and valley terrain decreased the number of planting spots by 150–450 spots ha–1. The number and quality of mounds varied considerably according to the operating conditions, but with careful selection of timing and sites the quality obtained by a continuously advancing mounder can be improved.
article id 1665, category Research article
Reliability of self-control method in the management of non-industrial private forests. Silva Fennica vol. 52 no. 1 article id 1665. https://doi.org/10.14214/sf.1665
Highlights: Self-control method was found reliable at the main stages of the forest regeneration process; Only slight overestimation was found in self-control results of soil preparation and planting and small underestimation in self-control of young stand management; Diverse utilizing of self-control data is possible in support of service providers operations.
This study seeks to determine the extent to which self-control data can be relied upon in the management of private forests. Self-control (SC) requires the forest workers to evaluate their own work quality to ensure the clients’ needs are met in terms of soil preparation, planting and young stand management. Self-control data were compared to an independent evaluation of the same worksites. Each dataset had a hierarchical structure (e.g., sample plot, regeneration area and contractor), and key quality indicators (i.e., number of prepared mounds, planted seedlings or crop trees) were measured for each plot. Self-control and independent-assessments (IA) were analyzed by fitting a multi-level multivariate model containing explanatory variables. No significant differences were observed in terms of soil preparation (number of mounds) or young stand management (number of crop trees) between self-control and independent-assessments. However, the self-control planting data included a slight but significant overestimation of the number of planted seedlings. Discrepancies are discussed in terms of sampling error and other explanatory factors. According to overall results, self-control methods are reliable at every stage of the forest regeneration process. As such, the diverse utilizing of self-control data is possible in support of service providers operations.
article id 982, category Research article
Labour consumption models applied to motor-manual pre-commercial thinning in Finland. Silva Fennica vol. 48 no. 2 article id 982. https://doi.org/10.14214/sf.982
Highlights: When a young stand grows and gets older, the work time needed to make pre-commercial thinning increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hardwoods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively.
Labour models were developed to estimate the time required to Pre-Commercially Thin (PCT) with a clearing saw 4- to 20-year-old stands of the main commercial tree species in Finland. Labour (i.e., work-time consumption) was estimated from the density and stem diameter of the removal of 448 stands via an existing work productivity function. The removal based estimator attained was used as the basis for a priori mixed linear regression models. The main finding was that when a young stand grows and gets older, the work time needed to make a PCT increases. The stands of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and hardwoods (Betula spp.) required an additional 8.2%, 5.2%, and 3.3% work-time per year, respectively. Site fertility also played a role in that the most fertile site (mesic OMT) had an estimated labour requirement 114% higher than that for dryish VT. We also note that, per unit area, small stands require less labour than large ones and soil preparation method had a minor effect on the labour estimate. The stands which had previously gone through PCT were separately analysed. In those stands, the only significant variable concerning the labour estimate was age. The a priori models described here can help foresters to develop economic management programmes and issue quotes for forestry services.
article id 893, category Research article
Soil preparation method affects outplanting success of Norway spruce container seedlings on till soils susceptible to frost heave. Silva Fennica vol. 47 no. 1 article id 893. https://doi.org/10.14214/sf.893
Soil preparation is a common practice that precedes outplanting of Norway spruce (Picea abies (L.) Karst.) in Finland as it enhances the survival and early growth of seedlings. Mounding in particular has become more common with Norway spruce planting in recent years. However, on fine-grained soils, the postplanting performance of seedlings has been poorer than on coarser soils even with mounding. This study examined the effects of different soil preparation treatments (spot and ditch mounding with varying mound height, inverting, unprepared control with or without a herbicide) on the postplanting performance of Norway spruce container seedlings on till soil susceptible to frost heave in two outplanting forest sites in central Finland. The results indicate higher soil temperature and lower soil water content especially in the highest mounds. Mounds, however, subsided gradually during the study years. Seedling mortality was higher and the proportion of vigorous seedlings was lower in the unprepared treatments, mainly due to increased pine weevil (Hylobius abietis L.) damage. Frost heave was present mainly on ditch mounded and inverted spots. Glyphosate herbicide treatment showed no benefit compared to the untreated control in two years. Consequently, seedling damage and conditions in the planting spots were reflected in seedling growth which was enhanced in the mounded spots. However, varying mound height or thickness of mineral capping showed no clear difference in seedling growth. The results therefore suggest that ditch or spot mounding should be used on frost heave susceptible forest soils to promote plantation establishment. Inverting or having no soil preparation with or without herbicide is not recommended.
article id 919, category Research article
Estimating the need for early cleaning in Norway spruce plantations in Finland. Silva Fennica vol. 46 no. 5 article id 919. https://doi.org/10.14214/sf.919
Effective management of Norway spruce (Picea abies (L.) Karst.) plantations requires detailed information on stand development, which is costly to measure. However, estimating the need for early stand management from site attributes that persists stabile after ones measured, may provide an inexpensive alternative. This study compared hardwood competition in spruce plantations of varying ages and tested the usability of this information in estimating the need for early cleaning. The data included 197 spruce plantations (4–7 years old) inventoried in southern Finland in 2007. The level (Low, Substantial, High) of need for early cleaning was subjectively determined by contrasting location and size of competing hardwoods to a conifer crop tree. Then the stage of the need for early cleaning was modelled according to site and stand attributes. Nearly 60% of the conifer crop trees in the plantations were subjectively judged to require early cleaning (Substantial 37.2%, High 21.2%), but only 10 per cent of the evaluated area was cleaned. Need for cleaning was intense on peatlands or damp soils, whereas it was mild on unprepared soils or cleaned sites. Traditional site characteristics used in forest management planning can be useful for recognising the peripheral cases, where need for cleaning is probably high or low. However, on a typical mineral soil plantation (uncleaned, soil prepared) the model indicates the differences in the need for early cleaning weakly. The need for early cleaning was already high in 4-year-old plantations, why stand age did not have significant effect on development of the need. Thus, the timing of an operation can not be predicted with the model. Nonetheless, early cleaning very likely opens growth space of crop trees in a 4–7-year-old spruce plantation. Therefore, from an aspect of crop growth, an uncleaned Norway spruce plantation in this age group is quite consistently worth cleaning.
article id 146, category Research article
Effect of soil preparation method on economic result of Norway spruce regeneration chain. Silva Fennica vol. 44 no. 3 article id 146. https://doi.org/10.14214/sf.146
Economic result of forest regeneration chains, based either on spot mounding or on disc trenching and planting of Norway spruce (Picea abies [L.] Karst.) seedlings, were clarified and compared to each other. First, effects of soil preparation method on early development of Norway spruce stands were measured from field experiments. Second, the effects of soil preparation method on stand level management programs were modelled. The modelling was based on growth simulation and investment calculations. The soil preparation methods substantially affected early development of a stand. The density of the removed trees in early cleaning was 56% higher on the disc-trenched area compared to the spot-mounded area. The difference was especially high (120%), close by (< 25 cm) the remained spruce seedlings. There was also a difference between the methods in the growth of crop spruces; at biological age of 8 years, the mean height of spruce was 110 cm on the spot-mounded area and 68 cm on the disc-trenched area. The differences led to divergent management programs between the areas. The disc-trenched area needed three young stand management operations whereas two was enough at the spot-mounded area. Although disc trenching is a less expensive method than spot mounding, the total management costs were higher in disc trenching than in spot mounding. Furthermore, incomes from the first commercial thinning were higher when regeneration based on spot mounding. At the interest rate of 3%, the investment in spot mounding had 329 EUR ha–1 higher net present value than the investment in disc trenching.
article id 157, category Research article
The effect of quality management on forest regeneration activities in privately-owned forests in southern Finland. Silva Fennica vol. 44 no. 2 article id 157. https://doi.org/10.14214/sf.157
This study describes the effect of quality management on forest regeneration activities in privately-owned forests in southern Finland. The study material consists of two mail surveys conducted in 2006 and 2007. The questionnaires were sent to forestry professionals in Forest Owners’ Associations (FOAs), who had either participated (participants) or not (non-participants) in the forest regeneration quality management interventions in years 2000–2006. Quality management interventions of the FOAs included field inventories, feedback meetings, and education sessions about quality techniques. The activities of participant and non-participant FOAs were compared in terms of the available resources, the actions taken, and the aspirations for improvement. In the FOAs, which had participated in quality management, the number of excavator contractors had increased by 16% more than in the non-participant FOAs. The contractors had acquired 23% more soil preparation equipment under the supervision of the participant forestry professionals. The soil preparation method used in conjunction with Norway spruce that had most increased in use was patch mounding. Seedlings that were 1.5 years and older were used by participant forestry professionals in the planting of Norway spruce 11% more than by non-participants. The planting workers had attended 14% more educational sessions, while the use of self-control measurements in soil preparation and planting density had been adopted 10% more frequently under the supervision of the forestry professionals participating in the quality management. A greater interest in obtaining feedback by using quality control inventories was also found among forestry professionals who participated in quality management.
article id 217, category Research article
Variation in the results of Norway spruce planting and Scots pine direct seeding in privately-owned forests in southern Finland. Silva Fennica vol. 43 no. 1 article id 217. https://doi.org/10.14214/sf.217
This study describes the variation in the planting results for 3-year-old Norway spruce (Picea abies (L.) Karst.) and 4-year-old Scots pine (Pinus sylvestris L.) using direct seeding in privately-owned regeneration areas in southern Finland. The study material consists of operative forest regeneration quality management inventory areas from the years 2000–2006. The effect of both the regional and the administrative levels as well as ecological factors was modelled on the basis of the hierarchy structure forestry centre, Forest Owners’ Association (= FOA), forestry professional, regeneration area and sample plot. The major part of the variation occurred at the sample plot and regeneration area level. Particular attention was paid to observation of the clustered spatial distribution of Scots pine seedlings. The FOA and forestry professional levels explained 5% of the variation in Norway spruce planting and 11% of the variation in Scots pine direct seeding. Applied forest regeneration operations, site and soil characteristics were included in the fixed effects. In the planting of Norway spruce the most important factor explaining the regeneration result was soil preparation. Mounding produced better results than patching and disc trenching. The site and soil characteristics were other important factors in the operations. The selection of direct seeding of Scots pine on too fertile, fine textured or moist sites yielded poor results.
article id 274, category Research article
Cleaning methods in planted Scots pine stands in southern Finland: 4-year results on survival, growth and whipping damage of pines. Silva Fennica vol. 41 no. 4 article id 274. https://doi.org/10.14214/sf.274
The effects of four cleaning treatments on the survival, growth of, and whipping damage to Scots pine (Pinus sylvestris L.) main stems were studied in young planted pine stands in southern Finland. Treatments were: no cleaning, point-cleaning of broadleaves (mainly birch, Betula pendula Roth and B. pubescens Ehrh.) within a radius of 1 m from the pine, topping of competing broadleaves, and total cleaning of broadleaves. A randomised complete block design with three replicates was established in five sapling stands: the mean height of the pines was 1.5 m in the three younger stands (6 or 7 years old), and 3 m in the two older stands (9 years old). Measurements taken four growing seasons later showed that in the younger stands, all cleaning treatments significantly (P < 0.05) decreased the mortality and increased the diameter increment of the pines. The height increment of the pines on point-cleaned and topped plots was significantly greater than on totally cleaned plots. In the older stands, the effects of cleaning treatments on the mortality and increment of pines were non-significant. In the younger and older stands, point-cleaning and total cleaning significantly reduced the whipping damage to pines, whereas the topping of competing broadleaves did not. The preliminary results support the use of point-cleaning in planted Scots pine stands when the mean height of the pines is about 1.5 m.
article id 405, category Research article
Regeneration process from seed crop to saplings – a case study in uneven-aged Norway spruce-dominated stands in southern Finland. Silva Fennica vol. 38 no. 4 article id 405. https://doi.org/10.14214/sf.405
The dynamics of spruce regeneration, from seed crop to saplings, was studied based on five permanent plots in uneven-aged, spruce-dominated, boreal forest stands, cut with single-tree selection in the beginning of the 1990’s. The annual fluctuation of the spruce seed crop was very similar in uneven-aged and even-aged stands. The correlation between seed crop and number of germinants was significant; but stem number, basal area or volume of the stand did not influence on seedling emergence. The effects of good seed crops were seen as peaks or an increase in the number of germinants and smallest seedlings. The mean number of ‘stabilised’ spruce seedlings (height 11 cm to 130 cm) varied from 6000 ha–1 to over 25 000 spruce seedlings ha–1 from one monitoring plot to another. On a monitoring plot the number of ‘stabilised’ spruce seedlings was stable over time. Neither stand basal area nor stand volume influenced the number of ‘stabilised’ spruce seedlings, but the height of these seedlings was higher on subplots with lower stand volume and smaller basal area. In this study the monitoring period, 5–10 years, was too short to obtain reliable figures for ingrowth, i.e. the transition of seedlings to the sapling stage (h > 130 cm). The adjusted mean ingrowth was 26 stems ha–1 year–1.
Category: Review article
article id 10172, category Review article
Influence of mechanical site preparation on regeneration success of planted conifers in clearcuts in Fennoscandia – a review. Silva Fennica vol. 54 no. 2 article id 10172. https://doi.org/10.14214/sf.10172
Highlights: Mechanical site preparation (MSP) increases seedling survival rates by 15–20%; Survival rates of 80–90% ca. 10 years after MSP and planting conifers are possible; MSP can increase tree height 10–15 years after planting by 10–25%; The increase in growth rate associated with MSP may be temporary, but the height enhancement probably persists.
In the Nordic countries Finland, Norway and Sweden, the most common regeneration method is planting after clearcutting and, often, mechanical site preparation (MSP). The main focus of this study is to review quantitative effects that have been reported for the five main MSP methods in terms of survival and growth of manually planted coniferous seedlings of Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and lodgepole pine (Pinus contorta var. latifolia Engelm.) in clearcuts in these three countries. Meta analyses are used to compare the effects of MSP methods to control areas where there was no MSP and identify any relationships with temperature sum and number of years after planting. In addition, the area of disturbed soil surface and the emergence of naturally regenerated seedlings are evaluated. The MSP methods considered are patch scarification, disc trenching, mounding, soil inversion and ploughing. Studies performed at sites with predominately mineral soils (with an organic topsoil no thicker than 0.30 m), in boreal, nemo-boreal and nemoral vegetation zones in the three Fenno-Scandinavian countries are included in the review. Data from 26 experimental and five survey studies in total were compiled and evaluated. The results show that survival rates of planted conifers at sites where seedlings are not strongly affected by pine weevil (Hylobius abietis L.) are generally 80–90% after MSP, and 15–20 percent units higher than after planting in non-prepared sites. The experimental data indicated that soil inversion and potentially ploughing (few studies) give marginally greater rates than the other methods in this respect. The effects of MSP on survival seem to be independent of the temperature sum. Below 800 degree days, however, the reported survival rates are more variable. MSP generally results in trees 10–25% taller 10–15 years after planting compared to no MSP. The strength of the growth effect appears to be inversely related to the temperature sum. The compiled data may assist in the design, evaluation and comparison of possible regeneration chains, i.e. analyses of the efficiency and cost-effectiveness of multiple combinations of reforestation measures.
Category: Research note
article id 10195, category Research note
The efficacy of Chondrostereum purpureum against sprouting of deciduous species after mechanized pre-commercial thinning. Silva Fennica vol. 53 no. 3 article id 10195. https://doi.org/10.14214/sf.10195
Highlights: Fungal treatments increased stump mortality compared to the control (cutting only); The fungal treatment did not decrease the number of sprouts per stump; Application during mechanized pre-commercial thinning did not yield as high stump mortalities as in earlier treatments performed manually.
The use of a white-rot fungus, Chondrostereum purpureum (Pers. Ex Fr.) Pouzar, as a biocontrol agent against sprouting has been studied with good results. The aim of the study was to investigate the efficacy of two pre-commercial thinning machines, Tehojätkä and Mense, to spread an inoculum of C. purpureum as a biocontrol agent on freshly cut birch (Betula pendula Roth and B. pubescens Ehrh.), European aspen (Populus tremula L.), rowan (Sorbus aucuparia L.), and goat willow (Salix caprea L.) stumps (the fungal treatment) and compare that to the control (cutting only, done by Tehojätkä). Efficacy was investigated in terms of stump mortality and the number of sprouts per stump. This study was conducted in one stand and sprouting was investigated for three years after treatment. The fungal treatment resulted in higher mortality of stumps (34.0% for Tehojätkä and 41.5% for Mense after three years), compared to the control (13.4%). However, the fungal treatment did not decrease the number of sprouts per stump compared to the control. The low occurrence of basidiomata indicates that the accuracy of the spreading mechanism was not satisfactory, causing low mortality figures for the fungal treatment compared to previous studies. In the future, this mechanized method may provide a promising alternative in sprout control if the spreading mechanisms, the accuracy of the treatment, and consequently the efficacy could be improved.
article id 403, category Research note
Multilevel modelling of height growth in young Norway spruce plantations in southern Finland. Silva Fennica vol. 39 no. 1 article id 403. https://doi.org/10.14214/sf.403
Height development of Norway spruce (Picea abies (L.) Karst.) transplants was studied on 22 sites prepared by disc trenching or mounding. At the age of 4–9 years the plantations were surveyed using a multistage sampling design. For every planted spruce on a plot, the past annual height increments were measured as far into the past as possible. Multilevel mixed linear modelling was used to analyse the variation in growth at different levels (year, stand, cluster, plot, tree) and the effects of climatic and site characteristics on height growth. The within-plantation variation in height growth was higher on mounded sites than on disc-trenched sites. The mean temperature and the precipitation sum of the summer months affected height growth positively. Soil characteristics measured from undisturbed soil did not explain the height growth of seedlings on mounded sites, whereas on disc-trenched sites, the depth of the organic layer and the soil temperature had a positive effect and the depth of the eluvial horizon a negative effect. The modelling approach used proved to be a useful method for examining the sources of variation in development of young plantations.