Category: Research article
article id 526, category Research article
The opportunity costs of forest conservation in a local economy. Silva Fennica vol. 36 no. 4 article id 526. https://doi.org/10.14214/sf.526
Costs generated by nature conservation are repeatedly under discussion. Most often the costs of conservation are estimated as aggregate figures at the national or regional level or alternatively, for a forest owner. In this study they were examined at the local level, in the forestry dependent municipality of Ilomantsi in Eastern Finland. The estimations of lost net revenues (stumpage income less silvicultural costs), wages, entrepreneurial income and profits, employment and value added were based on alternative forest management plans calculated for conservation areas. The annual losses as regards employment during the first decade were estimated to be 5.7–20.4 jobs. Later, the employment effects were estimated to be 2.4–6.3 lost jobs. Although the value added lost during the first decade was estimated to be at maximum only 3.4% of the present total value added of the municipality, the share of the value added of forestry was estimated to be higher than the mere protected forest land share would indicate. The use of conservation areas for forestry would create a moderate increase of employment in forestry, i.e. 3.8–14%, during the first decade, but it would later stabilise at a much lower level. Employment impacts at the municipal level were estimated as very small (at maximum 0.9%), but on the other hand, for some villages even single jobs may matter. The main reasons for the minor impacts were the high mechanisation rate of logging and the major flow of stumpage income outside the locality.
article id 525, category Research article
Value of complete information on red heartwood formation in beech (Fagus sylvatica). Silva Fennica vol. 36 no. 4 article id 525. https://doi.org/10.14214/sf.525
Beech (Fagus sylvatica L.) is the most important deciduous tree species in Germany. The wood of beech shows normally a bright colour (white beech) as long as no coloured heartwood has been formed. The facultative heartwood formation is induced when oxygen enters central parts of older trees, where dead or at least less vital parenchyma exist. The coloured heartwood is usually called ‘red heartwood’. Beech without red heartwood can preferably be found in younger trees which show a high water content even in central parts of the stem. The presence of red heartwood is regarded as a severe reduction of timber quality. Numerous studies have investigated opportunities to derive information on the presence and characteristics of red heartwood of standing beech trees. But until now it has not been tested whether such information could be helpful to improve the economics of beech-silviculture. This paper investigates whether complete information on the heartwood of standing beech could be useful to control the proportion of discoloured timber harvested during one rotation. It is also examined, which kind of information on the heartwood could be used to improve the economic results. To verify this, simulations based on simple algorithms were conducted. The general assumption was made that all information on the heartwood would be available. The results show that information which is restricted on the mere existence of red heartwood is neither suited to significantly reduce the amount of coloured timber nor is it possible to improve economic results based on this information. Only based on information on the recent formation of red heartwood of beech, which is actually still white the amount of discoloured timber can be reduced significantly. Consequently the discounted cash flows can only be substantially improved based on information on an expected formation of recent red heartwood.
article id 524, category Research article
Thinning response and thinning bias in a young Scots pine stand. Silva Fennica vol. 36 no. 4 article id 524. https://doi.org/10.14214/sf.524
The study analyses the annual post-thinning response and thinning bias of a young Scots pine stand as a function of tree size, competition faced by the tree, and competition that is removed around the tree in the thinning treatment. The thinning response of a tree was defined as the change of tree growth due to a thinning treatment. The thinning bias was defined as the difference between the true growth and model prediction. A distance-dependent (spatial) and a distance-independent (non-spatial) growth model were used in the calculations. The empirical data were measured from a thinning experiment consisting of ten plots, each 40 x 30 m in size, which were thinned to different stand densities. The ten-year post-thinning growth of every remaining tree was measured. The results indicated that the highest thinning response is among medium-sized and co-dominant trees. The thinning response is quite small, and even negative for some trees, for two years after thinning but it becomes clearly positive from the third year onwards. The spatial model underestimated the growth of small trees (which usually face high competition) while the non-spatial model overestimated the growth of trees that are small or face much competition. The spatial model used in this study overemphasized the effect of competition while the non-spatial model underestimated this effect. Both growth models overestimated the growth of trees in heavily thinned places, but this bias disappeared in two years. The negative bias was more pronounced with a spatial growth model because the tendency of the non-spatial model to underestimate the growth of trees facing little competition partly compensated for the negative bias.
article id 523, category Research article
Effect of early thinning on the diameter growth distribution along the stem of Scots pine. Silva Fennica vol. 36 no. 4 article id 523. https://doi.org/10.14214/sf.523
The absolute and relative effects of the first thinning on the diameter growth distribution along the stems were studied in 98 Scots pines (Pinus sylvestris L.) at heights of 1.3, 4, 6 and 8 m. The data cover one 3-year pre-thinning period and four 3-year post-thinning periods in plots with densities varying from 575 to 3400 stems ha–1. A shift in the point of maximum diameter growth down the bole was found during the first 3 years after thinning, with a shift back up the stem later. The thinning response over the whole 12-year post-thinning period was strongest the nearer the stem base and the heavier the thinning. The largest trees had the highest diameter growth after thinning in absolute terms, and the growth was greater the heavier the thinning. The absolute thinning response over the 12-year post-thinning period was highest in the medium tree size and in the largest trees, especially on the heavily thinned and lightly thinned plots. Whereas in the moderately thinned stand the smaller and larger trees responded more than did those of medium size on average. In relative sense, however, the small trees on heavily or moderately thinned plots responded more rapidly and more strongly than the medium-sized or large trees over the whole stem. The small trees on the lightly thinned plots responded only slightly to thinning. The results suggest that it is possible to affect the uniformity of wood properties (such as ring width) both within and between trees by thinning.
article id 522, category Research article
Anticipating the variance of predicted stand volume and timber assortments with respect to stand characteristics and field measurements. Silva Fennica vol. 36 no. 4 article id 522. https://doi.org/10.14214/sf.522
Several models and/or several variable combinations could be used to predict the diameter distribution of a stand. Typically, a fixed model and a fixed variable combination is used in all conditions. The calibration procedure, however, makes it possible to choose the measurement combination from among many possibilities, although the model used is fixed. In this study, the usefulness of utilizing additional stand characteristics for calibrating the predicted diameter distribution is examined. Nine measurement strategies were tested in predicting the total stand volume, sawlog volume and pulpwood volume. The observed errors of these variables under each strategy were modeled as a function of basal area, basal area median diameter and number of stems. The models were estimated in three steps. First, an Ordinary Least Squares (OLS) model was fitted to the observed errors. Then, a variance function was estimated using the OLS residuals. Finally, a weighted Seemingly Unrelated Regression (SUR) analysis was used to model the observed errors, using the estimated variance functions as weights. The estimated models can be used to anticipate the precision and accuracy of predicted volume characteristics for each stand with different variable combinations and, consequently, to choose the best measurement combination in different stands.
article id 521, category Research article
Site index conversion equations for mixed trembling aspen and white spruce stands in northern British Columbia. Silva Fennica vol. 36 no. 4 article id 521. https://doi.org/10.14214/sf.521
White spruce and trembling aspen are two important commercial species in British Columbia. They often grow in association, particularly in the Boreal White and Black Spruce and Sub-Boreal Spruce biogeoclimatic zones. Site index conversion equations are useful for estimating the site index of one species from the site index of another species. This study fills a need for site index conversion equations for mixed spruce/aspen stands. Seventy 0.01 ha study plots were established in mixed spruce/aspen stands. One site tree of each species was selected from each plot. The height and breast height ages of the site trees were measured and the site index was estimated with these data. The correlation between the site index of spruce and aspen was 0.6. Geometric mean regression was used to estimate the parameters of a linear site index conversion equation. The analysis did not reveal any differences in the conversion equations across the three major biogeoclimatic units (BWBSmw1, BWBSmw2, and SBS) that were sampled. Therefore, only one conversion equation is required.
article id 520, category Research article
Foliage and branch biomass estimation of coniferous and deciduous tree species. Silva Fennica vol. 36 no. 4 article id 520. https://doi.org/10.14214/sf.520
Under changing environmental conditions, biomass development on the tree and the stand level may differ from today, regardless if the induced change is due to a shift in the general climate properties or to forest management. Under these conditions, tree biomass can not be derived from tables based on former investigations but has to be defined from particular biomass investigations, which generally calculate tree and stand biomass from sample branches using allometric relationships. Therefore, sample measurements on harvested trees are needed. In this paper, foliage and branch biomass estimation for 6 Norway spruces (Picea abies) and 6 beeches (Fagus sylvatica) harvested in a 56-year-old mixed stand in southern Germany is presented. Different allometric models are investigated to derive branch biomass from branch dimension for both species. The equations that are based on branch length, foliated branch fraction, and branch diameter are used for tree and stand level estimates. However, the variation within the 6 trees of each species was too large for a reliable calculation of stand biomass, especially in case of beech branch wood. Furthermore, the necessity of allometric relations and their applicability in individual-tree models is discussed, and the importance of suitable branch- and tree selection is underlined.
article id 519, category Research article
Sensitivity of Picea abies to butt rot in pure stands and in mixed stands with Pinus sylvestris in southern Sweden. Silva Fennica vol. 36 no. 4 article id 519. https://doi.org/10.14214/sf.519
Repeatedly sampled data from permanent experimental plots in southern Sweden were used to model butt rot development in Norway spruce growing in pure stands and in mixed stands with Scots pine. The data come from 29 sites with pure spruce, altogether 100 plots, and from 15 sites of mixed spruce and pine, altogether 22 plots. A logistic model provided the best fit to the data. The study material revealed that in mixed stands the proportion of spruce trees with butt rot is lower than in pure Norway spruce stands. The difference in the incidence of butt rot cannot be explained by silviculture or windthrow since both factors are accounted for in the study. The most significant effect on butt rot development in Norway spruce by an admixture of Scots pine, was found when the Scots pine admixture was 50%. In order to reduce the incidence of butt rot in Norway spruce, the study material indicate that there is little to be gained by increasing the Scots pine admixture to much more than 50%.
article id 518, category Research article
Timing of seed dispersal in Pinus sylvestris stands in central Sweden. Silva Fennica vol. 36 no. 4 article id 518. https://doi.org/10.14214/sf.518
The objective of the study presented here was to describe the variation in timing of seed dispersal from Scots pine (Pinus sylvestris L.) seed trees in central Sweden. Seeds were collected in traps at two sites, for three years at one, and four years at the other . The traps were emptied from March to August each year at 1–2 week intervals during the main period of seed dispersal. The annual seed fall varied between 200 000 and 1.6 million seeds per hectare. The seed fall started in mid to late April, shortly after the heat sum had started to accumulate. The most intensive seed fall took place in early to mid May. The peak period, when 50% of the total seed dispersal occurred, lasted for 18–28 days at the different sites and years. The variation in timing among years seemed to be mainly due to climatic factors – high temperatures promoted seed dispersal, for instance. The results may be useful for planning the time of scarification to optimise the natural regeneration of Scots pine. The data suggest that scarification in the spring, no later than mid-May, would generally create a good seed-bed for most of the current year’s seeds, whereas scarification in late May or June would bury a large proportion of this cohort.
Category: Discussion article
article id 527, category Discussion article
Socioecological landscape planning: an approach to multi-functional forest management. Silva Fennica vol. 36 no. 4 article id 527. https://doi.org/10.14214/sf.527