Spruce forest stands in a stationary state

We present stationarity criteria for forest stands,and establish embodiments using a Norwegian empirical stand development model.The natural stationary states only slightly differ from the outcome of long-term simulations previously implemented using the same empirical model.Human interference in terms of diameter-limit cutting is introduced.Consequently,stationary states differing from the natural one appear.Standing volume,growth and monetary value appear low but the financial return rate may be significant.Volume yield and financial return clearly contradict each other,the former arising from harvesting large trees,the latter from frequent removal of small trees.An exponential tree size distribution does not appear to comply with the stationarity criterion.     

Immediate impacts of partial cutting strategies on stand characteristics and value

This study evaluated the impacts of partial cutting on stand characteristics, product recovery, and financial return in mature black spruce-balsam fir stands in Quebec. Four harvesting strategies (clearcut with advance growth protection, irregular shelterwood cutting leaving small merchantable stems, and two patterns of selection cutting) were each applied four times in 20 ha harvest blocks representing irregular black spruce-balsam fir stands. Before the four harvesting strategies were applied, there were no significant differences in stand characteristics (i.e., quadratic mean DBH, basal area, and merchantable stem volume) or expected product recoveries (i.e., lumber volume and value, chip volume and value, and total product recovery) estimated using the Optitek sawing simulation package. There was no significant difference in stand characteristics or product recovery values of the harvested stems between the selection cutting approaches (p > 0.05). However, significant differences in stand characteristics and product recovery values of the harvested stems existed between these treatments and both of the two other treatments. After cutting, the two selection cutting treatments had the lowest impacts on stand characteristics, as compared to the two other treatments. The selection cutting approach which used temporary skidding trails and where cutting was initially concentrated over half of the stand resulted in the highest benefit/cost ratio, relatively high net income and high total product value of residual trees.     

Comparison of tree size structure and growth for partially harvested and even-aged hemlock-spruce stands in southeast Alaska

The effects of partial cutting on tree size structure and stand growth were evaluated in 52 plots in 13 stands in southeast Alaska that were partially harvested 53–96 years ago and compared with 50-year-old even-aged stands that developed after clearcutting. The net basal-area growth was greater in the partially cut plots than in the uncut plots, and basal-area growth generally increased with increasing cutting intensity. However, the basal-area growth of all of the partially harvested stands was significantly less than the growth of 50-year-old even-aged stands, and net basal area growth over the 50 year period since partial harvesting was about 33–43% of the growth of the even-aged stands. Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effect on tree species composition. The tree size distribution of the partially harvested stands was far more complex and well distributed in comparison with the 50-year-old even-aged stands, and included the presence of several trees with diameters of more than 100 cm. These trees included both large-diameter spruce and hemlock trees and were a distinctive structural feature that was noticeably lacking in the even-aged stands.     

Forest regeneration 50 years following partial cutting in mixedwood ecosystems of southern Quebec,Canada

The impact of winter harvesting on regeneration 50 years after an experimental diameter-limit cutting was examined in mixed deciduous–coniferous ecosystems of southern Quebec, Canada. The study was conducted in La Mauricie National Park, Quebec, Canada. Regeneration data in two balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), sugar maple (Acer saccharum Marsh.), and yellow birch (Betula alleghaniensis Britt.) ecosystem types were analyzed. Comparisons between uncut and cut stands were obtained from a total of 63 sample plots. For both ecosystems, there were no significant differences between uncut and cut plots for regeneration density and stocking. The most abundant regeneration species were balsam fir, red spruce, sugar maple, red maple (Acer rubrum L.), yellow birch and American beech (Fagus grandifolia Ehrh.). The type of diameter-limit cutting described in the study did not affect regeneration density and stocking but its impact on productivity, timber quality and genetics is still unknown.     

Applying portfolio optimisation to the harvesting decisions of non-industrial private forest owners

The non-industrial private forest owner's optimal harvesting and investment strategies are studied at forest holding level by including individual forest stands in an asset class portfolio. The forest owner can either clearcut mature stands and invest the capital in financial or real asset classes (bank deposits, government bonds, stocks, apartments) or postpone clearcutting and retain capital in standing trees. Forest inventory data from actual forest holdings in Southwest Finland, the simulation–optimisation software MELA, and statistics on timber prices are utilised to compute the return series for forest stands. The numerical results show that the optimal level of clearcutting decreases markedly with initial non-forest wealth, especially at low risk-free rates of interest. It may therefore be rational for non-industrial private forest owners to consider shorter rotation periods than those of investors with diversified portfolios. The correlations between returns from forest stands are high, implying that increasing the variety of stand structures achieved by planting different species is not likely to bring substantial diversification benefits. The favoured investment outlet for harvesting revenues (apartments, government bonds or stocks) is sensitive to the period of historical data used to compute the return series and risk-free rate of interest. The value growth of forest stand can be used to estimate annual returns only for those stands that are readily mature. An alternative method of computing returns on stands in any development phase is proposed, based on net present value of stand adjusted for fluctuations in forest land prices. This method applies if selling forest land is considered an option. If selling is not an option, the ratio of maximised net present value to value at immediate harvest can be used as a ‘maturity index’ for ranking the stands for portfolio optimisation.     

Profitability of alternative management regimes in Scots pine stands on drained peatlands

In drained, forested peatlands, ditch network maintenance (DNM) is often considered necessary for tree growth, but it also constitutes additional management costs. Commercial thinnings, in turn, in addition to their silvicultural benefits, are generally applied to enhance the financial performance of stand management but results from peatland stands are scarce. In this study, our aim was to find financially feasible management practices for Scots pine-dominated stands on drained peatland sites in Finland. Using mainly inventory data sets, we compiled altogether 29 typical model-stands for four climatic areas, four site types, and two stand conditions according to need for silvicultural care. We used MOTTI stand simulator to predict the development of the model-stands according to different management regimes consisting of various combinations of 0–2 DNM and 0–2 thinnings with different timings and thinning intensities. We then calculated and compared the financial feasibility of the regimes using net present value (NPV; discount rate 3%) analysis. The separate effect of DNM on the profitability was marginal, but the positive effect of thinnings was clear. The harvesting removals varied within a wide range, depending on the timing and intensity of thinnings, but on average, the NPV doubled due to the thinnings. In the stands of initially good silvicultural condition, regimes including only one thinning and a DNM operation generally displayed a good financial result. In the stands of initially poor silvicultural condition due to neglected early care, regimes with two thinnings produced the best NPV regardless of the often low-yielding first thinning.     

海南霸王岭陆均松类热带山地雨林伐后林结构与物种多样性研究

霸王岭林区是海南岛最典型的热带山地雨林分布区.在该区,现存分布面积最广、资源数量最大的是热带山地雨林的各种伐后林.以霸王岭分布最广的以陆均松(Dacridium pierrii)为主的山地雨林的伐后林为对象,研究了其组成、径级、高度结构和物种多样性特征,对比分析了伐后林与原始林以及伐后林不同类型之间的异同.结果表明:原始热带山地雨林经采伐后中小乔木和灌木的优势度增大,而大乔木树种的优势度则明显下降.阳性树种的种类、数量和相对重要性随采伐破坏的程度而增加.伐后林中矮、小树木在林分中比例随采伐破坏的程度增加,而高、大树木,特别是进入主林层树木的比例则随采伐破坏的程度明显下降.从林分测树因子的变化来看,采育择伐和径级择伐的林分要优于大强度择伐和皆伐的林分.原始林的物种丰富度大于伐后林,但其多样性指数和均匀度指数大都小于伐后林.组成上与原始林相似性较大的伐后林是各种择伐后的林分,而皆伐后的林分与原始林在组成上已有很大差别.     

常绿阔叶林择伐伐区作业综合评价优化模型

以最大净收益与对林地破坏最小为目标 ,综合考虑了采伐作业对林地破坏、林木损伤、生产成本等因素 ,建立常绿阔叶林最优择伐模型。     

Responses of polypore fungi following disturbance-emulating harvesting treatments and deadwood creation in boreal Norway spruce dominated forests

ABSTRACT

The emulation of natural disturbances in harvesting has become a widely accepted approach to reach ecologically sustainable forest management. The purpose of this study was to examine the responses of polypore fungi (species richness and composition) on four different cutting methods (selection, gap, patch, and clear-cutting) plus uncut controls, and the creation of high stumps and cut logs in combination with harvesting. Polypores were inventoried one year before, and two and seven years after cutting. A total of 71 polypore species were found, but no red-listed species were recorded seven years after cutting. Irrespective of the treatment, the variation in polypore richness was best explained by the number of deadwood objects in the stands. Species richness per deadwood object was the highest on natural logs. Species richness per volume of spruce deadwood was the highest on small-diameter deadwood and stumps, intermediate on natural logs and lower on cut logs and high stumps. These results indicate that cut logs created in harvesting cannot compensate the loss of deadwood in cutting and energy wood harvesting. Our results demonstrate the difficulty in rapidly creating habitats for red-listed polypores in commercially managed forests.     

The effects of partial cutting on stand structure and growth of western hemlock–Sitka spruce stands in southeast Alaska

The effects of partial cutting on species composition, new and residual-tree cohorts, tree size distribution, and tree growth was evaluated on 73 plots in 18 stands throughout southeast Alaska. These partially cut stands were harvested 12–96 years ago, when 16–96% of the former stand basal area was removed.Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effects on tree species composition. The establishment of new-tree cohorts was positively related to the proportion of basal-area cut. The current stand basal area, tree species composition, and stand growth were significantly related to trees left after harvest (p<0.001). Trees that were 20–80 cm dbh at the time of cutting had the greatest tree-diameter and basal-area growth and contributed the most to stand growth. Diameter growth of Sitka spruce and western hemlock was similar, and the proportion of stand basal-area growth between species was consistent for different cutting intensities.Concerns about changing tree species composition, lack of spruce regeneration, and greatly reduced stand growth and vigor with partial cuts were largely unsubstantiated. Silvicultural systems based on partial cutting can provide rapidly growing trees for timber production while maintaining complex stand structures with mixtures of spruce and hemlock trees similar to old-growth stands.     

Profit�CSize Relationships: A Wood Value Expression to Facilitate Stand Management Decision Making

This paper presents an alternative approach to expressing net value of wood in standing trees in relation to important tree characteristics. The approach aims at increasing woodlot owners’ and managers’ understanding of stand profit production and lead to consideration of stand interventions with higher profitability than those suggested by commonly used guidelines designed for maintaining biologically desirable stock levels. Our investigation showed that determining net wood value in individual trees for stand management purposes is not only feasible but relatively simple to do, requiring little additional information than typically used in stand level cash flow analysis. The presentation of wood value in the form of profit–size relationships presents two major improvements over traditional stand average values and product stumpage values: (1) it links both revenues and costs to determinant tree characteristics, providing a clearer picture of actual financial contributions of trees to stand value. (2) it gives the value of all wood grown and not just the value of volume sold. These two improvements allow landowners and managers to actually see where value is produced in specific stands, and design treatments accordingly to capture financial opportunities that would otherwise go unnoticed.     

Forest carbon sequestration changes in response to timber harvest

Forest succession contributes to the global terrestrial carbon (C) sink, but changes in C sequestration in response to varied harvest intensities have been debated. The forests of the Central Appalachian region have been aggrading over the past 100 years following widespread clear-cutting that occurred in the early 1900s and these forests are now valuable timberlands. This study compared the history of ecosystem C storage in four watersheds that have been harvested at different frequencies and intensities since 1958. We compared NPP, NEP, and component ecosystem C fluxes (g C m⁻² year⁻¹) in response to the four different harvest histories (no harvest, clear-cutting, single tree selection cutting, and 43 cm diameter-limit cutting). Clear-cutting had short-term negative effects on NEP but harvest did not significantly impact long-term average annual C sequestration rates. Average plant C (g C m⁻²) since 1950 was about 33% lower in response to a clear-cut event than plant C in an un-harvested forest, suggesting that the C sequestration associated with clear-cutting practices would decline over time and result in lower C storage than diameter-limit cut, selective cut, or un-harvested forests. Total C stored over a 55-year period was stimulated ∼37% with diameter-limit cutting and selective cutting relative to un-harvested forests.     

Partial cutting does not maintain spider assemblages within the observed range of natural variability in Eastern Canadian black spruce forests

In boreal black-spruce forests of Eastern Canada, a cohort model of ecosystem management has been proposed whereby a combination of both partial and more intensive cutting are used to emulate old-growth stands and the re-establishment of stands following severe wildfire. As with other approaches to coarse filter conservation, partial cutting is hypothesized to maintain and potentially recreate plant and animal assemblages consistent with a range of natural variability. In this study, we used ground-dwelling spiders (Araneae) to evaluate whether partial cutting and a cohort model of ecosystem management are sufficient to preserve biodiversity found in mature and over-mature boreal black spruce stands prone to paludification. We compared the spider fauna (11,628 individuals representing 136 species) in replicated partial cuts, clear cuts and uncut control stands with a chronosequence of mature and over-mature naturally regenerated stands (94-288 years since the last fire) [25 stands in total] in the same region of the northern Clay belt in Québec (Canada). In stands that were old-growth prior to cutting, harvesting had strong repercussions on spider assemblages that were not attenuated by less intensive, partial cutting. The most obvious changes in spider assemblages were related to increased recruitment of species that were nearly absent in uncut stands. Several cosmopolitan species that were widely distributed among stands prior to harvest increased in cut stands. Spider assemblages collected following either cutting methods were not consistent with assemblages found within the chronosequence and thus fell outside the observed range of natural variability. However we did not observe a similar recruitment effect for spider species in younger stands with relatively higher levels of retention. We demonstrate that the interaction between stand age prior to cutting, the degree of paludification as well as remnant basal area are important considerations when evaluating the efficacy of partial cutting to maintain forest spider assemblages and biodiversity at large in black-spruce stands. “We also suggest that retention levels in partial cuts will have to be substantially increased to maintain spider communities within their range of natural variation in managed forested landscapes.” However partial cutting with higher levels of retention, particularly in younger stands, may be useful in coarse filter management particularly for establishing or accelerating spider assemblages towards those found in old-growth stands.     

Comparison of stand dynamics after dieback caused by pine wilt disease among pine forests with different management regimes in western Japan

In pine forests damaged by pine wilt disease, in western Japan, the effect of protection regimes of pine trees on the stand dynamics were examined in the following four stands: (1) lightly damaged stand (age 30–40 years) with no procedure in operation for protecting pine trees; (2) severely damaged stand (age 30–40 years) with no procedure in place for protecting pine trees; (3) severely damaged stand (age 50 years) with a selective cutting of infected trees; (4) severely damaged stand (age 30–40 years) with a selective cutting of infected trees. All the stands had been abandoned before the pine wilt disease damage. The understory structure of the severely damaged stand with no protection procedure was similar to that of the lightly damaged stand. Frequent invasion by tree species and acceleration in the growth of understory trees occurred after the dieback in the selective cutting stand. These results suggest that a deficiency in the canopy layer caused by the dieback resulted in low disturbance intensity in the early stages after the dieback, but the selective cutting increased the intensity by the reduction in the understory as well as the canopy layer. The intensity of the disturbance in the selective cutting stands was larger in the younger stand because it had a higher density of selectively cut pine trees. The different stand structure of pine forests occurred after the dieback because the intensity of the disturbance varied as a result of the selective cutting operation and the stand age.     

论抚育间伐对小蠹虫危害的抑制作用

抚育间伐增强云南松林分的转化功能，使死亡量减少而净生长量增多，从而增强林分系统的内能。云南松林分抵御病虫危害的功能与立地环境的优劣有关，也与本身的转化功能有关。间伐被压木乃至间伐Ⅲ级木，林分在蠹害过程中表现出强大的抵御能力。在立地条件相似的环境中，抚育间伐促进林分的转化功能，所以林分抵御蠹害的抗性也随间伐强度增大而增强     

Model-based investigation on the effects of spatial evenness,and size selection in thinning of Picea abies stands

Size and spatial distribution of trees are important for forest stand growth, but the extent to which it matters in thinning operations, in terms of wood production and stand economy, has rarely been documented. Here we investigate how the choice of spatial evenness and tree-size distribution of residual trees impacts wood production and stand economy. A spatially explicit individual-based growth model was used, in conjunction with empirical cost functions for harvesting and forwarding, to calculate net production and net present value for different thinning operations in Norway spruce stands in Northern Sweden. The in silico thinning operations were defined by three variables: (1) spatial evenness after thinning, (2) tree size preference for harvesting, and (3) basal area reduction. We found that thinning that increases spatial evenness increases net production and net present value by around 2.0%, compared to the worst case. When changing the spatial evenness in conjunction with size preference we could observe an improvement of the net production and net present value up to 8.0%. The magnitude of impact differed greatly between the stands (from 1.7% to 8.0%) and was highest in the stand with the lowest stem density.     

Spatial patterns and genetic structures within beech populations (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) of forked and non-forked individuals

Analyses of distribution patterns and genetic structures of forest stands can address distinct family structures and provide insights into the association of genetic and phenotypic variation patterns. In this study, point pattern analysis and spatial autocorrelation were used to examine the spatial and genetic structures in two naturally generated beech stands, which differ in age, trunk morphology, and stand management. Significant tree clumping was observed at distances up to 20 m in the young forest stand, whereas dispersion at distances under 10 m was observed in the old stand. The spatial analysis based on Ripley’s k function of the two different groups of trees showed that the non-forked trees match in both stands the spatial pattern of all trees while the forked were randomly distributed. Additionally, according to the bivariate analysis, forked trees in both stands were randomly distributed as related to non-forked tree positions. Finally, Moran’s I values were not very high, though significant genetic autocorrelation was identified at distances up to 20 m in the young stand, suggesting the existence of distinct family structures. However, no significant genetic structuring was observed in the old stand. Our findings suggest that spatial genetic patterns are impacted by stand age, environmental factors and human activities. The spatial distribution of forked trees was not clearly associated to family structures. Random effects and also micro-environmental variation could be additional factors explaining forking of beech individuals.     

Public compensation for windstorm damage reduces incentives for risk management investments

Governments of some European countries compensate landowners for windstorm damage to forests. We analyze the impact of such programmes on non-industrial private forest owner decisions to purchase an insurance policy for windstorm coverage and other natural events and/or invest in risk-reducing forest management activities. We develop a theoretical model to predict demand for an insurance policy or risk-reducing forest management activity, and improve upon previous efforts by varying the damage losses proportional to timber stand value. We characterize the comparative static effects on risk management investments of variations in the price of insurance, landowner risk attitude, timber stand value, and presence or absence of public compensation. Then we discuss public policy implications and analyze some alternative approaches. We conclude that providing public financial assistance to non-industrial private forest owners after damage-causing events may reduce their incentive to purchase insurance or invest in protective forest management activities.     

An Economic Evaluation of a Small-Scale Timber Harvesting Operation in Western Maryland, USA

As forests of the eastern United States become fragmented into smaller ownership parcels, there is a growing need for timber harvesting contactors who can economically harvest timber and perform silvicultural operations on small tracts. Traditional large-scale harvesting operators are ill-suited for work on small parcels, due to their high fixed costs. By contrast, small-scale operators, characterized by few workers and low capital investment, offer an opportunity to serve this landowner segment. This paper presents financial and productivity results from a small-scale timber harvesting pilot study conducted on small forested parcels in western Maryland, USA. Acceptable financial performance is possible for these operations, provided that the operator pays close attention to the important factors determining productivity and profitability, including: (1) average tree volume, (2) net delivered price, (3) time utilization, and (4) distance to the site. Although profitable harvesting of saw log quality trees on parcels less than 10 ha is possible, harvesting of small or poor-quality trees remains economically unattractive.     

Spatial harvest scheduling approach for areas involving multiple ownership

This study presents a practical harvest scheduling approach for multiple ownership planning. The approach has both spatial and non-spatial goals, namely, a spatial landscape-level goal to cluster ecologically valuable resources is considered simultaneously with timber production goals. Harvest scheduling is based on the location of the stand, on one hand, and on an economic variable depicting the cutting maturity of the stand, on the other hand. Proximity to valuable resources decreases the likelihood that the stand is cut. Therefore, harvests tend to be located outside potential resource clusters with small and isolated economically mature stands being cut first. In the application of the approach the landscape-level spatial objective was to cluster old forest stands (age⩾80) and simultaneously maintain a predefined cutting volume. A stand's economic cutting maturity was measured with value increment percentage. In the top-down application of the approach the timber harvest target was specified only for the whole planning area. In the bottom-up application it was specified separately for individual holdings, aiming at promoting the acceptability of the plan. The presented approach was clearly able to cluster old forest patches. In the case study area, the mean size of old forest patches increased from 3.4 to 5.7 ha in 30 years in the top-down plan, and to 4.6 ha in the bottom-up plan. An application of the current planning practice (referred to as the reference plan) decreased the mean patch size to 2.9 ha. The presented approach is easy to apply in forest planning practice.