Key message

Pertinence of alternative adaptation strategies to business as usual, namely reactive, active, and robust adaptation strategies, can be evaluated by incorporating the expected costs and benefits of adaptation, climate change uncertainty, and the risk attitudes of decision-makers.

Context

Forest management is used to coping with risky and uncertain projections and estimates. However, climate change adds a major challenge and necessitates adaptation in many ways.

Aims

This paper highlights the dependency of the decisions on adaptation strategies to four aspects of forest management: (i) the costs of mitigating undesirable climate change impacts on forests, (ii) the value of ecosystem goods and services to be sustained, (iii) uncertainties about future climate trajectories, and (iv) the attitude of decision-makers towards risk (risk aversion level).

Methods

We develop a framework to evaluate the pertinence of reactive, active, and robust adaptation strategies in forest management in response to climate change.

Results

Business as usual may still be retained if the value of the forest and cost of climate impacts are low. Otherwise, it is crucial to react and facilitate the resilience of affected forest resources or actively adapt in advance and improve forest resistance. Adaptation should be robust under any future climate conditions, if the value of the ecosystem, the impacts from climatic changes, and the uncertainty about climate scenarios are very high.

Conclusion

The decision framework for adaptation should take into account multiple aspects of forest management under climate change towards an active and robust strategy.

? Key message

Insurance might be an efficient tool to strengthen adaptation of forest management to climate change. A theoretical model under uncertainty is proposed to highlight the effect, on adaptation decisions, of considering adaptation efforts in forest insurance contracts. Results show that insurance is relevant to increase adaptation efforts under some realistic conditions on forest owner’s uncertainty and risk preferences, and on the observability or not of adaptation efforts.

? Context

One of the challenges of forest adaptation to climate change is to encourage private forest owners to implement adaptation strategies.

? Aims

We suggest the analysis of forest insurance contracts against natural hazards as a vector to promote the implementation of adaptation efforts by private forest owners.

? Methods

We propose a theoretical model of insurance economics under risk and under uncertainty.

? Results

Our results indicate that when climate change makes the probability of the occurrence of the natural event uncertain, then it may be relevant to include adaptation efforts in the insurance contract, leading to an increase in the adaptation efforts of risk-averse and uncertainty-averse forest owners. In addition, we show that the relevance of insurance as a vector to promote adaptation efforts is greater when the forest owner’s effort is unobservable by the insurer as compared to a situation of perfectly observable effort.

? Conclusion

Under some realistic assumptions, the forest insurance contract seems to be a relevant tool to encourage forest owners to adapt to climate change.

Key message

When predicting forest growth at a regional or national level, uncertainty arises from the sampling and the prediction model. Using a transition-matrix model, we made predictions for the whole Catalonian forest over an 11-year interval. It turned out that the sampling was the major source of uncertainty and accounted for at least 60 % of the total uncertainty.

Context

With the development of new policies to mitigate global warming and to protect biodiversity, there is a growing interest in large-scale forest growth models. Their predictions are affected by many sources of uncertainty such as the sampling error, errors in the estimates of the model parameters, and residual errors. Quantifying the total uncertainty of those predictions helps to evaluate the risk of making a wrong decision.

Aims

In this paper, we quantified the contribution of the sampling error and the model-related errors to the total uncertainty of predictions from a large-scale growth model in Catalonia.

Methods

The model was based on a transition-matrix approach and predicted tree frequencies by species group and 5-cm diameter class over an 11-year time step. Using Monte Carlo techniques, we propagated the sampling error and the model-related errors to quantify their contribution to the total uncertainty.

Results

The sampling variance accounted for at least 60 % of the total variance in smaller diameter classes, with this percentage increasing up to 90 % in larger diameter classes.

Conclusion

Among the few possible options to reduce sampling uncertainty, we suggest improving the variance–covariance estimator of the predictions in order to better account for the multivariate framework and the changing plot size.

Key message

Natural disturbance can disrupt the anticipated delivery of forest-related ecosystem goods and services. Model predictions of natural disturbances have substantial uncertainties arising from the choices of input data and spatial scale used in the model building process, and the uncertainty of future climate conditions which are a major driver of disturbances. Quantifying the multiple contributions to uncertainty will aid decision making and guide future research needs.

Context

Forest management planning has been able, in the past, to rely on substantial empirical evidence regarding tree growth, succession, frequency and impacts of natural disturbances to estimate the future delivery of goods and services. Uncertainty has not been thought large enough to warrant consideration. Our rapidly changing climate is casting that empirical knowledge in doubt.

Aims

This paper describes how models of future spruce budworm outbreaks are plagued by uncertainty contributed by (among others): selection of data used in the model building process; model error; and uncertainty of the future climate and forest that will drive the future insect outbreak. The contribution of each to the total uncertainty will be quantified.

Methods

Outbreak models are built by the multivariate technique of reduced rank regression using different datasets. Each model and an estimate of its error are then used to predict future outbreaks under different future conditions of climate and forest composition. Variation in predictions is calculated, and the variance is apportioned among the model components that contributed to the epistemic uncertainty in predictions.

Results

Projections of future outbreaks are highly uncertain under the range of input data and future conditions examined. Uncertainty is not uniformly distributed spatially; the average 75% confidence interval for outbreak duration is 10 years. Estimates of forest inventory for model building and choice of climate scenario for projections of future climate had the greatest contributions to predictions of outbreak duration and severity.

Conclusion

Predictions of future spruce budworm outbreaks are highly uncertain. More precise outbreak data with which to build a new outbreak model will have the biggest impact on reducing uncertainty. However, an uncertain future climate will continue to produce uncertainty in outbreak projections. Forest management strategies must, therefore, include alternatives that present a reasonable likelihood of achieving acceptable outcomes over a wide range of future conditions.

Key message

Non-stochastic portfolio optimization of forest stands provides a good alternative to stochastic mean-variance optimization when available statistical data is incomplete. The suggested approach has a theoretical background in the areas of robust optimization, continuous multicriteria decision-making, and fuzzy theory. Resulting robust portfolios only show slight economic losses compared to the efficient frontier of a stochastic optimization.

Context

Economic optimization addressing diversification in mixed uneven-aged forest stands is a useful tool for forest planners.

Aims

The study aims to compare two approaches for optimizing rotation age cohort portfolios under risk. Rotation age cohorts emerge from age-based regeneration-harvesting operations simulated for two tree species: Picea abies and Fagus sylvatica.

Methods

The first optimization approach is a stochastic mean-variance approach. The second is a non-stochastic optimization approach, which has rarely been applied to optimize tree species composition and the distribution of harvested timber over many periods. It aims at relatively good solutions, even if the deviation from the initially assumed return is very high. The objective function for both approaches is sensitive to the selection of various harvesting periods for different parts of the stand. For the stochastic approach, the objective function maximizes the annuitized net present value (economic return) for specific levels of risk by allocating area proportions to harvesting periods and tree species. In the non-stochastic approach, the allocation of area proportions instead minimizes the maximum deviation from the greatest possible economic return among many uncertainty scenarios (non-stochastic approach).

Results

Portfolios from both approaches were diverse in rotation age cohorts. The non-stochastic portfolios were more diverse when compared with portfolios from the efficient frontier, which showed the same standard deviation. However, P. abies clearly dominated the non-stochastic portfolios, while stochastic portfolios also integrated beech to a greater extent, but only in very low risk portfolios. The economic losses of the non-stochastic portfolios compared to the efficient frontier of the mean-variance approach lay between 1 and 3% only for different levels of accepted risk.

Conclusion

The non-stochastic portfolio optimization over a large uncertainty space is so far uncommon in forest science, yet provides a viable alternative to stochastic optimization, particularly when available data is scarce. However, further research should consider ecological effects, such as increased resistance against hazards of conifers in mixed stands.

Key message

Natural regeneration patterns of conifer species were studied. Seedling regeneration follows patterns responding to stand structure and site condition factors along shade and drought tolerance gradients. Our findings can assist in adaptive forest management for maintaining sustainable regeneration and plant biodiversity.

Context

Seedling regeneration can vary with stand factors of overstory trees and understory non-tree vegetation and site conditions.

Aims

Natural seedling regeneration patterns of coniferous species were investigated using Forest Inventory and Analysis (FIA) data of 10 common species across the Inland Northwest, USA.

Methods

Zero-inflated negative binomial models were developed to understand the responses of natural regeneration to stand factors and site conditions.

Results

Seedling occurrence varies along shade and drought tolerance gradients responding to stand structure and site conditions. Two moderate shade-tolerant species of different drought tolerance contributed as a transition. Strong response patterns were revealed for seedling density, in which seedling density was improved with the presence of conspecific trees while limited by competition, especially from the understory vegetation layer.

Conclusion

Overstory structure and understory vegetation could improve or hinder natural regeneration of coniferous tree species given different shade tolerance and site conditions. Our findings can be effectively implemented in adaptive forest management for maintaining sustainable regeneration of specific conifers in broad temperate mixed forests.

Key message

We generate flexible management rules for black pine stands, adaptable to alternative stand management situations and entailing thinnings, final-felling, and salvage cuts, based on the results on 270 stand level optimizations.

Context

Forest management instructions often rely on the anticipated prediction of the stand development, which poses a challenge on variable economic and environmental conditions. Instead, an alternative approach to better adapt forest management decisions to changing conditions is defining flexible rules based on thresholds that trigger management operations.

Aims

This article develops rules for the adaptive management of P. nigra stands in Catalonia (Spain) addressing the risk of fire and post-fire forest management.

Methods

The stochastic version of the simulation-optimization system RODAL was used to optimize the management of forest stands in three sites under different fire probability levels. A total of 270 optimizations were done varying site fertility, fire probability, and economic factors. The results of the optimizations were used as the basis of flexible forest management rules for adaptive stand management.

Results

The developed management rules defined the basal area limit for thinning, the thinning intensity, the mean tree diameter at which regeneration cuttings should start, and the basal area below which a salvage cutting should be done. Fire risk was not a significant predictor of the models for thinning and final cutting rules.

Conclusion

The presented rules provide a flexible tool for forest management during the stand development and under changing conditions when the management objective is to maximize economic profitability of timber production.

Key message

We present a data-driven technique to visualize forest landscapes and simulate their future development according to alternative management scenarios. Gentle harvesting intensities were preferred for maintaining scenic values in a test of eliciting public’s preferences based on the simulated landscapes.

Context

Visualizations of future forest landscapes according to alternative management scenarios are useful for eliciting stakeholders’ preferences on the alternatives. However, conventional computer visualizations require laborious tree-wise measurements or simulators to generate these observations.

Aims

We describe and evaluate an alternative approach, in which the visualization is based on reconstructing forest canopy from sparse density, leaf-off airborne laser scanning data.

Methods

Computational geometry was employed to generate filtrations, i.e., ordered sets of simplices belonging to the three-dimensional triangulations of the point data. An appropriate degree of filtering was determined by analyzing the topological persistence of the filtrations. The topology was further utilized to simulate changes to canopy biomass, resembling harvests with varying retention levels. Relative priorities of recreational and scenic values of the harvests were estimated based on pairwise comparisons and analytic hierarchy process (AHP).

Results

The canopy elements were co-located with the tree stems measured in the field, and the visualizations derived from the entire landscape showed reasonably realistic, despite a low numerical correspondence with plot-level forest attributes. The potential and limitations to improve the proposed parameterization are discussed.

Conclusion

Although the criteria to evaluate the landscape visualization and simulation models were not conclusive, the results suggest that forest scenes may be feasibly reconstructed based on data already covering broad areas and readily available for practical applications.

Key message

Norway spruce seed has been traded extensively for at least three centuries throughout the natural distribution range in Europe and beyond. However, our knowledge about these transfers is limited. Historic data are essential tools to trace back human-mediated gene flow and for interpretation of recent genetic studies.

Context

Human-mediated gene flow can potentially have a major impact on the genetic composition of forest tree populations, yet our knowledge about seed sources used within the current species’ range is still limited. Norway spruce is one of the most important coniferous species in European forestry, and data drawing conclusions about the genetic composition of current populations are vital with regard to gene conservation and sustainable forest management. Because molecular data are not available on a more detailed scale, historic records provide crucial information about translocations.

Aims

Our aim is to provide the first pan-European review on Norway spruce translocations from the seventeenth until the twentieth century.

Methods

We analysed historic and recent literature compiling information on the cultivation and transfer of Norway spruce reproductive material. Historic records are compared with recent molecular studies.

Results

Seed exchanges have profoundly altered the native genetic population structure of Norway spruce. Especially, Central European seeds have been used throughout and beyond the natural distribution area. Figures illustrating the historic plantings in Europe are provided.

Conclusion

Recent molecular data reveal persisting effects of past translocations. Historical records can be extremely useful for providing information about autochthony and thus guide gene conservation strategies and explain the performance of extant populations.

Key message

Soil texture and temperature-related variables were the variables that most contributed to Nothofagus antarctica forest height in southern Patagonia. This information may be useful for improving forest management, for instance related to the establishment of silvopastoral systems or selection of suitable sites for forest reforestation in southern Patagonia.

Context

Changes in forest productivity result from a combination of climate, topography, and soil properties.

Aims

The relative importance of edaphic and climatic variables as drivers of productivity in Nothofagus antarctica forests of southern Patagonia, Argentina, was evaluated.

Methods

A total of 48 mature stands of N. antarctica were selected. For each study site, we measured the height of three mature dominant trees, as an indicator of productivity. Seven soil, five spatial, and 19 climatic features were determined and related to forest productivity. Through partial least squares regression analyses, we obtained a model that was an effective predictor of height of mature dominant trees in the regional data set presented here.

Results

The four variables that most contributed to the predictive power of the model were altitude, temperature annual range, soil texture, and temperature seasonality.

Conclusion

The information gathered in this study suggested that the incidence of the soil and temperature-related variables on the height of dominant trees, at the regionally evaluated scale, was higher than the effect of water-related variables.

Key message

High-elevation forests in the Alps protect infrastructure and human lives against natural hazards such as rockfall, flooding, and avalanches. Routinely performed silvicultural interventions maintain the required stand structure but are not commercially viable in remote forests due to high operational costs. Financial subsidies for the management of high-elevation protection forests are an efficient strategy to ensure sustainable forest cover.

Context

Presently, many high-elevation forests in the Alps are managed in order to ensure the provision of ecosystem services with emphasis on the minimization of natural hazards.

Aims

We studied the possible economic performance of a high-elevation protection forest from an owner’s perspective. We investigated whether the increase in productivity due to climate change and a favorable market for the dominating cembran pine (Pinus cembra L.) are sufficient for profitable timber production in protection forests.

Methods

We simulated the standing timber stock and the soil carbon pool for a 100-year period with climate-sensitive models and compared harvesting costs with expected revenues. Our scenarios included different climates, intensities of timber extractions, parameters of the timber market, and the availability of government subsidies.

Results

Overall, the productivity of forests increases by approximately 15% until the end of the century. In a zero-management scenario, the forest accumulates carbon both in the aboveground biomass and the soil. In the case of an extensive management with moderate timber extractions every 50 years, the carbon stocks decline both in biomass and soil. A more intensive management scenario with extractions every 30 years leads to substantial losses of the soil and biomass carbon pools. In addition, the stand structure changes and the protective function of the forest is not sustainably ensured. Timber production can be economically successful only with high selling prices of cembran pine timber and the availability of governmental subsidies for forest management. The admixed European larch (Larix decidua Mill.) contributes only marginally to the economic success. The main challenge are harvesting costs. The costs of timber extraction by a long-distance cableway logging system exceed the value of the harvested timber.

Conclusion

The intensification of forest management cannot be recommended from the perspective of timber production, sustainable forest management, and protection against natural hazards. Our simulation experiment shows that the extraction of timber at decadal intervals depletes the carbon stock that is insufficiently replenished from aboveground and belowground litterfall. Leaving the forest unmanaged does not impose a particular threat to stand stability and is under the encountered situation, a justified strategy.

Key message

Detailed measures of growth pattern and structural heterogeneity applied in this study helped to quantify the immediate effects of various thinning regimes on forest structure and the resulting alterations in tree size as well as observed longer term stand dynamics.

Context

Forest management, stand structure, and tree growth are highly inter-correlated. Prior analyses, however, have resulted in mixed outcomes with limited success in revealing ecological mechanisms.

Aims

The study aimed at evaluating the relationship between forest structure and stand dynamics by applying several sophisticated measures of growth pattern and structural heterogeneity.

Methods

Data from a controlled and fully stem-mapped commercial thinning experiment with seven contrasting treatments including a non-thinned control at six locations across the Acadian Forest of Maine, USA, was used. Stand-level attributes examined included tree size and growth heterogeneity, spatial tree distribution, and growth dominance.

Results

Thinning generally reduced stand structural heterogeneity compared to the non-thinned control. In addition, the spatial arrangement of trees changed from fully random (non-thinned control) to a more clustered (removal of dominant and co-dominant individuals) or regular distribution (removal of intermediate and suppressed individuals). Overall, stand growth exhibited increasing (non-thinned control, removal of intermediate and suppressed individuals) or decreasing growth dominance of large trees (removal of co-dominant competitors). Forwarder trails increased basal area growth of individual trees up to a distance from the trail of approximately 5 m.

Conclusion

Findings of this study validate an earlier insight according to which interactions between management practices, forest structure, and tree growth form a permanent feedback loop.

Key message

The diversity of forest management systems and the contrasted competition level treatments applied make the experimental networks of the GIS Coop, a nationwide testing program in the field of emerging forestry topics within the framework of the ongoing global changes.

Context

To understand the dynamics of forest management systems and build adapted growth models for new forestry practices, long-term experiment networks remain more crucial than ever.

Aims

Two principles are at the basis of the experimental design of the networks of the Scientific Interest Group Cooperative for data on forest tree and stand growth (GIS Coop): contrasted and extreme silvicultural treatments in diverse pedoclimatic contexts.

Methods

Various forest management systems are under study: regular and even-aged stands of Douglas fir, sessile and pedunculate oaks, Maritime and Laricio pines, mixed stands of sessile oak, European silver fir, and Douglas fir combined with other species. Highly contrasted stand density regimes, from open growth to self-thinning, are formalized quantitatively.

Results

One hundred and eighty-five sites representing a total of 1206 plots have been set up in the last 20 years, where trees are measured regularly (every 3 to 10 years). The major outputs of these networks for research and management are the calibration/validation of growth and yield models and the drawing up of forest management guides.

Conclusion

The GIS Coop adapts its networks so that they can contribute to develop growth models that explicitly integrate pedoclimatic factors and thus also contribute to research on the sustainability of ecosystems under environmental and socio-economic changes.

Key message

Forty years after clear-cutting mixed old-growth forest (broadleaf/Korean pine) in the Changbai Mountain area (Northeast China), a mixed forest with natural broadleaf regeneration and larch plantation displayed larger microbial biomass and activity in the soil than either a naturally regenerated birch forest or a monospecific spruce plantation.

Context

Clear-cutting with limited restoration effort was until the end of the twentieth century the norm for managing primary forests in Northeast China. Forest restoration plays an important role in the recovery of soil quality after clear-cutting, but the effects of different regeneration procedures on forest soil quality remain poorly known in Northeast China.

Aims

We assessed the effects of three regeneration procedures, i.e., (i) naturally regenerated birch forest, (ii) spruce plantation, and (iii) naturally regenerated broadleaf species interspersed with planted larch on soil quality and microbial activity in the Changbai Mountain area. An old-growth mixed broadleaf/Korean pine forest was used as a reference.

Methods

Physical and chemical properties and microbial biomass were recorded in the soil. Basal respiration and carbon mineralization were measured with a closed-jar alkali-absorption method.

Results

Microbial biomass was smaller in the birch forest and spruce plantation than in the old-growth and the mixed broadleaf/larch forests. Moreover, microbial biomass, microbial quotient, and potentially mineralizable carbon were larger in the mixed broadleaf/larch than in the birch forest, while no difference was found between spruce plantation and birch forest for microbial biomass and microbial quotient. Basal respiration and metabolic quotient were larger in the birch forest as compared to the three other forest types, indicating a larger energy need for maintenance of the microbial community and lower microbial activity in the naturally regenerated birch forest.

Conclusion

Mixed broadleaf/larch forest displayed a larger microbial biomass and higher substrate use efficiency of the soil microbial community than either naturally regenerated birch forest or spruce plantation. The combined natural and artificial regeneration procedure (mixed broadleaf-larch forest) seems better suited to restore soil quality after clear-cutting in the Changbai Mountain.

Key message

A new system of additive tree biomass equations was developed for juvenile white birch plantations based on tree diameter at breast height (DBH) and tree height (HT). Compared with previous equations developed for natural white birch forests, the new system included one more biomass component and provided more accurate predictions.

Context

Accurate estimates of tree component and total biomass are necessary for evaluating alternative forest management strategies for biomass feedstock, carbon sequestration, and products. Previous biomass equations developed for white birch trees in natural stands provided substantially biased predictions for white birch plantations.

Aims

A new system of additive tree biomass equations was developed for juvenile white birch plantations in the northeastern China.

Methods

With destructive biomass sampling data from 501 trees sampled from white birch provenance and family trails at ages 7, 9, 10, and 13 in three provinces, a system of nonlinear additive tree biomass equations based on DBH and tree height was developed using the nonlinear seemingly unrelated regressions (NSUR) approach.

Results

Compared with previously published equations developed for natural white birch forests, the new system provided more accurate predictions of white birch tree component and aboveground and total biomass, especially of branch, foliage, and root biomass.

Conclusion

The new system extended the applicability of biomass equations to white birch plantations in the northeastern China.

Key message

This study assessed the effect of ecological variables on tree allometry and provides more accurate aboveground biomass (AGB) models through the involvement of large samples representing major islands, biogeographical zones and various succession and degradation levels of natural lowland forests in the Indo-Malay region. The only additional variable that significantly and largely contributed to explaining AGB variation is grouping based on wood-density classes.

Context

There is a need for an AGB equation at tree level for the lowland tropical forests of the Indo-Malay region. In this respect, the influence of geographical, climatic and ecological gradients needs to be assessed.

Aims

The overall aim of this research is to provide a regional-scale analysis of allometric models for tree AGB of lowland tropical forests in the Indo-Malay region.

Methods

A dataset of 1300 harvested trees (5 cm ≤ trunk diameter ≤ 172 cm) was collected from a wide range of succession and degradation levels of natural lowland forests through direct measurement and an intensive literature search of principally grey publications. We performed ANCOVA to assess possible irregular datasets from the 43 study sites. After ANCOVA, a 1201-tree dataset was selected for the development of allometric equations. We tested whether the variables related to climate, geographical region and species grouping affected tree allometry in the lowland forest of the Indo-Malay region.

Results

Climatic and major taxon-based variables were not significant in explaining AGB variations. Biogeographical zone was a significant variable explaining AGB variation, but it made only a minor contribution on the accuracy of AGB models. The biogeographical effect on AGB variation is more indirect than its effect on species and stand characteristics. In contrast, the integration of wood-density classes improved the models significantly.

Conclusion

Our AGB models outperformed existing local models and will be useful for improving the accuracy on the estimation of greenhouse gas emissions from deforestation and forest degradation in tropical forests. However, more samples of large trees are required to improve our understanding of biomass distribution across various forest types and along geographical and elevation gradients.

Key message

Wood-anatomical traits determining the hydraulic architecture of Larix sibirica in the drought-limited Mongolian forest steppe at the southern fringe of the boreal forest respond to summer drought, but only weakly to variations in microclimate that depend on forest stand size.

Context

Siberian larch (L. sibirica Ledeb.) is limited by summer drought and shows increasing mortality rates in the Mongolian forest steppe. The climate sensitivity of stemwood formation increases with decreasing forest stand size. The trees’ hydraulic architecture is crucial for drought resistance and thus the capability to deal with climate warming.

Aims

We studied whether hydraulic traits were influenced by temporal or forest size-dependent variations in water availability and were related to tree-ring width.

Methods

Hydraulic traits (tracheid diameter, tracheid density, potential sapwood area-specific hydraulic conductivity) of earlywood were studied in stemwood series of 30 years (1985–2014) and were related to climate data. Tree-ring width was measured for the same period. Trees were selected in stands of four different size classes with increasing drought exposure with decreasing stand size.

Results

Tracheid diameters and hydraulic conductivity decreased with decreasing late summer precipitation of the previous year and were positively correlated with tree-ring width. Forest stand size had only weak effects on hydraulic traits, despite known effects on stemwood increment.

Conclusion

Decreasing tracheid diameters and thus hydraulic conductivity are a drought acclimation of L. sibirica in the Mongolian forest steppe. These acclimations occur as a response to drought periods but are little site-dependent with respect to stand size.

Key message

Liming, an ameliorative method for acidified forest soils, affected the relative abundance of prey of ground-hunting spiders and consequently reduced densities of functionally similar species of these predators.

Context

Liming, an ameliorative method for acidified forest soils, may modify the structure of an arthropod community by altering the soil characteristics and/or the availability of food resources.

Aims

We investigated the effect of liming on the community structure of ground-hunting spiders in a birch forest.

Methods

We established six experimental birch stand plots. Each stand was exposed to one of three experimental treatments: control, 1.5 t/ha, or 3 t/ha of dolomitic limestone. We collected spiders using pitfall traps during 5 years. We characterized the community in terms of activity density, species richness, community-weighted mean body size, and functional diversity and evenness in body size. We further investigated the potential links through which the liming might affect spiders, namely soil characteristics, effect of liming on birch, and densities of potential prey.

Results

The commonly used dosage of 3 t/ha reduced densities of functionally similar species which led to the reduced functional evenness in body size and increased functional divergence in body size. Liming increased soil pH only slightly but decreased the densities of spiders’ preferred prey.

Conclusion

The liming affected the community of ground-hunting spiders, at least partially, through reduced densities of their preferred prey.

Key message

Static site indices determined from stands’ top height are derived from different forest inventory sources with height and age information and thus enable comparisons and modeling of a species’ productivity encompassing large environmental gradients.

Context

Estimating forest site productivity under changing climate requires models that cover a wide range of site conditions. To exploit different inventory sources, we need harmonized measures and procedures for the productive potential. Static site indices (SI) appear to be a good choice.

Aims

We propose a method to derive static site indices for different inventory designs and apply it to six tree species of the German and French National Forest Inventory (NFI). For Norway spruce and European beech, the climate dependency of SI is modeled in order to estimate trends in productivity due to climate change.

Methods

Height and age measures are determined from the top diameters of a species at a given site. The SI is determined for a reference age of 100 years.

Results

The top height proves as a stable height measure that can be derived harmoniously from German and French NFI. The boundaries of the age-height frame are well described by the Chapman-Richards function. For spruce and beech, generalized additive models of the SI against simple climate variables lead to stable and plausible model behavior.

Conclusion

The introduced methodology permits a harmonized quantification of forest site productivity by static site indices. Predicting productivity in dependence on climate illustrates the benefits of combined datasets.