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Abstract: The forest growth model 4C was used to investigate how conversion management of a Scots pine (Pinus sylvestris L.) stand towards a mixed oak–birch stand would affect stand structural development – and hence biodiversity and productivity – in the long term. For this purpose the 4C model was parameterised for natural regeneration of light demanding species and extended for management of multi-layered stands. A series of structural indicators was selected to describe key factors of forest biodiversity at the stand scale. Two consecutive aspects of Scots pine conversion were tested: (1) the choice of conversion strategy between thinning and gap creation and (2) the choice of conversion regime in terms of cutting cycle, thinning type and pine tree retention. Three simulated conversion strategies aim at the gradual removal of the pine canopy but differ in the spatial organisation of pine cuttings and hence result in different light conditions for regeneration. Only the directed gap creation strategy was able to maintain and increase birch admixture to the stand and to approach natural stand structural development. Simulation of 12 conversion regimes for the directed gap creation strategy indicated that thinning type (from above or from below), pine tree retention at final felling (50% of the standing volume or none) and cutting cycle (6, 9 or 12 years) all significantly influence stand structural development. These effects were clearest for oak development. Birch occurred in a few mixed clusters, but tended to disappear when longer cutting cycles were used. Based on a multi-criteria analysis we conclude that the optimal conversion regime – in which both stand productivity and biodiversity objectives can be combined – implies thinning from above, pine tree retention, and cutting cycles of 6 years. The conceptual validity of the model as well as the applicability of the results are discussed. [Copyright &y& Elsevier]

Volume growth and survival (VGS) graphs, which show volume growth rate and risk of mortality for individual trees (or tree size classes), have been proposed as a tool for assessing the validity of models that describe the development over time of tree size distributions within forest stands. We examined the utility of the VGS method in evaluating four process-based models. The performance of the models FORSKA, 4C, MORG, and PipeQual is analyzed against long-term data from a Scots pine stand in Evo, Finland, and the models FORSKA and 4C are also assessed with respect to data from a beech stand in Fabrikschleichach, Germany. Comparison of the measurement-based VGS graphs with those produced from the model-based data shows that although the models yield similar stand-level predictions, they can differ widely in their projections of individual tree growth and size distributions. Examination of the discrepancies between models and data in the context of the VGS graphs reveals several areas in which the models could be improved. We conclude that the method is useful in model evaluation, especially if used in combination with indicators of stand structure, such as the height/diameter ratio. [ABSTRACT FROM PUBLISHER]

We investigated the relationships within forest stands between tree size and (a) stem volume growth rate and (b) risk of mortality for individual trees. Values of both x and y variables were plotted relative to the largest value in the stand. We refer to the resultant presentations as relative volume growth and relative survival graphs (VGSs). A pair of VGSs can be produced readily from an individual-tree growth model. It can also be constructed from consecutive sets of field measurements. Comparison of VGSs derived from model and measurement data provides a test of the validity of the components of the growth model.We have analyzed VGSs based on measurement data for Scots pine (Pinus sylvestris L.) in central Finland and for beech (Fagus sylvatica L.) in southern Germany. The graphs based on measurement data varied as a consequence of differences in competition, stand management, and tree species.We analyzed the relationship between VGSs and stand dynamics using a simple growth model. We found that different features of the VGSs imply characteristic tree size distributions in subsequent years. Thus, we conclude that if the VGSs generated by a model do not correspond to those based on field measurements, the model cannot be relied on to reproduce the development of tree-size distribution correctly. Relative growth and survival graphs thus provide a tool for evaluating complicated growth models. [ABSTRACT FROM PUBLISHER]

The knowledge about potential climate change impacts on forests is continuously expanding and some changes in growth, drought induced mortality and species distribution have been observed. However despite a significant body of research, a knowledge and communication gap exists between scientists and non-scientists as to how climate change impact scenarios can be interpreted and what they imply for European forests. It is still challenging to advise forest decision makers on how best to plan for climate change as many uncertainties and unknowns remain and it is difficult to communicate these to practitioners and other decision makers while retaining emphasis on the importance of planning for adaptation. In this paper, recent developments in climate change observations and projections, observed and projected impacts on European forests and the associated uncertainties are reviewed and synthesised with a view to understanding the implications for forest management. Current impact assessments with simulation models contain several simplifications, which explain the discrepancy between results of many simulation studies and the rapidly increasing body of evidence about already observed changes in forest productivity and species distribution. In simulation models uncertainties tend to cascade onto one another; from estimating what future societies will be like and general circulation models (GCMs) at the global level, down to forest models and forest management at the local level. Individual climate change impact studies should not be uncritically used for decision-making without reflection on possible shortcomings in system understanding, model accuracy and other assumptions made. It is important for decision makers in forest management to realise that they have to take long-lasting management decisions while uncertainty about climate change impacts are still large. We discuss how to communicate about uncertainty – which is imperative for decision making – without diluting the overall message. Considering the range of possible trends and uncertainties in adaptive forest management requires expert knowledge and enhanced efforts for providing science-based decision support. [ABSTRACT FROM AUTHOR]

• We propose a framework for the optimal supply of forest biodiversity. • We define optimal wood and biodiversity streams to maximize social welfare. • Climate change has important implications for biodiversity-oriented policy mechanisms. • Current management undersupplies biodiversity and is inefficient under climate change. Forest biodiversity underpins social welfare by preserving ecosystem multifunctionality and the provision of ecosystem goods and services. Still, the social value of biodiversity is not adequately incorporated into forest management and decision support models. This study proposes a novel approach for defining socially optimal biodiversity levels, wood supply and taxation schemes under climate change. We developed a partial equilibrium model to maximize consumers' and producers' surplus until the end of the century, including climate change impacts as productivity shocks in a coupled ecological-economic framework. In our model, we consider a first-best and a second-best taxation scheme to internalize the value of forest biodiversity into forest planning. The framework developed here was applied to a temperate forest landscape in southwestern Germany, where biodiversity has a high social value. Our results indicate an increasing consumption of wood and supply of biodiversity (up to 38.4 %) until the end of the century. Moreover, climate change may affect forest productivity, optimal harvesting rates and taxation schemes. Crucially, current management is unable to capture the adequate social value of biodiversity and is inefficient under climate change. Policy mechanisms are therefore required to correct biodiversity provision in temperate forest landscapes. [ABSTRACT FROM AUTHOR]