Model-based analysis of management alternatives at stand and regional level in Brandenburg (Germany)

Abstract

The model-based analysis of the effects of management options at stand and regional levels on forest functions such as carbon storage and groundwater recharge provides a basis for optimisation of forest planning under global change. The physiologically based model 4C (‘FORESEE’—FORESt Ecosystems in a changing Environment) can be used to evaluate a broad variety of silvicultural treatments for mono- and mixed-species forest stands. In this study, we present the testing and evaluation of the 4C management submodel, using data from long-term experimental plots in selected stands in the Federal State of Brandenburg, Germany. Comparison of experimental data with model simulations, by means of diameter distributions, demonstrated that the applied thinning operations preserved the diameter distribution of the stands. 4C realistically described the effects of management options on stand dynamics as proved by long-term simulations. Furthermore, the investigation of the effects of management options, thinning intensity, and rotation length on carbon storage in biomass and soil, yield, and groundwater recharge showed the applicability of the model 4C for the evaluation of forest functions in managed forests. We present the analysis of management effects on forest functions at a regional scale, based on a grid of forest monitoring sites (“Ökologische Waldzustandskontrolle”—ÖWK) in Brandenburg, which is mainly dominated by Scots pine ( Pinus sylvestris L.). The model was applied at the sites with three management options under current climate and a climate change scenario (i.e., temperature increase of 1.4 °K by 2055). The results of 50-year simulation runs were analysed for forest growth units with respect to total carbon storage ( C sum) and groundwater recharge. More intensive management decreased the C sum after 50 years and slightly increased groundwater recharge. Climate change led to a reduction of groundwater recharge by about 40%, averaged over all sites. C sum was increased at some sites because of the extension of the growing season in spite of slight decreases in precipitation, but at several other sites, C sum decreased due to increased dryness. The question arises whether these negative effects of climate change can be minimised by adaptive management operations. In this study, we concluded that the potentials of adaptive management based on changes in rotation length and thinning is very limited in this region, which is characterised by poor sites and dry climatic conditions. We concluded that it is necessary to include forest transformation strategies in management impact analyses for forest planning under global change.