Predicting structural changes and growth in pure and mixed stands of European beech, Norway spruce, and Douglas-fir
PhD studentJan Schick
Research OutlineOur overarching goal is to investigate the underlying fourth hypothesis of the RTG, i.e. the structural diversity and productivity of mixtures is higher than that of pure European beech stands.
In this subproject we project future forest development on the 8 research plot quintets to analyze how functional traits and ecosystem functioning will be influenced by internal factors like tree age, inter- and intraspecific competition and external factors like changing climatic conditions and nitrogen deposition. Furthermore, we explore how to sustain or enhance ecosystem functioning by means of forest management.
In order to provide reliable estimates of future forest development we develop statistical models which are capable of estimating above-ground tree growth based on environmental variables and consider the characteristics of pure and mixed stands. In particular, we will focus on height and diameter growth, as well as the development of the crown structure. The latter builds upon the results achieved in SP 9-1, whose models will be refined using, among others, the laser scan data of SP 8-2. Tree growth shall be assessed by advancing already existing site index models, available at the Northwest German Forest Research Institute (NW-FVA). The improvements will come from an updated database with new data points as well as new predictors or new modifications of the old ones, respectively, but also by exploring different height growth functions which may offer more flexibility. For diameter growth a new set of models has to be derived.
As both height and diameter growth models will include climatic variables, the effects of climate change can be incorporated in the predictions through the use of scenarios, thus depicting the uncertainty of future development. The resulting values for height and diameter growth will be used for scenario simulations of mixed stands, whose economic aspects will be analyzed by SP 11-2. Said values can also be the basis of silvicultural recommendations.