European ecosystems on a changing planet : Integrating climate change and land-use intensity data

Dynamic global vegetation models are mathematical models that provide a bottom-up description of plant communities. They explicitly model physiological and population-level processes such as growth, photosynthesis, carbon allocation, regeneration and mortality.However, there are a number of challenges to meet in the context of mechanistic vegetation models which can be extrapolated to new environmental conditions.This thesis aims to advance our knowledge of the vegetation model LPJ-GUESS by analyzing both sensitivity and uncertainty towards input datasets such as climate and land-use intensity data and their derivation. It further aims to improve the model performance by including former neglected processes like land-use intensity and daily management for grasslands. Beyond these rather technical aims, this thesis also investigates possible trade-offs between society relevant ecosystem functions like crop yield and carbon storage via integrating climate data and up-to-date land-use intensity information.The results show that simulations with LPJ-GUESS for Europe were most sensitive to the spatial resolution of the input climate data followed by the choice of the climate model. When driven with projections of climate and land-use intensity in form of nitrogen fertilizer, simulations of maize yield and nitrogen leaching were most sensitive to nitrogen applications followed by climate while wheat yield was most sensitive to changes in carbon dioxide followed by nitrogen applications.While future yields of wheat and maize increased in Europe under representative concentration pathways 4.5 and 8.5, these increases were accompanied with increases of nitrogen leaching in many regions. However, leaching decreased in about 53% of the regions under pathway 4.5 while it increased in 76% of the regions under pathway 8.5.It is also shown in this thesis that grassland productivity cannot be adequately captured without including land-use intensity data in form of nitrogen fertilizer. Incorporating daily grassland management and fertilizer applications into LPJ-GUESS improved the model significantly. Finally, afforestation had overall positive effects both on plant species richness and carbon storage in Saxony, Germany. However, a number of locations were identified for which afforestation would lead to a decrease in plant species richness