Tree diversity effects on the temporal stability of forest productivity

• Applicant: Dr. Florian Schnabel
• Subject Area: Forestry
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576058672

The rising frequency, intensity, and duration of climate extremes threaten tree growth and survival worldwide. This may critically limit ecosystem functions and services provided by forests. Stability, the capacity of a forest to maintain functioning over time and under different environmental stressors, is therefore a focus of forest adaptation during the 21st century. One key management strategy to increase stability may be to increase tree species richness in planted or semi-natural forests. However, we lack robust and context-specific knowledge on diversity-stability relationships across forest ecosystems. The overall objective of the proposed project is to determine whether tree diversity (species richness and functional diversity) stabilises forest ecosystem functioning in the face of climate extremes. I will use the experimental planted forests of TreeDivNet, the largest network of diversity experiments worldwide, to address this question across a broad range of climates and biomes. My aim is to identify and disentangle the drivers of forest stability. The analysis will be based on repeated stand inventories from 25 experiments. This data will allow the project team and me to calculate annually-resolved proxies of tree productivity at the tree, species, and community level. Subsequently, we will subject this data to a hypothesis-driven modelling framework. We will test for direct and indirect tree diversity effects on the temporal stability of productivity - a commonly used proxy for the stability of forest ecosystem functioning - across levels of biotic organization and spatio-temporal scales. In WP1, we will analyse diversity-stability relationships across levels of biotic organization to test our hypothesis that tree species richness increases the stability of productivity at the community but not at the species or individual tree level. In WP2, we will analyse the trait-based mechanism behind diversity-stability relationships. In WP3, we will for the first time examine if diversity-stability relationships in forests strengthen over time based on measurements in the oldest tropical TreeDivNet experiment. Finally, in WP4, we will analyze changes in diversity-stability relationships across the large-scale ecological gradients covered by TreeDivNet experiments and under experimental manipulations of water and nutrient availability in a subset of experiments. I expect that the proposed project, which is based on data from well-designed experimental tree plantations, will lead to a profound understanding of the diversity-driven mechanisms that lend stability to forests. The proposed analysis, which focuses on the stability of forest ecosystem functioning, is particularly relevant in light of accelerating climate change.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Jürgen Bauhus; Professor Dr. Michael Scherer-Lorenzen