Analysis of diversity effects on above-ground productivity in forests: advancing the mechanistic understanding of spatio-temporal dynamics in canopy space filling using mobile laser scanning

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Woody biomass storage and productivity are key ecosystem functions in forests, and it has often been shown that they are positively influenced by tree diversity. Recent work suggests an improved canopy space filling in diverse forests, achieved by means of two different mechanisms: interspecific architectural complementarity of crowns and intraspecific crown plasticity. However, whether or not this results in greater levels of ecosystem functioning, and how it changes through space and time remains unclear. Main aim of the research project is to analyse the underlying mechanisms of diversity effects on above-ground wood volume and productivity in natural forests using data from mobile laser scanning (MLS). MLS is a non-destructive sequential measurement technique that delivers high-resolution three-dimensional (3D) point clouds of the observed objects. Although only few studies of MLS recording for vegetation sampling exist, they demonstrate a strong potential for the use in forest biodiversity-ecosystem functioning (BEF) research. This is strongly supported by a pilot study which we conducted in a structurally complex and species-rich forest in northern Germany. MLS data provide very detailed and precise information on individual-tree biomass allocation and crown architecture, effectively recorded over large areas. The main limitation for a widespread use of MLS in forest BEF research is the lack of methods for automatic individual-tree segmentation and species identification, and for the precise quantification of canopy space filling and spatio-temporal dynamics in tree-tree interactions for space in the canopy. Thus, our proposed project has two main goals: to resolve current methodological constraints preventing a widespread use of MLS in forest BEF research and to develop methods by which MLS data can be used to directly tease apart the mechanisms underlying diversity effects in forests.