iDiv Annual Conference 2026

Hugging trees - A refined look at physical tree-tree interactions

Not scheduled

20m

Talk Functions

Speaker

Alexander Täuber (Technical University Dresden, DE; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, DE)

Description

Tree-tree interactions have been identified as a key mechanism linking biodiversity to ecosystem functioning. The complementary occupation of canopy space by coexisting species increases canopy packing and promotes community productivity. Several studies have applied the theoretical volumetric complementarity approach using the crown complementarity index (CCI). While effective at quantifying vertical stratification, this approach does not account for the distance between trees or the volume of interacting crowns.
To address these gaps, we developed the crown overlap index (COI) based on existing concepts of crown overlap and distance weighting. The index quantifies the volume of crown interactions within a distance threshold derived from 3D laser scanning point cloud data. We calculated both CCI and COI for 115 tree pairs within the BEF-China experiment and found a negative relationship between the two indices. At high CCI values, COI was consistently low, whereas at lower CCI values COI showed considerable variation. This indicates that canopy complementarity cannot be fully captured by a single spatial index alone.
To demonstrate the ecological utility of the COI, we investigated its response and that of the CCI to leaf functional trait dissimilarity as well as dissimilarity in the amount of tree structural complexity. We could show contrasting effects, with CCI showing weak significant effects towards the trait dissimilarity and a strong correlation with the dissimilarity in structural complexity. The COI reacted inversely, with a marginal effect of leaf trait dissimilarity and a significant relationship with structural complexity dissimilarity.
In conclusion, the crown overlap index as a refined spatial metric of physical tree-tree interactions could be very useful for research questions regarding the influence of structural crown interactions, such as biotic interactions between trees and organisms interacting with and on them.