Effects of tree diversity on canopy space occupation vary with tree size and canopy space definition in a mature broad-leaved forest

Publikation: Beiträge in ZeitschriftenZeitschriftenaufsätzeForschungbegutachtet

Authors

  • Louis Georgi
  • Matthias Kunz
  • Andreas Fichtner
  • Anne Bienert
  • Hans-Gerd Maas
  • Goddert von Oheimb

A more efficient use of limited canopy space and, thus, a higher canopy space occupation (CSO) in forests can result in an increased absorption of photosynthetically active radiation, which in turn can promote productivity. Although there is some evidence for a positive relationship between tree diversity (TD) and CSO, the generality of this hypothesis is still under debate. Here, we propose a conceptual framework that accounts for both the spatial complexity of canopy space and size-dependent interspecific tree interactions and tested it using mobile laser scanning data across larger spatial scales. We assessed the CSO at high resolution with two diversity indices, tree species richness (TSR) and the effective number of species (ENS) along a TSR gradient ranging from monocultures to 8-species mixtures in a mature and structurally complex mixed-species temperate forest. We found that the direction and strength of the TD-CSO relationship largely depended on the way how canopy space is defined and which tree size classes are considered to calculate TSR. Using an broad deliniation of canopy space no significant relationship between TD and CSO was evident. In contrast, when considering only the upper canopy space, a significant effect of TSR on CSO emerged. Importantly, the direction of this relationship was critically dependent on the tree size threshold underlying the TSR determination. For all trees with a diameter at breast height > 7 cm, we observed a significant negative relationship, while the opposite was the case when considering only large-sized trees. Our novel conceptual framework demonstrates that accurate estimation of canopy space complexity and tree size dependence is key to better understanding the processes underlying CSO. However, further information on diversity-canopy space occupation relationships from studies in different forests and forest types is needed.

OriginalspracheEnglisch
Aufsatznummer109055
ZeitschriftAgricultural and Forest Meteorology
Jahrgang323
ISSN0168-1923
DOIs
PublikationsstatusErschienen - 15.08.2022

Bibliographische Notiz

Funding Information:
We thank the Forestry Offices of the City of Lübeck County for permission to conduct this study in their forests. The MLS registration was made on the Taurus HPC cluster of the ZIH of the Technische Universität Dresden. Moreover, we would like to thank the anonymous reviewers for their comments and suggestions on the manuscript. L.G. and A.B. were funded by the German Research Foundation ( DFG 320926971 ) through the project “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”. L.G. was also supported by the Graduate Academy of TU Dresden.

Funding Information:
We thank the Forestry Offices of the City of Lübeck County for permission to conduct this study in their forests. The MLS registration was made on the Taurus HPC cluster of the ZIH of the Technische Universität Dresden. Moreover, we would like to thank the anonymous reviewers for their comments and suggestions on the manuscript. L.G. and A.B. were funded by the German Research Foundation (DFG 320926971) through the project “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”. L.G. was also supported by the Graduate Academy of TU Dresden.

Publisher Copyright:
© 2022

DOI