The role of stand structural complexity and canopy space occupation for shaping biodiversity-productivity relationships: insights from tree diversity experiments

Tama Ray

AutorIn

Tama Ray

Titel

The role of stand structural complexity and canopy space occupation for shaping biodiversity-productivity relationships: insights from tree diversity experiments

Zitierfähige Url:

https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-981407

Erstveröffentlichung

2025

Datum der Einreichung

16.12.2024

Datum der Verteidigung

22.05.2025

Abstract (EN)

The increasing deforestation incites climate change, and climate change threatens the carbon mitigation potential of forests. Mixed-species tree communities are often promoted to improve ecosystem functioning and meet human needs. However, there is still a lack of understanding of the extent and dynamics of the mechanisms underlying positive biodiversity-productivity relationships (BPRs). Using data from two tree biodiversity-ecosystem functioning experiments, I examined the effects of tree diversity and mycorrhizal associations on stand structural complexity and productivity (study 1, MyDiv experiment, Germany) and the effects of tree species richness and leaf functional traits on canopy space filling and productivity (study 2, Sardinilla experiment, Panama). In addition, following my 2nd study, I tried to estimate the relative canopy space filling (RCSF) in different delineated canopy spaces and identify the canopy space that best correlated to productivity in my 3rd study (study 3, Sardinilla experiment). Terrestrial laser scanning was used to precisely quantify the three-dimensional characteristics of the stands. Tree growth data were used to analyse aboveground stand productivity at both study sites. The results of study 1 showed that tree species richness increased stand productivity by increasing stand structural complexity with high light interception through functional diversity of shade tolerance, while mycorrhizal associations had no significant effect. I found in study 2 that species identity effect plays a crucial role than richness effect in canopy space filling, where communities dominated by conservative resource use showed higher canopy space filling and higher canopy space filling led to higher stand productivity. In both studies, positive biodiversity effects on stand structural complexity (study 1) and canopy space filling with functional diversity of leaf traits (study 2) arose due to taxonomic diversity of tree communities contributing to overyielding. Following study 2, study 3 demonstrated that positive and significant RCSF-productivity relationships were robust, while the strength of the relationships varied across different canopy space definitions. Interestingly, excluding the uppermost part and including the lowest part of the canopy resulted in distinct variations in explained variance in productivity. Additionally, mixtures played a very important role in RCSF-productivity relationships compared to monocultures. This thesis contributes to a better understanding of the mechanisms of how tree diversity effect and identity effect simultaneously shape the forest structures and contribute to the biomass allocation patterns of the forest. All in all, the insights from this thesis recommend enhancing functional and taxonomic diversity in the afforestation and reforestation projects, contributing structural diversity to increase biomass allocation in order to combat the current climatic challenge.

Freie Schlagwörter (EN)

Biodiversity, Ecosystem functioning, Stand structural complexity, Canopy space filling, BEF experiments

Klassifikation (DDC)

634

Klassifikation (RVK)

ZC 72950

GutachterIn