Journal
FOREST ECOSYSTEMS
Volume 8, Issue 1, Pages -Publisher
KEAI PUBLISHING LTD
DOI: 10.1186/s40663-021-00306-y
Keywords
Biodiversity; Tree growth; Crown architecture; Quantitative structure models; Terrestrial laser scanning; Neighbour classification
Categories
Funding
- German Research Foundation [DFG 320926971]
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Species-specific genotypic features, local neighbourhood interactions, and resource supply play significant roles in determining tree stature and growth rate. The diversity-mediated biomass allocation in mixed-species forests is considered a fundamental mechanism for positive biodiversity-productivity relationships. Local neighbourhood diversity has been shown to increase crown dimension and wood volume of target trees, with size-dependent effects on tree productivity. Neighbour inclusion approach also significantly impacts the outcome, with overlapping crowns being recommended for relevant scale of local neighbourhood interactions.
Background Species-specific genotypic features, local neighbourhood interactions and resource supply strongly influence the tree stature and growth rate. In mixed-species forests, diversity-mediated biomass allocation has been suggested to be a fundamental mechanism underlying the positive biodiversity-productivity relationships. Empirical evidence, however, is rare about the impact of local neighbourhood diversity on tree characteristics analysed at a very high level of detail. To address this issue we analysed these effects on the individual-tree crown architecture and tree productivity in a mature mixed forest in northern Germany. Methods Our analysis considers multiple target tree species across a local neighbourhood species richness gradient ranging from 1 to 4. We applied terrestrial laser scanning to quantify a large number of individual mature trees (N = 920) at very high accuracy. We evaluated two different neighbour inclusion approaches by analysing both a fixed radius selection procedure and a selection based on overlapping crowns. Results and conclusions We show that local neighbourhood species diversity significantly increases crown dimension and wood volume of target trees. Moreover, we found a size-dependency of diversity effects on tree productivity (basal area and wood volume increment) with positive effects for large-sized trees (diameter at breast height (DBH) > 40 cm) and negative effects for small-sized (DBH < 40 cm) trees. In our analysis, the neighbour inclusion approach has a significant impact on the outcome. For scientific studies and the validation of growth models we recommend a neighbour selection by overlapping crowns, because this seems to be the relevant scale at which local neighbourhood interactions occur. Because local neighbourhood diversity promotes individual-tree productivity in mature European mixed-species forests, we conclude that a small-scale species mixture should be considered in management plans.
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