More efficient aboveground nitrogen use in more diverse Central European forest canopies

We hypothesized that biodiversity improves ecosystem functioning and services such as nutrient cycling because of increased complementarity. We examined N canopy budgets of 27 Central European forests of varying dominant tree species, stand density, and tree ∗Corresponding author: [email protected] †University of Berne, Institute of Geography, Hallerstrasse 12, 3012 Berne, Switzerland ‡Friedrich Schiller University of Jena, Institute of Geography, Löbdergraben 32, 07743 Jena, Germany §University of Berne, Institute of Plant Sciences and Botanical Garden, Altenbergrain 21, 3013 Berne, Switzerland ¶Rheinische Friedrich Wilhelms University of Bonn, Institute for Crop Science and Resource Conservation, Division Soil Science and Soil Ecology, Nussallee 13, 53115 Bonn, Germany ‖Max Planck Institute for Biogeochemistry, HansKnöll-Strasse 10, 07745 Jena, Germany ∗∗Karlsruhe Institute of Technology (KIT), Institute of Geography and Geoecology, Kaiserstrasse 12, 76131 Karlsruhe, Germany and shrub species diversity (Shannon index) in three study regions by quantifying bulk and fine particulate dry deposition and dissolved below canopy N fluxes. Average regional canopy N retention ranged from 16% to 51%, because of differences in the N status of the ecosystems. Canopy N budgets of coniferous forests differed from deciduous forest which we attribute to differences in biogeochemical N cycling, tree functional traits and canopy surface area. The canopy budgets of N were related to the Shannon index which explained 14% of the variance of the canopy budgets of N, suggesting complementary aboveground N use of trees and diverse understorey vegetation. The relationship between plant diversity and canopy N retention varied among regional site conditions and forest types. Our results suggest that the traditional view of belowground complementarity of nutrient uptake by roots in diverse plant communities can be transferred to foliar uptake in forest canopies.