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Abstract

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 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.