Subproject 5: Carbon storage and nutrient cycling
The functional significance of forest diversity: N-pools, fluxes and N-uptake complementarity
PI: Michael Scherer-Lorenzen, Dr. (ETH Zurich)
Co-PI: Andy Hector, Prof. Dr. (University of Zurich)
Summary
The carbon and nitrogen cycles are intimately connected and may be simultaneously impacted by changes in biodiversity. Subproject 5, together with our Chinese collaborators, aims to identify impacts of forest diversity (trees and shrubs) on species` allometries and C and N pools. We will do this through small-scale satellite experiments and measurements of both the experimental and comparative plots. Despite the tight link between C and N cycling, for organisational reasons this subproject is separated into a C-flux focused work package led by our Chinese counterparts (Jin-Sheng He, Dali Guo), and a more N-orientated work package (this proposal).
During the initial three years we will establish site- and species-specific allometries to convert estimates of differences in growth rates of trees into estimates of nitrogen stocks in aboveground timber (PhD student funded through University of Zurich). We will focus on (i) tree diversity effects on litter N pool dynamics, decomposition and mineralization, directly affecting nitrogen cycling and soil nitrogen availability; on (ii) the relationship between tree/shrub diversity and standing plant N pool sizes and soil N pool sizes, and their temporal variations. Finally, we will (iii) mechanistically investigate N use complementarity among coexisting species with 15N tracers.
Objectives
The general objective of SP 5 is to study the functional significance of tree/shrub diversity for ecosystem nitrogen cycling.
The overarching research questions are:
1. What is the effect of tree/shrub diversity on litter N pool dynamics, decomposition and mineralization, directly affecting nitrogen cycling and soil nitrogen availability?
2. What is the relationship between tree/shrub diversity and standing plant N pool sizes and soil N pool sizes? Is the temporal variability in these pool sizes dependent on tree diversity?
3. Can complementarity in soil nitrogen uptake explain positive diversity effects on tree productivity and plant N pools?