The fate of phosphorus in forest and treeline ecosystems in Ecuador
The overarching objective of this project is to assess the fate of fertilized P in the organic layer and in mineral soil and to elucidate the processes involved in P cycling in soil (immobilization and release rates by microorganisms, sorption/desorption, precipitation/dissolution) along the NUMEX-X altitudinal gradient (1000, 2000, 3000, 4000m; the latter including a Polylepis and a Páramo ecosystem). We will assess P fractions in soil and use a combination of 33P tracer studies and incubation experiments to disentangle biological and geochemical processes controlling P retention. The mechanistic understanding gathered by this project is crucial for predictions of ecosystems responses to the continuously high atmospheric N (and P) deposition, because single mechanisms might respond differently (and oppositionally) in the long run. Because the processes involved in P cycling are expected to respond faster to environmental changes than e.g., P pools in soil, these different responses are an essential basis to evaluate effects of environmental change and finally, to develop “early-warning” ecosystem indicators for environmental change.