Abstract
The project will explore processes delaying or preventing vegetation recovery following decreased nitrogen (N) input to ecosystems. It will focus on soil-plant-pathogen/insect herbivore interactions in boreal forests subjected to human-induced N enrichment. The project will investigate how biogeochemical feedback mechanisms in this system may maintain N induced vegetation changes although N input to the ecosystem is reduced. This is a central issue in order to understand the very long-term consequences of N enrichment on ecosystem stability and species diversity. Nitrogen enrichment of ecosystems has been regarded as a fully reversible process due to an observed rapid decline in chemical parameters as exchangeable N in soils and N concentrations in run-off water following decreased N input. There is however strong indications that effects on boreal biota can persist for a considerable longer time (at least for 50 years) than the effects on chemical parameters. This discrepancy between chemical and biological recovery will be explored in the proposed research by studying complex interactions between plant tissue N concentrations, plant damage by pathogens/insect herbivores, plant community species composition and soil N turnover.
Sweden