Ina Hoeft, Prof. Dr. Edzo Veldkamp

Grassland diversity effects on soil nitrogen dynamics and losses

Globally strong decreases in biodiversity are projected for the coming decades. Within the GRASSMAN experiment on functional grassland diversity different manipulations will be done where diverse grasslands (control) are compared with treatments of less diversity: monocot-dominated and dicot-dominated. Our project deals with grassland diversity effects on soil processes and functions. More specifically, the goal of this project is to evaluate the effects of herb diversity and management intensity on soil nitrogen dynamics and related nitrogen losses. We conduct year-round measurements of soil nitrogen turnover, soil trace gas emissions (N2O and NO) and nitrate leaching. The results of our project will help to evaluate whether decreases in herb diversity affect the internal nitrogen cycle and possibly water and air quality.

Andreas Keuter, Prof. Dr. Edzo Veldkamp

Effects of grassland biodiversity and the activity of herbivorous insects on soil nitrogen dynamics and losses and nitrogen fixation

In this project we investigate how grassland biodiversity, mowing frequencies, fertilisation and the activity of herbivorous insects affect soil nitrogen cycling and losses. We measure soil nitrogen dynamics using field incubations, nitrate leaching and nitrous oxide emissions. Furthermore, we asses how management intensity and biodiversity affect nitrogen fixation by free-living micro-organisms. For this purpose, we will conduct assays measuring the nitrogenase activity (acetylene reduction assay and 15N tracing). Finally we contribute to a field experiment where the effects of above ground herbivory on below ground N clycling is quantified. Our research will lead to a better understanding of the impacts of grassland biodiversity on the soil nitrogen cycle with regard to groundwater quality and climate change.