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Abstract:
Managed grasslands cover 35% of the European agricultural landscape (184 Mio ha). Within the next century temperature and atmospheric CO2 increase will significantly affect this ecosystem type. In Hesse (Germany) 0.6 degrees C warming of air temperatures occurred already since 1960. At our grassland field site, we will treat ring plots (14.5 with elevated CO2 (+20%), air temperature warming (+2 degrees C) and a combination of these two factors throughout the year, (at least) for three years.
We use deep rRNA sequencing (Illumina RNAseq) to reveal bacterial phylogenetic community composition, analyze plant species diversity (Shannon and Ellenberg index) and then integrate treatment response across these traditional disciplines. Finally, measurements of N2O, CH4 and CO2 emissions measured by closed chambers approach and automated systems (LI-COR 8100), support the balance of emitted CO2 equivalents.
GHG emissions emerge from both plants and microbes in the soil, and are associated with changes in the community composition of soil microbes. Furthermore, plant functional types can affect ecosystem net GM emission.
We expect that elevated CO2 will improve the plant water-use efficiency,and soil moisture differences will decrease, with consequences for diversity(1). Elevated air temperatures will most likely stimulate transpiration and increase the VPD (water vapour deficit) causing rather a soil drying effect. Hence we expect that warming combined with elevated CO2 will be antagonistic. Besides the drying effect, the warming will have an impact on phenology and aboveground biomass production of the vegetation, consequently affecting GHG emissions.
As elevated CO2 in the 15 year long running Giessen-FACE led to a doubling of N2O emissions, a slight increase in CO2 emissions(3) and a reduction in CH4 oxidation, turning the system from a GHG sink to a GHG source, we want to test if the combined air temperature warming will enforce those processes or if it will drive antagonistic processes. (C) 2015 The Authors. Published by Elsevier B.V
