Management, not climate, controls net CO2 fluxes and carbon budgets of three grasslands along an elevational gradient in Switzerland

In Switzerland, the traditional three-stage grassland farming system consists of grazed or cut grasslands along a gradient from lowland to alpine elevations. We measured carbon dioxide (CO2) fluxes at three grassland sites (400, 1000, 2000 m elevation) and estimated carbon sequestration for two years (2006 and 2007). Grasslands at higher elevations (>1000 m), managed at lower intensities, exhibited a larger net CO2 uptake compared to intensively managed grasslands at lower elevations (400 m). Nevertheless, net CO2 uptake rates during optimal growth were very similar for all three sites. Taking into account harvest outputs as well as manure inputs, we calculated the carbon stocks and their changes for grasslands at 400 m and 1000 m during two years. Similar to the cumulative net ecosystem CO2 fluxes, the seasonal course of carbon stock changes was strongly driven by management intensity, in particular by timing and amount of manure applications. Despite differences in environmental and management conditions with elevation, both grassland sites were carbon sinks during 2006 and 2007 (between 60 and 150 g C m a).