Determinants of growing season soil CO2flux in a Minnesota grassland

Soil CO₂ flux was measured across 947 plots at 7 experimentalgrassland sites at the Cedar Creek Natural History Area in order to determinethe relationships between soil CO₂ flux and environmental factors,living plant biomass, and soil C and N. Soil CO₂ flux increased asthe day progressed, and was positively related to aboveground biomass,belowground biomass, and soil % C. However, most of the variation in soilCO₂ flux explained by a multiple regression model(r ² = 0.55) was attributed to the different experimental sites (61%).Soil CO₂ flux increased with increasing aboveground plant biomass(explaining 16% of the model variation),belowground plant biomass (12%), and soil C and C:N ratio(6%). The length of time between aboveground biomass in aplot was clipped and soil CO₂ flux variedamong plots. Soil CO₂ flux declined with increased timesince clipping, supporting the idea that recently fixedcarbon is a significant component of soil CO₂ flux.Soil CO₂ flux did not follow standard Q₁₀relationships. Over a 20 °C temperature range,soil CO₂ flux tended to be lower in warmer plots.More work is necessary to understand what factors explainthe large differences that were seen among experimentalsites in soil CO₂ flux that could not be explainedby biomass or soil properties.