Climate warming increases soil erosion, carbon and nitrogen loss with biofuel feedstock harvest in tallgrass prairie

Anthropogenic soil erosion severely affects land ecosystems by reducing plant productivity and stimulating horizontal carbon and nitrogen movement at the surface. Climate warming may accelerate soil erosion by altering soil temperature, moisture, and vegetation coverage. However, no experiments have been carried out to quantify soil erosion with warming. In a long-term field experiment, we explored how annual clipping for biofuel feedstock production and warming caused soil erosion and accompanying carbon and nitrogen losses in tallgrass prairie in Oklahoma, USA. We measured relative changes in soil surface elevation between clipped and unclipped plots with or without experimental warming. Our results show that average relative erosion depth caused by clipping was 1.65 +/- 0.09 and 0.54 +/- 0.08 mm yr-1, respectively, in warmed and control plots from November 21, 1999 to April 21, 2009. The soil erosion rate was 2148 +/- 121 g m-2 yr-1 in the warmed plots and 693 +/- 113 g m-2 yr-1 in the control plots. Soil organic carbon was lost at a rate of 69.6 +/- 5.6 g m-2 yr-1 in the warmed plots and 22.5 +/- 2.7 g m-2 yr-1 in the control plots. Total nitrogen was lost at a rate of 4.6 +/- 0.4 g m-2 yr-1 in the warmed plots and 1.4 +/- 0.1 g m-2 yr-2 in the control plots. The amount of carbon and nitrogen loss caused by clipping is equivalent to or even larger than changes caused by global change factors such as warming and rising atmospheric CO2 concentration. In addition, soil erosion rates were significantly correlated with clipping-induced changes in soil moisture. Our results suggest that clipping for biofuel harvest results in significant soil erosion and accompanying losses of soil carbon and nitrogen, which is aggravated by warming.