Stoichiometric response of dominant grasses to fire and mowing in a semi-arid grassland

Prescribed burning and mowing are widely used grassland management strategies that potentially alter plant nutritional status, with consequent influences on community structure and ecosystem function. We evaluated the effects of annual burning and mowing on stoichiometric ratios (C:N, C:P, and N:P) of three dominant grasses (Leymus chinensis, Stipa grandis, and Cleistogenes squarrosa) in a semi-arid grassland in northern China. After treatments were applied for two years, both fire and mowing did not affect nutrient concentrations and stoichiometric ratios in green leaves. Fire reduced C:N and C:P in senesced leaves. There was no interaction between fire and mowing to affect stoichiometric ratios in green and senesced leaves. Averaged across the three grass species, fire reduced both N and P resorption efficiency. These results indicate that short-term (2-yr) annual burning and mowing would have limited effects on nutritional status of dominant grass species in this semi-arid grassland. Annual burning would lead to rapid nutrient cycling due to its positive effects on litter quality. These results suggest that prescribed burning may affect above- and below-ground processes of semi-arid grassland through changes in foliar stoichiometric ratios, and that the responses of green and senesced leaves to fire may differ greatly due to changes in nutrient resorption.