SOIL RESPIRATION OF A LEYMUS CHINENSIS GRASSLAND STAND IN THE XILIN RIVER BASIN AS AFFECTED BY OVER-GRAZING AND CLIMATE

This two year study of CO 2 evolution from Leymus chinensis grassland soil using the alkali absorption method in the Xilin River Basin, examines seasonal trends and CO 2 efflux in relation to grazing and climatic factors.The seasonal pattern of CO 2 evolution rate had a single peak, late July in both 1998 and 1999.Soil respiration was significantly correlated with air temperature, and could be described by the equation of Res=256.75 T 0.6557 ( R 2= 0.5779 , p 0.001).The Q 10 value ranged between 2.5 and 3.0.The relationship between soil respiration rate and the combined effect of temperature and soil water content was LnRes=5.8596+0.0125 M +0.0394 T +0.0049 M × T ( R 2 =0.7096, p 0.001).From observed values and model predictions the soil CO 2 flux ranged from 249.4 gC·m -2 ·a -1 to 320.7 gC·m -2 ·a -1 at the intact study site, and 237.0 gC·m -2 ·a -1 to 305.6 gC·m -2 ·a -1 at the grazed site.From this analysis,and to the extent that other factors were equal,we can conclude that the influence of grazing on soil respiration at the studied area was negligible.