The response of grassland productivity, soil carbon content and soil respiration rates to different grazing regimes in a desert steppe in northern China

Soil respiration is a major process for organic carbon losses from arid ecosystems. A field experiment was conducted in 2010 and 2012 on the responses to continuous grazing, rotational grazing and no grazing on desert steppe vegetation in northern China. The growing season in 2010 was relatively dry and in 2012 was relatively wet. The results showed that mean soil respiration was the highest with no grazing in both growing seasons. Compared with no grazing, the soil respiration was decreased by 23.0% under continuous grazing and 14.1% under seasonal rotational grazing. Soil respiration increased linearly with increasing soil water gravimetric content, aboveground net primary productivity (ANPP), belowground net primary productivity (BNPP) and soil carbon and nitrogen contents across the 2 years, whereas a negative correlation was detected between soil respiration and soil temperature. A significant decrease in soil respiration was observed under both continuous grazing and in seasonal rotational grazing in the dry growing season, but no significant difference was detected in the wet growing season. In the wet year, only a non-significant difference in soil respiration was observed between different grazing types. Patterns of seasonal precipitation strongly affected the temporal changes of soil respiration as well as its response to different grazing types. The findings highlight the importance of differences in abiotic (soil temperature, soil water gravimetric content and soil carbon and nitrogen contents) and biotic (ANPP, BNPP and litter mass) factors in mediating the responses of soil respiration to the different grazing regimes.