Effects of grazing on microbial biomass C, N and respiration in Artemisia frigida rhizosphere soil

Artemisia frigida is a common plant, especially in degraded grasslands, on the Inner Mongolian steppes. To reveal the effects of grazing disturbance on soil microorganisms of the A. frigida rhizosphere, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and basal respiration and correlation were discussed, by the chloroform fumigation extraction method and the LI-7000 CO2/H2O system. Rhizosphere soil of A. frigida (ARS) and non-rhizosphere soil (NRS) under three grazing intensities, no grazing (CK) plot, light grazing (LG) plot, heavy grazing (HG) plot, were chosen as experimental sites in the Inner Mongolian steppes. Results showed that compared with the control group, the soil microbial biomass carbon, nitrogen and basal respiration after light grazing treatment increased by 22.7%, 45.0%, 17.2%, respectively. These bio-indicators in A. frigida rhizosphere soil were higher than non-rhizosphere soil of A. frigida (P < 0.05). Also, the increasing rate of MBN in rhizosphere and non-rhizosphere soil was higher than that of MBC. In the rhizosphere soil of Artemisia frigida, MBC had a positive correlation with organic matter (r = 0.737), total N (r = 0.798), available N (r = 0.945), and total K (r = 0.697). The MBN had a positive correlation with organic matter (r = 0.906), total N (r = 0.915), available N (r = 0.937), and total K (r = 0.691).The basal respiration had a positive correlation with organic matter (r = 0.507), total N (r = 0.446), available N (r = 0.805), and total K (r = 0.898). The light grazing treatment can contribute to a increase to microbial biomass and basal respiration rate. This study provided a theoretical basis for further exploring of ways that A. frigida could help resist grassland degradation.