Effects of warming on microbial biomass carbon and nitrogen in the rhizosphere and bulk soil in an alpine scrub ecosystem

Abstract

To understand the effects of climate warming on the rhizosphere ecological process in the alpine scrub ecosystem, the responses of microbial biomass carbon and nitrogen in the rhizosphere and bulk soil to experimental warming were examined in a Sibiraea angustata scrubland on the eas-tern Qinghai-Tibetan Plateau, China. The results showed that the concentrations of microbial biomass carbon and nitrogen in the rhizosphere and bulk soil in the early growing season were significantly higher than those in the middle and late growing seasons. Experimental warming did not significantly affect the concentrations of microbial biomass carbon and nitrogen of the rhizosphere soil in the most growing seasons. In the bulk soil, however, the effects of experimental warming on the microbial biomass carbon and nitrogen differed among the growing season. Experimental warming significantly decreased microbial biomass carbon but increased microbial biomass nitrogen in the early growing season. In the middle growing season, warming significantly increased both microbial biomass carbon and nitrogen. In the late growing season, there was no significant effect. The rhizosphere effects of soil microbial biomass carbon and nitrogen also differed with the growing season. The rhizosphere effects of microbial biomass carbon and nitrogen were negative in the early growing season but positive in the middle growing season. In the late growing season, there were negative rhizosphere effects of soil microbial biomass carbon and positive rhizosphere effects of soil microbial biomass nitrogen. Furthermore, experimental warming significantly increased the rhizosphere effects of soil microbial biomass carbon and nitrogen in the early growing season, but decreased those in the middle and late growing seasons. These results uncovered the changing mechanism of the biologi-cal process in the rhizosphere and bulk soil in the alpine scrub ecosystems under the background of climate warming.