Effects of simulated climate change on soil microbial biomass and enzyme activities in young Chinese fir (Cunninghamia lanceolata) in subtropical China

Abstract

Global warming and nitrogen deposition have been responsible for numerous environmental disturbances, and have attracted much attention from researchers, government agencies and international community. Recent studies indicate that the trend of global warming and nitrogen deposition will continue over the next few decades. These changes not only affect the growth of aboveground vegetation, but also change the belowground soil environment, and thus directly or indirectly affect the microbial process. The microbial biomass and soil enzymes play significant roles in terrestrial environments, particularly through the decomposition of soil organic matter, dynamic fluctuation between carbon sink and source, and the transformation of soil nutrient. However, little is known about that how global warming and nitrogen deposition will affect the soil microbial and soil enzymes in the subtropical zone.In the present study, we aim to evaluate the responses of the microbial biomass and soil enzyme activity to short-term simulated warming and nitrogen deposition in young Chinese fir (Cunninghamia lanceolata) in Sanming Fujian province in subtropical China. The results showed that soil warming increased microbial biomass carbon content and improved the activity of acid phosphatase and lignin enzymes significantly (P<0.05). Additionally, microbial biomass carbon content was significantly higher than that of the control after the application of nitrogen fertilizer. Besides, nitrogen addition also significantly raised the C/N ratio of microbial biomass. It also reduced the activity of lignin and cellulose hydrolysis. The combination of warming and nitrogen treatment was more effective than individual warming and nitrogen treatments, increasing the content of soil microbial biomass carbon and nitrogen, decreasing the activity of lignin hydrolytic enzymes and chitinase, and leading to further acidification of the soil. Redundancy analysis (RDA) showed that moisture and pH are the major determinants of soil enzyme activity at the 0–10cm depth. However, at the 10–20cm depth, the major determiner is microbial biomass. In summary, the simulated warming and nitrogen deposition affected soil microbial biomass and enzyme activity significantly in the short-term, and the interaction of the two factors was significant. That suggests that the climate change could have a profound effect on soil microbial processes. Therefore, the effects of simulated warming and nitrogen deposition on microbial biomass and soil enzyme activity and the mechanism of their interaction with soil, microorganisms and plants need to be studied further, in order to reveal the responses and feedback mechanisms of Chinese fir plantations to global climate change in subtropical China.