The Influence of Long-term Warming on Soil Enzyme Activities

Global warming is a key environmental factor affecting the soil carbon and nitrogen cycle process, and its influence effect varies depending on different soil types. However, the regulatory mechanism of extracellular enzymes in the soil within it remains unclear. To study the response of extracellular enzyme activities in soil to long-term warming, continuous warming simulation experiments were carried out in this study. Six common soil, namely red soil, laterite, black soil, brown soil, purple soil and loess, were selected as the research objects. The Open warming system(FATI)was used to conduct all-day warming of winter wheat throughout its growth period. The activities of soil sucrase (S-SC), cellobiose hydrolase (CBH), β -glucosidase(βG), β -xylitase(βX), urease(S-UE), β -acetylglucosidase(NAG), phosphatase(AP)and catalase(CAT)were determined. The results show that the warming(+2 ℃)treatment significantly enhanced the soil enzyme activities, and there were extremely significant differences in the response characteristics of different enzymes in different soil types (P<0.01). The sucrase activity in black soil showed the strongest temperature sensitivity, with an increase of 104.7% in its activity, significantly higher than that of other soil types (P<0.01). The urease activity in loess responded most significantly to temperature increase, with an increase of 79.22% in its activity, significantly higher than that of the normal temperature control treatment (P<0.01). There were significant differences in carbon cycle enzymes, nitrogen cycle enzymes and phosphorus cycle enzymes among different soil types (P<0.01). Warming increased the activities of carbon cycle enzymes and nitrogen cycle enzymes in red soil, while reduced the activities of nitrogen cycle enzymes and phosphorus cycle enzymes in purple soil. Among the carbon cycle enzymes, the βX enzyme and catalase in alkaline soil were significantly higher than those in other soil types (P<0.01). Among nitrogen cycle enzymes, the urease activity in acidic soil was significantly higher than that in other soil types (P<0.01), and among phosphorus cycle enzymes, the phosphatase activity in neutral soil was significantly higher than that in other soil types (P<0.01). Whether or not the temperature increases, the microorganisms in the six types of soil are jointly limited by carbon (C) and phosphorus (P). Enzyme stoichiometric analysis reveals that the enzyme activity vector angles of all soil samples were significantly greater than 45° (P<0.05), which indicates that microorganisms were more sensitive to the limitation of P element. These results indicate that there is an interaction between warming and soil type on the activities of soil carbon, nitrogen and phosphorus cycling enzymes, and particular attention to phosphorus cycling enzymes is needed.