长期模拟升温对崇明东滩湿地土壤微生物生物量的影响

以崇明东滩芦苇湿地为对象,采用开顶室生长箱(Open top chambers OTCs)原位模拟大气升温试验,研究了连续升温8a对崇明东滩湿地0—40cm土层土壤微生物生物量碳氮含量的影响。结果表明:连续升温显著提高了崇明东滩湿地土壤微生物生物量碳氮含量,从土壤表层到深层(0—10,10—20,20—30,30—40cm),微生物生物量碳分别增加了39.32%、70.79%、65.20%、74.09%,微生物生物量氮分别增加了66.46%、178.27%、47.24%、64.11%。但升温对土壤微生物生物量的影响因不同土层和不同季节并未表现出统一的规律,长期模拟升温显著提高4月0—20cm土层和7月0—40cm土层微生物生物量碳氮含量,对10月0—40cm土层微生物生物量碳含量没有影响,但是显著提高了10月0—40cm土层微生物生物量氮含量,同时,微生物生物量碳氮比在7月也显著提高。相关分析表明:无论在升温条件还是在对照条件下,土壤温度、含水量、总氮与土壤微生物生物量碳氮及微生物生物量碳氮比均无相关关系,升温条件下,有机碳与微生物生物量碳氮含量以及微生物生物量碳氮比呈显著正相关,但是在对照条件下有机碳与微生物生物量碳氮含量以及微生物生物量碳氮比呈显著负相关。因此,土壤有机碳是影响土壤微生物生物量碳氮含量对长期模拟升温响应的重要生态因子。

Responses of soil microbial biomass to long-term simulated warming in Eastern Chongming Island wetlands, China

Climate warming is one of the main characteristics of global climate change and has a significant impact on the structure and function of terrestrial ecosystems. Soil microbial biomass is a crucial component of soil ecosystem and plays an important role in biogeochemical cycles and energy flow in ecosystems. However, soil microbial biomass is highly sensitive to environmental changes, and increase in air temperature will significantly affect soil microbial biomass. Several studies have investigated the effect of warming on soil microbial biomass, but most studies have focused on the effect of short-term simulated warming on soil microbial biomass in ecosystems such as forests, croplands, and grasslands, whereas little is known about the response of soil microbial biomass to long-term simulated warming in wetland ecosystems. Therefore, an in situ simulated warming experiment was conducted in a wetland ecosystem on Eastern Chongming Island, China. Open-top chambers (OTCs) were applied to simulate climate warming. This study investigated the effects of eight years of continuous warming on soil microbial biomass carbon and nitrogen contents at soil depths of 0-40cm in a wetland on Eastern Chongming Island. The results showed that continuous warming significantly increased soil microbial biomass carbon and nitrogen contents. From surface to deep soil layers (0-10, 10-20, 20-30, and 30-40cm), microbial biomass carbon increased by 39.32%, 70.79%, 65.20%, and 74.09%, whereas microbial biomass nitrogen increased by 66.46%, 178.27%, 47.24%, and 64.11%, respectively. However, the effect of simulated warming on soil microbial biomass at different soil depths and in different seasons did not show a uniform trend. Long-term simulated warming significantly increased soil microbial biomass carbon and nitrogen contents at the 0-20cm soil depth in April and at 0-40cm soil depth in July, but had no effect on soil microbial biomass carbon in October, although soil microbial biomass nitrogen content also significantly increased at 0-40cm soil depth. The ratio of microbial biomass carbon to microbial biomass nitrogen significantly increased in July. Correlation analysis showed that soil microbial biomass carbon and nitrogen were not significantly correlated with soil temperature, soil water content, and total nitrogen in the OTC and control group. Soil microbial biomass carbon and nitrogen contents and the ratio of microbial biomass carbon to microbial biomass nitrogen showed a positive correlation with the soil organic carbon in the OTC, but showed a negative correlation with the soil organic carbon in the control group. Thus, soil organic carbon is an important ecological factor affecting the responses of soil microbial biomass carbon and nitrogen to long-term simulated warming.