水分和温度对若尔盖湿地和草甸土壤碳矿化的影响

The effect of moisture and temperature on soil C mineralization in wetland and steppe of the Zoige region,China

土壤碳矿化及其温度和水分敏感性是研究生态系统碳循环的重要指标。以若尔盖高寒湿地和草甸为对象,在不同水分(70%,100%,130%饱和含水量(SSM))和温度(5,10,15,20,25℃)培养下定期测定土壤碳矿化速率(或土壤微生物呼吸速率),探讨水分和温度对高寒湿地和草甸土壤碳矿化的影响,为揭示未来暖干化对若尔盖地区碳贮存及其碳汇功能的潜在影响提供科学依据。实验结果表明:增温显著促进了高寒湿地和草甸土壤碳矿化,而水分过高会抑制土壤碳矿化;此外,高寒湿地土壤碳矿化速率高于高寒草甸。土壤水分和草地类型对土壤碳矿化温度敏感性(Q10)的影响比较复杂。高寒草甸Q10随水分升高而显著升高,培养7 d时的Q10变化趋势为70%SSM(1.21)<100%SSM(1.76)<130%SSM(2.80),培养56 d的Q10从1.17上升为4.53。高寒湿地的Q10在培养7 d差异不显著,但整个56 d培养期内Q10随水分升高而显著增加。在评估暖干化对若尔盖地区碳贮量和碳汇功能的影响时,应更加重视高寒草甸和高寒湿地Q10对水分和温度变化的不同响应。

Soil carbon （C） mineralization and its response to temperature and moisture are important components of an ecosystem＇s C cycle. In this study, soils of alpine wetlands and meadows in the Zoige region were incubated at various temperatures （5, 10, 15, 20, and 25℃） and soil moisture regimes （70%, 100%, and 130% saturated soil moisture （SSM） ）. Soil C mineralization rate （ or soil microbial respiration rate ） was measured regularly. The main objectives were to （ 1 ） explore whether the responses of soil C mineralization and in particular, its temperature sensitivity （ Q10）, are different between alpine wetland and meadow soil types, and （2） to reveal impact of warming and drying scenarios on soil C storage and C sequestration in alpine wetlands and steppe environments. The results showed that soil C mineralization increased significantly with increasing incubation temperature, but excessive soil moisture depressed soil C mineralization. The soil C mineralization capacity in the alpine wetland soil was higher than that of the alpine meadow, regardless of soil moisture. Moreover, soil water content and grassland types interactively influenced Q10 of soil C mineralization （F= 14.79 ,P〈0. 001 ）.In the meadow, the values of Q10 increased significantly with increasing water content, as follows： 70% SSM （1.21） 〈 100% SSM （1.76） 〈 130% （2.80） in the 7-day incubation experiment, and rose from 1.17 to 4.53 in the 56-day incubation experiment. The Q,0 values were not significantly different in the wetland under different soil moisture in the 7- day incubation experiment; but the Q10 values increased significantly with increasing soil moisture in the 56-day incubation experiment. On the basis of the different Q10 values, we concluded that soil C mineralization of the meadow soil is more sensitive to future regional warming and drying scenarios than that of the alpine wetland. When evaluating the effect of warming and drying scenarios on soil C storage and sequestration within alpine wetland and steppe environments, the phenomenon that the Q10 responds differently to changes in soil moisture and temperature in the alpine meadow and alpine wetland ecosystems should be considered.