降雨对干旱半干旱区湿地和农田土壤CO_2短期释放的影响

本研究以巴音布鲁克湿地和农田灰漠土原状土为研究对象,进行原位模拟降雨试验,利用LI-8100土壤碳通量自动测量系统测定土壤的CO_2排放,研究了不同降雨量对土壤CO_2排放的影响。结果表明:降雨导致湿地土壤CO_2释放速率显著增加(P0.01),而农田土壤无显著差异。在其含水量无明显差异下,湿地不同降雨处理组的CO_2排放量均大于农田组,湿地土壤CO_2日累积排放量降水10 mm组降水20 mm组对照组,土壤有机碳高的湿地土壤随降雨量增加,土壤短期碳损失高,而对低有机碳土壤(西北干旱区贫瘠土壤)短期碳损失影响不显著。降雨后农田土壤降水10 mm组CO_2排放与地表温度和5 cm地温相关性极显著(P0.01),其他各处理均未呈现显著相关。说明在干旱半干旱区降雨量对土壤CO_2排放速率有着重要的影响。

Response of Soil CO2 Short-term Emissions to Simulated Rainfalls in Arid and Semi-arid Area

Precipitation is one of the key factors that influence the soil respiration. A simulated precipitation experiment focused on response of wetland and farmland soil CO2 emissions to simulated rainfalls using a LI-8100 automated soil CO2 flux system(LI-COR, Lincoln, Nebras-ka, USA)was carried out. The dynamics of diurnal soil respiration rate and the correlations between soil respiration rate and soil temperature were also evaluated in this paper. Results showed that precipitation could stimulate wetland soil CO2 emission rate(P<0.01),but this phe-nomenon could not be found in farmland soil. Under the same soil water content, different precipitation groups of CO2 emissions in wetland soil were greater than that in farmland. The wetland soil cumulative CO2 emissions was greatest at 10 mm precipitation group, followed by 20 mm precipitation group, and control group had the smallest values. With the increase of rainfall,the wetland soil that had high organic carbon released high CO2 in short-term, and soil of low organic carbon(arid zone of northwest arid soil)had insignificant effect on soil carbon loss. Farmland soil CO2 emission rate was significantly correlated with soil temperature(0 cm, 5 cm)under 10 mm precipitation group(P<0.01). The change of the farmland soil cumulative CO2 was in accordance with the change of wetland soil. This finding indicated that precipitation was the important factor influencing the response of soil CO2 emissions in arid and semi-arid area.