高寒草甸土壤温室气体释放对水分变化的响应

Responses of Greenhouse Gases Emissions from Alpine Meadow Soil to Moisture Contents

青藏高原未来气候变化引起的降水量再分配,将影响土壤水分含量状况,这会对土壤温室气体的释放产生直接影响。为了探明土壤含水量对土壤温室气体释放的影响,以青藏高原高寒草甸土为研究对象,采用室内培养的方法,研究了田间持水量30%、45%、60%、75%和90%不同水分梯度对土壤CO2、CH_4和N_2O三种温室气体释放的影响。结果表明:(1)高寒草甸土壤CO_2和N_2O累积释放量在土壤水分含量为田间持水量的60%时最大,分别为2.74 g kg^(-1)和1.54 mg kg^(-1);(2)土壤水分含量在田间持水量的30%~60%范围内,高寒草甸土壤是CH_4的"汇",土壤水分含量在田间持水量的75%~90%范围内,高寒草甸土壤转变为CH_4的"源";(3)CH_4累积释放量与土壤NO_3^--N含量呈极显著负相关关系,N_2O累积释放量与土壤NO_3^--N含量呈显著负相关关系;(4)不同水分梯度高寒草甸土壤释放温室气体的全球增温潜能(GWP)由大至小顺序为:60%>75%>90%>45%>30%。研究结果可为未来气候变化背景下青藏高原高寒生态系统土壤温室气体释放的估算和管理提供一定的科学依据。

Redistribution of precipitation in the Qinghai-Tibetan Plateau caused by future climate change would directly affect the status of soil moisture contents in alpine meadows of this region, which would further cause the changes in greenhouse gas emissions from alpine meadows. In this paper, an incubation experiment in laboratory was conducted to examine the effects of different moisture contents on carbon dioxide（CO_2）, methane（CH_4） and nitrous oxide（N_2O） emissions from alpine meadow soils sampled in Qinghai-Tibetan Plateau. Five moisture content gradients（30%, 45%, 60%, 75% and 90% water-holding capacity（WHC）） were set up in this study. The results showed that the largest cumulative emissions of CO_2 and N_2O were 2.74 g kg^-1 and 1.54 mg kg^-1, respectively, which occurred at60% WHC. Alpine meadow soil acted as a sink of CH_4 when soil moisture contents ranged from 30% to 60% WHC.Alpine meadow soil acted as a source of CH_4 when soil moisture contents were in the range of 75% to 90% WHC.There were significant negative correlations between cumulative CH_4 emission and soil NO3^--N concentration and between cumulative N_2O emission and soil NO3^--N concentration. The global warming potential（GWP） increased in the order of 60% WHC〉 75% WHC 〉90% WHC〉 45% WHC〉 30% WHC. The results of this study could provide a scientific basis for the evaluation and management of greenhouse gas emissions from alpine meadow soils in the Qinghai-Tibetan Plateau in terms of climate change.