Annual methane uptake by typical semiarid steppe in Inner Mongolia
Annual methane uptake by typical semiarid steppe in Inner Mongolia
复制标题
内蒙古典型半干旱草原年甲烷吸收量
DOI：
10.1029/2009jd013783
复制
发表时间：
2010-08-10
影响因子：
4.4
通讯作者：
Zheng, Xunhua
中科院分区：
文献类型：
--
作者：
Chen, Weiwei;Wolf, Benjamin;Zheng, Xunhua
草原生态系统约占全球陆地面积的10%。最近的测量表明，草原土壤作为一个重要的汇大气甲烷（CH 4）。然而，准确量化草原每年吸收的CH 4受到很少测量汇率的挑战，这往往只涵盖生长季节。为了了解CH 4交换的年动态和大小，特别是非生长季节的贡献，累积年CH 4交换，我们进行了全年的CH 4通量测量在两个相邻的草原站点在高时间分辨率。一个是未放牧和围栏自1999年以来（UG 99），另一个是放牧在冬季（WG 01）。测量还得到了土壤剖面中甲烷浓度的观测结果。研究地点位于内蒙古典型的羊草草原。结果表明，典型半干旱草原全年都是大气CH 4的汇。即使在春季土壤解冻期间，表层土壤含水量高的时期，CH 4吸收也占主导地位。CH 4吸收的季节性表现出强烈的依赖于土壤温度的季节变化。当温度不是限制因素时，土壤水分的重要性增加。例如，夏季降雨之后，甲烷排放率急剧下降。未放牧的UG 99和冬季放牧的WG 01站点的CH 4年吸收量分别为3.7和2.1千克C公顷（-1）。非生长季（12月-4月）对CH 4年累积吸收量的贡献约为30%（25%-36%）。此外，我们的数据表明，冬季放牧显着改变草原土壤吸收CH 4的能力。然而，需要更多的测量在配对的未放牧/放牧的网站，以评估放牧可能会影响草原土壤的CH 4吸收能力在更大的区域或全球范围内。
Steppe ecosystems cover approximately 10% of the global land surface. Recent measurements have shown that steppe soils function as a significant sink for atmospheric methane (CH4). However, precise quantification of the annual CH4 uptake by steppe is challenged by infrequent measurements of exchange rates, which often only cover the growing season. In order to understand the annual dynamics and magnitude of CH4 exchange, especially contribution of nongrowing season to the cumulative annual CH4 exchange, we conducted year-round CH4 flux measurements at high temporal resolution at two adjacent steppe sites. One was ungrazed and fenced since 1999 (UG99) and the other was grazed during the winter (WG01). The measurements were supplemented with observations of CH4 concentrations in the soil profile. Sites were located in typical Leymus chinensis steppe in Inner Mongolia, China. The results show that the typical semiarid steppe functioned exclusively as a sink for atmospheric CH4 throughout the entire year. Even during the spring soil thawing, a period with high water content in the top soil, CH4 uptake was dominant. The seasonality of CH4 uptake displayed a strong dependency on the seasonal variation in soil temperature. Soil moisture increased in importance when temperature was not the limiting factor. For example, CH4 rates decreased sharply following summer rainfall events. The annual CH4 uptake by the ungrazed UG99 and the winter-grazed WG01 sites was 3.7 and 2.1 kg C ha(-1), respectively. The contribution of the nongrowing season (October-April) to the cumulative annual CH4 uptake was approximately 30% (25%-36%). Additionally, our data suggest that winter grazing significantly alters the capacity of steppe soils for CH4 uptake. However, more measurements at paired ungrazed/grazed sites are needed to assess how grazing might affect the CH4 uptake capacity of steppe soils at a larger regional or global scale.