Pasture degradation modifies the water and carbon cycles of the Tibetan highlands
Pasture degradation modifies the water and carbon cycles of the Tibetan highlands
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DOI：
10.5194/bg-11-6633-2014
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发表时间：
2014-01-01
期刊：
影响因子：
4.9
通讯作者：
Foken, T.
中科院分区：
文献类型：
--
作者：
Babel, W.;Biermann, T.;Foken, T.
青藏高原对大气环流，特别是季风有重要作用。封闭的植被和开放的裸露土壤之间的变化是不可持续的牧场管理或气候变化所观察到的土地利用退化的显著影响之一，但调查地表性质和过程以及大气反馈变化的实验很少，而且尚未在世界上两个最大的高山生态系统-青藏高原的高山草原和矮嵩草牧场-中进行。我们连接测量的微蒸渗仪，室，C-13标记，涡度协方差和结合的观测与陆地表面和大气模型，适应高原条件。这使我们能够分析三个退化阶段如何影响草地的水和碳循环的景观尺度内的核心区域的小嵩草生态系统。该研究表明，嵩草草坪的日益退化影响了碳分配，并强烈降低了碳吸收，损害了嵩草牧场作为碳汇的功能。植被退化导致从蒸腾到蒸发的转变，而在一个较长的时期内，蒸散总量的变化无法得到证实。结果表明，对流和云生成的早期发病，可能引发的蒸发蒸腾时间的转变时，占主导地位的蒸发。因此，降水开始较早，云减少了入射的太阳辐射。总之，在高原上发现的草地退化的表面特性的变化有显着的影响，在更大的尺度。
The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, C-13 labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales.