Humid Subtropical Forests Constitute a Net Methane Source: A Catchment‐Scale Study
Humid Subtropical Forests Constitute a Net Methane Source: A Catchment‐Scale Study
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DOI：
10.1029/2019jg005210
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
Longfei Yu;Longfei Yu;Jing Zhu;Jing Zhu;Xiaoshan Zhang;Zhangwei Wang;P. Dörsch;J. Mulder
中科院分区：
文献类型：
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作者：
Longfei Yu;Longfei Yu;Jing Zhu;Jing Zhu;Xiaoshan Zhang;Zhangwei Wang;P. Dörsch;J. Mulder
通常，排水良好的森林土壤是甲烷（CH 4）的净汇，而地下水排放区排水不良的土壤可能会导致大量的CH 4排放。预计气候变化将给亚热带带来更多的夏季极端降水，这可能影响森林CH 4平衡。中国的森林通常具有丘陵地形，山坡排水良好，地下水排放区明显。虽然不同的景观要素可能有不同的源和汇功能的CH 4，在流域尺度上的CH 4收支的气候影响仍然很少研究。在这里，我们测量了CH 4通量超过三年沿着地形梯度在中国西南部的亚热带森林流域。CH 4通量表现出清晰的空间模式，表明山坡上排水良好的土壤中有中度CH 4吸收或排放（-5.8至+1.0 kgCH 4-C·ha-1·年-1），而地下水排放区较湿润的土壤中有大量CH 4排放（94.3至479.5 kg CH 4-C·ha-1·年-1）。尽管地下水排放区对流域的贡献很小（0.6%），但在季风夏季，地下水排放区排放了大量的CH 4，影响了整个流域的预算。在湿润气候条件下，坡地土壤对CH 4的吸收能力较弱，甚至成为一个小的CH 4源。对流域尺度CH 4收支的估计表明，亚热带森林流域可以从干旱年份的CH 4净汇转变为湿润年份的CH 4净源，突出了年际气候变化的重要性。我们的研究结果表明，预计气候变化下的亚热带森林可以贡献一个净CH 4源的区域CH 4平衡的后果。
Commonly, well‐drained forest soils are net methane (CH4) sinks, whereas poorly drained soils in groundwater discharge zones could contribute significant CH4 emissions. Climate change is projected to bring more summer precipitation extremes to subtropics, which may affect forest CH4 balance. Chinese forests often have a hilly topography with well‐drained hillslopes and pronounced groundwater discharge zones. Although different landscape elements are likely to have different source and sink functions for CH4, the climatic influence on CH4 budget at the catchment scale remains poorly studied. Here, we measured CH4 fluxes over three years along a topographic gradient in a subtropical forested catchment in SW China. CH4 fluxes exhibited a clear spatial pattern indicating moderate CH4 uptake or emission from the well‐drained soils on the hillslope (−5.8 to +1.0 kg CH4‐C·ha−1·year−1) and significant CH4 emission from the wetter soils in the groundwater discharge zone (94.3 to 479.5 kg CH4‐C·ha−1·year−1). Despite its small area contribution to the catchment (0.6%), the groundwater discharge zone emitted substantial amounts of CH4 in monsoonal summers, affecting the whole‐catchment budget. Hillslope soils showed weaker CH4 uptake or even turned into a small CH4 source under wet climatic conditions. Estimates of catchment‐scale CH4 budgets indicate that subtropical forest catchments can tip from a net CH4 sink in drier years to a net CH4 source in wetter years, highlighting the importance of interannual climate variabilities. Our findings suggest that subtropical forests under projected climate change could contribute a net CH4 source with consequences for the regional CH4 balance.