美国西弗吉尼亚大学Kannenberg, Steven A.近日的研究揭示了土壤湿度在调节旱地生态系统碳和水通量中的主导作用。这一研究成果发表在2024年1月4日出版的国际学术期刊《自然—地球科学》上。
研究综合了美国西部地区的涡动相关数据、遥感产品和地表模式输出，以量化了旱地总初级生产力和蒸散量对各种水文气象驱动因素的敏感性。研究发现，从涡度协方差得到的总初级生产力和蒸散量对土壤湿度波动最敏感，对蒸发压差的敏感性较低，对气温和光照的敏感性很小或没有。研究还发现，遥感数据准确地捕获了涡旋相关通量对土壤湿度的敏感性，但在很大程度上高估了对大气驱动因素的敏感性。
相比之下，地表模型低估了约45％的总初级生产力对土壤湿度波动的敏感性。在关于不断增加的蒸发压差在气候变化中的作用的争论中，研究人员得出结论，土壤湿度是美国旱地碳—水通量的主要驱动因素。因此，在遥感通量产品中，既要改进模型对土壤水分限制的表征，又要更真实地表征大气驱动因素对旱地植被的影响。
据介绍，旱地由于其在空间和时间上的巨大异质性，对全球碳循环和水循环的年际变化具有强烈影响。生态系统通量的这种可变性对理解其主要驱动因素提出了挑战。
附：英文原文
Title: Dominant role of soil moisture in mediating carbon and water fluxes in dryland ecosystems
Author: Kannenberg, Steven A., Anderegg, William R. L., Barnes, Mallory L., Dannenberg, Matthew P., Knapp, Alan K.
Issue&Volume: 2024-01-04
Abstract: Drylands exert a strong influence over global interannual variability in carbon and water cycling due to their substantial heterogeneity over space and time. This variability in ecosystem fluxes presents challenges for understanding their primary drivers. Here we quantify the sensitivity of dryland gross primary productivity and evapotranspiration to various hydrometeorological drivers by synthesizing eddy covariance data, remote sensing products and land surface model output across the western United States. We find that gross primary productivity and evapotranspiration derived from eddy covariance are most sensitive to soil moisture fluctuations, with lesser sensitivity to vapour pressure deficit and little to no sensitivity to air temperature or light. We find that remote sensing data accurately capture the sensitivity of eddy covariance fluxes to soil moisture but largely over-predict sensitivity to atmospheric drivers. In contrast, land surface models underestimate sensitivity of gross primary productivity to soil moisture fluctuations by approximately 45%. Amid debates about the role of increasing vapour pressure deficit in a changing climate, we conclude that soil moisture is the primary driver of US dryland carbon–water fluxes. It is thus imperative to both improve model representation of soil water limitation and more realistically represent how atmospheric drivers affect dryland vegetation in remotely sensed flux products.
DOI: 10.1038/s41561-023-01351-8
Source: https://www.nature.com/articles/s41561-023-01351-8