PDF(Pubmed)
Abstract：
Unique ecosystems distributed in alpine areas of the Qinghai-Tibetan Plateau play important roles in climate change mitigation, local food supply, and conservation of species diversity. To understand the water use efficiency (WUE) of this fragile and sensitive region, this study combined observed data from the eddy covariance system and the Shuttleworth-Wallace (S-W) model to measure the continuous mass exchange, including gross primary productivity (GPP), evapotranspiration (ET), and canopy transpiration (T) throughout 2 or 3 years (2016-2018) in three common alpine ecosystems (i.e., alpine steppe, alpine meadow, and alpine swamp). These ecosystems represent a water availability gradient and thus provide the opportunity to quantify environmental and biological controls on WUE at various spatiotemporal scales. We analyzed the ecosystem WUE (WUEe; defined as the ratio of GPP to ET) and canopy WUE (WUEc; defined as the ratio of GPP and canopy T). It was found that the yearly WUEe was 1.40, 1.63, and 2.16 g C kg-1 H2O, and the yearly WUEc was 8.93, 2.46, and 5.19 g C kg-1 H2O in the three typical ecosystems, respectively. The controlling factors of yearly WUE diverged between WUEe and WUEc. We found that plant functional group proportion (e.g., gramineous and Cyperaceae) highly explained the yearly WUEe variation across sites, and a good correlation was observed between community species diversity and WUEc. These findings suggest that community composition and trait change are critical in regulating WUEe and WUEc across different alpine ecosystems and that the regulation mechanisms may differ fundamentally between WUEe and WUEc.
摘要：
青藏高原高寒地区分布的独特生态系统在减缓气候变化中起着重要作用。当地食品供应,保护物种多样性。为了了解这个脆弱和敏感区域的用水效率(WUE)，这项研究结合了来自涡度协方差系统和Shuttleworth-Wallace（S-W）模型的观测数据来测量连续质量交换，包括毛初级生产力(3GPP)，蒸散量（ET），在三个常见的高山生态系统中，在2或3年内(2016-2018年)和冠层蒸腾作用(T)(即，高山草原，高山草甸,和高山沼泽）。这些生态系统代表了水的可用性梯度，因此提供了在各种时空尺度上量化对WUE的环境和生物控制的机会。我们分析了生态系统WUE（WUEe；定义为GMP与ET的比率）和冠层WUE（WUEc；定义为GMP与冠层T的比率）。发现每年的WUEe为1.40、1.63和2.16gCkg-1H2O，在三个典型的生态系统中，每年的WUEc分别为8.93、2.46和5.19gCkg-1H2O，分别。年度WUE的控制因素在WUEe和WUEc之间存在差异。我们发现植物官能团比例(例如，禾本科和莎草科）高度解释了站点之间的年度WUEe变化，群落物种多样性与WUEc之间具有良好的相关性。这些发现表明，群落组成和性状变化对于调节不同高山生态系统中的WUEe和WUEc至关重要，并且WUEe和WUEc之间的调节机制可能根本不同。
