Temporal and among-site variability of inherent water use efficiency at the ecosystem level
Temporal and among-site variability of inherent water use efficiency at the ecosystem level
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DOI：
10.1029/2008gb003233
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发表时间：
2009-06-11
影响因子：
5.2
通讯作者：
Wohlfahrt, G.
中科院分区：
文献类型：
--
作者：
Beer, C.;Ciais, P.;Wohlfahrt, G.
对陆地生态系统和大气之间二氧化碳和水蒸气净交换的半小时测量提供了生态系统一级和每日至年度时间尺度上的初级生产总值和蒸散量估计数。这些量的比率代表生态系统水利用效率。它与平均日光蒸气压差（VPD）相乘，得到一个我们称之为“固有水利用效率”（IWUE*）的量。IWUE* 对环境条件的依赖性表明，生态系统生理可能会适应性调整，以应对不断变化的环境。IWUE* 在一系列植物功能类型和气候条件下的43个地点进行分析。IWUE* 在短期中度干旱条件下增加。平均每年IWUE* 变化的因素3之间的所有网站。这部分是由于土壤水分在田间容量，特别是在落叶阔叶林。冠层光截获设定了冠层光合作用的上限，并解释了草本生态系统和万年青针叶林之间年度IWUE* 的一半差异。IWUE* 的知识提供了有价值的改进生态系统过程模型中的碳和水耦合的表示。
Half-hourly measurements of the net exchanges of carbon dioxide and water vapor between terrestrial ecosystems and the atmosphere provide estimates of gross primary production (GPP) and evapotranspiration (ET) at the ecosystem level and on daily to annual timescales. The ratio of these quantities represents ecosystem water use efficiency. Its multiplication with mean daylight vapor pressure deficit (VPD) leads to a quantity which we call "inherent water use efficiency" (IWUE*). The dependence of IWUE* on environmental conditions indicates possible adaptive adjustment of ecosystem physiology in response to a changing environment. IWUE* is analyzed for 43 sites across a range of plant functional types and climatic conditions. IWUE* increases during short-term moderate drought conditions. Mean annual IWUE* varied by a factor of 3 among all sites. This is partly explained by soil moisture at field capacity, particularly in deciduous broad-leaved forests. Canopy light interception sets the upper limits to canopy photosynthesis, and explains half the variance in annual IWUE* among herbaceous ecosystems and evergreen needle-leaved forests. Knowledge of IWUE* offers valuable improvement to the representation of carbon and water coupling in ecosystem process models.