Satellite and Station Observations Demonstrate Water Availability's Effect on Continental-Scale Evaporative and Photosynthetic Land Surface Dynamics
Satellite and Station Observations Demonstrate Water Availability's Effect on Continental-Scale Evaporative and Photosynthetic Land Surface Dynamics
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DOI：
10.1029/2018wr023726
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发表时间：
2019-01-01
影响因子：
5.4
通讯作者：
Entekhabi, Dara
中科院分区：
文献类型：
--
作者：
Gianotti, Daniel J. Short;Rigden, Angela J.;Entekhabi, Dara
蒸散和光合碳吸收都受到水资源的限制，假定水有限和水独立，但能量有限的制度。我们调查水的可用性与蒸发通量和光合措施在大陆尺度上使用地面和卫星观测的关系。观察驱动的方法是独立于先前的基于模型的估计。我们发现水有限和水独立的制度，能源和碳循环过程中的空间和时间的聚合，在整个生态水文区域的水限制关系的差异，和更一致的迹象，在光合作用比蒸发过程中的水限制。生态系统水分利用效率对水分有效性的响应在时间和空间上一般随干旱状态变化，但在时间异常上表现为负相关。从卫星和气象站的数据中，我们发现了这些过程与可用水量之间的简单关系。尽管蒸发和CO2吸收是通过植物叶片的水分损失联系在一起的，但我们发现这些与土壤有效水量之间的关系是不同的;似乎植物CO2吸收对湿润和干燥环境中的有效水量同样敏感，而蒸发在干燥环境中更为敏感。在美国西部，景观中用于类似光合作用的水量随着土壤湿度的变化而变化，但在美国东部保持相对恒定。
Evapotranspiration and photosynthetic carbon uptake are both constrained by water availability, with presumed water-limited and water-independent but energy-limited regimes. We investigate water availability's relationships with evaporative fluxes and photosynthetic measures at continental scale using surface and satellite-based observations. The observation-driven approach is independent of prior model-based estimates. We find water-limited and water-independent regimes for both energy and carbon cycle processes in spatial and temporal aggregate, differences in water-limitation relationships across ecohydrological regions, and more consistent signs of water limitation in photosynthetic than evaporative processes. Ecosystem water use efficiency's response to water availability changes in sign with aridity state across time and space generally but shows negative correlations in temporal anomalies.Plain Language Summary Evaporation and plant CO2 uptake both require water to be available at the land surface. From satellite and weather station data, we find simple relationships between these processes and the amount of available water. Even though evaporation and CO2 uptake are linked through water loss from plant leaves, we find that the relationships between each of these and the amount of available soil water are different; it seems that plant CO2 uptake is similarly sensitive to the amount of available water, in wet and dry environments, while evaporation is much more sensitive in dry environments. The amount of water used in the landscape for similar amounts of photosynthesis changes with soil wetness in the Western United States but remains relatively constant in the eastern United States.