Global-scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO2 sink. However, such analyses are poorly constrained by measured CO2 exchange in drylands. Here we address this observation gap with eddy covariance data from 25 sites in the water-limited Southwest region of North America with… More

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The eddy covariance technique is a widely used and accepted method to quantify ecosystem-scale mass and energy fluxes. Eddy covariance measurements of evaporation, also known as evapotranspiration, are used to determine local, regional and global water budgets, calibrate and validate land surface models, and acquire understanding of ecosystem processes. This paper assesses the accuracy of… More

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The vegetation in the core region of the North American monsoon (NAM) system changes dramatically after the onset of the summer rains so that large changes may be expected in the surface fluxes of radiation, heat, and moisture. Most of this region lies in the rugged terrain of western Mexico and very few measurements of… More

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Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide range of structural diversity in semiarid ecosystems. Therefore, we used eddy covariance measurements to quantify how net ecosystem production of carbon dioxide (NEP) differed with… More

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Information about the ratio of transpiration (T) to total evapotranspiration (T/ET) is related to critical global change concerns, including shrub encroachment and non-native species invasion. In this study, a new approach was developed to partition measurements of ET into daily evaporation (ED) and daily transpiration (TD) in a semiarid watershed based on the low-cost addition… More

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Global modeling efforts indicate semiarid regions dominate the increasing trend and interannual variation of net CO2 exchange with the atmosphere, mainly driven by water availability. Many semiarid regions are expected to undergo climatic drying, but the impacts on net CO2 exchange are poorly understood due to limited semiarid flux observations. Here we evaluated 121 site-years… More

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Despite their prevalence, little attention has been given to quantifying arid land soil and ecosystem carbon fluxes over prolonged, annually occurring dry periods. We measured soil [CO2] profiles and fluxes (Fs) along with volumetric soil moisture and temperature in bare interplant canopy soils and in soils under plant canopies over a three-month hot and dry… More

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