The movement of water from soils, through plants, and into the atmosphere via transpiration, is a critical component of the global hydrologic cycle. When and where plants take up soil moisture through their roots varies considerably between species, ecosystems, and climates. Previous research has demonstrated that some species of plants are intensive water users that quickly exploit any available soil moisture, while other plants are extensive water users that extract water more slowly and may persist in withdrawing water at lower soil moisture levels. Quantifying the strategies that plants employ to regulate their water use is needed to accurately model soil moisture dynamics and the productivity of natural and agricultural systems. Plant ecophysiologists have examined the water potentials at which plant stomata are fully open and closed, and these critical hydraulic thresholds have now been characterized for a number of plants, especially important crop and tree species. The soil water potentials at which plants alter stomata behavior represent specific plant strategies, and measurements in both natural and agricultural settings have revealed a wide variation. Land surface models typically also include a parameterization of these hydraulic thresholds, with these values broadly fixed for each land use type. However, we lack a global assessment of these plant water use strategies, and it is not known how much variability exists in water use strategies both within and across land cover and plant functional types.
This is a global project funded by NASA.