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The canopies of woody plants in semiarid ecosystems modify the microclimate beneath and around them, with canopy patches usually having lower soil temperatures than intercanopy patches. However, lacking are studies that have evaluated how heterogeneity in soil temperature, induced by woody plant canopies, influences soil evaporation rates and the consequent effects on plant-available water. Soil temperatures were measured and soil evaporation rates were estimated for canopy and intercanopy patches in a semiarid pinyon-juniper woodland (Pinus edulis and Juniperus monosperma) in northern New Mexico. Soil temperature was measured at 2-cm depths in four canopy and four intercanopy locations during 1994. Maximum soil...
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Increases in the abundance or density of woody plants in historically semiarid and arid grassland ecosystems have important ecological, hydrological, and socioeconomic implications. Using a simplified water-balance model, we propose a framework for conceptualizing how woody plant encroachment is likely to affect components of the water cycle within these ecosystems. We focus in particular on streamflow and the partitioning of evapotranspiration into evaporation and transpiration. On the basis of this framework, we suggest that streamflow and evaporation processes are affected by woody plant encroachment in different ways, depending on the degree and seasonality of aridity and the availability of subsurface water....
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In many semiarid regions, runoff and erosion differ according tovegetation patch type. These differences, although hypothesized tofundamentally affect ecological processes, have been poorly quanti-fied. In a semiarid pinon-juniper woodland [Pinus edulis Engelm.and Juniperus monosperma (Engelm.) Sarg.] in northern New Mexico,we measured runoff and erosion from the three patch types thatcompose these woodlands: Canopy patches (those beneath woodyplants), vegetated patches in intercanopy areas, and bare patches inintercanopy areas. The bare intercanopy patches exhibited the highestrates, followed by vegetated intercanopy patches and then by canopypatches. Large convective summer storms, though relatively infre-quent,...
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