| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4392864 | Journal of Arid Environments | 2015 | 12 Pages |
•ET/PPT determines runoff and recharge in semiarid environments.•Flux tower ET data were scaled to wide areas with satellite imagery for grasslands, shrublands and mesquite savannas.•ET increased linearly with PPT across plant communities but the slope was less than 1.0.•Encroachment of mesquites into grasslands and replacement of native by introduced grasses did not alter ET/PPT.•Conversion of a grassland into a creosote shrubland did result in lower ET/PPT.
Evapotranspiration (ET) and the ratio of ET to precipitation (PPT) are important factors in the water budget of semiarid rangelands and are in part determined by the dominant plant communities. Our goal was to see if landscape changes such as tree or shrub encroachment and replacement of native grasses by invasive grasses impacted ET and ET/PPT and therefore watershed hydrology in this biome. We determined ET and ET/PPT for shrublands, grasslands and mesquite savannas in southern Arizona at five moisture flux towers and determined the environmental factors controlling ET in each plant community. We then scaled ET over areas of 4–36 km2, representing homogeneous patches of each plant community, using the Enhanced Vegetation Index (EVI) from MODIS sensors on the Terra satellite. Over wide areas, estimated ET/PPT projected from MODIS EVI ranged from 0.71 for a sparsely-vegetated shrub site to 1.00 for grasslands and mesquite savannas. The results did not support hypotheses that encroachment of mesquites into grasslands or that replacement of native grasses with introduced Eragrostis lehmanniana (lehmann lovegrass) have increased rangeland ET.
