|Dugas, William - TX AG EXPER STA|
|Hicks, Ralph - TX AG EXPER STA|
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 5, 1995
Publication Date: N/A
Interpretive Summary: During the past 150 years, shrubs which utilize the C3 photosynthetic pathway have invaded extensive areas of former grasslands where the C4 photosynthetic pathway predominates. We measured energy balance components of grass and shrub communities in the Chihuahuan Desert. Differences in surface energy balance components, e.g., net radiation, soil heat flux, and dlatent heat flux, were generally small and were more related to surface characteristics (e.g. leaf area) and water supply than to photosynthetic pathway or vegetation type. In this desert environment a high percentage of solar radiation is incident upon the soil surface and about 30% of total evapo-transpiration is made up by evaporation from the soil. Vegetation change has had a minimal effect on surface energy balances except where grasslands have changed to coppice mesquite dunes.
Technical Abstract: During the past 150 years, the C3 shrubs creosotebush (Larrea tridentata (DC.) Cov.), mesquite (Prosopis glandulosa (Torr.) Var. Glandulosa), and tarbush (Flourensia cernua DC.) have invaded extensive areas of former C4 grasslands in deserts of the southwestern United States. We measured energy balance components of these grass and shrub communities in the Chihuahuan Desert. Midday net radiation in the mesquite community was about 20% less than that in the others, where it was about equal. Midday soil heat flux was large in all communities and was greater in communities with lower leaf area. Midday and daily latent heat fluxes (or the evapotranspiration, ET) were about equal in all communities, except in the tarbush community where they were about 50% greater due to greater leaf area and water supply. The fraction of ET made up of soil evaporation varied from 0.3 to 0.6 and was greater in creosotebush and mesquite communities. Differences in surface energy balance components in plant communities in this desert environment were generally small and were more related to surface characteristics (e.g. leaf area) and water supply than to photosynthetic pathway or vegetation type.