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United States Department of Agriculture

Agricultural Research Service

Title: Structure and Function of C3 and C4 Chihuahuan Desert Plant Communities. Standing Crop and Leaf Area Index

Authors
item Gibbens, Robert
item Hicks, Ralph - TX AG EXPER STA
item Dugas, William - 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, native shrubs have invaded and dominated extensive areas of former grasslands in deserts of the southwestern United States. This vegetation shift has caused large changes in several aspects of the structure and function of these plant communities. To aid in the interpretation of energy fluxes in these communities we measured above- ground biomass and leaf area in grass and shrub communities on sandy and clay soils in the Chihuahuan Desert. Above-ground live biomass ranged from 700 to 1600 lbs/acre in grass communities and from 2500 to 3100 lbs/acre in shrub communities. Leaf area in shrub communities was about twice that of grass communities. The greatest leaf area was found in a shrub community on a clay soil that also had a herbaceous understory. Shrubs are successful in desert environments in part because they are better equipped to utilize impinging energy than are grasses.

Technical Abstract: During the past 150 years, native C3 shrubs have invaded and dominated extensive areas of former C4 grasslands in deserts of the southwestern United States. This vegetation shift has caused large changes in several aspects of the structure and function of these plant communities. We measured above-ground biomass and leaf area index (LAI) in grass and shrub plant communities and canopy cover and shrub density in shrub communities on sandy and clay soils in the Chihuahuan Desert. Above-ground, live biomass ranged from 800 to 1800 kg ha**-1 for grass communities and from 2,800 to 3,500 kg ha**-1 for shrub communities. The LAI in grass communities was typically 0.1 to 0.2 and in shrub communities was 0.3 to 0.4. The greatest LAI was in the shrub community on a clay soil that also had a herbaceous understory. Shrub canopy cover varies from 17% (tarbush) to 33% (mesquite). On sandy soils, this vegetation shift has resulted in a areplacement of herbaceous vegetation with shrubs, while on clay soils herbaceous vegetation has remained. Biomass and LAI differences have implications for energy balance measurements described in the second paper of this series.

Last Modified: 7/27/2014
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