Some Impacts of 2,4,5-T on a Mesquite Duneland Ecosystem in Southern New Mexico: A Synthesis

Abstract

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Effects of fire, grazing, and the presence of shrubs on Chihuahuan desert grasslands

“…Biomass of primarily perennial grasses was less in areas where shrubs were present compared to areas where they had been complete-killed with herbicide (Gibbens et al, 1986). Shrubs such as P. glandulosa may outcompete forbs and grasses for moisture during excessively dry conditions because they possess expansive underground root systems that can proliferate rapidly and spread over longer distances than herbs (Heitschmidt et al, 1988;Gile et al, 1997).…”

“…Compared to the summer rainy season, winter precipitation occurs at lower intensity and covers larger areas (Gibbens et al, 1992). Mean monthly maximum and minimum temperatures occur in June (363C) and January (133C) respectively (Gibbens et al, 1986;1992;Reynolds et al, 1999). Though the frost-free period averages 200 days, the effective growing season is only 90 days (Gibbens et al, 1992).…”

“…These soils are underlain by a layer of calcium bicarbonate (caliche) at soil depths from a few centimeters to '1 m (Gibbens et al, 1986). Desert grasslands of the JER were once dominated by C 4 perennial grasses such as B. eriopoda.…”

“…Further, overgrazing has not only locally expanded shrub distributions and abundances, but has also contributed to soil erosion, making regrowth, reproduction, and establishment of perennial grasses increasingly difficult (Hennessy et al, 1983;Schlesinger et al, 1990). The presence of shrubs within existing desert grasslands may adversely affect the growth of dominant perennial grasses, especially during periods of drought (Scifres & Polk, 1974;Dahl et al, 1978;McDaniel et al, 1982;Herbel et al, 1983;Gibbens et al, 1986). When precipitation is equivalent to or greater than the long-term average, grazing activities, rather than shrub dominance, may have greater impact on recovery of indigenous herbaceous species (Warren et al, 1996).…”

Water controls on nitrogen transformations and stocks in an arid ecosystem

“…Topography is flat (1-3% slopes) and soils are coarse-textured, well-drained, sandy loams (Typic Paleorthids) (Soil Survey Staff 1999). A layer of calcium carbonate is often found at depths from 64-76 cm (Herbel et al 1972, Gibbens et al 1986). …”