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Riparian area response to altering season of use and intensity of cattle grazing in the Gila National Forest, New Mexico.
LUCAS, RICHARD1, BAKER, TERRELL2, WOOD, M3, 1 2 3
ABSTRACT- Preserving riparian ecosystems and managing their sustainable use depends on our understanding of these complex systems. Scientific literature has failed to adequately address the effects of livestock grazing on riparian areas in the American southwest. Most of the literature is observational research, based on unreplicated experiments, and compares heavily grazed areas to areas from which livestock have been completely excluded. The current study in the Black Range of the Gila National Forest compares effects of a range of seasons (winter, spring and summer) and a range of intensities (light, moderate and none) of cattle grazing on young Cottonwood (Populus angustifolia) populations, stream bank morphology and sedimentation rates in two southwestern riparian areas. Twig length measurements, stream-cross sections and rainfall simulations were done before and after grazing treatments to estimate the effect each treatment had on the riparian areas. Cottonwoods on lightly grazed plots received 17% (SE 0.009) use and on moderately grazed plots 29% (SE 0.011) use. Lightly and moderately grazed plots were significantly different (P < 0.0033, P < 0.0001 respectively) from ungrazed plots which experience net growth of 1.2% (SE 0.011). Cottonwood use on grazed plots were also compared with each other and found to be significantly different (P < 0.0132). Stream cross-sections and sedimentation rates were not significantly different between treatments. This leads us to believe perhaps riparian ecosystems are more robust than previously thought.
KEY WORDS: riparian, Populus angustifolia, cattle grazing