Effects of livestock grazing exclosure on aquatic macroinvertebrates in a montane stream, New Mexico
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Authors: J. N. Rinne
Date: 1988
Journal: Great Basin Naturalist
Volume: 48
Number: 2
Pages: 146-153
Summary of Methods: Ten years after livestock grazing exclosures were created, macroinvertebrate populations were sampled to determine the effects of this management on stream quality. The measured water quality and visual estimates of riparian vegetation and bank stability were lower in the grazed areas than the ungrazed areas, which probably affected the macroinvertebrate communities. Macroinvertebrate species, densities, and biomass differed between the grazed and ungrazed areas; where the grazed areas had greater populations of more tolerant macroinvertebrates. Although the data suggests that grazing is the cause of the differences in the macroinvertebrate communities, no pre-treatment data was collected prior to the building of the exclosures and it is not possible to imply direct cause and effect.
Article Summary / Main Points: : Densities of macroinvertebrates were greater in stream reaches within grazed areas during the first two years of the study. Macroinvertebrate biomass estimates were greater along grazed stream reaches than ungrazed during the first year of the study but were not different during the next two years. Grazed areas had greater populations of more tolerant macroinvertebrates. The tolerance quotient was higher on ungrazed sites than on grazed sites during the first year and the reverse during the second year. Biotic condition indices was greater along the ungrazed reaches than grazed reaches of stream.
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: macroinvertebrate tolerance, water quality, indicator species, grazing exclosure, riparian vegetation, biotic condition indices
Annotation: The results from this three year non-replicated study are only applicable to this stream in northwestern New Mexico. The trends may be the same for a wide variety of riparian areas and streams but the lack of replication limits the wide spread applicability of these results. As with all grazing research results apply most directly to similar landscapes, seasons, livestock types and weather conditions. Although the data suggests that grazing is the cause of the differences in the macroinvertebrate communities, no pre-treatment data was collected prior to the building of the exclosures and it is not possible to imply direct cause and effect. Future research on the effects of livestock grazing on stream environments and biota should consider pre-treatment information collected prior to the building of exclosures and also long-term study design. The results of grazing exclusion on fish populations are reported in Rinne 1988 (N. A. J. Fish Manage 8: 240-247) available in the RSIS database. The Great Basin Nat changed its name to West N Am Naturalist in 2000.
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