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Effects of long-term livestock grazing and habitat on understory vegetation

Bakker, Jonathan D. and Rudebusch, Faith and Moore, Margaret M. (2010) Effects of long-term livestock grazing and habitat on understory vegetation. Western North American Naturalist, 70 (3). pp. 334-344. ISSN 1527-0904


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Publisher’s or external URL: http://dx.doi.org/10.3398/064.070.0306


The herbaceous understory stratum contains most of the plant diversity in ponderosa pine (Pinus ponderosa P. & C. Lawson var. scopulorum Engelm.) forests of the American Southwest and provides critical food and habitat for many wildlife species. During the last century, this stratum has been affected by livestock grazing and by increased dominance of overstory trees. We sampled a unique grazing exclosure to examine the relative importance of long-term livestock grazing (grazed or ungrazed) and habitat (park or tree) on the understory community. We sampled 3 plots of 192 contiguous quadrats (each quadrat 0.5 m2) in each of the 4 treatment combinations, for a total of 2304 quadrats. Species-area curves were generated by aggregating quadrats into nonoverlapping areas at grain sizes of 0.5 to 576 m2. The effects of habitat and grazing on species density were evident at very different scales. Species density was higher in park than tree plots at scales ≤32 m2 but did not differ between habitats at larger scales. Species density differed minimally between grazed and ungrazed treatments at small grains, but grazed plots contained more species than ungrazed plots at larger grains. Grazing treatments differed at smaller grains (to 4–8 m2) than did habitats (to 32 m2), with respect to density of native species and graminoids. Grazed plots had more exotic species than ungrazed plots at all grain sizes, though few exotics were present. Twenty-two species were identified as indicator species associated with habitats and/or grazing treatments. Evaluations of plant community response to treatments would be improved by accounting for the grain at which data have been collected and analyzed and by identifying indicator species associated with various treatments. These data would enable more-informed conservation and management decisions.

Item Type: Article
ID number or DOI: 10.3398/064.070.0306
Keywords: Ponderosa pine (Pinus ponderosa), Grazing, Indicator species, Species-area curves, Hill plots, ERI Library
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
S Agriculture > SD Forestry
NAU Depositing Author Academic Status: Faculty/Staff
Department/Unit: College of Engineering, Forestry, and Natural Science > School of Earth Sciences and Environmental Sustainability
College of Engineering, Forestry, and Natural Science > School of Forestry
Date Deposited: 12 Feb 2016 22:37
URI: http://openknowledge.nau.edu/id/eprint/1435

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