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

Jonathan D. Bakker, Faith Rudebusch, Margaret M Moore

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)334-344
Number of pages11
JournalWestern North American Naturalist
Volume70
Issue number3
DOIs
StatePublished - Oct 2010

Fingerprint

understory
long term effects
livestock
grazing
vegetation
habitat
habitats
Pinus ponderosa
indicator species
Southwestern United States
grain size
overstory
species-area relationship
effect
community response
plant communities
wildlife
indigenous species
native species
plant community

Keywords

  • Hill plots
  • indicator species analysis
  • livestock grazing
  • Pinus ponderosa
  • species-area curves

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology

Cite this

Effects of long-term livestock grazing and habitat on understory vegetation. / Bakker, Jonathan D.; Rudebusch, Faith; Moore, Margaret M.

In: Western North American Naturalist, Vol. 70, No. 3, 10.2010, p. 334-344.

Research output: Contribution to journalArticle

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