Influence of livestock grazing and climate on pinyon pine (Pinus edulis) dynamics

Nichole N. Barger, Henry D. Adams, Connie Woodhouse, Jason C. Neff, Gregory P. Asner

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Over the last century there has been marked expansion and infilling of pinyon (Pinus spp.)juniper (Juniperus spp.) woodlands into grassland and shrubland ecosystems across the western United States. Although range expansions in pinyon-juniper populations have been documented with changing climate throughout the Holocene, over the last century, local scale impacts such as livestock grazing, changes in fire regimes, and increasing atmospheric CO 2 concentrations are thought to be more recent drivers of pinyon-juniper woodland distribution. Our objective was to examine the role of historical livestock grazing relative to past climate in regulating pinyon (Pinus edulis Engelm.) recruitment and growth over the last century in a persistent pinyon-juniper woodland. We compared pinyon dynamics on a remote mesa site, minimally grazed by domestic livestock, to a nearby historically grazed site in southeastern Utah. The presence of a significant number of old trees (>200 yr) at both sites suggests that these populations were well established prior to the 20th century. No differences in pinyon density or basal area were observed between grazed and ungrazed sites. Stand age structure data showed that pinyon recruitment across these sites was highly synchronous, with a large recruitment event occurring during the early 1900s; 17 of the pinyons on both sites dated to the 1920s. Climatic conditions during this decade were consistently cool and wet-conditions known to support enhanced recruitment and growth in pinyon pines. Pinyon growth was also strongly synchronous across sites (r0.96). Pinyon growth was significantly correlated with winter/spring precipitation and negatively correlated with June temperature. Taken together, our results suggest that past climate may be more important in structuring pinyon populations than historical land use in these persistent pinyon-juniper woodlands. Given future climate projections of increasing temperature and more extended drought periods, regeneration of pinyon populations following the recent regional-scale dieback may be slow. Moreover, prolonged drought combined with potentially slow regeneration times for pinyon under future climate scenarios could result in substantial declines in pinyon populations across the region, a result that land managers should consider when planning for future restoration treatments in persistent pinyon-juniper woodlands.

Original languageEnglish (US)
Pages (from-to)531-539
Number of pages9
JournalRangeland Ecology and Management
Volume62
Issue number6
DOIs
StatePublished - Nov 2009
Externally publishedYes

Fingerprint

pinyon-juniper
Pinus edulis
livestock
woodland
grazing
woodlands
climate
regeneration
Pinus
drought
wooded grasslands
Juniperus
wet environmental conditions
dieback
fire regime
Western United States
range expansion
shrubland
basal area
age structure

Keywords

  • Age structure
  • Climate change
  • Grand StaircaseEscalante National Monument
  • Land use change
  • Pinyon
  • Tree growth
  • Tree ring
  • Woodland expansion
  • Woody encroachment

ASJC Scopus subject areas

  • Ecology
  • Animal Science and Zoology
  • Nature and Landscape Conservation
  • Management, Monitoring, Policy and Law

Cite this

Influence of livestock grazing and climate on pinyon pine (Pinus edulis) dynamics. / Barger, Nichole N.; Adams, Henry D.; Woodhouse, Connie; Neff, Jason C.; Asner, Gregory P.

In: Rangeland Ecology and Management, Vol. 62, No. 6, 11.2009, p. 531-539.

Research output: Contribution to journalArticle

Barger, Nichole N. ; Adams, Henry D. ; Woodhouse, Connie ; Neff, Jason C. ; Asner, Gregory P. / Influence of livestock grazing and climate on pinyon pine (Pinus edulis) dynamics. In: Rangeland Ecology and Management. 2009 ; Vol. 62, No. 6. pp. 531-539.
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