Differential tree mortality in response to severe drought: Evidence for long-term vegetation shifts

Rebecca C. Mueller, Crescent M. Scudder, Marianne E. Porter, R. Talbot Trotter, Catherine A. Gehring, Thomas G. Whitham

Research output: Contribution to journalArticle

329 Citations (Scopus)

Abstract

1 Although drought frequency and severity are predicted to increase across numerous continental interiors, the consequences of these changes for dominant plants are largely unknown. Over the last decade, the south-western US has experienced six drought years, including the extreme droughts of 1996 and 2002, which led to widespread tree mortality across northern Arizona. 2 We examined the impact of these droughts on the co-dominant tree species of the pinyon-juniper woodland (Pinus edulis and Juniperus monosperma), a major vegetation type in the US. 3 Pinyon mortality following both droughts was 6.5-fold higher than juniper mortality. In addition, large pinyons suffered 2-6-fold greater mortality than small pinyons, a pattern associated with higher mortality of reproductively mature trees and survival of smaller pinyons resulting from facilitation by established vegetation. Differential mortality of large pinyons resulted in a vegetation shift such that the pinyon-juniper woodlands are becoming dominated by juniper, a species that is typical of lower elevations and more arid conditions. 4 Sites that experienced high pinyon mortality during the first drought suffered additional mortality during the second drought, so that reductions in tree densities and the resulting release from below-ground competition did not buffer surviving pinyons against additional mortality during the second drought. Such repeated mortality events also suggest that these stands may suffer chronic stress. 5 Reductions in biotic associations (e.g. avian seed dispersers, ectomycorrhizas and nurse plants) that will probably result from extreme mortality of large pinyons ensure that the observed vegetation shifts will be persistent. Because approximately 1000 species are associated with pinyon pine, the shift in the structure of these woodlands has large-scale community consequences.

Original languageEnglish (US)
Pages (from-to)1085-1093
Number of pages9
JournalJournal of Ecology
Volume93
Issue number6
DOIs
StatePublished - Dec 2005

Fingerprint

tree mortality
drought
mortality
vegetation
pinyon-juniper
woodlands
woodland
Juniperus monosperma
Pinus edulis
nurse plants
nurse plant
fold
continental interior
ectomycorrhizae
dry environmental conditions
facilitation
vegetation types
vegetation type
buffers
Pinus

Keywords

  • Climate change
  • Differential mortality
  • Drought
  • Facilitation
  • Juniperus monosperma
  • Pinus edulis

ASJC Scopus subject areas

  • Ecology

Cite this

Differential tree mortality in response to severe drought : Evidence for long-term vegetation shifts. / Mueller, Rebecca C.; Scudder, Crescent M.; Porter, Marianne E.; Talbot Trotter, R.; Gehring, Catherine A.; Whitham, Thomas G.

In: Journal of Ecology, Vol. 93, No. 6, 12.2005, p. 1085-1093.

Research output: Contribution to journalArticle

Mueller, Rebecca C. ; Scudder, Crescent M. ; Porter, Marianne E. ; Talbot Trotter, R. ; Gehring, Catherine A. ; Whitham, Thomas G. / Differential tree mortality in response to severe drought : Evidence for long-term vegetation shifts. In: Journal of Ecology. 2005 ; Vol. 93, No. 6. pp. 1085-1093.
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