Variability in the expansion of trees and shrubs in boreal Alaska

Jedediah F. Brodie, Carl A. Roland, Sarah E. Stehn, Ekaterina Smirnova

Research output: Contribution to journalArticle

Abstract

The expansion of shrubs and trees across high-latitude ecosystems is one of the most dramatic ecological manifestations of climate change. Most of the work quantifying these changes has been done in small areas and over relatively recent time scales. These land-cover transitions are highly spatially variable, and we have limited understanding of the factors underlying this variation. We use repeat photography to generate a data set of land-cover changes in Denali National Park and Preserve, Alaska, stretching back a century and spanning a range of edaphic, topographic, and climatic conditions. Most land-cover classes were quite stable, with low probabilities of transitioning to other land-cover types. The advance of woody vegetation into low-stature tundra, and the spread of conifer trees into shrub-dominated areas, were both more likely at low elevations and in areas without permafrost. Permafrost also reduced the likelihood of herbaceous vegetation transitioning to woody cover. Exceptions to the general trend of relative stability included nearly all (96%) of the broadleaf forest–dominated areas being invaded by conifers, an expected successional trajectory, and many open gravel river bars (17.8%) transitioning to thick shrubs. These floodplain areas were distinctly not at equilibrium, as only 0.1% of shrub-dominated areas converted to gravel. Warming temperatures in coming decades and concomitant declines in the extent of permafrost are predicted to enhance the spread of woody vegetation in Denali further, but only by ~3%. Land-cover transitions, notably the rapid advance of trees and shrubs observed in other studies, could be less likely and more spatially heterogeneous here than in other high-latitude systems.

Original languageEnglish (US)
Article numbere02660
JournalEcology
Volume100
Issue number5
DOIs
StatePublished - May 1 2019
Externally publishedYes

Fingerprint

land cover
shrub
shrubs
permafrost
gravel
vegetation
conifers
coniferous tree
photography
tundra
floodplains
trajectories
preserves
floodplain
national parks
national park
warming
trajectory
climate change
timescale

Keywords

  • arctic
  • boreal
  • climate change
  • land cover
  • shrubification
  • succession
  • tree line

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Cite this

Variability in the expansion of trees and shrubs in boreal Alaska. / Brodie, Jedediah F.; Roland, Carl A.; Stehn, Sarah E.; Smirnova, Ekaterina.

In: Ecology, Vol. 100, No. 5, e02660, 01.05.2019.

Research output: Contribution to journalArticle

Brodie, Jedediah F. ; Roland, Carl A. ; Stehn, Sarah E. ; Smirnova, Ekaterina. / Variability in the expansion of trees and shrubs in boreal Alaska. In: Ecology. 2019 ; Vol. 100, No. 5.
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