Mary V. Price and Nickolas M. Waser. 2000. Responses
of subalpine meadow vegetation to four years of experimental warming. Ecological
Applications 10:811-823.
Abstract. Ecosystems at high elevations may be
especially sensitive to global warming, because productivity is limited
to a snow-free growing season and warming is expected to cause earlier snowmelt.
Here we report on vegetation responses to experimental warming in a subalpine
meadow in the Colorado Rocky Mountains. We found no evidence that the plant
community changed during 4 yr of warming. Species composition in warmed
plots did not change more through time than in control plots, nor did warmed
plots diverge from adjacent control plots through time. Contrary to an
earlier report, we found no evidence that warming facilitated adults or
seedlings of sagebrush, a shrub characteristic of lower-elevation ecosystems;
nor did it facilitate short-lived plant species as a group. Total vegetation
cover, as well as cover of graminoids, forbs, and shrubs, did not differ
between control and warmed plots, nor did species richness or species' distributions
along a small elevational gradient within each plot. Shrub cover tended
to increase more, and forb cover to decrease more, in warmed than in control
plots during one summer season, but not significantly so. This lack of
detectable plant community response contrasts with pronounced responses
to warming in some arctic and alpine ecosystems over similar time spans.
Warming in these ecosystems is thought to act indirectly via increased
mobilization of soil nutrients. One possible reason for the lack of response
in our system is that drying of soil limits microbial activity, photosynthesis,
and plant growth sooner in the season in warmed plots, cancelling out effects
of earlier snowmelt. If this is correct, and if summer precipitation patterns
are unchanged under global warming, then vegetation in arid high-elevation
ecosystems may change only slowly.