Kilgore, Jason , Telewski, Frank W. .
Influence of cold tolerance on upper elevation range limits in isolated mountain island Ponderosae.
Upper elevational range limits in mountain systems are determined by physiological tolerance to dynamic and shifting environmental conditions, especially cold. In this study, we investigated the influence of cold in the field, greenhouse, and laboratory on two closely related species of Ponderosae, Pinus ponderosa var. scopulorum and P. arizonica, whose elevational distributions overlap in the Santa Catalina Mountains of the American Southwest. In winter, field-grown saplings did not differ by species or elevation in predawn photosynthetic efficiency, measured by chlorophyll fluorescence, while midday efficiency was higher for sympatric P. ponderosa var. scopulorum. Following complete soil freezing, potted P. ponderosa var. scopulorum seedlings had higher photosynthetic efficiency than P. arizonica seedlings. Greenhouse container-grown seedlings of P. ponderosa var. scopulorum had higher pre-freezing photosynthetic efficiency during a 7-week acclimation period and at the third week of simulated winter than P. arizonica seedlings. No significant differences in photosynthetic efficiency or cambial mortality were observed between species during the acclimation and deacclimation phases. However, P. ponderosa var. scopulorum seedlings were 5° C more cold hardy in whole-plant freeze tests during the simulated winter. The lower cold tolerance of P. arizonica during winter conditions restricts its survival within the higher elevation distribution of P. ponderosa var. scopulorum. In spite of differential distributions, a 3° C increase in local mean winter temperature predicted by both IPCC and HadCM2 climate models may drastically increase the elevation at which P. arizonica can survive. Other species on mountain islands may face this same opportunity and pressing need for rapid plant migration as tolerance for conditions at the lower elevation limit constrain survival. We predict climate change to disproportionately affect species in refugial mountain islands by eliminating already limited high elevation habitable niche space thus leading to extirpation of these species. Land management agencies will soon face these conservation issues.
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1 - Michigan State University, Department of Plant Biology, W.J. Beal Botanical Garden, 166 Plant Biology Laboratory, East Lansing, MI, 48824, USA
Presentation Type: Poster:Posters for Topics
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM