RAPID: Using a natural extreme freeze in New Mexico to test predictions regarding the physiological basis of freezing tolerance in natural populations.

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In plants, like other organisms, physiological limits define environmental conditions allowing survival and growth. For most species, especially evergreens, the rare extremes of local climate may exceed physiological limits, killing plants or severely limiting their function. The effects of extreme events can persist for decades, affecting the ecological (growth, reproduction, species composition, etc.) and sociological (aesthetic qualities, land value, freshwater, etc.) functions of that ecosystem. This project will test predictions from past measurements of the physiological limits of creosotebush (Larrea tridentata), a widespread evergreen desert shrub dominating millions of acres in the southwest, following an extreme freeze in central and southern New Mexico in February 2011. The project will measure freezing damage and recovery of creosotebush in central and southern NM, test the ability of characteristics identified in recent research to predict the damage caused by the natural freeze and, use satellite images to quantify the broad patterns of plant damage (measured as plant canopy greenness) throughout the season and link them to our present understanding of the physiological limits of creosotebush. We expect known physiological limits will explain immediate post-freeze damage but mortality in plot and satellite measurements will be reduced by regrowth from roots. This project will improve our understanding and ability to predict plant responses to extreme events and the large-scale effects of these responses. We need to understand the response to extreme events because ongoing climate change may alter them and thus their effect on vegetation. This project will train a postdoctoral scientist and two graduate students and results will be disseminated to primary and undergraduate students and the general public.