Collaborative Research: Alternative leaf water use strategies in hot environments

Collaborative Research: Alternative leaf water use strategies in hot environments Collaborative Research: Alternative leaf water use strategies in hot environments Episodic heat waves that are increasing in duration, frequency and intensity will likely amplify plant thermal stress and mortality. For many plants, especially those occurring on the warm edge of a species distribution, temperature buffering is critical for maintaining leaf carbon balance. In hot environments where leaf function is vulnerable to impaired (Tcrit), plants must cool leaves below this limit (i.e. Tleaf < Tcrit). Transpiration can achieve this cooling, and notably could occur independent of changes in photosynthesis when conditions are thermally stressful, contrary to leading stomatal regulation models. Recent studies have reported such alternative water use strategies in several species, which then do not maximize carbon gain for a fixed level of stomatal conductance or hydraulic risk. However, the prevalence and drivers of these alternate water use strategies remain unknown. This project will quantify alternative water use behavior across a broad taxonomic range of arid-adapted plants as possible. The project will (1) determine the prevalence of alternative water use strategies across a diverse set of species via experimental manipulation of environments, (2) determine the trait predictors of this behavior, (3) develop optimality theory to predict when this behavior should occur, and lastly will validate predictions along a desert montane elevation gradient. Intellectual Merit This project will test a leading set of hypotheses for plant ecophysiological responses to hot and dry conditions, which are becoming increasingly prevalent in future climates. In doing so it will advance theory for stomatal regulation, a core topic in the fields of plant ecology and Earth system modeling. It will also provide one of the largest and most standardized datasets for plant responses to extreme environmental conditions, yielding a data resource of high value to other investigators. These findings can then be used to directly inform a revised representation of plant water use in Earth System Models. This representation will ultimately yield more useful predictions under climate change scenarios. Broader Impacts. The Broader Impacts will primarily take place along four directions: 1) evaluation of alternative water use strategies in Earth Systems Models (ESMs), 2) postdoctoral and student training, 3) public outreach, and 4) curriculum development / teaching activities. The fact that Earth Systems Models (ESMs) that use stomatal conductance do not account for alternative water use behavior suggests that estimates of carbon and water cycling in these ecosystems, and their feedbacks on hydrology, carbon storage and regional and global climate, are potentially biased. We will establish a steering committee as part of this project to develop guidelines for how current versions of the Community Land Model (CLM5), for example, could be revised to incorporate alternative water use behavior. The project will contribute to the training of one postdoctoral researcher, one graduate student, and 6 paid undergraduate interns. Students will be given opportunities to manage smaller components of the overall project and carry out their own independent investigations, as well as to contribute to larger data analyses and publications. The PIs have a track record of supporting underrepresented minority students through effective mentoring practices, and have had positive outcomes in terms of student retention and further career/education progression in STEM fields. Public outreach will focus on developing an outdoor exhibit for the Desert Botanical Garden reaching ~500K people/year. The bilingual display will engage visitors around the physiological costs of heat waves on plants and the ways in which plants regulate their temperatures through leaf morphology, hydraulic architecture, phenology and evaporative cooling. The interactive display will include live data streams of leaf temperatures from individual plants at the DBG having different leaf morphologies and plant life forms. Curriculum development will occur from a fall semester course at Arizona State Universitys Plant Biology and Conservation Program in the School of Life Sciences. The course will focus on identifying challenges and opportunities for plant conservation under changing environmental conditions. The three-credit course will combine classroom lectures with hands-on field training at the Desert Botanical Garden. All materials will be freely online for others to use in their learning and teaching.