Postdoctoral Fellowship: CREST-PRP: Ecophysiological response of tidal freshwater tree ecosystem engineers to chronic thermal, hydric, and salinity stressors in the Caribbean.

University Of Puerto Rico-Rio Piedras, San Juan PR

Investigators

Abstract

In tropical ecosystems the weather is typically stable and warm but in the past decade climate change has been causing changes in temperature and shifts in rain and sea level in coastal wetlands that are impacting tropical flora and fauna. Lacking tools to adjust to these changes, tropical plants might struggle to survive. This study will investigate how two tree species, Pterocarpus officinalis and Dalbergia ecastaphyllum, cope with changes in temperatures and water supply and how these changes are affecting their physiology. The study site is located in the Corredor Ecológico del Noreste, a natural reserve in the Caribbean that represents freshwater coastal wetlands. Working with natural resource managers, community, and scientists, data will be collected to characterize the effects of climate change on these trees with the goal of advance knowledging that can be applied to inform management decisions about coastal wetlands restoration. In the past decade, Puerto Rico and the broader Caribbean region have witnessed a historical increase in temperature. Trends suggest that this warming trajectory will continue, accompanied by other climatic extremes, including rising sea levels, extreme precipitation events, and intensified atmospheric disturbances. Coastal tropical vegetation is in a perilous situation, where in the context of a warmer planet and rising sea levels, vegetation might not have the physiological mechanisms for acclimation. This study’s goal is to assess the ecophysiological responses of nitrogen-fixing species in tidal freshwater wetlands in response to warmer temperatures and increased salinity under the same mesoclimate conditions. The research will investigate 1) how warmer climate and increased salinity affects photosynthesis and regulation of osmotic balance, and 2) how these environmental changes affect activity and efficiency of nitrogen fixation. Using an interdisciplinary approach involving plant physiology, ecology, climate change science and metabolomics, the study will include field observations of two tree species, Pterocarpus officinalis and Dalbergia ecastaphyllum, that share the same mesoclimate but different hydrologic conditions, and greenhouse experiments in which air temperature and saline conditions will be modified. Data examined will include light and temperature response curves to assess leaf thermal tolerance, plant morphological traits, hydraulic conductance, osmotic potential, 13C and 15N isotopic analyses for nitrogen fixation, as well as nutrient analysis and non-targeted metabolomic analyses to create a profile of metabolites related to salt stress and temperature changes. The combined approach will be applicable to informing plant selection in conservation management efforts, thus enhancing the potential benefits these critical ecosystems provide. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.