Ecophysiological vulnerability to climate change : water stress responses in four tree species from the central mountain region of Veracruz, Mexico

Ecophysiological vulnerability can be understood as the degree of susceptibility or inability of an organism to adapt their physiological functions to ecological and environmental changes. Changes in water availability and water stress are critical for species, which may respond differentially to different precipitation events. We analyzed the response of leaf water potential (Ψ) and stomatal conductance (gs) to water stress to assess the ecophysiological vulnerability and evaluated the drought tolerance of four tree species from the central mountain region of Veracruz, Mexico: Alnus acuminata, Quercus xalapensis, Liquidambar styraciflua, and Pinus ayacahuite. Drought stress was imposed for 15 days (except for Q. xalapensis) and then watered for 25 days in order to evaluate the species recovery under three watering treatments: 16.67, 33.33, and 50 % field capacity. Individuals were screened throughout the experiment. Ψand gs were measured daily showing significant decrement and differential recovery for each species. L. styraciflua and P. ayacahuite needed more water and more days to recover, whereas Q. xalapensis needed less water and resisted more days without water. We found A. acuminata as a drought-tolerant/avoider species. After analyzing the precipitation and temperature trends for the region, we found negative precipitation trends with an increase in consecutive dry days, and we found positive temperature trends. We also developed potential distribution maps for all the species in the region, and after analyzing the precipitation and temperature changes, the potential distribution maps, the resistance to water stress, the number of days before leaf drop, the Ψ and stomatal responses, and the water amount and number of days required to recover, we found L. styraciflua as the most vulnerable species and Q. xalapensis as the least vulnerable.