Paubrasilia Echinata Growth in Climate Change Scenarios of Atlantic Forest, Brazil : Ecophysiological Strategies of Tolerance

Concerning the climate change scenarios foreseen for the Atlantic forest biome, a question arises: how will tropical tree species respond to these new environmental conditions? Thus, we seek to understand the impacts of climate changes on Paubrasilia echinata, a native species from this biome that contains three divergent ecotypes in terms of ecological habits. In this context, we evaluated the growth and gas exchange of seedlings from both ecotypes, the small leaf (shade-tolerant) and the medium leaf (sun-tolerant) under climatic conditions of RCP 4.5 and 8.5 scenarios. Therefore, seedlings were cultivated for 90 days in three diferent scenarios: current Atlantic forest (control), RCP 4.5 with an increase of 2.0 ºC in the average temperature and 580 ppm of [CO2] and RCP 8.5 with an increase in 3.5 °C and 936 ppm of [CO2]. Within each scenario, two substrate moisture conditions were established, 40% and 80% of the maximum water holding capacity of the substrate. The initial growth and leaf gas exchange were analyzed. Both ecotypes showed similar behavior, tolerating climate change scenarios through adjustments in growth and gas exchange, such as higher stem height, total dry mass, net assimilation of CO2, intracellular carbon, lower stomatal conductance and transpiration. These responses resulted in increased water use efficiency and carboxylation efficiency. The results indicate that in the next hundred years, in warm regions, the increase in the [CO2] level may boost the growth of P. echinata ecotypes, even with lower substrate moisture, contributing for cultivation expansion and the conservation of specie