Estratégias de sobrevivência à seca de plantas jovens de clima tropical sazonalmente seco

Abstract

Future climate scenarios predict an increase in temperature and a decrease in precipitation. Extreme droughts will lead to increased plant mortality rates and such events will potentially affect the composition and structure of communities. Understanding how saplings respond to increased drought is important to help understand how plants will respond to increased drought due to climate change. In addition, it enables the identification of which species will be most vulnerable to climate change. We investigated which are the drought survival mechanisms of 13 species saplings that occur in tropical seasonally dry climate. These species present diverse phenological and physiological responses, being grouped in different functional groups. We select saplings and simulated an extreme drought event of 214 days in a greenhouse. We analyzed which plant traits are related to the drought resistance ability and the importance of green stems and underground reserve organs in the carbon balance and drought recovery capacity. As well, we evaluated the traits that influence leaf longevity (LF), our indicator of resistance to drought. We measured biomass, relative water content in the fractions root, stem and leaf; and non-structural carbohydrate concentration (NSC) in root and stem, photosynthetic rate, stomatal conductance, predawn and midday water potential, transpiration, instantaneous efficiency in water use, and intrinsic efficiency in water use. Our results demonstrated that LF is influenced by all the traits analyzed, and that the higher resistance to drought was influenced by reserves of leaf water and NSC in stem. We also demonstrated that the combination of the functional traits photosynthetic stems, underground storage organs and low wood density enables the increasing reserve of NSC, which allowed the survival after extreme drought of the plants with such traits. Species that are more resistant to drought, that is, longer LF, and that have post-drought recovery strategies will potentially be the least vulnerable to drought due to climate change.