The role of morpho-physiological traits in frost tolerance of neotropical savanna trees

Abstract

Key Message: Frost-sensitive and frost-resistant Cerrado tree species differ in their morphological and physiological traits, which are linked with their resprout strategies and can affect their persistence under recurrent frost events. Abstract: Although fire is the most common disturbance affecting neotropical savannas, frost events are locally common and are sometimes severe enough to cause dieback of savanna trees at their southern limit of distribution. However, it is yet to be elucidated how physiology and morphology determine which species are frost sensitive. In this study, we evaluated morphological and physiological responses of trees to controlled low temperatures and to a severe frost event that occurred in 2016 at savanna sites of Southeastern Brazil. We determined the degree of bud protection, branch bark thickness, resprout strategies, and recovery of height and biomass 1 year after frost occurrence, and we performed an experiment to measure the photosynthetic capacity of leaves after exposure to low temperatures. We found that frost-sensitive species had unprotected buds, but were able to recover their lost biomass 1 year after frost. Frost-resistant species had buds with a greater degree of protection and maintained higher photosynthetic capacity under sub-zero temperatures. We did not find any differences in bark thickness between frost-resistant and frost-sensitive species. Frost-resistant and frost-sensitive species had different strategies to persist under frost events; however, if frost were more frequent, it could severely affect the height and carbon gain of sensitive species.