Mapping seasonal and interannual Non-Structural Carbohydrate variation to drought-resistance strategies in eastern Amazon tree species

Carbon allocation to non-structural carbohydrates (NSC) is essential for plant metabolism playing an important role in tree responses to drought. It is still unclear if and how interspecific hydraulic trait variation modulates NSC concentration dynamics in different plant organs, particularly in tropical tree species. We investigated whether drought-resistance strategies (inferred from hydraulic traits) explain seasonal and interannual NSC dynamics in leaves, branches, trunks, and roots in seasonal eastern Amazon tree species in Brazil. We measured NSC concentration in eight abundant species during three years, including the end of the wet and dry seasons of the typical regular years (2013-2014) and the extreme drought induced by El Niño–Southern Oscillation in 2015 (ENSO). Organs have an important contribution to explain the starch (ST), soluble sugar (SS), and NSC variance among trees. We showed seasonal and year-to-year homeostasis in ST and SS concentrations in a majority of organs during 2013 and 2014, but SS increased in all organs during the extreme ENSO drought, while the ST concentration did not. The increase in SS concentration was more evident in woody organs from species with intermediate and tolerant drought strategies. The drought-tolerant species maintain higher root starch concentrations and mobilize more SS during extreme drought.