biostudies-literatureSilva MCMet OfficeNatural Environment Research CouncilRoyal Society2787-2799https://www.ebi.ac.uk/biostudies/studies/S-EPMC12917452biostudies-literatureUnknown249(6)Droughts pose a major threat to the Amazon rainforest, yet the mechanisms enabling trees to maintain growth under prolonged drought remain poorly understood, particularly in the understory layer. We leveraged a 22-yr Throughfall Exclusion (TFE) in a 1-ha plot in eastern Amazonia, paired with a Control plot, to test whether small understory trees (1-10 cm diameter) grow faster under long-term drought due to acquisitive resource-use strategies and competition release, given that the TFE plot experienced large-tree mortality and canopy gap formation over time. Despite a 51% reduction in density, small trees grew 2.2 times faster in the TFE than in the Control. At the species scale, growth rates increased with acquisitive traits, such as high foliar nutrient concentrations, greater hydraulic cThe New phytologistSmall understory trees increase growth following sustained drought in the Amazon.PMC12917452RSWF/211008NE/W006308/15389381NE/N014022/1Bartholomew DCGiles ALSelman ROliveira RSMartius LRMencuccini MTeodoro GSda Costa ACLSanchez-Martinez PSilva MCMeir PBinks OBittencourt PRLRowland LSilva Junior JARodrigues VNReis JPfalseSmall understory trees increase growth following sustained drought in the Amazon.Droughts pose a major threat to the Amazon rainforest, yet the mechanisms enabling trees to maintain growth under prolonged drought remain poorly understood, particularly in the understory layer. We leveraged a 22-yr Throughfall Exclusion (TFE) in a 1-ha plot in eastern Amazonia, paired with a Control plot, to test whether small understory trees (1-10 cm diameter) grow faster under long-term drought due to acquisitive resource-use strategies and competition release, given that the TFE plot experienced large-tree mortality and canopy gap formation over time. Despite a 51% reduction in density, small trees grew 2.2 times faster in the TFE than in the Control. At the species scale, growth rates increased with acquisitive traits, such as high foliar nutrient concentrations, greater hydraulic c2026-01-01T00:00:00Z2026 Mar2026-07-16T07:52:11.218Z2026-07-09T10:46:17.752ZS-EPMC129174524147929910.1111/nph.70873