Tree hydrological niche acclimation through ontogeny in a seasonal Amazon forest

Mauro Brum, Luciana F. Alves, Raimundo C. de Oliveira-Junior, Victor Hugo Pereira Moutinho, Natalia Restrepo-Coupe, Karoline Chaves, Deliane Penha, Neill Prohaska, Plínio Barbosa de Camargo, Grazielle Sales Teodoro, Sebastião Ribeiro Xavier Júnior, Scott C. Stark, José M.S. Moura, Rodrigo Silva, Rafael S. Oliveira, Scott R. Saleska

Research output: Contribution to journalArticlepeer-review

Abstract

How tropical plants cope with water availability has important implications for forest resilience, as severe drought events are expected to increase with climate change. Tree size has emerged as a major axis of drought vulnerability. To understand how Amazon tree species are distributed along size-linked gradients of water and light availability, we tested the niche acclimation hypothesis that there is a developmental gradient in ontogenetic shift in embolism resistance and tree water-use efficiency among tree species that occurs along the understory-overstory gradient. We evaluated ontogenetic differences in the intrinsic water-use efficiency (iWUE) and xylem hydraulic traits of abundant species in a seasonal tropical forest in Brazil. We found that saplings of dominant overstory species start with a high degree of embolism resistance to survive in a dense understory environment where competition for water and light among smaller trees can be intense during the prolonged dry season. Vulnerability to embolism consistently changed with ontogeny and varied with tree species' stature (maximum height): mature individuals of larger species displayed increased vulnerability, whereas smaller species displayed unchanging or even increased resistance at the mature stage. The ability to change drought-resistance strategies (vulnerability to embolism) through ontogeny was positively correlated with ontogenetic increase in iWUE. Ecologically, overstory trees appear to shift from being hydraulically drought resilient to persisting under dry soil surface layer conditions to being more likely physiological drought avoiders as adults when their roots reach wetter and deeper soil layers.

Original languageEnglish (US)
Pages (from-to)1059-1073
Number of pages15
JournalPlant Ecology
Volume224
Issue number12
DOIs
StatePublished - Dec 2023

Keywords

  • Amazon rainforest
  • Embolism resistance
  • Hydrological niche segregation
  • Ontogenetic shift
  • Phenotypic plasticity
  • Stable isotope
  • Water-use efficiency
  • δC

ASJC Scopus subject areas

  • Ecology
  • Plant Science

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