The effects of eCO2 on the hydraulic trait hypervolume of Amazonian trees

• Grant number: 25/20588-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: October 01, 2025
• End date: September 30, 2027
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Tomas Ferreira Domingues
• Grantee: Maria Jucicléa dos Santos Medeiros
• Host Institution: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (FFCLRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Associated research grant: 23/09046-5 - AmazonFACE: assessing the effects of increased atmospheric CO2 on the ecology of the Amazon Forest, AP.TEM

Abstract

Plant Hydraulic Strategies Under Elevated CO¿: AmazonFACE Research FrameworkResearch Context and ObjectivesPlants balance carbon acquisition through photosynthesis with water conservation through coordinated tissue properties across roots, xylem, mesophyll, stomata, and cuticle. This multi-dimensional coordination creates diverse functional strategies within hyperdiverse Amazon forests, enabling varied responses to elevated atmospheric CO¿ (eCO¿). Understanding these strategies proves essential for predicting forest ecosystem responses to future atmospheric conditions.Primary Research Question: How will eCO¿ affect water use by tropical and temperate trees?Specific Research QuestionsWill tropical trees and lianas experience reduced dry season stress through lower stomatal conductance under eCO¿?Can observed eCO¿ responses classify species into meaningful functional groups for both trees and lianas?Will incorporating observed trait diversity and eCO¿ responses into dynamic vegetation models produce realistic tree community scenarios?Task 1: Hydraulic Trait CharacterizationWater Status MonitoringMonthly measurements of predawn and midday leaf water potential will quantify the hydration span from fully saturated to maximum xylem tension. This approach captures real-time plant water stress across dominant AmazonFACE species.Embolism Vulnerability AssessmentResearchers will measure P50 values (50% hydraulic conductivity loss threshold) using vulnerability curves on 1-2m branch sections. Hydraulic safety margins calculated from minimum annual leaf water potential and P50 values reveal species' drought vulnerability and adaptive capacity.Hydraulic Conductance PlasticityMaximum hydraulic conductance (Ks_max) and native embolism measurements will occur seasonally to detect eCO¿-induced changes in water transport efficiency. This monitoring reveals potential trade-offs between transport efficiency and hydraulic safety under changing atmospheric conditions.Task 2: Statistical Functional GroupingComprehensive Trait IntegrationThe analysis will combine existing functional traits (leaf chemistry, wood density) with newly collected hydraulic measurements, ensuring complete trait profiles for selected species. This comprehensive approach strengthens functional group classifications beyond traditional successional categories.Advanced Statistical MethodsPrincipal Component Analysis (PCA) on normalized datasets, followed by cluster analysis algorithms, will identify natural functional groupings. Correlation matrices will guide trait selection, excluding variables with coefficients below 0.5 to optimize group definition accuracy.Expected Ecological ImpactsResource-acquisitive pioneer species will likely demonstrate stronger growth responses to eCO¿ compared to conservative shade-tolerant species. The research anticipates that reduced stomatal conductance under eCO¿ will improve water status and reduce drought stress across tropical forest communities.This functional trait approach represents a significant advancement over subjective successional groupings, providing quantitative frameworks for predicting diverse tropical forest responses to global atmospheric change. The methodology offers scalable insights for dynamic vegetation modeling and ecosystem management strategies. (AU)