When the forest turns green: a systematic review of environmental drivers of leaf flushing in the Amazon forest

• Grant number: 25/13041-4
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: September 08, 2025
• End date: March 07, 2026
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Leonor Patricia Cerdeira Morellato
• Grantee: Mateus Geovane Lima da Silva
• Supervisor: Ramiro Aguilar
• Host Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil
• Institution abroad: Universidad Nacional de Córdoba (UNC), Argentina
• Associated to the scholarship: 24/02380-0 - Can we define leaf exchange functional groups in ever wet rainforest trees? A test using leaf temporal traits, BP.MS

Abstract

Although the Amazon is considered an evergreen forest, its leaf canopy phenology exhibits seasonal leaf dynamics, which influences water and carbon fluxes, and seasonal forest productivity. However, debate still remains regarding the environmental factors that regulate leaf phenology in the Amazonian. To address this question, we conducted an accurate systematic review to answer the following question: which environmental factors influence leaf flush in the Amazon forest? Preliminary searches in scientific databases using search terms such as "leaf phenology", "leaf flush*, "Amazon* rainforest", and "drivers" retrieved a total of 3.786 articles. From these, 70 articles met our criteria and were selected. We found that most studies converge to show that leaf flushing is concentrated during the driest months. Solar radiation is the main environmental driver considered to cue leaf flushing, followed by water in different regions. In terms of monitoring methods, satellites were the most common approach used, followed by tower-mounted digital cameras, and field observation. Based on these preliminary results, we are intended to refine this narrative synthesis and explore the potential for conducting a meta-analysis (qualitative approach) with the inclusion of the effect size from the observational studies that report statistical association between leaf flush and environmental factors. A comprehensive understanding of the environmental cues driving leaf phenology across the Amazon forest is a required information to understand how this forest may respond to ongoing climate change and to identify potential regions where forest may be more vulnerable or sensitive. (AU)