Sunlight and soil pH predict when tropical forests drop leaves
Ali AA, Magar AT
Phenology
The same seasonal cues that trigger leaf drop in these tropical forests, shortening days and shifting rainfall, are the ones your deciduous trees and shrubs read each fall to decide when to let go.
Some tropical forests aren't evergreen or fully deciduous, they lose their leaves for just a few weeks a year, and scientists have struggled to figure out what triggers this. By combining leaf-fall data from 31 sites worldwide with climate and soil records, researchers found that less sunlight, shorter days, less rain, and more acidic soil all line up with heavier leaf drop. But when they tested the pattern at new sites, it only worked about half as well, suggesting the specific plants growing there matter just as much as the weather and dirt.
Key Findings
Radiation, day length, rainfall, and soil pH together explained 51% of litterfall variation across 31 tropical semi-deciduous sites used for model calibration.
All four key predictors were negatively correlated with litterfall rate, meaning less light, shorter days, less rain, and more acidic soil were linked to more leaf drop.
When applied to independent sites, the model's explanatory power dropped to 24%, indicating species composition, vegetation structure, and functional traits likely play a major additional role.
chevron_right Technical Summary
Scientists studying tropical forests that briefly drop their leaves each year found that sunlight, day length, rainfall, and soil acidity together explain about half of why some sites shed more leaves than others, but the pattern breaks down at new locations, meaning something else about the plants themselves is also driving the timing.
Abstract Preview
Original paper
Climate and Edaphic Factors Partly Explain Leaf Litterfall Rates of Species From Tropical Semi-Deciduous Ecosystems.
Carbon cycling in semi-deciduous ecosystems is difficult to observe because plant species shed leaves for only a short period (4-6 weeks), and some remain dormant for only a few weeks. These short ...
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