Unravelling the role of contrasting light environments in shaping leaf functional traits: a global meta-analysis

Leaf functional traits play a decisive role in harnessing plant performance and the functionality of leaf functional traits is largely governed by change in light environments yet at global scale this mechanistic relationship of leaf functional traits with light under diverse plant communities and abiotic conditions is still poorly understood due to conflicting findings across regions. To quantify this relationship globally, we aimed to verify the effects of contrasting light environments on leaf functional traits worldwide in (I) different plant community factors; plant functional group, leaf form and leaf habit (II) different abiotic variables, that is, mean annual precipitation (MAP), mean annual temperature (MAT), elevation and climate; and (III) verify whether leaf functional traits exhibit variations in different regions across the globe in contrasting light environments. we conducted a meta-analysis of worldwide experimental data from 1980-2024 including 536 pairwise comparisons to evaluate the influence of different light environments on leaf functional traits both morphological such as specific leaf area, stomatal density, leaf mass area and physiological leaf traits such as net photosynthetic rate, chlorophyll content, leaf dry matter content. Our results showed that leaf morphological traits significantly responded to contrasting light environments and these effects were more pronounced in areas with moderate climatic conditions (MAT 5>15 °C and >500 mm of MAP) and species with evergreen leaves. Leaf physiological functional traits showed more significant sensitivity to moderate to high temperature (MAT >15 °C) and deciduous leaf habit along with regional variations due to integrating effects of MAP and MAT. However, negligible support was found for leaf dry matter content. Our work provides trait-level plastic responses along natural light gradient, modulated by climate and plant community factors and provide an insight into leaf functional traits adaptive strategies across light gradient worldwide.