Phenological type- and diameter-dependent effects of individual light availability and interannual climate variation...

Tree growth is a critical carbon sink for tropical forests, yet how light and climate jointly shape long-term individual-level growth remains poorly understood. Using 34 years of data from 2881 trees (10 species: six evergreen, four deciduous) in a Costa Rican wet forest, we examined how interannual climate variation and individual light availability influence tree growth in diameter at breast height, height and above-ground biomass across phenological types and size classes. Light availability consistently emerged as the primary growth driver, with deciduous species more responsive than evergreen species; however, light effects diminished with increasing tree size. Higher mean daily maximum temperatures enhanced radial growth in evergreen trees and height growth in deciduous trees, whereas elevated minimum temperatures suppressed radial growth in evergreen trees. Increased wet-season precipitation (WSP) reduced radial growth in both phenological types and height growth in evergreen trees, whereas higher dry-season precipitation decreased radial growth in deciduous trees. Notably, larger trees exhibited weaker positive radial growth responses to maximum temperatures but stronger negative responses to WSP. These findings underscore the dominance of light over climate in regulating tropical tree growth and highlight the necessity of incorporating tree sizes and functional groups into ecological modelling and forest management.