Removal and decomposition of fruit respond in opposite ways to canopy cover in a biodiversity experiment

Finn Rehling , Luisa Martha Senger, Franz Tillmann Niedernhoefer, Nora Anderson, Tim Diekötter, Alexandra Erfmeier, Yi Li, Alexandra-Maria Klein

Trees often produce more fruits than frugivores consume. As a result, many fruits fall to the ground, where they are either secondarily removed by vertebrates, potentially leading to seed dispersal, or they are decomposed by arthropods. Although often neglected, fallen fruits are an important component of forests and contribute to their functioning via these two distinct pathways. While fruit removal is well studied, the environmental drivers of fruit decomposition remain poorly understood. We tested the effects of tree species richness and the association with canopy cover on fruit removal and fruit decomposition in a forest biodiversity experiment in subtropical China (BEF-China). We placed 1005 plums across 95 plots, spanning from monoculture to 24 tree species mixtures, in autumn 2025. After four days, 27.2% of fruit were removed while the remaining fruit lost 55.7% of their mass (95% CI: 14.6-84.3%) due to decomposition. Fruit removal varied markedly across plots and decreased by 23% with canopy cover, whereas mass loss increased with canopy cover by 29%. Tree species richness had no detectable effect on either process. Accordingly, removal and decomposition of fruits were only weakly coupled across the forest, with higher overall fruit turnover in open forests. These results suggest that canopy cover, rather than tree species richness, drives fruit turnover by decoupling the pathways of removal and decomposition in young subtropical forests. Fruit decomposition experiments, such as the one used in this study, provide a rapid and simple proxy for assessing forest functioning and contribute to advancing necromass ecology.