Environmental gradients drive context-dependent seed fate: Synergistic roles of forest succession, edge effects, and masting in shaping rodent dispersal dynamics

Abstract

Seed dispersal by scatter-hoarding rodents is pivotal for forest regeneration, yet how forest succession, edge effects, and masting cycles collectively shape seed fate remains poorly understood. Over four years (2020−2023) in subtropical forests of Dujiangyan, China, we conducted a field experiment with Quercus variabilis, integrating seed tagging, rodent mark-recapture, and seed rain surveys across nine forest patches representing early-, mid-, and late-successional stages. We found that seed fates varied with ecological context: late-successional forest interiors promoted longer seed retention, particularly during mast years, due to reduced seed predation risk via predator satiation. In contrast, early-successional forest edges functioned as seed removal sinks during mast years, characterized by significantly elevated rates of seed removal and consumption. Scatter-hoarding probabilities reached their peak in late-successional forest interiors during mast years, while non-mast years induced longer dispersal distances across all successional stages. Edge effects were context-dependent: although forest edges universally accelerated seed consumption, they facilitated seed scatter-hoarding in late-successional forests during non-mast years. Rodent abundance drove seed removal rates, whereas per capita seed availability reduced consumption rates. Our study reveals that seed fates are governed by interactions among forest succession, edge effects, and masting, with critical implications for forest regeneration. Prioritizing late-successional forest interiors as refugia, restoring edge habitats to reduce seed predation risk, and leveraging masting cycles to enhance seed caching services are recommended for mitigating regeneration bottlenecks in fragmented forests. These findings advance mechanistic understanding of context-dependent seed-rodent dynamics, offering novel strategies for forest conservation.