Tree diversity promotes insect herbivory in subtropical forests of south-east China

Abstract

1. Insect herbivory can strongly affect ecosystem processes, and its relationship with plant diversity is a central topic in biodiversity–functioning research. However, very little is known about this rela-tionship from complex ecosystems dominated by long-lived individuals, such as forests, especially over gradients of high plant diversity. 2. We analysed insect herbivory on saplings of 10 tree and shrub species across 27 forest stands differing in age and tree species richness in an extraordinarily diverse subtropical forest ecosystem in China.Wetestedwhetherplant species richness significantly influences folivory inthesehighlydiverse forestsorwhetherother factorsplayamore important roleat suchhighlevelsofphytodiversity. 3. Leaf damage was assessed on 58 297 leaves of 1284 saplings at the end of the rainy season in 2008, together with structural and abiotic stand characteristics. 4. Species-specificmeandamageof leafarearangedfrom3%to16%.Herbivory increasedwithplant species richness even after accounting for potentially confounding effects of stand characteristics, of which stand age-related aspects most clearly covaried with herbivory. Intraspecific density depen-denceorotherabiotic factorsdidnot significantly influenceoverall herbivoryacross forest stands. 5. Synthesis. The positive herbivory–plant diversity relationship indicates that effects relate