Disentangling intrinsic and extrinsic drivers of herbivory across forests: Leaf functional traits, insect richness, and climatic factors

Leaf herbivory substantially affects plant physiology and performance, and may intensify under ongoing climate change. Nevertheless, how leaf functional traits, insect richness and climate jointly drive variation in herbivory remain unclear. We measured leaf herbivory and 11 leaf functional traits of 61 woody species across five forests representing a climatic and biodiversity gradient in China. The mean leaf herbivory was 6.47% across forests. Species with high leaf silicon concentration and photosynthetic capacity, low leaf mechanical strength and heat tolerance suffered less herbivory, implying a silicon-based defense strategy independently of leaf carbon economics, partly rejecting the resource availability hypothesis, respectively. Evergreen species suffered more severe herbivory than deciduous species, and plants grow in hot and wet habitats with high local insect richness tend to experience greater herbivory. We highlight that leaf functional traits explain herbivory better than environmental factors, and a comprehension of both intrinsic and extrinsic drivers will advance the understanding of herbivory patterns across natural forests.