Herbivory

The consumption of living tissue by herbivores. Herbivory short-circuits the nutrient cycle by consuming living tissues prior to senescence and litterfall. Many of the nutrients may be returned directly to the ecosystem by herbivore defecation and death or the nutrients may be transferred to other ecosystems by herbivore migration. In most forest ecosystems, herbivores consume less than 10% of the annual net primary productivity. However, periodic outbreaks of insects, such as gypsy moths and mountain pine beetle, or introduction of new species, such as deer or possums, can result in consumption of a significant fraction of an ecosystem’s net primary production. High herbivory rates can result in loss of vigor or even death of susceptible species leading to changes in the species composition of a forest. Quantification of herbivory is commonly determined by setting up exclosures to physically prevent herbivore access to plots or a portion of the canopy. The vegetation within the exclosure is then compared to the vegetation outside of the exclosure to determine the extent of herbivore activity.