Intensive land management practices provide for a growing human population by increasing the production and uniformity of crops. As more forest land is being intensively managed as plantations, the homogenization of forest ecosystems may alter the interactions between wildlife and their habitats. We hypothesized that by homogenizing regenerating forest vegetation, intensive forest management practices alter large herbivore foraging behavior; the compounding effects of herbivory and management intensity should further simplify plant communities and favor crop tree development. To test this hypothesis, we constructed 225 m2 wild deer and elk exclosures, nested within a manipulated gradient of management intensity (3 herbicide treatments and a no-spray control), replicated at the scale of whole harvest units in the Pacific Northwest (PNW), USA.
Herbivory had a disproportionate effect on vegetation within managed plantations that received a commonly-used herbicide prescription. Herbivory exacerbated the effect of herbicide treatment on native forage species, favoring crop-tree growth as a result of trees being released from competition. Deer and elk thus provided an ecosystem “service” to plantations by browsing plants that compete with crop trees, although this service came at the cost of reduced native forage regeneration. However, untreated, vigorously regenerating and diverse native plant communities were resilient to herbivore pressure. Our findings suggest that the effect of herbivory on plant communities is mediated by land management practices that alter forage composition and availability. Our results support the hypothesis that management intensity and herbivory interact to drive not only plant community structure, but ecosystem services valued by humans.