The invasive annual grass, Microstegium vimineum, is associated with reduced native species seed predation by small mammals in eastern deciduous forests

Abstract

Invasive plants can negatively impact native plant communities through indirect apparent competition driven by altered habitat structure for herbivores and seed predators. The annual invasive grass Microstegium vimineum greatly increases ground-level understory vegetative cover in US eastern deciduous forests, potentially altering foraging patterns by small mammals, which in turn could increase seed consumption of native plant species by mammals that take advantage of increased cover. To test this, we conducted a seed predation study using pans containing small and large native seeds placed in uninvaded and Microstegium-invaded habitats across four seasons. Counter to our predictions, we found that seed removal was 19% higher in uninvaded areas than Microstegium-invaded areas. While our results may be initially interpreted as positive for native species, reductions in small mammal seed foraging could also reduce scatterhoarding of large-seeded tree species, negatively impacting forest regeneration.