Response to soil biota by native, introduced non-pest, and pest grass species: is responsiveness a mechanism for invasion?

Soil biota have been credited with helping to maintain native plant diversity in multiple systems. Recent evidence suggests that introduced species may be less responsive to soil communities than most native species. If response to soil communities is correlated with invasive ability, we predict that introduced pest species should be less responsive to soil communities than introduced non-pest species or natives. In this study we test whether response to soil biota from two diverse grassland communities differs between four introduced pest, six introduced non-pest, and five native species in grasses in Yolo County, California. We found no variation in plant size or response to soil biota between introduced pest and introduced non-pest species, and these were combined in subsequent analyses. Overall, all introduced species grew significantly faster than native species. Native species showed greater variation in response to soil communities than both groups of introduced species, and native species' response varied with soil community. Variation among native species' response to soil nutrients and biota through processes like soil feedbacks may be key to maintaining diversity across landscapes in uninvaded environments. Introduced species appear less responsive to landscape variability in soil communities, which may allow them to establish and dominate plant communities in multiple habitats.