Lespedeza cuneata invasion alters soils facilitating its own growth.
Lespedeza cuneata (sericea) is an Asian legume introduced to the US in the 1930s for erosion control and forage, but it can strongly reduce the abundance of native grassland plants. One possible explanation for this high invasive capacity is that L. cuneata is able to alter soil conditions to either improve its own growth, or reduce growth of native plants. To test for soil alteration following invasion, we collected soil from a previous 3-year field experiment in which L. cuneata was established in or excluded from randomly selected plots in a restored grassland. These soil history treatments were crossed with soil autoclaving - to disrupt microbial communities potentially important to plant interactions. For each treatment combination, a native plant, Sorghastrum nutans, was grown with L. cuneata or a conspecific in a 12-week greenhouse experiment. Although we found no evidence for competitive effects on the native species, L. cuneata biomass increased when grown in soil with a L. cuneata history as opposed to non-invaded soil (F1, 16=4.79, P=0.04). Additionally, nodulation of L. cuneata increased in invaded compared to non-invaded soil (F1, 16=6.01, P=0.026). These results indicate that, within three years of invasion, L. cuneata is able to alter soils to facilitate its own growth and suggest that at least part of the invasive success of L. cuneata is linked to altered soil conditions.