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Lespedeza cuneata is an invasive, non-native species of bush clover that is invading prairies where the native Lespedeza capitata grows. Both species of bush clover are legumes, which are nitrogen fixers. Legumes and their senescent leaves (i.e., “litter”) are well known for increasing levels of available nitrogen in the soil. However, the exotic L. cuneata also produces tannins that reduce the rate of germination in some prairie plants. The purpose of this study was to clarify whether these compounds in the litter of the invasive species of bush clover deter early growth in its native competitors, and to determine whether litter of each species of legumes would increase growth of native prairie plants. To address the influences of L. cuneata, we tested whether the impact of L. cuneata litter on growth of prairie plants (Goldenrod and Wild Quinine) was consistent with the effect of toxic tannins or improved nitrogen supply. Each prairie plant was divided into three groups of different treatments: native litter, exotic litter, and a control group with no litter. The plants were measured for height weekly, and at 9 weeks harvested, dried, and weighed. Growth trajectories suggested litter treatment was affecting the two species. In the analysis of dry shoot mass, the effect of litter treatment was significant). Surprisingly, for both species of plants, the exotic treatment (L. cuneata) displayed the best growth of all groups involved in the study. Addition of L. cuneata litter increased final mass more than either the control or addition of L. capitata litter, and the control produced greater growth than native L. capitata litter. Goldenrod was significantly larger than wild quinine but the two species did not differ in their response to the litter treatment. Based on the statistical findings, both the Goldenrod and Wild Quinine exotic treatment groups responded with increased growth and increased mass when the opposite had been predicted. These results question assumptions about exotic species and indicate that L. cuneata, despite prior findings, may benefit some members of the prairie community.
Gardner, Asher, "Exotic Legume's Leaf Litter Beneficial to Prairie Plants" (2021). Biology. 7.