An invasive legume increases perennial grass biomass: An indirect pathway for plant community change.

Jennifer M Fill,Raelene M Crandall,Eleanor Pearson,Tiffany M Knight,Mai-He Li

doi:10.1371/journal.pone.0211295

Abstract

The presence of native grasses in communities can suppress native forbs through competition and indirectly benefit these forbs by suppressing the invasion of highly competitive exotic species. We conducted a greenhouse experiment to examine the potential of direct and indirect interactions to influence the aboveground biomass of four native forb species in the presence of the native perennial grass Schizachyrium scoparium and exotic invasive Lespedeza cuneata. We examined patterns of growth for the invasive legume, the perennial grass, and four native species in four scenarios: 1) native species grown with the grass, 2) native species grown with the legume, 3) native species grown with both the grass and legume together, and 4) native species grown alone. Schizachyrium scoparium significantly decreased biomass of all forb species (p<0.05). In contrast, L. cuneata alone only significantly affected biomass of Asclepias tuberosa; L. cuneata increased the biomass of A. tuberosa only when the grass was present. When S. scoparium and L. cuneata were grown together, L. cuneata had significantly lower biomass (p = 0.007) and S. scoparium had significantly greater biomass (p = 0.002) than when each grew alone. These reciprocal effects suggest a potential pathway by which L. cuneata could alter forb diversity in grassland communities In this scenario, L. cuneata facilitates grass growth and competition with other natives. Our results emphasize the importance of monitoring interactions between exotic invasive plant species and dominant native species in grassland communities to understand pathways of plant community change.

Highlights

Native perennial grasses are a keystone functional group of grassland and savanna communities
We examined patterns of growth for the invasive legume, the perennial grass, and four native species in four scenarios: 1) native species were grown with an established native perennial grass, 2) native species were grown with an invasive legume, 3) native species were grown with both the established grass and invasive legume together, and 4) native species were grown alone
Native forbs grown with S. scoparium had lower biomass than those grown alone, but counter to our hypothesis, native forbs were generally not affected by the invasive legume

Summary

Introduction

Native perennial grasses are a keystone functional group of grassland and savanna communities. They influence fundamental ecosystem processes such as fire regimes and nutrient cycling [1,2,3] but they have been shown to increase ecosystem resilience and community resistance to invasion [4,5,6]. As long-lived individuals that achieve high biomass, native perennial. A pathway for plant community change provided by a grant to Washington University in St. Louis from the National Science Foundation Advancing Informal STEM Education Program (DRL 0739874). The funders had no role in study design, data collection and analysis, decision to publish,or preparation of the manuscript

Methods

Results

Conclusion