Identifying Sustainable Grassland Management Approaches in Response to the Invasive Legume Lespedeza cuneata: A Functional Group Approach

Abstract

We propose combining the filter framework model of community assembly with the passenger-driver model of non-native species behavior to help clarify the impacts of invasive species in the communities they invade and to guide sustainable management protocols. Observational field surveys and a greenhouse experiment explored the role of the invasive legume Lespedeza cuneata in the communities it invades and how natives in three functional groups—grasses, forbs, and legumes—respond to its presence. Within-site analyses from the field survey revealed differences in invaded and uninvaded areas in half of the sites, suggesting that site-specific characteristics influences whether L. cuneata’s presence corresponds to local differences in species composition. The greenhouse experiment found higher levels of saprophytic and arbuscular mycorrhizal fungi in soil conditioned by L. cuneata than in unconditioned soil. However, competition between L. cuneata or the native congener L. capitata and nine native species illustrated stronger aboveground competitive effects than belowground soil effects due to soil conditioning, with impacts differing among functional groups. The response of L. cuneata was reduced in the presence of grasses and other legumes but not forbs. Assessing the impact of L. cuneata with the combined community assembly model revealed this invasive plant acts as a driver because it alters abiotic and biotic filters to impact species composition. Managing for high grass abundance and planting native legumes will help sustain grasslands from L. cuneata invasion.

Timing of invasive species removal influences nonnative biotic resistance and trajectories of community reassembly

“…In both mesocosm and field experiments, removal of the broom, instead of favouring rose growth, favoured the establishment of other nonnative species. These findings are in line with a growing body of evidence suggesting that invasive legumes facilitate other nitrophilic species, mainly nonnative grasses and herbs, due to increases in soil nitrogen content that persist as a legacy after their removal (Corbin & D'Antonio, 2004;Garrett & Gibson, 2020;Grove et al, 2015;Slesak et al, 2022). This effect could also have been amplified by strong release in above-ground competition after broom removal.…”

The role of dominant prairie species ecotypes on plant diversity patterns of restored grasslands across a rainfall gradient in the US Great Plains

“…For instance, restoration practitioners are advised to choose native species with functional traits overlapping invasive species or use diverse seed mixes (Hulvey & Aigner, 2014;Garrett & Gibson, 2020).…”

“…To date, ecological restoration practitioners have employed assembly filter models to examine community assembly, mostly by manipulating biotic filters (Funk et al, 2008; Cleland et al, 2013). For instance, restoration practitioners are advised to choose native species with functional traits overlapping invasive species or use diverse seed mixes (Hulvey & Aigner, 2014; Garrett & Gibson, 2020). Because dominant species are those taxa that are highly abundant and competitive in communities, manipulating dominant species tends to have a significant effect during community assembly (Gibson et al, 2012).…”