Growing Season Fires and Herbicide May not Be the Silver Bullet to Lespedeza cuneata Management

Abstract

Invasive species are generally managed across rangelands to achieve livestock productivity and biodiversity maintenance objectives. The invasive legume Lespedeza cuneata (Dum. Cours.) G. Don. is managed across much of the Great Plains with aerially applied herbicides that target broadleaf forbs and dormant season (late March−early April) fire. It is hypothesized that altering fire timing to the growing season or integrating late-season herbicide into fire management may lead to more successful reduction of L. cuneata without negatively affecting rangeland plant communities. However, most of the literature outlining the effects of L. cuneata and its management is limited to small scale (< 100 m2), highly controlled studies that are not transferrable to large working rangelands. We manipulated eight large (333−766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to assess whether growing and dormant season fires, herbicide application, or the interactive effect of fire timing and herbicide reduced L. cuneata without negatively affecting broad rangeland plant composition (i.e., functional group cover) from 2019 to 2021. Our study was performed at two scales relevant to rangeland management: the pasture and burn patch scales. None of our treatments (i.e., fire timing, herbicide application, or the interaction of fire timing and herbicide) had a significant effect on L. cuneata canopy cover at either the pasture or patch scale. Our treatments also did not affect forb or shrub cover at the pasture or patch scales. Grass and sedge cover was significantly increased post herbicide at the patch scale, but not at the pasture scale. Grass and sedge cover was unaffected by any other treatment at both scales considered in this study. Our results add to nearly two decades of research, conducted elsewhere, that pyric herbivory alone may be sufficient to manage L. cuneata and promote rangeland biodiversity in the tallgrass prairie.