Return of Exotic Grasses in Native Pastures: Challenges for Restoration in Working Grasslands
Wednesday, July 26, 2017
Replacing exotic forages with native warm-season grasses could have benefits for livestock producers, but grazing also may help the return of exotic grasses after removal, according to new research in Restoration Ecology.
| Grasshopper at the site, photo Adrian Moore
In the Southeastern United States, exotic forages such as bermudagrass (Cynodondactylon) and tall fescue (Schedonorus arundinaceus) were established on millions of hectares for forage production, but their structure and management has likely reduced habitat for wildlife, including many insects. Native warm-season grasses are increasingly promoted as a sustainable alternative because of their lower fertilizer requirements and competitive yields, and their tall and complex structure could provide opportunities for wildlife. Still, native forages may be less resistant to repeated, heavy grazing than their exotic counterparts, which could create opportunities for exotic grasses to return.
Initially, the researchers from Mississippi State University and University of Georgia set out to compare insect communities in exotic pastures and pastures recently converted to native grasses. However, by the second year they noticed a 101-190% increase in coverage of bermudagrass in grazed native pastures, but not in native pastures without livestock. They also found correlations between two insect communities and bermudagrass coverage.
The authors hypothesized that tall native grasses may be more effective at competing for resources such as light compared with low-growing grasses like bermudagrass, but that grazing may alter this competitive advantage and allow bermudagrass to re-establish.
native pastures, with native bunchgrasses grazed short and bermudagrass encroaching, photo Adrian Moore
"These results illustrate the importance of completely eradicating exotic forages when establishing native grasses” says lead author Adrian Monroe. “Otherwise, these exotic grasses could return which may then increase costs for producers and affect wildlife such as insects.”
The authors also point to changes in management to help native forages keep exotic grasses like bermudagrass in check, such as reduced stocking rates, deferment, or rest from grazing, or varying the application of prescribed fire.
Citation: Monroe, Adrian P. and Hill, JoVonn G. and Martin, James A (2017), Spread of exotic grass in grazed native grass pastures
and responses of insect communities. Restoration Ecology, 25: 539-548,doi: 10.1111/rec.12472
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