Recoupling cross-scale interactions in tall fescue-invaded tallgrass prairie

Authors: RAYNOR, EDWARD; HILLHOUSE, HEIDI - UNIVERSITY OF NEBRASKA; DEBINSKI, DIANE - MONTANA STATE UNIVERSITY; MILLER, JAMES - UNIVERSITY OF ILLINOIS; SCHACHT, WALTER - UNIVERSITY OF NEBRASKA

Submitted to: Landscape Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2021
Publication Date: 10/11/2021
Citation: Raynor, E.J., Hillhouse, H.L., Debinski, D.M., Miller, J.R., Schacht, W.H. 2021. Recoupling cross-scale interactions in tall fescue-invaded tallgrass prairie. Landscape Ecology. 1-17. https://doi.org/10.1007/s10980-021-01348-x.
DOI: https://doi.org/10.1007/s10980-021-01348-x

Interpretive Summary: This study evaluated the role of moderate and heavy grazing pressure coupled with prescribed spring fire in enhancing landscape-level structural heterogeniety of tallgrass prairie invaded by an invasive forage plant, tall fescue (Schedonorus arundinaceous). Application of fire and cattle grazing at two levels of grazing intensity (moderate and heavy) did not reduce production or utilization of tall fescue; however, contrast in vegetation structure between recently-burned mangement patches and patches not burned in two years was 50% of the contrast expected for native-dominated tallgrass prairie. In addition, crude protein content of standing live herbage was maintained at levels greater than 7% throughout the April to September grazing season, which was likely driven by the availability of both native and exotic grasses. Thus, native and non-native species acted as complementary forages that maintained high pasture-level crude protein availability, which was above the level to stress rumen microbe populations in beef cattle. Our results suggest that the lack of landscape-scale heterogeneity induced by patch-level fire and grazing management is mediated by the landscape-level dominance of tall fescue, which, unlike native grasses, provides access to high-quality forage in unburned patches through its low-stature growth form.

Technical Abstract: Context Vegetation quantity and quality influence the degree large grazers drive grassland structural heterogeneity. Invasive plants threaten the function of cross-scale interactions that exist when multiscale effects such as fire and grazing interplay to shape structural heterogeneity patterns. Objectives We investigated how grazing pressure and time since fire at the patch-scale influenced forage utilization and herbage production as well as forage quality in a grassland dominated by an invasive plant, tall fescue (Schedonorus arundinaceous). We also assessed the response of tall fescue utilization and production to interactive fire-and-grazing under moderate and heavy grazing pressure. Methods We collected data on vegetation quantity and quality over two years at six points over each grazing season to evaluate the role of fire and grazing across time in shaping contrast among patches in invaded tallgrass prairie in Iowa, USA. We anticipated greater initial patch-scale utilization in patches burned for the first time in 2 years than patches not burned in 2 years. We expected that greater utilization in recently-burned patches would reduce tall fescue production, especially where grazing pressure was highest. Results The contrast in utilization of standing live herbage between management patches was half the level typical for native-dominated tallgrass prairie. Under increased grazing pressure, the interplay between fire and grazing did not result in greater patch contrast nor reduction of an invasive plant. Conclusion Our results suggest that the lack of landscape-scale heterogeneity induced by patch-level management is mediated by the landscape-level dominance of tall fescue, which, unlike native grasses, provides access to forage in unburned patches through its low-stature growth form. Diminished cross-scale interactions in invaded tallgrass prairie may facilitate distribution expansions and structural homogenization.