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

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

This article was published online Oct. 11, 2021 in Landscape Ecology.

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Abstract

Context

Vegetation quantity and quality influence the degree to which large grazers shape grassland structural heterogeneity. Invasive plants threaten the function of cross-scale interactions that exist when multi-scale effects such as fire and grazing interplay to form patterns of grassland structural heterogeneity.

Objectives

We investigated how grazing pressure and time since fire at the patch scale influenced patch utilization and production as well as forage quality in experimental grassland pastures dominated by an invasive grass, 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 grazing seasons to evaluate the role of fire and grazing across time in shaping structural heterogeneity among patches in invaded tallgrass prairie in Iowa, USA. We anticipated greater initial patch-scale utilization in patches burned for the first time in two years than patches not burned in two years in our experimental pastures. We expected that greater utilization in recently-burned patches would reduce tall fescue production, mostly where grazing pressure was highest.

Results

The contrast in the availability of live herbage between 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 broad-scale heterogeneity (among-patch heterogeneity) or an invasive grass reduction in experimental pastures. Yet, increased grazing early in the season did promote native-grass production in this invaded grassland landscape.

Conclusion

Our results suggest that the dominance of tall fescue mediates the lack of structural heterogeneity induced by patch-level prescribed fire and grazing. Unlike native perennial grasses, tall fescue provides access to forage in unburned patches through its low-stature growth form. Diminished cross-scale interactions through a weak coupling of fire and focal grazing in invaded tallgrass prairie may facilitate structural homogenization of fire-dependent grassland.

Keywords:     Cross-scale interactions; Forage quality; Herbivore-plant interactions; Prescribed fire; Pyric herbivory; Schedonorus arundinaceus

Citation

Raynor, Edward J., Heidi L. Hillhouse, Diane M. Debinski, James R. Miller, and Walter H. Schacht. "Recoupling cross-scale interactions in tall fescue-invaded tallgrass prairie." Landscape Ecology (2021): 1-17.

Effects of fire seasonality and intensity on resprouting woody plants in prairie-forest communities

This article was published May 28, 2021 in Restoration Ecology

https://doi.org/10.1111/rec.13451

Abstract

Woody plant expansion is one of the greatest contemporary threats to fire-dependent ecosystems. Reducing woody plant prevalence is often a primary objective of prescribed burns, yet little attention has been given to understanding the efficacy of burning to reduce their abundance. Fire intensity characteristics and plant phenology/physiology, which are sometimes presented as competing hypotheses, influence how woody plants respond to a fire event. Little work has been done in the prairie-forest region of the upper Midwest to understand how fire characteristics interact with woody species phenology and/or physiology. Using a controlled field experiment, we examined effects of timing (seasonality) and intensity (temperature and duration) of fires on top-kill and resprouting of three invasive woody plants in this region (common buckthorn, Rhamnus cathartica; bush honeysuckles, Lonicera spp.; and a native species, northern pin oak Quercus ellipsoidalis). Honeysuckles and pin oak burned in the spring dormant period, a common practice in the region, resulted in low levels of top-kill and high levels of resprouting. Burning during the late growing season yielded highest levels of top-kill and lowest levels of resprouting for honeysuckles and pin oaks. However, there was no apparent effect of season or fire intensity treatment for buckthorn stems. Under all treatment combinations, buckthorn was easily top-killed but resprouted prolifically. Collectively, most prescribed burning in the Midwest appears to be conducted during the least effective season (early growing season), when top-kill is reduced and/or resprouting most pronounced. Our results indicate that fire use could be better prescribed in this region for controlling woody plants.

Citation

Meunier, Jed, Nathan S. Holoubek, Yari Johnson, Tim Kuhman, and Brad Strobel. "Effects of fire seasonality and intensity on resprouting woody plants in prairie‐forest communities." Restoration Ecology: e13451.