Exotic-Dominated Grasslands Show Signs of Recovery with Cattle Grazing and Fire

Abstract

In grasslands, overgrazing by domestic livestock, fertilization, and introduction of exotic forage species leads to plant communities consisting of a mixture of native and exotic species. These degraded grasslands present a problem for land managers, farmers, and restoration ecologists concerned with improving biodiversity while continuing to use the land for livestock production. Here we assessed the response of butterfly and plant community composition to the use of fire and moderate grazing by domestic cattle on degraded grasslands dominated by exotic plants. We evaluated change by comparing experimental pastures to two reference sites that were grasslands dominated by native plants. We used two burning and grazing treatments: 1) patch-burn graze, a heterogeneously managed treatment, where one third of the pasture is burned each year and cattle have free access to the entire pasture, and 2) graze-and-burn, a homogenously managed treatment, where the entire pasture is grazed each year and burned in its entirety every three years. We tested for change in the butterfly and plant community composition over seven years using Bray-Curtis dissimilarity measures. Over the course of seven years, degraded pastures in both treatments became more similar to reference sites with respect to the butterfly and plant communities. Only two butterfly species and two plant functional guilds exhibited significant linear trends over time, with varying responses. Compositional changes in both the butterfly and plant communities indicate that the use of moderate grazing and fire may shift butterfly and plant communities of exotic-dominated grasslands to be more similar to reference tallgrass prairies over time.

Low‐intensity cattle grazing is better than cattle exclusion to drive secondary savannas toward the features of native Cerrado vegetation

“…Here, we tested if low‐density cattle grazing could be compatible with conservation of secondary savannas in the Cerrado, by reducing the biomass of the exotic grass and allowing the native vegetation to recover and persist. Aligned with previous studies showing benefits of well managed cattle grazing on different ecosystems (Beck et al, 2015; Delaney et al, 2016; Ingty, 2021; Lunt et al, 2007; Rahmanian et al, 2020; Sühs et al, 2020; Young et al, 2018), our results show that cattle were highly efficient in reducing the dry biomass of the exotic grasses (which increased in 3.4 Mg/ha in ungrazed plots over a year), thus allowing increases in both richness and abundance of native herb species. However, the average number of plant species per 100 m 2 (16 in grazed and 19 in ungrazed plots) did not differ between treatments, and both are still far from species richness recorded in undisturbed savanna (58 species per 100 m 2 , Dalle Laste et al, 2019).…”

“…In savannas, this equation becomes even more complex due to the strong positive interaction between invasive grasses and fire, leading to a rather different regime from that of fire burning native vegetation (Fusco et al, 2019; Rossiter et al, 2003). By grazing the exotic grasses, cattle can potentially contribute to interrupt that fire‐invasion cycle, but this role has rarely been assessed (e.g., Delaney et al, 2016).…”

Cooperatively improving tallgrass prairie with adaptive management

“…southern tallgrass prairie have been relatively well documented (Collins 1990), and numerous benefits to native vegetation have been demonstrated (Bragg 1995, Engle and Bidwell 2001, Kral et al 2018. Studies have also shown that appropriate use of grazing can be an important disturbance that improves prairie quality (Briske et al 2011, Delaney et al 2016. The predicted relationship between whether the proportion of native indicators goal was met (0 = not met; 1 = met) and (A) the proportion of years grazed, (B) the proportion of years burned, and (C) the initial state of a transect.…”

Responses of Flowering Plant and Butterfly Communities to Experimental Herbicide and Seeding Treatments for Native Grassland Restoration

“…Grazing provided another key disturbance to prairies through continual stress by herbivory, leading to a higher diversity of forb species (Joern 2005). Moderate stocking by cattle in combination with burning can return some of these historic disturbances to grassland sites (Fuhlendorf and Engle 2001) and community composition can shift greatly in as few as three years after management (Camill et al 2004, Delaney et al 2016). However, even in grasslands that are currently managed with moderate grazing and fire, the legacy of disturbances from past agricultural practices (Isbell et al 2019) and prevalence of dominant exotic plant species (Wilsey et al 2009) can leave tallgrass prairie in a state of low biodiversity that can be difficult to restore.…”

“…These sites ranged from 18 to 34 ha in size and all had a relatively high level of invasion by fescue, with average percent cover exceeding 30%. The three sites used in this study were part of a larger suite of sites previously used to assess butterfly and floral response to combinations of grazing and prescribed fire in a multiyear experiment (Moranz et al 2012, Delaney et al 2016). However, our study takes place on the three sites used for only one treatment from those studies: annual grazing by cattle from April to September and burning in March every third year.…”