Management of remnant tallgrass prairie by grazing or fire: effects on plant communities and soil properties

Abstract

Tallgrass prairie is a disturbance‐dependent ecosystem that has suffered steep declines in the midwestern United States. The necessity of disturbance, typically fire or grazing, presents challenges to managers who must apply them on increasingly small and fragmented parcels. The goal of this study was to compare effects of management using cattle grazing or fire on vegetation and soil characteristics to aid managers in making decisions regarding the kind of disturbance to apply. We selected 73 sites, of which 27 were managed solely by cattle grazing and 46 solely by fire, for at least 11 yr leading up to the study. We stratified the sites by prairie type (dry, mesic, and wet) and sampled frequency of plant species on randomly placed transects, supplemented with botanist‐directed walks, and collected and composited five soil cores on a randomly selected transect within each prairie type at each site. We calculated rarefied richness and Shannon evenness from the transect data and mean coefficient of conservatism (CofC) from the total list of species. Soil samples were analyzed for texture, bulk density, total N and C, and potential net N nitrification and mineralization. A nonmetric multidimensional scaling analysis of the plant community data revealed differences in species associated with mesic and wet prairies, but no separation by management type. Similarly, none of the vegetation variables we calculated varied by management type, as determined by mixed‐effects models, but soil bulk density was 17.5% higher and total N was 22% higher on grazed sites than burned sites. Sites burned more recently had higher species richness and mean CofC, but fire was not associated with any soil variables. Sites grazed more recently had higher bulk density, total N and C, and faster N cycling rates. Overall, 28% of plant species were found exclusively in one management type or the other, but these species did not vary in mean CofC. We conclude that, at the levels of burning and grazing intensity we studied, both management approaches produce similar C storage and vegetation responses. To maintain maximum diversity across the landscape, however, both approaches are necessary.

Does Pastoral Land-Use Legacy Influence Topsoil Carbon and Nitrogen Accrual Rates in Tallgrass Prairie Restorations?

“…However, most remnants experienced either minimal change or reductions in soil bulk density, which facilitated soil kg C and N m −2 loss and could be due to land management. In a study of over 70 remnant tallgrass prairies, Larson et al [66] found that grazing increased soil bulk density more than other management types, and it is possible that remnant prairie at Midewin remains affected by the soil compaction caused by grazers present up until 1997. However, Larson et al [66] reported average bulk densities of approximately 1.0 g cm −3 for grazed remnants and 0.8 g cm −3 for burned, which are consistent with our results where the bulk density at Midewin's remnants are also lower (Figure 2).…”

“…In a study of over 70 remnant tallgrass prairies, Larson et al [66] found that grazing increased soil bulk density more than other management types, and it is possible that remnant prairie at Midewin remains affected by the soil compaction caused by grazers present up until 1997. However, Larson et al [66] reported average bulk densities of approximately 1.0 g cm −3 for grazed remnants and 0.8 g cm −3 for burned, which are consistent with our results where the bulk density at Midewin's remnants are also lower (Figure 2). Removal of grazing and periodic prescribed burning in remnants decreases soil compaction and promotes organic matter accumulation, which both facilitate decreases in soil bulk density, but soil factors such as drainage that are variable between Midewin remnants play important roles in the rate at which SOM accumulates.…”

Twenty years of tallgrass prairie restoration in northern Illinois, USA

“…Another critical management approach at Nachusa has been regular prescribed fire, and the average fire return interval is less than 2 years. Regular fire is critical to maintaining levels of plant species richness and coefficient of conservatism (Larson et al, 2020), and has consistently been identified as necessary to maintain intact tallgrass prairie habitat (Alstad et al, 2016;Bowles & Jones, 2013;Ratajczak, Nippert, Briggs, & Blair, 2014). Regular prescribed fire is likely the primary driver in sustaining the rare native plant communities in Nachusa native prairies.…”

Evaluating the Impact of Grazing Cessation and Reintroduction in Mixed Prairie Using Raster Time Series Analysis of Landsat Data

“…Follett et al's [3] study of grazing practices indicted that long-term, moderate grazing can improve soil health and stabilize sandy soil. Larson et al [22] compared the outcomes of grazing and prescribed fire, and reported that grazing increased soil bulk density and total soil nitrogen while recent fire did not alter any soil properties but increased species richness. Teague et al [15] compared the restoration outcomes of grazing prescriptions (light continuous season-long grazing, heavy continuous grazing, and multi-paddock grazing) on ungrazed prairie, and found that multi-paddock grazing is better for biodiversity conservation than continuous season-long grazing.…”

“…Despite these studies comparing the outcomes of grazing versus prescribed fire, and grazing of varying duration and intensity, it is still a challenge for native prairie managers to decide what practices to apply [22]. This is because the outcomes of native prairie management remain difficult to predict and contain significant uncertainties [8,23].…”