Abstract
Heterogeneity has emerged as a fundamental principle for rangeland management and the importance of environmental heterogeneity for biological diversity has raised questions about the appropriateness of rangeland practices that seek to promote uniform grassland structure and composition. Principles of uniformity in rangeland management reflect a utilitarian target of “managing for the middle” by minimizing both overgrazing and underutilization while avoiding or preventing fire and other disturbances that consume aboveground biomass. We implemented a study to evaluate pioneering efforts to restore historical fire-grazer interactions via patch burning in an effort to increase spatial heterogeneity in the Nebraska Sandhills, a sandy soil, mixed-grass ecoregion with a long history of “management for the middle”. The application of patch burning did not increase landscape heterogeneity of vegetation structure or composition in the Nebraska Sandhills. Instead, grassland structure exhibited greater temporal variability than spatial variability in growing and dormant seasons. The low stocking rate and the rapid regrowth of live herbaceous vegetation following fire likely constrained the degree of spatial heterogeneity observed in our study and highlights the challenges of balancing forage supply and demand in semi-arid grasslands.
Highlights
The rangeland discipline has undergone a recent ideological shift to embrace heterogeneity as a fundamental principle for grassland management (Fuhlendorf et al, 2017)
Patch burning has been introduced as a method for increasing spatial heterogeneity and biodiversity in grasslands by applying fire in patches on a contiguously grazed landscape with heterogeneity emerging between patches (Fuhlendorf and Engle, 2001)
The basis of patch burning is the development of landscape scale heterogeneity with variability in vegetation structure emerging among patches within the landscape, as opposed to finer scales, to provide for multiple ecosystem services (Fuhlendorf and Engle, 2001; Fuhlendorf et al, 2009)
Summary
The rangeland discipline has undergone a recent ideological shift to embrace heterogeneity as a fundamental principle for grassland management (Fuhlendorf et al, 2017). Heterogeneity is the spatial and temporal variability in vegetation structure and composition essential for ecosystem function (Wu and Loucks, 1995; Fuhlendorf and Engle, 2004). Environmental heterogeneity begets greater diversity across multiple trophic levels (MacArthur and MacArthur, 1961; Tews et al, 2004), causing academics and natural resource professionals to question the appropriateness of grassland practices that seek to promote uniform grassland structure and composition (Fuhlendorf et al, 2012). Grassland species evolved within a dynamic, disturbance-driven spatially, and temporally heterogeneous landscape with specialist niche space for flora and fauna (Biondini et al, 1989; Fuhlendorf and Engle, 2004; Tews et al, 2004; McGranahan et al, 2012).
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