While the size and diversity of the Sandhills prairie makes it resilient in many ways, many ranchers are also careful to keep enough vegetation cover in their pastures to prevent wind-driven soil erosion. Those ranchers fear the creation of sand blowouts, which can grow progressively larger, leading to extensive areas of bare sand. As a result of ranchers’ caution, Sandhills pastures are rarely grazed intensively, and cattle are often rotated out of a pasture when grass height is roughly half (or less) of what it was when they came in.
This conservative grazing approach, and the strong social pressure that perpetuates it, certainly reduces the likelihood of chronic overgrazing and the negative impacts it can cause. At the same time, habitat heterogeneity in the Sandhills may be restricted by a scarcity of intensively grazed and/or burned habitat patches. Areas of short, sparse vegetation, including patches of bare ground, provide important habitat for both plants and animals, as do transitional plant communities that accompany the recovery of grasses after fire or grazing events. Because of the value of habitat heterogeneity and the species diversity it fosters, a limited range of available habitat types could end up working against the overall resilience of the Sandhills.
Fortunately, recent research at the University of Nebraska–Lincoln has significantly changed the way we understand soil erosion in the Sandhills. Studies have shown that destabilization of Sandhills dunes is not influenced primarily by aboveground vegetative cover, but instead it’s the belowground root structure of Sandhills prairie that holds the soil in place, regardless of what is aboveground. Even if all aboveground vegetation is repeatedly killed with herbicides, the network of fine roots will continue to hold the soil for several years before breaking down and allowing dunes to destabilize and blow.
Breaking through that root layer, the bulk of which is within the top twenty inches (50 cm) of the soil, can very quickly cause dramatic soil erosion—as seen in blowouts that form along trail roads and permanent cattle trails in pastures. However, simply exposing the soil for short periods of time, as occurs after a prescribed fire or a season of intensive grazing, doesn’t trigger the same loss of dune integrity. Perhaps this knowledge will reassure ranchers who are considering fire or grazing treatments that expose bare ground for short periods of time. Rather than weakening the Sandhills, the increased heterogeneity of habitat caused by those treatments might actually make the prairie more resilient.