The interaction of two disturbances—bison grazing patterns and fire—increases biodiversity by creating a heterogeneous patchwork of plant communities in grasslands.

Introduction

The Great Plains are a huge expanse of grassland located west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. Millions of bison used to roam the tallgrass prairies that once covered the Great Plains, grazing in patches as they went. Fires caused by lightning or set intentionally by native peoples to renew the grasslands were also common. The relationship between fire and grazing patterns had a big impact on how plant communities developed in the tallgrass prairie.

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Bison prefer grazing recently burned grasslands, and their grazing patterns influence the size and intensity of fires.

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This restored tallgrass priarie in Illinois shows a patchy mix of diverse plants.

The Strategy

Fires are important to , because bison prefer to graze patches of grassland that have been burned recently. Bison grazing patterns also influence the size and intensity of fires. The interactions between these two different types of disturbances— fires and grazing patterns—helps create a heterogenous, or mixed, patchwork of plant communities. For example, these interactions lead to different plant heights, density, and mixtures of species. This helps support more biodiversity in tallgrass prairie ecosystems.

Scientists think of biodiversity on three levels—genetic diversity (different genes and combinations within a species), species diversity (the number of different species within an ecosystem), and ecosystem diversity (how many different ecosystems are found in a region). Biodiversity helps organisms adapt to environmental changes, maintain food webs, and provide services that life depends on, such as water retention and waste decomposition.

Today, most of the land that made up the Great Plains is managed as rangeland for cattle production. Land managers usually only manage the number of cattle and where and when they are grazing on the land. Fire is rarely used anymore as a way to manage cattle grazing. Instead, intensive rotational grazing approaches, where animals are moved rapidly between heavily grazed plots, have become more popular as a management approach. This style of grazing allows the plants that the cattle most like to eat to recover between grazing sessions. However, it does not produce the patchwork of plants that leads to greater biodiversity.

Preserving the Tallgrass Prairie

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This Oklahoma State University video takes viewers on a tour of TNC’s Tallgrass Prairie Preserve and talks about the impact of fire, grazing, and drought on the ecosystem:

The Potential

The Nature Conservancy has successfully used fires and continual cattle grazing to manage its Tallgrass Prairie Preserve in Oklahoma. This approach helps to promote biological diversity and increases agricultural productivity, and can help  support native plant and animal species. There is even some evidence that this approach, where appropriate, could reduce the need for supplements in cattle during winter months. This would lead to lower management costs.

Last Updated June 17, 2020