Complex sentence: The Nature Conservancy manages the preserve using the same natural forces which first created the prairies, partticularly controlled burns and grazing from a modest herd of buffalo--both of which keep shrubs and trees from encroaching and help renew the prairie.
Split into simpler sentences: The Nature Conservancy manages the preserve using the same natural forces which first created the prairies. These practices include controlled burns and grazing by herds of buffalo--both of which keep shrubs and trees from encroaching and help renew the prairie.