Effects of Historic Livestock Grazing on Vegetation at Chaco Culture National Historic Park [final report]
Floyd-Hanna L, Fleischner TL, Hanna DD. 2000. Effects of Historic Livestock Grazing on Vegetation at Chaco Culture National Historic Park [final report]. Project #CHCU-R98-0819. Prescott College Environmental Studies Program. Prescott, AZ
The introduction to this study of historic grazing impacts at Chaco Culture National Historic Park notes the various deleterious results livestock can have on the environment. As little ungrazed land is left in the western United States to allow comparisons which could document such changes, areas presently closed to grazing are important sources of information. The main part of Chaco, heavily grazed into the twentieth century, was closed and fenced in the 1930's and 1940's, with added park lands fenced in the mid 1990's, making this one of the largest arid-land "exclosures" available for study. Lands outside the park continue to be grazed, allowing comparisons among adjacent areas with one of three conditions: protected for over 50 years, protected for less than 5 years, and currently grazed. The investigators found the greatest differences in relation to biodiversity and cryptogamic crusts (important in soil nitrogen cycling). At all six study sites, biodiversity and density of biotic crusts were greatest in the areas afforded long-term protection. Less-consistent results were found with bare soils and cover of shrubs and grasses, suggesting to the authors delicate balances and long recovery times in some instances of significant human disturbance. Bibliography (pages 15-17), site location map, and color graphs showing plant species richness and cover of various types. The appendix contains a list of plant species by site, with indications for each species of occurrence in areas with 50, 5, and/or 0 years protection.
- Type
- Published Report
- Authors
- Floyd-Hanna, Lisa; Fleischner, Thomas; Hanna, David
- Date of Issue
- 2000-12-13
- Publisher
- Prescott College Environmental Studies Program
- Units
- CHCU
- Keywords
- Checklist, Grazing, Impacts, Plant Studies, Plants, Vegetation