Compare Site to its Climax Plant Community
Different plant communities occur on different sites, based on soil depth, texture, and chemistry. The best adapted and most productive combination of native plant species for each site is called the Climax Plant Community. Climax Plant Communities are also called Potential Natural Communities (PNC). They generally produce more consumable forage than any other combination of native species.
Range condition declines when dominant grasses in the PNC decline. Primary reasons for degradation of grassland plant communities are repeated years of overgrazing, the combination of grazing stress and drought, or elimination of fire. Overgrazing occurs when plants are unable to fully recover from the cumulative effects of stress before they are grazed in a subsequent year. Invasion of woody species, such as eastern red cedar in subhumid regions and mesquite in the southern Great Plains, also results in extensive degradation of rangeland.
A site in good to excellent range conditions will have native species present in proportions similar to the site's climax community.
To measure proportion of native species present compared to climate plant community:
- Using the clip and weigh method described below, clip all vegetation within a frame, near the end of the growing season.
- Identify plant species clipped.
- Compare air-dry weight of native plant species to the total standing, current-year herbage. Proportions are based on relative abundance in regions with widely spaced plants, such as in the desert grasslands (14-19" PZ) of west Texas.
The NRCS Web Soil Survey website includes ecological site assessments with photographs and lists of species for successional plant communities that occur on range sites in your area. How to Use websoilsurvey
Look for Indicator Species
Cattle always graze selectively. Plant species that decline most rapidly with repeated years of overgrazing are called Decreasers. Range condition is positively correlated to the relative abundance of decreasers. There are often more than 100 native plant species on well-managed ranches.