written by Karen Colson and Jason Karl
Description and Uses
The Key Species Method is a combination of the Landscape Appearance Method and the Ocular Estimate Method. This method bases utilization levels on an ocular estimate of the amount of forage removed by weight on individual key species with observations recorded in one of seven utilization classes. It was developed to be used in areas where perennial grasses, forbs, and/or browse plants are the key species.
Advantages and Limitations
With the Key Species method there is no need to disturb the vegetation (i.e., harvesting). It is also very rapid since the estimated percentage of forage removed is recorded in one of seven broad classes rather than as an exact percentage. This is also a more accurate approach since different observers are more likely to estimate utilization in the same classes than to estimate the same utilization percentages.
However, observer bias and subjectivity are a concern with this method making fairly rigorous training necessary. Observers must first compare their ocular estimates against actual weight values obtained by clipping and weighing to train themselves. Exclosures, cages, or fenced areas are also typically necessary for training purposes. Cages should also be used to provide ungrazed plants to observe while conducting the monitoring. Error can also be reduced by limiting observations to individual plants or small areas (quadrats).
- Utilization Studies and Residual Measurements (Technical Reference 1734-3) http://www.blm.gov/nstc/library/pdf/utilstudies.pdf
- Swanson, S. et al. 2006. Nevada Rangeland Monitoring Handbook, Second Edition. Educational Bulletin 06-03.
Technical and Application References
Related utilization and residue measurement methods include:
- Cole Browse Method
- Extensive Browse Method
- Stubble Height
- Paired Plot Method
- Utilization – Grazed Class Method
- Herbaceous Removal-Height-Weight Method
- Herbaceous Removal-Actual Weight Method
- Herbaceous Removal-Ocular Method