Contributors: Jason Karl

Quantitative

Residual biomass estimation

The Stubble Height method is a technique for measuring the height of vegetation that is left ungrazed at a site. This method should typically be used in an area for which stubble height standards for different plant communities have been developed. The Stubble Height method has mostly been applied in riparian plant communities.

The Stubble Height method is implemented as follows (Note: the technical references below contain much more detailed instructions on how to implement this method). Stubble height is measured at specified intervals along fixed-length transects. The number and length of transects as well as the observation interval along each transect should be determined beforehand - ideally from pilot study data. At each observation interval, the stubble height of the key species nearest to the observation point is recorded. Measurements are recorded as inches (or cm) of leaf length left on the plant. The site average stubble height by species is calculated and compared to the stubble height guidelines.

The Stubble Height method is very quick and easy to implement, and accordingly can be used to assess or monitor large areas with less time and effort than other methods of measuring utilization. Also, minimal training is required beyond plant identification to accurately implement this method.

One limitation of the Stubble Height method is that it has been applied mostly to riparian communities and more research into its utility in upland environments needs to be conducted and stubble height guidelines developed. Also, problems can arise from attempting to infer grazing impact from stubble height data in an area where no stubble-height guidelines exist. Stubble height guidelines are based on an observed statistical relationship between the stubble height and the amount of biomass removed. Application of stubble height without these guidelines is tantamount to trying to estimate the portion of plants that are no longer there by looking at what's left while not knowing how much was there to begin with.

• Utilization Studies and Residual Measurement: Interagency Technical Reference (BLM 1999). This manual includes field forms for the Paired Plot Method (see below).

_{Image from Utilization Studies and Residual\\Measurements Interagency Technical Reference}
Example of a filled-out Stubble Height form (front and back) from the Utilization Studies and Residual Measurements Manual.

• Anderson, E. William and Wilbur F. Currier. 1973. Evaluating zones of utilization. J. Range Manage. 26:87-91.
• Gierisch, Ralph K. 1967. An adaptation of the grazed plant method for estimating utilization of Thurber fescue. J. Range Manage. 20:108-111.
• Lommasson, T. and Chandler Jensen. 1938. Grass volume tables for determining range utilization. Science 87:444.
• Lommasson, T. 1943. Determining utilization of range grasses from height-weight tables. J. Forestry 41:589-593.
• McDougald, Neil K. and Richard C. Platt. 1976. A method of determining utilization for wet mountain meadows on the summit allotment, Sequoia National Forest, California. J. Range Manage. 29:497-501.
• Reid, E.H. and G.D. Pickford. 1941. A comparison of the ocular-estimate by plot and the stubble-height methods for determining percentage utilization of range grasses. J. Forestry 39:935-941.
• The USFS and BLM commissioned researchers at the University of Idaho to study the effectiveness and appropriate uses of stubble height as an indicator of livestock grazing. Their final report is available at
  http://www.cnrhome.uidaho.edu/documents/Stubble_Height_Report.pdf?pid=74895&doc=1

Related utilization and residue measurement methods include:

• Browse Removal - Cole Browse Method
• Browse Removal - Extensive Browse Removal
• Browse Removal - Twig Length Measurement Method
• Residue Measurement - Stubble Height
• Herbaceous Removal - Paired Plot Method
• Comparative Yield Method
• Utilization - Grazed Class Method (photo guides)
• Herbaceous Removal-Height-Weight Method
• Herbaceous Removal-Actual Weight Method
• Herbaceous Removal - Ocular Method
• Landscape Appearance Method
• Pasture Condition Scoring
• Utilization - Grazed Class Method (photo guides)
• Key Species Method
• Use Pattern Mapping

• The class notes from Range 357 at University of Idaho have a good, succinct comparison of different techniques for measuring utilization. http://www.cnr.uidaho.edu/range357/notes/Utilization.pdf.

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