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Dry Matter Content

Biomass is usually determined on a dry matter basis, which is the weight of plant material after the moisture within the plant material has been extracted. Moisture content varies among species and during the year, according to the stage of growth, growth form (herbaceous, woody, succulent), soil moisture levels, and atmospheric humidity. Standardizing weights on a dry matter basis facilitates comparisons of biomass among sites and over time by eliminating these other confounding factors.

Daubenmire Cover Class Method

The Daubenmire cover class method was developed in the 1950s by Daubenmire, an ecologist who worked in the forests and rangelands of northwest USA. It is accepted as a relatively accurate method that has been used extensively to determine cover in rangeland situations.

Grazed and Ungrazed Comparisons

Utilization can be estimated by comparing biomass from paired grazed and ungrazed sample units, with the difference representing the amount of forage consumed (or otherwise destroyed) during the grazing period. Data is collected at the end of the grazing period, by adopting an appropriate method to determine biomass.

Carrying Capacity

Carrying capacity describes the number of grazing animals a management unit is able to support without depleting rangeland vegetation or soil resources. While stocking rates may fluctuate in the short-term in response to fluctuations in the amount and quality of forage, carrying capacity reflects the average level of sustainable production over the long-term.

Canopy Cover

Canopy cover or crown cover describes the area represented by the vertical projection of plant foliage onto the ground. Canopy cover is determined as the perimeter of the plant at its widest horizontal plane. It generally assumes that small gaps within the foliage are included and an average crown perimeter is imagined to smooth irregular edges.

References and Further Reading

Daubenmire, R. 1968. Plant communities: A textbook on plant synecology. Harper Row, New York, NY. pp 42-43.

Browse

Browse is the biomass from trees, shrubs, and woody vines that is available for consumption by livestock and wildlife. It includes leaves and small twigs, but excludes branches and trunks that would not be consumed. Browse is also generally restricted to species or parts of plants deemed palatable to animals, but this issue is confused by the subjective nature of palatability and alternative forage sources.