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Angle of Points

With most techniques involving point sampling to estimate cover, points are placed vertically to the ground. However, some studies indicate that points inclined at about a 45° angle provide more accurate data for the cover of narrow-leaved species, particularly grasses.

References and Further Reading

Bonham, C.D. Measurements of terrestrial vegetation. John Wiley Sons, New York, NY. p 111-115.

Example to Calculate Carrying Capacity by Matching Forage Supply and Animal Demand

Problem

A 4,000 ha ranch in the black grama (Bouteloua eriopoda) semi-desert ranges of south-eastern Arizona produces 300 kg/ha/year of key forage species in an average year. Because range condition across the ranch is currently fair, allowable use is set at 30% with the objective of improving range condition.

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.