The use of comparative yield and dry-weight-rank techniques for monitoring arid rangeland

Abstract

The comparative yield (CY) method for estimating pasture dry weight and the dry-weight-rank (DWR) method for determining species composition were applied in a variety of arid vegetation types by several operators. The methods were evaluated for their suitability in a range monitoring program, on the basis of consistency of estimates and the time taken. Four calibration regressions for the CY technique were compared initially and, of these, linear regression of untransformed data is recommended. Differences among operators' yield estimates were unacceptably large, and the procedure of standard selection and calibration was too slow. We suggest that photographic standards can reduce the time taken and improve precision. The DWR technique was recommended because operators achieved consistent estimates of species composition within 80 minutes, which we regarded as a reasonable time for a monitoring procedure. Weighted multipliers did not improve composition estimates. The technique was easy to use but initial training of operators was important. While fixed quadrats would probably reduce differences caused by spatial variability, time spent relocating quadrats could be excessive.