Estimating botanical composition by the dry-weight-rank method in California's annual grasslands

Abstract

The dry-weight-rank method of estimating botanical composition on California's annual grasslands is a viable alternative to harvesting and sorting or methods using points. Two data sets of sorted species weights were available. One spanned nine years with quadrats harvested at peak of production. The second spanned one growing season with 20 harvest dates. Two existing sets of coefficients for the first, second, and third ranked species and one calculated from our data were used to estimate dry-weight composition. We tested the differences between the estimates and actual values. Differences were found (using the basic ranking method) for data from moderately grazed grassland, but one set of coefficients did not appear better than the others. The cumulative ranking correction produced more differences than the basic ranking method on ungrazed grassland with one dominant species. For the dominant species, cumulative ranking, nevertheless, produced more accurate estimates. Cumulative ranking with coefficients of 70 (rank one), 20 (rank two), and 10 (rank three) should serve well for most applications. Calculating coefficients for each new area should not be necessary.

Citation

Ratliff, Raymond D.; Frost, William E. 1990. Estimating botanical composition by the dry-weight-rank method in California's annual grasslands. Res. Note PSW-RN-410. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 5 p.