Rangeland alpha diversities: Harvey Valley, Lassen National Forest, California

Authors

Raymond D. Ratliff, Pacific Southwest Research Station, USDA Forest Service, Sierra, Fresno, California

Abstract

Monitoring diversity usually begins by estimating alpha diversity of a plant community on a specific site. The objectives of this study were to provide alpha diversity benchmarks and to determine whether rangeland community basal cover characteristics explained variation in diversity estimates. Plant and surface component cover percentages were estimated on 51 plots (representing four vegetation types) on the Lassen National Forest, CA. Each plot was sampled with 30 random, 102 basal point transects. Jackknife procedures were used to compute means and standard errors for Margalef's diversity index (D_m), which stresses species richness, and Simpson's index (D_s), which stresses species dominance. Within vegetation types, D_m and D_s did not rank all plots in the same order. Highest D_m values occurred with the most species. Highest D_s values occurred with comparatively few species but more uniform cover. With either index, average diversity declined from the meadow to grassland to open shrub-grass to timber-bunchgrass types. All possible subset regressions of diversity on the basal cover characteristics were computed. Portions of the variance accounted for by the best models were too low to allow prediction of D_m and D_s. The relation of alpha diversity to rangeland health is discussed.

Recommended Citation

Ratliff, Raymond D. (1995) "Rangeland alpha diversities: Harvey Valley, Lassen National Forest, California," Great Basin Naturalist: Vol. 55: No. 1, Article 5.
Available at: https://scholarsarchive.byu.edu/gbn/vol55/iss1/5