Evaluation of Sampling Techniques on Tall-Grass Prairie

Abstract

An evaluation of sampling techniques was conducted on a tall-grass prairie in eastern Oklahoma. The point transect, a modified point transect, line transect, angle order, quarter, quadrat, and wandering quarter methods were used. Relative and total density values were determined and compared with actual values obtained by hand count. The above methods, with the exception of the quadrat, underestimated the relative density of splitbeard bluestem (Andropogon ternarius), a dominant and densely cloned species, and overestimated switchgrass (Panicum virgatum), a subdominant, single-stalked species. Relative and total density values obtained by the quarter method were significantly less accurate than those obtained by the other methods; no method was significantly more accurate. With recalculation excluding splitbeard bluestem data, relative densities obtained by most of the methods agreed more closely with actual values, and the quarter method was again significantly less accurate. Results indicated that degree of clone density of the dominants and subdominants, as well as sampling time, should be noted prior to the selection of a sampling method in a highly aggregated grassland type. The modified point transect or quadrat methods are considered to be most applicable if the dominants are densely cloned as in splitbeard bluestem; however, the point transect or line transect methods may be adequate if the dominants are sparsely-cloned as in big bluestem (Andropogon gerardi) or little bluestem (Andropogon scoparius).