A COMPARISON OF THE LINE INTERCEPTION, VERTICAL POINT QUADRAT, AND LOOP METHODS AS USED IN MEASURING BASAL AREA OF GRASSLAND VEGETATION

Abstract

A study was designed to determine the most efficient sample size and number of samples when any one of the line-interception, vertical point quadrat, or loop methods of vegetation survey is used, on different range types in southern Alberta. The procedure has involved obtaining basal area measurements by all methods on ten transects, 100 feet long, within each range type.Sampling intensities sufficient to sample the dominant and minor species to within ± 10 per cent of their true mean basal area, and the precision obtained when minor species were sampled at intensities found adequate for the dominant species, were calculated. Measurement of minor species at the latter intensities was highly variable. The loop method was the most rapid in the field, detected least species, and gave the most variable data. Data collected by this method were especially variable when the dominant plant species were of the single stemmed type. The line interception method was the most time-consuming, detected more species than either the loop or point methods and gave data which were slightly more variable than the point method. The point method gave the least variable data and, in general, seemed the most satisfactory of the three methods in the vegetative types studied.