Some Considerations in the Use of Point Quadrats in the Analysis of Mixed Prairie Vegetation

The purpose of the study was to evaluate two variations of the point quadrat method of vegetation analysis in the Mixed Prairie. Percentage composition data was gathered by three methods; the clip quadrat, vertical, all-contacts point and the inclined, basal-contact point method. Each of these methods was employed on three range site study areas. Line transects were established across a breaks site, clay upland and a limy upland range site. All point and clip quadrats were taken along this transect. The coefficient of variability and sampling error were calculated for each method, on each area. Number of samples and the amount of time required by each of the methods, to sample area, with equal precision, were also calculated. The vertical, all-contacts phase of the point quadrat method proved to be as efficient as the inclined, basal-contact method. The all-contacts data gives several measures of plant growth, whereas the basal- contact point and clip quadrat give only one measure. From all-contact data, foliage cover, basal cover, percentage composition, and cover repetition can be calculated. Percentage composition, as calculated from all- contacts point data, compare favorably with figures calculated from clip quadrat data (herbage yield). By computing the difference between these values a correction value is obtained by which all- contact data can be converted to percentage composition by herbage yield. Total herbage yield can be determined quite rapidly, using six or seven square foot quadrats. Using the correction values, herbage yield per species can then be determined from all-contacts point data. These various methods of applying all-contacts point data to vegetation analysis make the method quite adaptable for use in the Mixed Prairie