Procedures to determine the amount of plant cover/basal area in field plots

Plant species compete for ground space in a variety of ways. The purpose of this research was to describe procedures to determine plant basal area (plant cover) to help understand ecosystem structure of a desert ecosystem. For one field plot (1089 m2), distance and direction of each plant were measured from either another plant or from a field marker. The diameter and height were recorded for each plant. Computer programs (1) provided the distances and directions among all the plants in the plot, (2) provided a listing of the plants (including species name, distance, direction, height, diameter and condition) within a pre-determined radius of each plant (a target plant), (3) computed the area of plant basal area (plant cover) within a 5-m radius around each plant in the plot and (4) produced a two-dimensional diagram to show the location of plant cover of all plants around each target plant with calculations of plant cover area for each plant. Two examples were selected to illustrate the versatility of the technique. For one example, the target plant with seven other plants within the 5-m radius (78.5 m2 total area) had a total plant cover of 10.2 m2. For this first target plant, the plant cover within a 3-m radius (total area of 28.3 m2) was shown to be 4.88 m2. For a second example target plant, there were 10 plants within a 5-m radius area that provided 21.6 m2 plant cover. For this second target plant, the calculated plant cover within a 3-m radius area was 12.6 m2. From the 5-m radius analysis to the 3-m radius analysis, only one of the 10 plants was not excluded. We believe that the combination of procedures and computer programs provide an accurate estimate of the amount of plant cover (basal area) around plants within desert field plots. These procedures may be combined with other ecological parameters, such as association analysis to make better estimates of ecosystem structure.