Canopy Area and Aboveground Mass of Individual Redberry Juniper (Juniperus pinchotii) Trees

There is increasing interest in using canopy area to quantify biomass of invasive woody plants on large land areas of rangelands for a variety of reasons. For those woody species that emphasize lateral canopy growth over vertical growth it may be possible to relate canopy area to aboveground mass (AGM). Our objective was to determine the utility of external canopy measurements (area, volume, and height) for predicting AGM and the percentage of AGM that is wood (PW; i.e., stems > 3 cm diameter) in individual redberry juniper (Juniperus pinchotii Sudw.) plants in west Texas. The canopy area to height relationship was curvilinear and indicated that at heights > 3 m, there was more lateral (canopy area) than vertical canopy growth. We found a strong linear relationship between canopy area and AGM (r(2) = 0.94; AGM range 9 kg to 688 kg) and it appeared that AGM could be predicted in individual trees from canopy area. Moreover, the canopy area/AGM relationship developed from smaller trees was able to adequately predict AGM of larger trees. Height was a less effective predictor of AGM (r(2) = 0.66), and incorporation of height with canopy area to determine canopy Volume did little to improve accuracy of estimating AGM over canopy area alone. The canopy area/PW relationship was curvilinear (the rate of increase in PW declined in larger trees) and PW reached 60-70% in the largest trees.