Sampling the density and basal area of trees is fundamental to quantitatively characterizing forests and woodlands. Commonly used sampling methods are well-suited for trees with single trunks, but are these methods also suitable for sampling multi-trunked trees? This question is especially important where multi-trunked trees are common, as is the case for Utah juniper ( Juniperus osteosperma, JUOS), a codominant of large areas of pinyon-juniper vegetation in western North America. This study addresses the question of suitability by comparing 3 methods for sampling JUOS. The Dbase Method has been commonly used, and it focuses on the bases of trees for both identifying individuals and measuring tree diameters. The Dbh Method, which parallels the standard for sampling single-trunked tree species, also has been used for multi-trunked trees, and it focuses on breast height (i.e., 1.4 m above ground) for both identifying individuals and measuring diameters. The third method, the Base-Dbh Method, is proposed as a possible improvement. It focuses on the bases of trees for identifying individuals and on breast height for measuring diameters. Application of these 3 methods to the same JUOS trees produced statistically significant differences in values of density and basal area and thereby also produced differences in relative values (when JUOS was compared to the codominant two-needle pinyon, Pinus edulis). Comparison of the 3 methods determined that the proposed Base-Dbh Method is superior in terms of (1) biological validity, (2) comparability to data from single-trunked tree species, and (3) consistent application by field personnel.
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24 July 2017
Methods for Sampling Density and Basal Area of Multi-Trunked Trees: Juniperus osteosperma in Pinyon-Juniper Vegetation
John L. Vankat
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Western North American Naturalist
Vol. 77 • No. 2
July 2017
Vol. 77 • No. 2
July 2017