Comparison of the Reference Unit Method and Dimensional Analysis Methods for Two Large Shrubby Species in the Caatinga Woodlands

Abstract

The reference unit technique was compared with the dimensional analysis approach for estimating large shrub foliage biomass in Northeast Brazil. The techniques were tested on coppicing jurema (Mimosa acutistipula Benth.) and pau branco (Auxemma oncocalyx [Fr. Alem.] Taub.). Both methods provided good estimates of foliage weight. The coefficients of determination for the reference unit approach ranged from .890 to .985. The r2 values obtained in applying the dimensional analysis method were .937 and .948. Improvements in estimates with the reference unit method were obtained when (1) a branch unit of 19% of total plant foliage was used versus a unit of only 7%, (2) the branch unit resembled the appearance of the branching of the plant being estimated, and (3) estimations of 3 judges were averaged.