TROPICAL FOREST BIOMASS ESTIMATION FROM TRUNCATED STAND TABLES

Total aboveground forest biomass may be estimated through a variety of techniques based on commercial inventory stand and stock tables. Stand and stock tables from tropical countries commonly omit trees below a certain commercial limit, often greater-than-or-equal-to 35 cm. Biomass estimates made from such tables will fail to include from 25-45% of the total stand biomass. Using stand tables generated for large forested areas, we describe several methods of estimating the numbers of stems in one or two missing small-diameter classes (truncated stand tables) based on the numbers of stems in the larger size classes. We show that an exponential model reasonably approximates diameter distributions among most diameter classes in various types of tropical moist forest. The most accurate method of estimating the number of stems in smaller (missing) diameter classes used the ratio of the numbers of stems in the two smallest diameter classes. The error of estimation of total stand biomass using this approach (10-12%) was always less than the error incurred by omitting the missing classes (25-45%).