![]() ![]() The primary data needed for this approach is VOB/ha, that is inventoried volume over bark of free bole, i.e. ![]() It should be used for closed forest only because the original data base used for developing this approach was based on closed forests. ![]() The method presented here is based on existing volume per ha data and is best used for secondary to mature closed forests only, growing in moist to dry climates. USE OF INVENTORIES OF OPEN FORESTS AND WOODLANDS In the next two sections, details of the methods for using existing forest inventory data for biomass density estimation are presented.ĮXAMPLES OF CALCULATIONS OF BIOMASS DENSITYĪDJUSTMENTS TO APPROACH USING VOLUME EXPANSION FACTORS (VEF) Many of the inventories are old, 1970s or earlier, and the forests may have disappeared or changed.ĭespite the above problems, many inventories are very useful for estimating biomass density of forests.Very little descriptive information is given about the actual condition of the forests, they are often described as primary, but diameter distributions and volumes suggest otherwise (e.g., Brown et al.The definition of inventoried volume is not always consistent.Inventory reports often leave out critical data, and in most cases, field measurements are not archived and are therefore lost.Not all tree species are included, only those perceived to have commercial value at the time of the inventory.The actual diameter distribution of these large trees significantly affects aboveground biomass density. The maximum diameter class in stand tables is generally open-ended with trees greater than 80 cm in diameter often lumped into one class.The minimum diameter of trees included in inventories is often greater than 10 cm and sometimes as large as 50 cm this excludes smaller trees which can account for more than 30% of the biomass.Inventories tend to be conducted in forests that are viewed as having commercial value, i.e., closed forests, with little regard to the open, drier forests or woodlands upon which so many people depend for non-industrial timber.However, inventories are not without their problems. Data from forest inventories are generally more abundant and are collected from large sample areas (subnational to national level) using a planned sampling method designed to represent the population of interest. Use of forest inventory data overcomes many of the problems present in ecological studies. There is no way to extrapolate from inventories that do not measure all species. To use either of these methods, the inventory must include all tree species. Thus, not all countries in the tropics are covered by these estimates. The disadvantage is that a smaller number of inventories report stand tables to small diameter classes for all species. The advantage of this second method is that it produces biomass estimates without having to make volume estimates, followed by application of expansion factors to account for non-inventoried tree components. They are applied to stand tables or measurements of individual trees in stands or in lines (e.g., windbreaks, live fence posts, home gardens). These regression equations are mathematical functions that relate oven-dry biomass per tree as a function of a single or a combination of tree dimensions. The second approach directly estimates biomass density using biomass regression equations. 1989, Brown and Iverson 1992, Brown and Lugo 1992, Gillespie et al. The first approach is based on the use of existing measured volume estimates (VOB per ha) converted to biomass density (t/ha) using a variety of "tools" (Brown et al. This primer discusses two approaches for estimating the biomass density of woody formations based on existing forest inventory data. METHODS FOR ESTIMATING BIOMASS DENSITY FROM EXISTING DATAĪPPROACH 1: BIOMASS DENSITY BASED ON EXISTING VOLUME DATAĪPPROACH 2: BIOMASS DENSITY BASED ON STAND TABLES METHODS FOR ESTIMATING BIOMASS DENSITY FROM EXISTING DATA ![]()
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