Brown 1997 Estimating Biomass.pdf [UPD]
In this article, we will explain how to apply Browns methodology to estimate biomass of tropical forests using forest inventory data. We will also discuss some of the advantages and limitations of this method, and provide some examples of its applications.
Brown 1997 Estimating Biomass.pdf
Steps to Estimate Biomass Using Browns Methodology
Obtain forest inventory data that include DBH, total height, and species identification for each tree in a sample plot or stand. The plot size and shape should be representative of the forest type and condition. The number and location of plots should be sufficient to capture the variability of the forest structure and composition.
Determine the wood density and Holdridge life zone for each tree species in the inventory data. Wood density is the oven-dry mass per unit volume of wood at a standard moisture content. Holdridge life zone is a classification system that defines bioclimatic regions based on temperature, precipitation, and potential evapotranspiration. Wood density can be obtained from published sources or measured directly from wood samples. Holdridge life zone can be derived from climatic data or maps.
Select the appropriate regression equation from Brown (1997) to estimate aboveground biomass of individual trees. Brown (1997) provides different equations for different life zones (moist, moist transition to dry, dry) and forest types (undisturbed, logged, nonproductive). The equations are of the form:
B = a + b * DBH + c * H + d * WD
where B is the aboveground biomass in kg, DBH is the diameter at breast height in cm, H is the total height in m, WD is the wood density in g/cm3, and a, b, c, d are coefficients that vary by life zone and forest type.
Apply the selected equation to each tree in the inventory data to obtain its aboveground biomass. Sum up the aboveground biomass of all trees in a plot or stand to obtain the total aboveground biomass per unit area.
If needed, convert the aboveground biomass to carbon stock by multiplying it by a conversion factor that ranges from 0.45 to 0.50 depending on the nature of the tree species. Carbon stock is an indicator of how much carbon is stored in the forest biomass.
If needed, estimate the belowground biomass by multiplying the aboveground biomass by a root-to-shoot ratio that ranges from 0.15 to 0.30 depending on the life zone and forest type. Belowground biomass is an indicator of how much organic matter is stored in the roots and soil.
If needed, estimate the biomass change over time by comparing the biomass estimates from different inventory periods or scenarios. Biomass change is an indicator of how much carbon is sequestered or emitted by the forest due to growth, mortality, or disturbance.
Advantages and Limitations of Browns Methodology
Browns methodology has several advantages over other methods for estimating biomass of tropical forests. Some of these advantages are:
It is based on a large and diverse data set of over 5,300 trees from 43 independent sample plots and 101 stand tables from four countries (Brazil, Colombia, Mexico, and Venezuela).
It accounts for variations in tree morphology, wood density, and bioclimatic conditions across different life zones and forest types.
It provides simple and robust equations that can be easily applied to forest inventory data without requiring complex calculations or models.
It allows for estimating biomass at different scales (individual tree, plot, stand, region) and for different purposes (carbon accounting, forest management, ecological research).
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