Forest-Based Biomass Basic Computations - Mathematics and Statistics for the Environment - page 326

13.2 FOREST BIOMASS COMPUTATIONS AND STATISTICS
Earlier, in Chapter 7, we provided a basic, fundamental review of statistics and a variety of example
statistical operations, all for a good purpose. Simply put, you cannot expect to work even at the
fringes or margin of any area of interest and specialization in the environmental profession without
a strong foundation in statistical methods. This is certainly the case in activities related to forest
and grassland management. Although we do not restate the statistical methods presented earlier,
following is a list of some of the important statistical methods routinely used by environmental
professionals in forest and grassland management:
• Simple random sampling
• Sample selection
• Standard errors
• Sampling and replacement
• Conidence limits for large and small samples
• Size of sample
• Va r ia nce
• Stratiied random sampling
• Estimates
• Proportional and optimum allocation
• Regression estimation
• Family of regression estimators
• Ratio estimation
• Mean-of-ratios estimator
• Double sampling
• Pace frequency
• Point intercept
• Double-weight sampling
13.3 SAMPLE FOREST-BASED BIOMASS COMPUTATIONS
Wise utilization of the forest resource relates to awareness of its value (Ince, 1979). The amount
of heat energy that can be recovered from wood or bark determines its fuel value. The amount of
recoverable heat energy varies with moisture content and chemical composition. Recoverable heat
energy varies among tree species and even within a species. In this chapter, we provide a summary
of information that may be used to estimate recoverable heat energy in wood or bark fuel, biomass
weight considerations, biomass weight examples, and methods for estimating stand-level biomass.
13.3.1 l oWer and h igher h eating v alues
The lower heating value (LHV) of a fuel is defined as the amount of heat released by combusting
a specified quantity (initially at 25°C) and returning the temperature of the combustion products
to 150°C; it is assumed that the latent heat of vaporization of water in the reaction produces is not
recovered. The LHV is the useful calorific value in boiler combustion plants and is frequently used
in Europe. The higher heating value (HHV), the gross calorific value or gross energy, of a fuel is
defined as the amount of heat released by a specified quantity (initially at 25°C) once it is combusted
and the products have returned to a temperature of 25°C, which takes into account the latent heat
of vaporization of water in the combustion products. The HHV is derived only under laboratory
conditions and is frequently used in the United States for solid fuels. Heating values in units of MJ/
kg are converted from heating values in units of Btu/lb. For solid fuels, the heating values in units
of BTU/lb are converted from the heating values in units of Btu/ton. The lower and higher heating