In the following example of a feasible approach to biomass sampling for above­ground components difficulties are outlined and possible solutions shown. The sampling is based on the selection of a number of representative trees from a population according to the principles of statistical sampling as described in Chap. 2. After this step further decisions about the sampling method that have to be made will include:

• the relevant biomass components;

• the sampling design of the stem biomass;

• the sampling design of the crown biomass; and

• the model to scale up from samples to the individual trees.

A plethora of different ways can be identified in the published literature to define the biomass components of a tree. A straightforward approach to calculate the aboveground biomass of trees, that can be used successfully in a good proportion of applications, is to divide the tree hierarchically. It is first divided in stem and crown, the stem is then further subdivided into bark and wood biomass and the crown into foliage and branches. Depending on the objective it might be useful to further differentiate fruits/cones, heart and sapwood, merchantable branches, dead branches or to add twigs as finer branch material to the components. High differentiation levels are usually warranted if nutrient budgets for sustainability assessments of biomass harvesting have to be established (see Chap. 10 and Seifert et al. 2006; Block et al. 2008; Dovey 2009; Ackerman et al. 2013b). In this example of a mid­rotation Pinus radiata tree (age 14 years) only the bark and wood of the stem, branches (bark and wood aggregated) and needles were used as components.