Inventory by Compartments

Inventory by compartments is the method typically used for acquiring data for traditional forest management planning purposes. It is based on the concept of the forest stand, which is traditionally defined as a geographically contiguous parcel of land whose site type and growing stock is homogenous (e.g. Lihtonen 1959 p. 9, Ilvessalo 1965 p. 159, Davis and Johnson 1987 p. 29, Poso 1994 p. 95). In this context, compartment can almost be considered a synonym for forest stand, but a compartment must be also a suitable cutting unit or treatment unit for silvicultural measures and need not necessarily be as homogenous as a forest stand. Detailed forest management plans cannot be produced without compartment-wise estimates of site characteristics and growing stock and without silvicultural treatment proposals for each compartment. The latter must be made within the field inventory, because otherwise the planner has no way of ensuring that in the optimum solution to the forest management planning problem every compartment will be treated silviculturally in a feasible manner. Models describing forests and forestry in forest management planning packages (e.g. MELA, Siitonen et. al. 1996) are merely simplifications of reality. Sampling theory could be used to estimate the sample size needed to attain a certain required level of accuracy in estimates of growing stock, but if the compartments are small the sample sizes become so large that the inventories will be too expensive. In Nordic countries and in Central Europe, where compartments are rather small, a solution to the problem has been found in terms of a subjective method called “inventory by compartments”, which is partially based on visual assessment of the growing stock. Inventory by compartments will be illustrated in this chapter by describing a Finnish application. The area of forestry land in Finland is about 26 million ha, of which 60% is owned by private persons. All the forests owned by the state or by