Utilisation of mathematical models and growth simulators for creating forest management plans and planning the tending felling

Abstract

Growth simulators (GS) or mathematical models focusing on forest stand development can be used as an important instrument of decision making when collecting data for forest management. Currently, the main source of information for the forest owner or the forest manager is Forest Management Plans (FMP). The problem is that FMPs are static works, created for 10 years, which do not directly deal with the modelling of mensurational variables. Therefore the informative value of FMP for the owner is rather limited. FMP offer very exact information in the first year of their validity, but they do not enable to determine the development and behaviour of mensurational variables during the whole period while the plan is still valid, and thus give a more accurate information base for successful forest management. This problem could be solved by mathematical modelling of development of mensurational variables, or rather complicated growth simulators, which would supply the above-mentioned information. These problems are not new, KNEIfl (2000) and SIMON (2001) mentioned them in their works.PRETZSCH et al. (2002) approached the term model as a system of equations and relations describing tree growth and competitive relationships, while simulator is an implementation of the model into a computer program, which enables us to interactively influence the process of simulation. The main objectives of the growth process modelling are prognosis of forest stand development and determination of optimum management strategy.Based on the known and given behaviour regularities of the individual growth processes, simulation models enable to foresee the condition in which the given forest stand will be with certain probability under the conditions of quantitatively chosen factors.Many Czech authors were dealing with mathematical modelling and its possible utilisation in their works. To name the most important: POLÁK (1972), SIMON et al. (1996) and ZACH (2001). On the international level, the following authors focused on forming the growth simulators -PRETZSCH and KAHN (1998), NAGEL (1975), and STERBA and MONSERUD (1995). As PRETZSCH et al. (2002) presents, it is difficult to use foreign models because of different environment and that is why such models do not give realistic results. The main problem of creating a GS that would be possible to use for simulation of greater territory units, is the need for enormous database and validation, which demands extensive measuring. This is, of course, very demanding and becomes an obstacle when constructing the GS. However, it is possible to use quite simple mathematical models that can be created while processing the FMP. On the one hand, their utilisation restricted is to the given property, but they give valuable information for the management and also for the processing of FMP.For the mathematical modelling of development of mensurational variables it is necessary to create mock time series from non-mixed forest stands of the same age on the given estate. According to ZACH (2001) the mock time se...