engleski

Process-based model of a selection forest stand as a support to uneven-aged forest management

This paper presents a designed structural and computerised continuous model of a selection forest stand supported by system dynamics (Cavlovic 1996a). Four basic processes have been selected to occur continuously and impulsively over the course of time: ingrowth of trees to the stand (recruitment) ; transition of trees from one diameter class into another ; volume increment ; and mortality and cutting. These processes are presented through verbal and structural models, of a uneven-aged stand dynamic system, and through a mathematical model. Aided by the quoted continuous model, the simulation of fir uneven-aged stand and fir-beech uneven-aged stand in five productivity classes was conducted. For each of the estimated uneven-aged stands was determined recruitment that supports the balanced, reverse “ J” distribution of uneven-aged stands. Therefore, recruitment is the most important process influencing structural changes in a uneven-aged stand. Simulations were performed to determine how a decrease in recruitment influences the dynamic structure of a uneven-aged stand (growing stock, diameter distribution of trees of different sizes and ages, and species composition) and its volume increment. On the basis of the measured structure, increment, and recruitment in real fir and fir-beech selection stands (Management unit Sungerski lug), a simulation was conducted to determine the possible development of these stands and the time needed to achieve a normal structure. According to the simulation research, the present method can be used to model the dynamic nature both of normal and real selection stands, and can form the basis for research into the changes in selection stands in terms of quality and quantity. These changes are the result of various disturbances occurring over the course of time (i.e. absence of regeneration, decrease in increment, tree dieback and replacement of species). The research can also support uneven-aged forest management.

dynamic system modelling; fir-beech selection stands; recruitment

nije evidentirano