Growth dynamics of Pinus sylvestris L., Picea abies (L.) H.Karst. and Pinus sibirica Du Tour coniferous stands: modified model

Modification of the growth dynamics model of the total biomass of forest stands is focused on using the age of physiological maturity (ripeness), which, as shown by previous calculations, is a constant for each species: Pinus sylvestris L., Picea abies (L.) H.Karst. and Pinus sibirica Du Tour. Validation of the modified model was carried out for coniferous stands – spruce, pine and cedar, biologically related. For stands of P. sylvestris, P. abies and P. sibirica is an allometric parameter that characterizes the relationship of biomass with the area of planting, does not depend on the class of bonus and is a constant for each species. The behavior of the parameter that characterizes the rate of resource consumption is individual for each type. For stands of P. abies, this parameter increases, and for P. sylvestris decreases with increasing bonus, for stands of P. sibirica, this dependence turns out to be nonlinear. In the future, this circumstance needs additional research. The statistical Nash-Sutcliffe criterion showed high accuracy (by coniferous stands of the second site class NSE = 0.9987 for P. sylvestris, NSE = 0.9828 for P. abies and NSE = 0.9781 for P. sibirica) of the modified model. Compared with similar calculations that do not take into account the age of physiological maturity, the quality of the modified model has increased by an order of magnitude. For all types of coniferous stands, the relative deviation of the calculation from empirical data was additionally calculated, which in general amounted to 1-2%, with the exception of ages lower than the physiological age of maturity. For these ages, the relative deviation increased to 5%, which, according to the authors, is associated with the processes of formation of coniferous plantations as an ecological system.