Kairiūkštis, L. and Juodvalkis, A. 2005. The Theoretical Fundamentals of Forming of the Most Productive Stands. Baltic Forestry, 11 (2): 38-50

The paper deals with the development of the theory of the most productive Picea abies Karst., Pinus sylvestris L., Quercus robur L., Fraxinus excelsior L., Betula pendula L., pure and mixed stands, the utilization of solar energy by trees and storeys, the interaction between trees, their productivity, optimal stand density, the influence of intermediate fellings on the increment of trees and stands. Also the construction of the models of the most productive stands and the development of the standards of intermediate fellings are analysed. For this the data gleaned over 30 years in more than 500 permanent experimental plots have been used. The revealed new phenomenon of the stress effect of trees while forming ecosystem enabled the density of forming young stands to be optimized according to the critical limit of crowns approach while the density of stands according to the maximally possible projection area of a storey and an optimal degree of crown overlapping. It ensures the largest increment of the most valuable wood in ontogenesis of ecosystem. It has been determined that the more the surface of a storey resembles the stairs, the more the solar energy penetrates into the stand. The most productive trees (class A) use the solar energy most effectively for the increment of wood. The most significant productivity of stands is achieved in case the stocking of a storey is maximal, the trees in the storey are maximally productive and the distance between them (crown overlapping) is optimal. In the paper tree prototype – models of the most productive stands and the standards of their forming by intermediate fellings are presented. It has been ascertained that at a certain interval of stand age and thinning intensities the increment of thinned stands exceeds that of stands where thinnings have not been applied. With increasing age of stands the feasibility to enlarge stand increment by regulating density is more seldom noted because stocking augments, up to which it is feasible to thin stands without diminishing their increment, in comparison to the increment of stands where thinnings have not been applied.

Key words: critical limit of crown approach, the effect of stress, maximal stand productivity, use of solar energy, optimal stand density, intermediate fellings, thinning intensity