Current issue: 57(2)
Under compilation: 57(3)
The most important fact to consider in attempting to develop an increment forecast method is the great dependency of the increment on the growing stock volume. Although the site (soil and climate) produces the increment and volume, there would be no increment without the volume as an increment capital. The cutting possibilities are still more dependent on the existing growing stock. Thus, the primary characteristics in management planning is the growing stock volume. The methodological starting point in this paper is that the increment is considered dependent variable which can be explained by other growing stock characteristics. The basis of the analysis and the primary object of this investigation is the increment percentage. Using available and measured sample plots the increment percentage will be analysed as a dependent variable by other growing stock characteristics.
The main emphasis will be the methods which can be used in connection with the interacting increment and drain. An increment-drain forecast should give at least approximately the allowable cut in timber products. Thus, it will be attempted to find the stock characteristics determining the amounts of timber products.
The article introduces the theory and basic concepts of the increment-drain process, increment functions and basal area – height method, and discusses estimation of timber products in increment-drain forecast, fluctuations of the increment, mortality in connection with the increment-drain forecast, and the scheme of cutting budget for desirable growing stock. Finally, it gives some proposals, based on the investigation, for preparing an increment-drain forecast for a large forest area.
The PDF includes a summary in Finnish.
The paper concerns the estimation of the increment of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) stands in the southern half of Finland. For the methods based on stand tables, tree functions forecasting the annual increment of diameter and height during the next 5-year period are presented. The main results of the study, however, are the functions for the volume increment percentage of pine and spruce stands. The independent variables are: forest site type, tree species, stand age and volume, and mean diameter. The standard error of estimate is about 17% in the best functions. Calculations were made also with regard to the application of the results in growth estimation of large forest areas.
The PDF includes a summary in English.