The Use of Multivariate Data Analysis in Assessing the State of Advance and After-Regeneration of Pine Forests after Selective Felling

Abstract

A research of qualitative and quantitative characteristics of regeneration after the first selective felling with an intensity of 20 to 50 % in pine forests of the northern part of the Krasnoyarsk forest-steppe has been carried out. Some of the plantations were covered by a ground fire 5 to 10 years before the felling. The aim of this research is a generalized analysis of the regeneration state in view of the forest type, the density of forest stand and exposure to fire before felling, as well as the disturbance of soil cover, the state of forest live cover and the microclimatic conditions in the felling areas. The methods of principal component analysis as well as correlation analysis and variance analysis for individual characteristics have been used. The advantages of multivariate data analysis using the method of principal component analysis for obtaining more information on the contribution and combined effects of various environmental factors on pine regeneration in felling areas are shown. The share of explained variance of the considered factors has equaled 87 %. The most significant factors for pine regeneration have turned out to be the type of forest (felling area) and exposure to fire. The second place in terms of importance has been taken by the density of forest stand before felling and the intensity of felling. Of the factors mediated by them, illumination intensity and soil moisture have turned out to be important. Based on the characteristics of the 4 main components, 2 options for combining the main factors for better regeneration of plantations have been established: 1) the large initial density of mature forest stands, as well as the moderate development of mosses and grasses in forest live cover make it possible to choose any felling intensity (within the studied limits), preferably in combination with preliminary burning of a part of the litter (or partial soil mineralization) 5 years before moderately-high or high intensity felling, 2) in case of lower initial density of the forest stand in forest types with significant development of forest live cover, preliminary burning of part of the litter or mineralization of the soil and the choice of a lower intensity of the the first felling (up to 20 %) are required. Analysis of the variability of linear increases in height-and-age groups of undergrowth confirmed the conclusions drawn from the analysis of the quantity and quality of regeneration, showed differences in the response of different groups of undergrowth to changes in microclimatic conditions in felling areas. The similarity of the northern forest-steppe with the southern taiga in terms of pine regeneration conditions has been noted. The results of the study can be used to clarify the requirements for felling and achieve better regeneration of pine forests.