Stand Structure of Northern Taiga Pine Forests

Abstract

In Northern taiga conditions pine forests occupy about 1.8 mln ha of the territory of the Komi Republic and are mainly represented by sphagnum, green-moss and lichen forest types. The studies were carried out at the Zelenoborsk Forest Station of the Institute of Biology of the Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences in green-moss and sphagnum pine forests developing at the site of fires and clearcuts. Tree layer has a mix composition with the predominance of pine trees and admixture of spruce, birch, larch and aspen. Pine stands form three types of age structure: conventionally evenaged; conventionally uneven-aged, represented by one generation; and stepped uneven-aged, consisting of two or three generations of pine trees. Trees left behind during clearcut and felling residuals at the cutting area by the burn method contribute to the formation of stands of stepped uneven-aged age structure. The variation coefficients of tree age are 5.8–10.8 % in pine forests with one generation and 39.7–45.6 % in forests with two or three generations. The number of generations and the type of age structure had no effect on the diameter and height of trees in the stand, which varied respectively within 25.2–49.5 % and 15.7–27.8 %. In pine forests developing after fires, the peak of pine settlement occur in the second or third decade, while in cutting areas, the maximum renewal occurs in the first or second decade after clearcuts. The amplitude of tree age fluctuations varies from 16 to 33 years in conventionally even-aged and conventionally uneven-aged forests developed after clearcuts and from 30 to 45 years in post-fire stands. In stepped uneven-aged stands tree age fluctuations changes from 120 to 167 years, and from 22 to 66 years in generations. The curves showing the distribution of trees by diameter in stands of pine trees had a left-handed shift, the asymmetry is represented by positive values and varies from 0.05 to 1.03. Trees of associate species are inferior in development, both in diameter and in height to pine trees of similar age. A close correlation between the diameter and height of trees in the stands was revealed. The relationship of age with diameter and height of trees varies from weak to significant at almost all of the sites studied. A close correlation between age and diameter was found in stepped uneven-aged pine forests (R = 0.79–0.96). The correlation between diameter and age increase with an increase in tree age fluctuations amplitude.