Thinning-Based Formation of Siberian Pine Forests in the Dark Chern Zone of Western Sayan

Abstract

We have tested management practices at monitoring plots of the Institute of Forest, Russian Academy of Sciences, in Ermakovo station (Western Sayan) to develop Siberian pine forests (Pinus sibirica Du Tour) from young coniferous–deciduous forests that were formed in the place of clearcuttings in tall-grass–fern fir and Siberian pine forests in the low-mountain dark Chern zone. The dynamics of all layers and structural elements of the communities were studied from 1966 to 2014 at two experimental monitoring plots (each with an area of 2500 m2) and compared to the control. The article considers the case of admitting the complete lighting of Siberian pine undergrowth at first thinning. This practice proved to be optimal for further forest-management recommendations. Siberian pine gained competitive advantages over aspen or fir after the first thinning for a short period until the dominant species (aspen, birch, or fir) started to actively regenerate. Repeated thinning made Siberian pine steadily dominant in stands. Our experiment has shown that highly productive Siberian pine forests can be formed for 50 years under the unique natural and climate conditions of the low-mountain Chern zone of the Western Sayan, while the natural course of succession could not yield this result even after 200 or more years. These forests are comparable to indigenous dark Siberian pine forests with respect to their density (0.4–0.6) and wood stock (182 m3/ha at the age of 70–80 years and 270 m3/ha at the age of 80–90 years); however, the managed stands yield many more nuts (about 300 kg/ha) at the age of 70–90 years. Thinning induced the growth of a stand dominated by Siberian pine, as well as the formation of a phytocenotic structure similar to indigenous dark Siberian pine forests, i.e., a structure with a high diversity.