Changes in the Effect of Tree Stand Competition on the Pinus sibirica Undergrowth during Postfire Successions in Mid-Taiga Birch Forests of the Urals

Abstract

The effect of light and root competition of the tree stand on the growth of the Pinus sibirica Du Tour undergrowth in post-fire birch forests of different ages is investigated using the example of mid-taiga forests of the Middle Urals. The studies were carried out on the basis of a microecosystem approach, using indices of light competition of the tree stand (Ilsc), root competition of the tree stand (Irsc) and integral competition of the tree stand (Irlsc). At the stage of the 13-year-old young birch stand with almost full illumination, the main factor determining the growth and development of Pinus sibirica undergrowth is root competition for soil nutrition. In the 32-year-old middle-aged birch stand, a joint, almost identical, effect of the factors of light and root competition on the growth of Pinus sibirica undergrowth is observed. In the mature 70-yearold birch stand, the main factor, influencing the growth of Pinus sibirica undergrowth, is the level of interception of photosynthetically active radiation by its canopy (light competition) with root competition is not expressed. In our opinion, this is due to the adaptive abilities and characteristics of the soil nutrition of the Pinus sibirica undergrowth and a change in the degree of soil saturation with organic compounds during the development of the post-fire birch forest.