Features of pine stand reforestation in clear-cuts of Male Polissia

Abstract

Introduction

Under modern conditions, the regeneration of pine forests is primarily achieved through the establishment of forest plantations. A review of scientific literature indicates that, in certain forest site conditions, greater emphasis should be placed on natural regeneration to enhance biocenotic diversity, improve the biological stability of pine forests, and support their adaptation to global climate change. The aim of the research was to evaluate the effectiveness of artificial, natural, and combined forest regeneration in clear-cuts following strip felling with width of 51–100 m.

Materials and Methods

Features of natural and artificial regeneration of Scots pine (Pinus sylvestris L.) in clear-cuts after 51–100 m width strip felling of the main use were studied in 2005–2021. The study was carried out in fresh and moist forest site conditions (B₂, B₃ and C₃) in five sample plots within the Male Polissia region (Branch “Brody Forestry” of the State Specialized Forest Enterprise “Forests of Ukraine”). The condition of natural regeneration was assessed using the methodology of the Ukrainian Research Institute of Forestry and Forest Melioration (URIFFM), the Instruction on Design (2016,) and the Sanitary Forests Regulations in Ukraine (2016). The research data were analysed using methods of variational statistics.

Results

The density of one-year-old natural regeneration in clear-cuts after 51–100 m width strip felling was 43,500 stems? ha^-1. For 3–5-year-old regeneration, the density was 23,800 stems·ha^-1, and for 10–11-year-old regeneration, it ranged from 13,100 to 23,750 stems?ha^-1. Such density of natural regeneration is sufficient for the growing of highly productive pine forests in the study region. The plant density of self-seeding and advanced growth was higher in sample plots where natural regeneration was actively promoted. Specifically, 71% of 3-year-old self-seeding and 57% of 4-5-year-old advance growth were concentrated in furrow bottoms, where grass cover was absent. At 10–11 years of age, the average height and height increment of plantations and natural regeneration were similar. In fresh relatively infertile site conditions, denser stands (over 40,000 stems?ha^-1) exhibited a lower productivity class (by one unit) compared to sparser stands (about 20,000 stems?ha^-1) in moist relatively infertile pine site conditions. Across all research sites, the amount of advanced growth was sufficient for growing the highly productive pine forests in the region.

Conclusions

In Male Polissia, in fresh and moist oak-pine forest and moist hornbeam-oak forest,  the most favourable conditions for pine seed germination and subsequent seedling growth on clear-cuts after 51–100 m width strip felling were achieved through the prior promotion of natural regeneration. In the first three years, 3–6 times more self-seeding appeared on such plots compared to plots where no support measures were implemented. When clear-cuts undergo both natural regeneration and simultaneous establishment of pine plantations using bare-root planting material, the planted seedlings initially grow faster during the individual growth phase (1–5 years) and up to the closure phase (6–8 years). However, beyond this stage, natural regeneration exhibits a higher height increment, and by the age of 10–11 years, the height of naturally regenerated and planted trees equalizes.

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