Pine stands of Forest-Steppe zone of Kharkiv Region: productivity and natural regeneration

Abstract

Introduction

Scots pine stands in Forest-Steppe in Kharkiv Region cover an area of almost 40 thousand ha. A considerable part of them belongs to the nature reserve fund, which allows studying natural processes and conducting long-term observations. The majority of pine forests in Kharkiv region is of artificial origin, so it is necessary to analyze the state of natural regeneration and how the ground vegetation influences it in order to maximize the use of natural regeneration and the formation of more stable natural stands.

The aim of the research was to assess pine stands in Kharkiv Region by means of forest-taxation indicators, their ground vegetation and natural regeneration.

Materials and Methods

The study was conducted on 27 sample plots, which were laid in the forest stands of State enterprise State Enterprise “Skrypayivske ERFE”, State Enterprise “Zhovtneve Forest Economy” and National Nature Park “Slobozhansky”. The type of forest, tree species composition, age, average height and diameter, density of stocking, site index, growing stock per 1 ha were determined on the sample plots. Species composition, age, density and state of the natural regeneration as well as a variety of ground vegetation were also evaluated.

Results

The stands’ density of stocking increases with age in dry and fresh infertile sites (A_1-2). As for the forest site types, the highest density of stocking is in fresh fairly infertile one (B₂). As the fertility increase (C₂), the stands’ density of stocking becomes slightly less, along with that more undergrowth appears. Based on the analysis of forest inventory data and our research on sample plots, the most common type of pine forest in Kharkiv Region is a fresh oak-pine forest in fairly infertile site condition (B₂). It includes a wide age range and has a high growing stock per hectare.

We have found that in areas with a density of stocking of 0.8 or more, there is much less pine undergrowth (500 stems ha^-1) than in areas with a density of stocking of 0.6 and less, especially in canopy breaks (2,500 stems ha^-1). The most productive undergrowth is usually can be found in groups near the edge of the gap, with partial shading.

Conclusions

The pine stands in Forest-Steppe of Kharkiv Region grow mainly in fresh fairly infertile (B₂), fresh infertile (A₂) and fresh relatively fertile (C₂) site conditions. Site index classes vary from I^a to II, growing stock ranges from 80 to 616 m³·ha^-1. At intensive monitoring plots in the State Enterprise “Zhovtneve Forest Economy” and National Nature Park “Slobozhansky” the annual change of growing stock in pine stands is 8.3 m³ ha^-1.

In the studied stands, the projective cover of the ground vegetation varies from 15 to 90%. The highest indices of vegetation diversity and the highest cover are observed in oak-pine forest in fairly infertile sites (B₂).

Natural regeneration is mainly formed by pine, with little participation of oak (on several plots). Pine trees of 4–8 years old predominate in fresh fairly infertile site condition (B₂), with their average height of 2.7 m, while in fresh fairly fertile (C₂) and fresh infertile site condition (A₂) the height of pines is 1 and 1.1 m, respectively. In A₂ conditions, the density of Scots pine undergrowth is 1,500 pc.·ha^-1, in B₂ there is a mix of species such as oak and birch, although pine undergrowth dominate in plots reaching 2,500 pc. ha^-1. In C₂ conditions, the undergrowth of oak reaches 50%.

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