Structural and mensurational characteristics of spruce stands in primeval forest communities of the Verkhovynskyi National Nature Park

Abstract

Introduction

The study of forest mensurational and silvicultural characteristics was conducted in primeval forest communities formed by Picea abies (L.) Karst. The relevance of this research lies in the investigation of the forest mensurational and silvicultural characteristics of spruce primeval forests as natural models of sustainable ecosystem functioning under current environmental conditions. The study of the productivity of primeval forest ecosystems is an important prerequisite for the implementation of close-to-nature forest management in other spruce stands, since primeval forests can serve as reference systems for the formation of biologically stable and highly productive forest communities. The aim of the study was to investigate the developmental processes of primeval forests involving Picea abies, their forest mensurational and silvicultural characteristics, and the condition of primeval forest communities.

Materials and Methods

The study was conducted between June and September 2025 at three sites of spruce primeval forests located within the Verkhovynskyi National Nature Park. The research covered the altitudinal vegetation belt of spruce forests (Piceeta abietis) within the elevation range of 1000–1600 m above sea level under conditions of the high-mountain humid spruce forest site type. For the purposes of the study, sites were selected in primeval forest stands representing specific phases of their development. The mensurational and silvicultural characteristics of the stands were determined, including the presence of trees approaching the limit of physiological longevity, as well as standing deadwood and fallen deadwood at different stages of decomposition. In addition, the quantitative and species composition, as well as the spatial distribution of the shrub layer, seedlings, saplings, and herbaceous ground vegetation were examined within the study plots. The presence or absence of traces of anthropogenic influence was also assessed at each site. The health condition of the stands was evaluated according to four categories: healthy (without signs of weakening), weakened, severely weakened, and dying. The criteria and indicators applied in the assessment of the investigated spruce forest stands fully correspond to those established for primeval forest communities.

Results

The growing stock of living trees at the site representing the early stage of the ageing phase amounted to 588 m³·ha^-1, at the site representing the late ageing phase – 596 m³·ha^-1, and at the site representing the initial phase of stand breakdown – 545 m³·ha^-1. The volume of standing deadwood was 24, 70 and 121 m³·ha^-1, respectively. The stands are composed of three vertical layers. The first layer is formed by the tallest trees, often with the largest diameters. The second layer is weakly expressed but represented by trees of similar diameter (20–32 cm) and height (12–26 m). The third layer consists of the youngest generation of trees, with diameters of 8–18 cm and heights of 6–15 m. The largest volume of standing dead trees, both in terms of number (10–41 trees·ha^-1) and stock (19–105 m³·ha^-1), was recorded in the first layer, which is also the oldest. In the second (8–32 trees·ha^-1) and third (10–38 trees·ha^-1) layers, the number of standing dead trees was similar or even higher than in the first layer; however, due to the smaller size of the trees, the volume of deadwood was considerably lower (4–13 and 1–3 m³·ha^-1, respectively). The number of regeneration individuals varies considerably and generally depends on the developmental phase of the stand: 4.8 thousand individuals·ha^-1 (early ageing phase), 13.6 thousand individuals·ha^-1 (late ageing phase), and 15.0 thousand individuals·ha^-1 (initial breakdown phase). Another factor contributing to the high variability in regeneration density among the sites is the different intensity of herbaceous ground vegetation development, which depends on canopy closure and the level of light availability within the forest stand. Seedlings and saplings are mainly concentrated on fallen logs at the fourth stage of decomposition.

Conclusions

The studied old-growth spruce stands are characterized by natural origin, uneven-aged structure, the presence of trees approaching the limit of physiological longevity, the occurrence of seedlings and saplings, and fallen deadwood at all stages of decomposition. Trees representing all developmental stages are present, and no signs of anthropogenic disturbance were detected. Thus, these stands exhibit all the characteristics typical of primeval forest communities. The health condition of the stands depends on the developmental phase of the primeval forest community and varies from “healthy” (sample plot 12, early ageing phase) to “severely weakened” (sample plot 13, initial breakdown phase). The study of natural processes occurring in primeval forest ecosystems is an important prerequisite for the implementation of close-to-nature forest management, since primeval forests can serve as reference systems for the formation of biotically stable and highly productive forest communities.

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