Monitoring of secondary Norway spruce stands condition in the Zacharovanyi Krai National Nature Park

Abstract

Introduction

The problem of Norway spruce forest dieback in the Ukrainian Carpathians is evident. In the Zacharovanyi Krai National Nature Park (hereinafter referred to as the NNP), secondary Norway spruce forests occupy 380.2 hectares, representing 6.6% of the forest-covered area. Studies on the condition of secondary spruce stands in the NNP began in 2020, when nine permanent sample plots (PSPs) were established. It was found that the age of quantitative maturity of secondary spruce stands occurs at 50–55 years, which is approximately five years earlier than reported in studies conducted in the 1980s. According to current regulatory documents, the maturity age of secondary spruce stands is 61–70 years.

Thіs study aimed to identify trends in changes in the health condition of secondary Norway spruce (Picea abies (L.) H. Karst.) stands in beech-type forests within the Zacharovanyi Krai National Nature Park.

Materials and Methods

Repeated assessments were conducted on the permanent sample plots established in 2020. Detailed descriptions of the study sites and methods are provided in Shyshkanynets et al. (2021). In 2025, remeasurements were carried out on six PSPs (2, 4, 5, 6, 7, and 8). Plots 1, 3, and 9 were not remeasured because the tree stands there were identical to those of PSP 2.

Results

A pronounced deterioration in the health condition of secondary spruce stands was observed. In 2020, the average proportion of dead spruce trees across the sample plots was 63.5%, increasing to 85.8% in 2025.  Excluding PSP 5, the proportion of dead spruce trees reached 97.0%. In PSPs 2 and 8, all spruce trees were dead (health condition index = 6.0), while in PSPs 4, 6, and 7, dead spruce trees were recorded sporadically (the spruce health condition index = 5.7–5.9). The average age of spruce trees on the studied sample plots ranged from 55 to 72 years. In 2025, the proportion of broken dead trunks (with stem height greater than or equal to 1.3 m) accounted for 35–45%, indicating advanced stand degradation.

As a result of dieback, complete mortality of spruce stands occurred in sites that had a pure spruce composition (100%) in 2020 (PSPs 2 and 9). In the stands with a spruce proportion of 70–80%, in 2020 (PSPs 7 and 8), sparse beech forests developed, with relative densities of stocking of 0.3 and 0.2, respectively. In sites with spruce accounting for only 30–40% in 2020 (PSPs 4 and 6), the tree stand changed to a beech-dominated one with an admixture of maple, which is typical for beech-type forests.

Conclusions

The proportion of dead spruce trees increased from 63.5% in 2020 to 97.0% in 2025, indicating mass dieback and degradation of secondary spruce stands at the age of maturity (60–70 years) under the influence of abiotic and biotic factors. In areas formerly occupied by pure spruce stands, successional processes involving pioneer species (birch, rowan, etc.) and spruce regeneration are underway. In secondary spruce stands with a beech proportion of 20–30%, sparse beech forests have formed, accompanied by pioneer species and spruce undergrowth. Where the parent stand contained six or more units of beech, no pronounced succession changes were observed.

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