Phytomass and sequestered carbon in the forests of the Poltavske Forestry Management Unit

Abstract

Introduction

Global climate change and the increasing concentration of greenhouse gases drive growing scientific interest in the carbon sequestration function of forest ecosystems. Forests represent one of the most efficient natural mechanisms for CO₂ sequestration; therefore, assessing their bioproductivity at the regional level is of critical importance for the development of adaptive strategies for sustainable forest management. Despite numerous studies on the forest carbon balance in Ukraine, a comprehensive assessment of phytomass stocks and sequestered carbon specifically for the forests of the Poltavske Forestry Management Unit of the Branch “Slobozhanskyi Forest Office”, State Specialized Forest Enterprise “Forests of Ukraine” has remained insufficiently explored.

The aim of the study was to determine total phytomass stocks by major fractions and to assess the carbon potential of the main forest-forming tree species in the studied region of the Left-Bank Forest-Steppe of Ukraine.

Materials and Methods

The object of the study is forest stands of the Poltavske Forestry Management Unit, with a total forest land area of 95,561 ha. The information base consisted of materials from the State Forest Inventory and compartment-level forest mensuration database of the Ukrainian State Forest Inventory Enterprise (VO “Ukrderzhlisproekt”), processed using the specialized software package “PERTA” (National University of Life and Environmental Sciences of Ukraine). The dataset included 1,137 sample plots obtained through sampling-based forest inventory methods and 3,248 relascope plots. Phytomass was estimated according to the methodology developed by P.I. Lakida, using a system of multifactor regression equations to calculate the mass of individual tree components (stem wood, bark, branches, foliage or needles, and root systems) in absolutely dry condition. Conversion of phytomass into sequestered carbon was performed using internationally recognized conversion factors: 0.50 for woody fractions and 0.45 for foliage and understory vegetation. Statistical data processing was carried out using Microsoft Excel and SPSS.

Results

The analysis of species composition revealed the dominance of coniferous tree species (74% of forested areas), among which Scots pine (Pinus sylvestris L.) overwhelmingly prevails (99.9%). Hardwoods (10%) and softwoods (16%) occupy smaller shares. The age structure is characterized by the predominance of middle-aged (37%) and maturing stands (28%); young stands account for 24%, while mature and overmature stands represent only 10%. The average growing stock of stem wood is 218 m³·ha^-1, with an annual increment of 4.0 m³·ha^-1. The total phytomass of forest stands within the super-forestry is estimated at 15,100.59 thousand tonnes of absolutely dry matter, of which 70.4% belongs to coniferous stands. The phytomass structure is dominated by stem wood and bark – 72% (10,876.94 thousand tonnes); root systems account for 17%, branch wood and bark for 6%, assimilation apparatus for 1%, and understory vegetation for 4%. The total amount of sequestered carbon equals 7,513.88 thousand tonnes. The highest carbon density was recorded in hardwood stands—10.7 kg·m^-2, which is 44.6% higher than in coniferous stands (7.4 kg·m^-2). The area-weighted average carbon density across the enterprise is 7.8 kg·m^-2.

Conclusions

It was evaluated that the total biomass of the forest stands in the Poltavske Forestry Management Unit, Branch “Slobozhanskyi Forest Office”, State Specialized Forest Enterprise “Forests of Ukraine” was 15,100.59 thousand tonnes of absolutely dry matter. This volume of organic mass ensures the accumulation of 7,513.88 thousand tonnes of carbon. It was revealed that although coniferous species dominate the enterprise’s forest fund (74 % of the area), the highest specific density of sequestered carbon was recorded in hardwood stands – 10.7 kg·m^-2. In the structural distribution of phytomass, the absolute majority falls on the wood and bark of the trunks (72 %). Root systems accumulate about 17 % of carbon, the crown (branches and assimilation apparatus) – 7 %, and understory vegetation – 4 %. The analysis of the age structure of forests showed a significant predominance of middle-aged and maturing stands (over 65 %), which indicates a high potential for carbon dioxide absorption in the coming years, but requires optimization to ensure uniform forest use. The obtained results have significant practical value for improving the national greenhouse gas inventory system, spatial planning of forestry activities, and the development of bioenergy in the region.

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