Dynamics of surface fuel accumulation in Scots pine (Pinus sylvestris L.) forests of green zones of the cities of Kyiv and Kharkiv

Abstract

The aim of this study was to investigate the dynamics of forest fuel accumulation in relation to fire hazard in the green zones forests of Kyiv and Kharkiv cities. The research employed analytical–calculative, monitoring and generalising methods to assess the formation and accumulation of forest fuels and to provide practical recommendations. The results identified key factors influencing the accumulation of surface forest fuels within these urban forests. In Kyiv’s green zone, pine stands growing under the most widespread forest site conditions (B2–3: fresh and moist subor types), the total litter load (in absolutely dry condition) ranged from 8.1 to 46.0 t/ha, with litter layer thickness varying between 2.1 and 8.1 cm. In Kharkiv’s green zone forests, significantly higher fuel loads were recorded, ranging from 15.6 t/ha in young pine stands to 60.0 t/ha in mature and overmature forests. A litter stock modelling approach was applied to estimate the accumulation of forest litter and duff in the periurban forests of Kyiv and Kharkiv using the conversion coefficients (Rv) derived from empirical stand parameters (DBH, density and age). The models demonstrated high accuracy (R² = 0.75–0.98) and confirmed that the highest surface fuel accumulation in pine stands occurs at 60–75 years. It was confirmed that pine stands in Kharkiv’s green zones growing under fresh subor conditions accumulate 22.8% more surface fuels. The difference in normalised mean values was statistically significant (tst = –1.89, tcrit = 1.69; p = 0.03).