Stand species composition as a key factor determining the amount of polycyclic aromatic hydrocarbons (PAHs) in forest soils

Abstract

The aim of the study was to determine the effect of stand species\ncomposition on PAHs accumulation. The study covered the soils of the\nstands of the Rybnik Forest District, which are under the influence of\none of the highest deposition of industrial emissions in Europe. Pine,\npine-oak and oak stands growing in the same soil conditions were\nselected for the study. Samples for further analyses were collected from\nthe organic horizon, from the humus mineral horizon and from the mineral\nhorizon. Organic C content, N content, pH, alkaline cation content, as\nwell as microbiological biomass of C, N, extracellular and intracellular\nenzyme activity were determined in the soil samples. PAH content was\ndetermined in the soil samples. Additionally, the soil organic matter\nfractions were determined: free light fraction (fLF), occluded light\nfraction (oLF) and mineral associated fraction (MAF). Pine stand soils\nwere characterized by the highest average PAHs content. The oak stand\nsoils were characterized by the lowest PAHs accumulation and high\nenzymatic activity. The study confirms the important role of the stand\nspecies composition in shaping the quality and quantity of SOM and soil\nacidification, which in turn is reflected in microbial activity and PAHs\naccumulation in forest soils. PAHs accumulation in forest soils is\nrelated to the fractional composition of SOM, which is the effect of the\ninfluence of species composition through the supplied aboveground and\nbelowground biomass. A strong correlation between the PAH content and C\ncontent of the light soil fraction of OM was noted.