Assessment of Spatial Variability of Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Soils and Fungal Disease Status of Trees Grown in Hong Kong Areas

This research investigates the relationship between the chemical parameters and pollutant concentration of soil and the extent of infection of wood decay fungi across various tree species in urban areas of Hong Kong. Notably, this research uncovered significant differences (p < 0.05) in fungal infection rates among different tree species (0.78–24.3%). The total concentration of PAHs in the soil samples collected ranged from 0.47 to 3.33 mg/kg (dry weight), with 13 out of the 18 sampling sites exceeding the Dutch Target Values (DTVs) of 1 mg/kg (dry weight). Principal components analysis (PCA) results revealed the influence of two principal components on the fungal infection rates among tree species. In particular, the first component was associated with electrical conductivity (EC) (PC1: 99.7%), while the second component involved redox potential and nitrate concentration (PC2: 0.2%). Furthermore, high concentrations of naphthalene were observed in soils at all sites across five major tree species, namely Spathodea campanulata, Ficus microcarpa, Acacia confusa, Cinnamomum camphora, and Lagerstroemia speciosa. The PCA results suggested that PAHs significantly contributed to fungal infection in these tree species. Such valuable baseline information can aid in the further development of effective urban tree management strategies in Hong Kong, mitigating the adverse impacts of soil quality on urban tree health, particularly in the face of global warming and extreme weather conditions.