Impact of urban green spaces, native tree species and seasons on soil pH in Kaunas, Lithuania

Abstract

Tree growth is sensitive to soil pH in urban areas and is often higher than in rural forest. However, there are knowledge gaps on how soil pH and alkalization are affected by urban environments and seasonal climate as well as the cascading effects on tree species. In order to fulfil these gaps, we analyzed the topsoil pHCaCl of four common native deciduous tree species: Acer platanoides, Tilia cordata, Quercus robur and Betula pendula in five different types of urban green spaces in Kaunas city municipality (Lithuania). The results show that topsoil pH in urban environments with Betula pendula sites were most alkaline (pH 7.04), whereas the topsoil pH of urban environments with Acer platanoides (pH 6.7) and Tilia cordata (pH 6.8) were most acidic. The topsoil pH of street tree greeneries were alkaline, while the topsoil profiles of the peri-urban forests and large urban parks were acidic. Differently to natural conditions in peri-urban forests, the topsoil pH level drop down by 0.5 is observed during spring-autumn period in broad street greeneries with largest urban pressure. The variation in soil pH of the different types of green space and tree species shows that city planner should consider the unique conditions of all green space to maximize their potential for human well-being.