Urban Grassland Afforestation as a Public Land Management Tool for Environmental Improvement: The Example of Krakow (Poland)

Afforestation can play a significant role in greenhouse gas emission reduction through increased carbon (C) sequestration in the biomass and soil. However, its environmental effects, especially through changes in soil characteristics as a result of afforestation, are still poorly understood. In this work, we studied the response of grassland soils derived from two different parent materials to afforestation. We measured the basic soil properties, including pH, C accumulation, nutrient contents and enzyme activity, in soils from grasslands and mature forests. We focused on the parameters associated with organic matter and the changes resulting from afforestation. We established that in the humus layers, habitat played a more important role in creating the soil properties, including organic-C accumulation, than land use (forest vs. grassland). We created models to explain the C storage in the soils, which indicated the substantial role of certain conditions in promoting the stabilisation of the organic matter, such as pH, and the amount of clay, humines and residue. We determined negative changes in the soil properties when compared with grassland and forest soils, but we found increased C storage, which counteracts the increased emission of carbon dioxide into the atmosphere. The results of our work may be of use for afforestation planners and urban managers.