We aimed to evaluate the changes in grassland soils resulting from forest tree planting using two soil quality indices-a soil evaluation factor (SEF) and a soil quality index (SQI). We studied the impact of introducing forest trees (conifers, broadleaves or mixed) on natural meadows. We examined how the soil properties were affected by the tree species and their ages (25, 35 and 65 years old). Soil samples were collected from meadows and their adjacent forests, all situated within the boundaries of Krakow (Poland). Before the trees were planted, all areas were grassland, used for agricultural and recreational purposes. The soil samples taken from surface and subsurface horizons were analysed for pH, nutrients (C, N, P, K, Mg), humus compounds and dehydrogenase activity (DHA), and basic cations (Ca 2+ , Mg 2+ , K + , Na +). The introduction of trees on the grasslands lowered the pH and DHA activity, and impoverished the soils in nutrients. The impact on the soil properties of the tree species was more important than their age. The biggest negative changes were found in the soils covered by coniferous trees, in which the lowest values of SEF and SQI (respectively, 9 and 0.24) were recorded. The highest values of both soil quality indices (SEF-147, SQI-0.66) were observed in the meadow soils. The soils of a 35-year-old deciduous forest and a 65-year-old forest with deciduous and coniferous tree species had similar SEF and SQI values. The deciduous trees adapted better to the meadow soils than the conifers and, over time, an improvement in the soil properties occurred as a result of the accumulation of tree residues.

Biogeosciences and Forestry Biogeosciences and Forestry Changes in the properties of grassland soils as a result of afforestation Milosz Podwika (1) , Katarzyna Solek-Podwika (2) , Krystyna Ciarkowska (3) The effects of afforestation on physical, physico-chemical, and biological properties of grassland soils were investigated in three sites (215-230 m a.s.l.) located within the urban area of Krakow (southern Poland) after 45-60 years since the introduction of forest tree species. We compared the contents of nutrients and the composition of humus between forest and adjacent grassland soils, as well as the quality of the forest soils in relation to the introduced tree species (alder, pine, oak, birch, maple, elm). We hypothesized that afforestation of grassland soils results in the increase of acidity and nutrient contents. Studied soils belong to Dystric Gleysols (forest) and Eutric Gleysols (grassland). Overall, 168 soil samples were taken from two layers (0-10 cm and 10-30 cm) both from forest and grassland soils. The results showed an increase of organic carbon (up to 150%), total nitrogen (up to 70%) and total acidity (up to 18 times), as well as a decrease of pH (up to 40%) and activity of dehydrogenase (up to 60%) in forest soils in relation to the respective grassland soils. The most intensive changes were observed in the topsoil layers (0-10 cm). We also calculated the Soil Quality index (SQI) based on PCA in which only soil parameters with high load factors were taken into consideration. SQI ranged from 0.39 to 0.41 in grassland soils and from 0.33 to 0.37 in forest soils. Among forest soils, the highest value of SQI was obtained for stands dominated by black alder, indicating that such species is the most suitable for afforestation purposes under the study conditions. The results may be helpful in the realization of afforestation plans of humid grassland soils.

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.