Concentrations of potentially toxic metals in surface soils are important to investigate before building new residential areas. Prior to development of a residential area in Sundsvall, northern Sweden, it was observed that barium (Ba) concentrations in the soil at the site exceeded the guideline value of 200 mg kg-1 outlined by the Swedish Environmental Protection Agency. In this study, I aimed at determining the reason for the high Ba concentrations in the O horizon of soils from this latter area. 49 O horizon samples were collected from two separate transects (about 36 km long). A total of 43 Scots pine (Pinus sylvestris) needles were collected from both transects to determine potential Ba accumulation in plants. The O horizon and pine needle samples were analyzed using X-ray fluorescence spectrometer (XRF) to determine Ba concentrations. The total mean concentration of Ba was 426±289 mg kg-1 without any relationship to industrial sources. Barium concentrations were negatively correlated to soil organic matter (r = -0.885). Correlations between Ba, aluminum (Al), silicon (Si) and potassium (K) was r = 0.565, r = 0.486 and 0.525, a finding that suggests a strong positive coupling to elements typically found in silicate minerals. Barium concentrations in pine needle samples were below limit of detection (<LOD) suggesting that “plant pumping” via roots to the soil surface was an unlikely explanation for high concentrations in the O horizon. I conclude that the minerals in the O horizon originate from inmixing from the underlying mineral soil, therefore, high Ba concentrations in the study area is likely due to naturally occurring minerals.

Understanding of carbon cycling in coniferous forests that represent a large carbon sink is crucial for our understanding of natural processes under global climate change. Recognition of fungi as fundamental decomposers can contribute to this understanding. Fungi are able to decompose numbers of substrates and possess a variety of enzymes to do so In this study I present litter decomposing fungi in mountain spruce forest from national park Šumava. The aim of my thesis was to follow succession and community changes of fungi from the early stages of decomposition of Picea abies needles until degradation of organic matter in the organic horizon of the soil. This aim was accomplished partly by recording the extracellular enzyme production of fungi in different stages of decomposition from needles attached to the twigs of a fallen tree to a litter material in later stages of decomposition on the soil surface. In addition to testing of fungi on their natural substrata - needle litter, enzyme activities were also measured in laboratory agar cultures, which allow comparison of diverse fungi with different origins. Enzyme activities were aimed at enzymes decomposing cellulose and compounds found in litter. Although ecology of endophytic and saprothrophic fungi suggest differences in enzyme production, these...