Soil total phosphorus and nitrogen explain vegetation community composition in a northern forest ecosystem near a phosphate massif

摘要

The relationship of the community composition of forest vegetation and soilnutrients were studied near the Sokli phosphate ore deposit in northern Finland.Simultaneously, the effects of the dominant species and the age of trees,rock parent material and soil layer on these nutrients were examined. Forthis purpose, 16 study plots were established at different distances fromthe phosphate ore along four transects. Phosphate mining may take place inSokli in the future, and the vegetation surveys and soil sampling conductedat the plots can be used as a baseline status for following the possiblechanges that the mining may cause in the surrounding ecosystem. The totalphosphorus (P) and nitrogen (N) contents of the soil humus layer werepositively related with species number and abundance of the understoreyvegetation, and the correlation was slightly higher with P than N. This isinteresting, as N usually has the most important growth-limiting role inboreal ecosystems. The spatial variation in the content of soil elements washigh both between and within plots, emphasizing the heterogeneity of thesoil. Dominant tree species and the soil layer were the most importantenvironmental variables affecting soil nutrient content. High contents of Pin the humus layer (maximum 2.60 g kg−1) were measured from thebirch-dominated plots. As the P contents of birch leaves and leaf litterwere also rather high (2.58 and 1.28 g kg−1,respectively), this may imply that the leaf litter of birch forms animportant source of P for the soil. The possible mining effects, togetherwith climate change, can have an influence on the release of nutrients toplants, which may lead to alterations in the vegetation communitycomposition in the study region.