Regional modelling of base cation losses from Swedish forest soils due to whole-tree harvesting

Abstract

Concern about the environment has made it desirable to reduce fossil fuel consumption and in Sweden energy production from forest biomass is seen as an attractive alternative. The Swedish forestry industry has so far been practising stem harvesting only with moderate impact on the forest ecosystems. Increased harvesting of forest biomass, i.e. foliage and branches which are comparatively rich in nutrients, will result in increased nutrient export from forest ecostystems. Long-term mineral weathering of base cations was estimated on 1508 plots throughout Sweden, using a regression model. Calcium, Mg and K weathering was compared to stem only and whole-tree accumulation of these nutrients. Base cation inputs from the atmosphere and outputs from leaching were not included in this modelling approach. The balance was mapped for forest land in Sweden. The results indicated that weathering alone can support biomass uptake of Mg and K, but not Ca. If increased biomass utilization, in the form of whole-tree harvesting, is to become a common practice in the future, Ca reserves in soils will become more depleted. For Mg and K, significant areas, especially in south Sweden, will also show depletion in the soil after whole-tree harvesting.