Soil acidification and element fluxes as related to tree species in deciduous forests of south Sweden

摘要

The influence of tree species on element fluxes in throughfall and litterfall and on chemical properties of the soil was studied in south Sweden. Mature, even-aged individual trees of Fagus Sylvatica L., Quercus robur L., Carpinus betulus L., Tilia cordata Mill. and Acer platanoides L., growing side by side on initially similar soils in mixed deciduous forests were compared. The pH(KCl) of the topsoil (0 to 5 cm) beneath tree canopies at 70 sites decreased in the order lime>maple>hornbeam(approx)oak>beech. Topsoil pH increased with distance from the trunk (except for maple). Topsoil pH differences between species are not always able to predict pH differences further down in the profile. Sulphate was the dominating ion in throughfall and about half the amount was due to dry deposition. There were obvious differencs between deciduous tree species in their ability to acidify the soil profile of cambisols, in terms of a decrease of exchangeable base cation pools, an increase of exchangeable Al and H pools, and usually a decrease in pH. Hornbeam, and in particular lime, acidified the underlying soil (0 to 70 cm) least among species at 'poor' sites, which was explained by a lower cation excess accumulation in biomass, and by a lower capacity to capture acid dry deposition depending on the smaller canopies of these species. Oak acidified the deeper parts of the soil most among species at 'rich' sites, which was explained by a higher total cation excess accumulation in biomass and by a greater acid deposition to the taller and wider canopy of this species. The major part (50 to 70%) of the calculated current annual total proton load (TPL) on the soil originated from atmospheric deposition, the remainder was due to biological sources. Oak had the highest current TPL, hornbeam and in particular lime, the lowest.