Modelling impacts of atmospheric deposition, nutrient cycling and soil weathering on the sustainability of nine forest ecosystems

• Main Authors: Salm, C. van der, Vries, W.de, Olsson, M., Raulund-Rasmussen, Karsten
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1999
• Subjects: Northern Sweden
• Online Access: https://curis.ku.dk/portal/da/publications/modelling-impacts-of-atmospheric-deposition-nutrient-cycling-and-soil-weathering-on-the-sustainability-of-nine-forest-ecosystems(f66e9d20-a1c0-11dd-b6ae-000ea68e967b).html; http://springerlink.metapress.com/content/k342301606147t71/fulltext.pdf

To assess the impact of acid deposition on the long-term sustainability of nine oak, pine and spruce stands on sandy to loamy sandy parent material in Sweden, Denmark and The Netherlands, a dynamic soil acidification model (ReSAM) was applied. Two deposition scenarios For the period 1990-2090 were used: a business as usual scenario (BAU) and a restrictive critical load scenario (CL). The BAU scenario leads to a strong decrease in both Al concentrations and pH in the topsoil of the Dutch and the Danish sites due to a decrease in the amount of amorphous Al compounds. The decline in pH leads to an enhanced release of base cations by silicate weathering. Despite the ongoing acidification: base saturation increases during the simulation period, due to both the increase in base cation weathering and an increased input from mineralization with the ageing of the tree stands. No change in Al concentration is predicted for northern Sweden as deposition levels are below critical loads. Soil chemistry at the recently replanted Swedish sites is dominated by changes in N cycling instead of by deposition. The CL scenario leads, especially after 2010, to a stronger decline in Al concentration compared with the BAU scenario, which is mainly caused by a reduction of the acid input. Up to 2010, a considerable acid input to the soil system is maintained as N supply is larger than the consumption of N by the trees. Despite the reduction of the deposition of S and N to critical loads, the readily available cation pools are still declining on the Danish and Dutch sites in 2090. It is concluded that deposition levels above critical loads lead to exhaustion of the pool of amorphous Al compounds and a decline in pH. Base saturation does not decline due to an increase in mineralization with stand age and an increase in weathering rate due to the decline in pH.