Edge Effects on Soil Acidification in Forests on Sandy Soils Under High Deposition Load

Abstract

This study investigated how forest soil acidification is affected by edge proximity. We measured pH(KCl) and exchangeable K, Ca, Mg and Al concentrations of the mineral topsoil (0–30 cm) from the exposed edge to the interior (128 m from the edge) of three deciduous and four coniferous forest stands. From the front edge to the interior of the deciduous stands, the pH(KCl) values decreased at 0–5 cm soil depth (from 3.07 to 2.98) but increased at 5–10 cm (from 3.26 to 3.32) and 10–30 cm (from 3.48 to 3.75) depth. In the coniferous stands, pH(KCl) values declined from edge to interior at all soil depths, i.e. from 3.10 to 2.89, from 3.26 to 3.06 and from 3.54 to 3.31 at 0–5, 5–10 and 10–30 cm, respectively. The concentrations of exchangeable cations decreased from edge to interior, with larger differences in the coniferous (of up to 265 %) than in the deciduous stands (up to 99 %). At forest edges, enhanced soil acidification due to higher potentially acidifying deposition could be counteracted in the upper mineral soil by higher base cation throughfall and litterfall, faster litter decomposition, higher soil organic matter content, lower nitrate leaching from the soil and/or lime fertiliser drift. Nonetheless, deeper in the soil of the deciduous stands, these buffer processes seem unable to counteract soil acidification due to potentially acidifying deposition at the edges. Edge effects on soil acidity are important since they can translate into effects on plant communities, soil biota, nitrogen cycling and carbon sequestration.