Soil Properties under Three Species of Tree in Southern England in Relation to Acid Deposition in Throughfall

Abstract

This paper reports a study of the pattern of soil pH, Ca and Al round individuals of three tree species (Pinus sylvestris, Betula pendula, Quercus robur) in an area subjected to acid precipitation. All three species created a pH gradient extending outwards to 5 m with the lowest pH close to the tree trunks. Pine had more effect than birch which had in turn more effect than oak. Acid deposition in throughfall under these tree species showed a similar pattern, pine having the highest deposition rate. However, Ca and Al are not behaving as predicted, Al being lowest under pine and Ca in general highest. Only under the pine canopy and in the surface layer close to the trunk of the birches is the Ca:Al ratio greater than 1, yet there is no above-ground visible injury which might indicate Al toxicity to roots. Possible mechanisms for these effects involve nutrient uptake and cycling, litter deposition and throughfall deposition - these are discussed.