A Podzol Development Sequence in Oakwoods and Heath in Central England

Abstract

A sequence of soils is described from a slightly podzolized sandy brown earth to humus-iron podzol. In this gradual degradation sequence morphological and chemical evidence is presented to suggest that the following succession of soil processes is involved :(a) translocation of clay; (b) chemical weathering of the A, horizon resulting in an association of iron with organic matter, and slight eluviation of iron : the stage of podzol intergrade ; (c) strong iron eluviation : the stage of iron podzol;( d ) eluviation of organic matter, which rests on or is incorporated in a previously Pollen analysis has helped to establish that podzolization can occur under oakwood where edaphic environments favour the accumulation of thick, moist, strongly acid organic layers.THE status in classification of many British soils is difficult to assess owing to extensive biotic effects. Deforestation, followed by ploughing and grazing, have altered the soils physically and chemically and changed their ecological relationships. In consequence there are few, if any, areas of natural vegetation, e.g. virgin forest, and relatively few areas of semi-natural vegetation. T h e importance of such sites is therefore often disproportionate to their size, as it is only in sites which most closely approach natural conditions that we can expect to discover the true relationships between natural vegetation and soil morphology.Evidence of podzolization' under oak conflicts with widely held views of the effect of this type of vegetation on soil formation. Dimbleby and Gill (1955), however, refer to mor humus formation under old oaks in the New Forest, where they noticed visible signs of leaching, though at the same time they state that there was no evidence to suggest that continuous oak forest produced a podzol. Anderson (1951) noted signs of degradation on infertile sites under Quercuspetraea and Q. robur, and similar podzolized horizons have been seen by the author under old oaks in Sherwood Forest. In his comprehensive study of the genus Quercus in Britain, Jones (1959) states that on the most nutrient-deficient soils derived from highly siliceous rocks, usually podzols or gley podzols, Quercus petraea is generally the principal species. Betula sp., Sorbus I The definition of podzolization used here involves the reactions concerned in the movement and accumulation in the soil profile of sesquioxides and organic matter in freely drained conditions and under raw humus horizons. These reactions although incompletely understood include (i) the breakdown of clay minerals in the A, horizon leading subsequently to differentiation of silica and sesquioxides, (ii) the mobilization of iron in A horizons in association with acid products of organic decomposition, (iii) the deposition of iron and organic matter in B horizons. developed iron B horizon : the stage of humus-iron podzol.

Influence of individual oak (Quercus robur) trees on saturated hydraulic conductivity

“…This review shows that while soil acidification by oak trees is less than that by coniferous trees, an increase in soil acidity relative to that beneath open grassland has been reported under oak stands (Mackney, 1961;Moffat and Boswell, 1990). Moffat and Boswell (1990) report a 0.5 of a unit decrease in soil pH value under oak stands in Yorkshire, UK.…”

“…As trees can influence K s through am enhancement of soil acidification , greater fines (i.e., clay and silt) translocation (Mackney, 1961) and organic matter accumulation (Berglund et al, 1981), the physical properties of pH, soil texture and organic matter content, respectively, were quantified at a 0.15 m depth at distances of 1, 5, 9 and 13 m from Tree No. 1, along a transect of bearing 1808.…”

Clustering of plant life strategies on meso-scale

“…The difference of influence on the soil between oak and beech is smaller (Norden 1994;Hagen-Thorn et al 2004), with soil under beech having a somewhat lower pH. Some studies indicate that the litter of oak or beech stands on poor soils closely resembles that of conifers (Mackney 1961;Beyer et al 1991).…”

The pedogenic effects of different species and vegetation types and the implications of succession

“…Broadleaved trees in Europe have been associated with a wider range of pedogenic trends than conifers, varying from podzolization to depodzolization. In general however, they seem to maintain higher topsoil pH values and to retard podzolization compared with most conifers, though podzolization has sometimes been reported under oak (Kubiena, 1953;Dimbleby & Gill, 1955;Mackney, 1961;Bublinec, 1973) and beech (Dimbleby & Gill, 1955;Andersen, 1979). However, mor humus production, acidification and podzolization under oak and beech seems to occur much less strongly than under pines or spruces (Petkov, 1969;Prudic, 1970Prudic, , 1973Wittich, 1972;Bublinec, 1973;Lhotsky, 1973).…”