Soil and soil solution chemical composition at three sites within the Loch Dee catchment, SW Scotland

Soil solution chemical composition was monitored over a 2–year period at three plots near the edge of an igneous intrusion in SW Scotland. Soil solutions were all strongly acidic with mean pH of approximately 4.0 at 0.20 m depth and 4.5 at 0.60 m. Chemical composition of the deeper soil solutions varied with geology. Greatest acidity and aluminium concentrations were found over metamorphosed Ordovician sedimentary rocks, with mean pH of 4.3 and A1 concentration of 22 mmol m^?3 at 0.60 m. At a site on similar rocks nearer the intrusion, mean pH at 0.60 m was 4.8, with very low A1 (3 mmol m^?3) and correspondingly greater Ca. At a peaty site on igneous rocks, increased pH with depth was associated with no change in base cations and A1 but a reduction in mean SO, from 41 mmolm^?3 at 0.20m to 10mmol m^?3 at 0.60m. Ion-exchange selectivity coefficients calculated from soil and solution chemistry differed slightly from currently used values for peaty upland soils, with larger coefficients for A1/K exchange and smaller coefficients for A1/Ca and A1/Mg exchange. Relations between A1 and H ion concentrations confirmed under-saturation of solutions with respect to gibbsite at 0.20 m. The differences between plots were consistent in different seasons, despite significant seasonal variability in Na, C1, dissolved organic carbon and Fe.     

Some Effects of the Plantation of Conifers on a Freely Drained Lowland Soil, Forest of Dean, U.K.

Acid brown soils under 50-year-old conifer plantations are comparedwith those at a control site under the previous vegetation ofmixed deciduous woodland. The soils under the conifers showsignificant signs of podzolization and associated with this,evidence of structural breakdown. The implications of thesechanges are briefly discussed.     

Contributions by fungi and bacteria to aggregate stability of cultivated soils

Stability changes during ageing (sterile) or incubation (non-sterile) of both natural field aggregates and remoulded aggregates from five soils were studied for periods up to 30 days. Growth of fungal hyphae, estimated by ergosterol measurement, corresponded to temporary stability increases in both types of aggregates during the first 15 days. Thereafter, fungal hyphae disappeared and were replaced by actinomycetes and bacteria. Increased stability due to entanglement by hyphae was comparable to that due to thixotropy in remoulded aggregates. Bacterial growth accompanied the fall in stability associated with fungal decline, but had little direct effect in stabilizing soil aggregates. Destruction of polysaccharides by periodate oxidation greatly diminished aggregate stability. The role of bacterial polysaccharides in soil aggregate stability is discussed.     

Annual losses of iron from moorland soils and their relation to free iron contents

The temporal pattern of iron loss from a moorland catchment was investigated by intensive stream water sampling. The total loss in 1 year was 2.11 kg ha^?1 of Fe, with a pronounced autumn maximum. Iron concentrations in stream water were strongly correlated with dissolved organic matter content, but again with seasonal variation. Free iron content measured on a number of soils in the catchment ranged from 3.1 to 8.7 kg m^?2. Assuming soil development over 10 000 years, predicted loss of iron from the catchment is comparable in quantity to the amounts of free iron in the soils.     

SOME CONTRASTS IN SOIL DEVELOPMENT BETWEEN GRASSLAND AND DECIDUOUS WOODLAND SITES

Soil profile and structural development were compared under two land-use types on acid and calcareous soils. The grassland soils were found to have better developed and more stable structures in the A horizon, but unchanged bulk density and infiltration capacity. In the B horizons the direction of difference was reversed. Profile development was deeper under woodland on the softer parent materials. The differences were primarily related to root density, penetration and more intimate incorportion of organic matter under grass.     

On the construction of shortest confidence intervals and Bayesian highest posterior density intervals

In this note it is argued that the principal characteristic of the confidence intervals proposed by Bartoszynski & Powers (1990) is not primarily the fact that they are of minimum length but that they are Bayesian highest posterior density intervals. A simple iterative process for determining the ends of the interval is presented.