EFFECTS OF TREE SPECIES AND SOIL PHYSICOCHEMICAL CONDITIONS ON THE NATURE OF SOIL ORGANIC-MATTER

Forty-one properties of the organic matter in surface soil samples col lected under oak (intermediate between Quercus petraea and e. robur) a nd yew (Taxus baccata) growing on soils overlying slate and limestone in N.W. England were studied using analysis of variance. Total C, N, p olysaccharides, and lipids, the amount of C extracted, and the amount of humic acid C, fulvic acid C, and of the C in the polyphenol fractio n of the fulvic acid were related more to the amount of organic matter in a sample than to its chemical nature. The greater C-to-LOI and C-t o-N ratios of the samples collected on slate were consistent with diff erent types of transformation of litter compounds by organisms in the soils. The lipid-to-LOI ratio appeared to be lower in soils with high biological activity. The type of humification on limestone was associa ted with lower ratios of humic acid carbon-to-fulvic acid carbon and a larger percentage of the carbohydrate fraction in fulvic acid, and a larger proportion of the total C was in polysaccharides. The loss of v anillyl units from plant lignin was greater under yew with no signific ant effect of geology, while the greatest loss of syringyl units occur red under yew on slate. There were statistically-significant, but nume rically small, differences in the compositions of the humic acids, the dearest differences being a greater C-to-N ratio and lower N-to- S ra tio on slate. The E-4-to-E-6 ratios were correlated positively with hu mic acid O and O-to-C ratio, which suggests that the ratio decreases w ith an increase in the degree of condensation. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.