Organic geochemical studies of soils from the Rothamsted Classical Experiments - VI. The occurrence and source of organic acids in an experimental grassland soil

Total lipid extracts (TLEs) of grass (aerial and sub-aerial, Holcus lanatus ) from a plot on a long-term grassland experiment, and associated soil, alo ng with the organic fraction of the TLE hydrolysates and the hydrolysates o f the solvent extracted vegetation have been separated into fractions conta ining specific compound classes and analysed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The distributions of n-al kylcarboxylic acids, omega-hydroxycarboxylic acids and dicarboxylic acids i n the grass and the underlying soil have been determined. Short-chain (< C- 20) n-alkylcarboxylic acids were designated as having derived from both aer ial and sub-aerial vegetation. However, longer-chain n-alkylcarboxylic acid s were ascribed to suberin as a predominant source. Moreover, omega-hydroxy carboxylic acids and dicarboxylic acids observed in the soil were designate d as having predominantly derived from inputs of free, extractable polyeste rs and suberin intimately associated with plant roots. This study indicates the importance of root material as a predominant source of aliphatic, orga nic acids in the soil of temperate grassland biomes. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.