Allelochemicals in the soil beneath Quercus mongolica Fisch var. grosseserrata Rehld. Wils.
Thirty-d tests in a phytotron revealed that soil collected from beneath Q. mongolica var. grosseserrata [Q. crispula] inhibited the growth of lettuces, green amaranth (Amaranthus viridis), wheat cv. Norin No. 59 and timothy (Phleum pratense) seedlings by 50-90%. Of the 4 phenolic extract fractions tested, the ethyl acetate fraction of the soil beneath Q. mongolica var. grosseserrata exhibited the greatest inhibition of the seed germination and growth of etiolated seedlings of the 4 species. Nine allelochemicals, 3,4-dihydroxybenzoic, p-hydroxybenzoic, 3,4,5-trimethoxybenzoic, 3,4-dimethoxybenzoic, vanillic, p-coumaric and ferulic acids, p-hydroxybenzaldehyde and kaempferol were identified in this fraction by HPLC, EI- [electron impact?]-MS and 1H-NMR. The concn of the 5 main phenolic compounds, p-coumaric, ferulic, vanillic and p-hydroxybenzoic acids, p-hydroxybenzaldehyde and kaempferol in the soil were found to be 13 382, 3542, 2952, 2164, 1378 and 990 µg/100 g soil, resp., greater than the concn in the soils in which Sasa cernua, Picea jezoensis, rice, corn [maize], potatoes, carrots, soyabeans and Beta vulgaris var. rapa [fodder beet] were grown, but lower than in the soil beneath red pine (Pinus densiflora). It was concluded that these allelochemicals might have important roles in the distribution of forest species and understorey grasses.