中文摘要：

模拟东北林区森林凋落物淋洗液中低分子有机酸浓度范围,研究了不同浓度外源草酸、柠檬酸溶液对暗棕壤中P、Fe、K等养分元素有效性、以及落叶松和水曲柳幼苗吸收P、Fe、K的影响。结果表明,合适浓度的草酸和柠檬酸促进暗棕壤中磷的活化,并促进落叶松和水曲柳苗木根系对磷的吸收,但较高浓度时（50.0mmol/L）水曲柳叶片含磷量却降低;合适浓度草酸和柠檬酸促进暗棕壤中Fe、K等金属元素的活化释放,并促进落叶松和水曲柳幼苗对Fe、K的吸收和运输;在有机酸活化土壤P、Fe、K养分、促进林木吸收的过程中,柠檬酸的作用效果强于同浓度草酸,这主要与柠檬酸较强的络合能力及较大的解离常数有关。

英文摘要：

By simulating low molecular-weight organic acids concentrations in forest litter leachates,a series of batch experiments were conducted to study the effects of oxalic and citric solutions on P,Fe,K availability in dark brown forest soils and nutrient absorption of Larix olgensis and Fraxinus mandshurica seedlings.The results showed that,oxalic and citric solutions of appropriate concentrations stimulated soil P release from dark brown forest soils supporting Fraxinus mandshurica and Larix olgensis seedings,and were helpful to P absorption by two kinds of seedings.However,oxalic and citric solutions of higher concentrations（50.0 mmol/L） inhibited P transportation to Fraxinus mandshurica leaves.Oxalic and citric solutions of appropriate concentrations also stimulated Fe and K release from dark brown forest soils,and were helpful in the course of Fe and K absorptions and transportation by Fraxinus mandshurica and Larix olgensis seedings.In the processes of nutrient mobilization and absorption,citric had higher release capacity than oxalic,and it was related to higher dissociation constants and organic ligand-metal stabilities of citric.