中文摘要：

用不同比例 A1和 B层暗棕壤混合（A1∶B=1∶2）制造土壤养分缺乏条件，栽植落叶松幼苗，通过模拟我国东北林区代表性森林凋落物淋洗液中有机酸的种类和数量，系统研究养分缺乏下，不同浓度外源有机酸对暗棕壤磷有效性和落叶松幼苗吸收运输磷素养分的影响及机理。结果表明， A1层与B层混合土壤速效磷含量降低，落叶松幼苗根系和叶片磷累积量和磷吸收效率降低，但磷利用效率增加。外源有机酸处理后，混合土壤的速效磷含量有不同程度提高，3种有机酸的作用强弱表现为琥珀酸〉柠檬酸〉草酸，一般以浓度5.0 mmol/L和处理20 d时提高效果最显著。有机酸不同程度提高了根系和叶片的磷累积量和磷吸收效率，但降低了磷利用效率。有机酸对磷累积量和磷吸收效率的提高程度因处理时间、有机酸浓度和种类而异：对于根系，20和30 d的结果高于10 d，叶片则10和20 d的结果高于30 d，说明处理前期磷被吸收后向叶片的转移量较多，而后期则更多地在根中积累；3种有机酸大多在10.0 mmol/L提高幅度最大；不同有机酸的促进程度为琥珀酸〉柠檬酸〉草酸。

英文摘要：

Different proportions of A1 and B horizons dark brown forest soils （A1∶B=1∶2） were utilized to set the soil nutrient deficient conditions, and Larix olgensis seedlings were cultivated. By simulating organic acids concentrations in forest litter leachates of northeast China, the effects and mechanism of different concentrations of organic acid solutions on phosphorus （P） availability of dark brown forest soils and P absorption of Larix olgensis seedlings with nutrient deficiency were studied. The results showed that, compared with A1 horizon soils, available P contents of mixed soils in A1 and B horizons decreased, and P accumulation and efficiency of P uptake in root and leaves of Larix olgensis seedlings also decreased, but efficiency of P utilization increased. After treatments of exogenous organic acids, available P contents of mixed soils increased and the impact sequence of different organic acids were succinic acid 〉 citric acid 〉 oxalic acid; the concentration of 5.0 mmol/L had the best function, and the best effect of organic acids was at 20 d. Organic acids also increased P accumulation and efficiency of P uptake in roots and leaves of Larix olgensis seedlings, but decreased efficiency of P utilization. The impact strength of organic acids on P accumulation and efficiency of P uptake varied with treatment time, type and concentration of organic acids. The results of 20 d and 30 d in roots were higher than those of 10 d, however, the results of 10 d and 20 d in leaves were higher than those of 30 d, thus, at the earlier stage of organic acids treatments, more P absorbed were transferred to leaves, and at the later stage, more P would be accumulated in roots. The concentration of 10.0 mmol/L had the best function, and the impact sequence of different organic acids was succinic acid 〉 citric acid 〉 oxalic acid. Therefore, organic acids might contribute to P absorption and accumulation by Larix olgensis seedlings, final y increasing the adaptability and endurance of Larix olgensis seedlin