中文摘要：

模拟森林凋落物淋洗液中苹果酸/盐浓度范围,研究不同浓度苹果酸/盐对风干暗棕壤中磷有效性的影响及机制,同时采用盆栽试验,在自然暗棕壤中对苹果酸/盐提高磷的有效性进行验证,并探讨苹果酸/盐对落叶松和水曲柳幼苗吸收运输磷素养分的影响。结果表明：苹果酸/盐溶液显著促进A1层和B层风干暗棕壤磷的活化,释放量随浓度增加而增大,但B层释放效应较弱。对A1层和B层风干暗棕壤磷的释放作用苹果酸盐强于同浓度的苹果酸,因此推断,苹果酸/盐促进暗棕壤磷释放的主要机理在于苹果酸阴离子反应。苹果酸/盐对暗棕壤磷的释放具有累加性,土壤磷释放量主要由苹果酸阴离子累积载荷量决定,以苹果酸盐加入时,磷释放量Y与苹果酸阴离子累积载荷量X间回归方程为：Y=-0.0005 X2＋0.1929 X＋1.8192,R2=0.959 3,初步估算森林凋落物层溶出的苹果酸/盐对暗棕壤A1层的磷释放量为3.04kg/（hm2.a）,约相当于当地中龄林年吸收磷量的1/4～1/3。自然暗棕壤中的添加试验也证实,合适浓度苹果酸/盐对提高暗棕壤中磷的有效性具有积极作用。苹果酸/盐还促进落叶松和水曲柳幼苗对磷的吸收运输,以1.0mmol/L或5.0mmol/L浓度时影响最显著,且苹果酸盐的作用强于苹果酸的。

英文摘要：

By simulating malic acid/malate contents in forest litter leachates,the effects and mechanism of different concentrations of malic acid/malate solutions on phosphorus（P） availability of air-dry dark brown forest soils were studied.By pot experiments,the role of malic acid/malate solutions on solublizing P were validated in natural dark brown forest soils,and the effects of malic acid/malate on P absorption of Larix olgensis and Fraxinus mandshurica seedlings were also discussed.The results showed that,malic acid and malate substantially encouraged soil P release of air-dry A1 and B horizons soils,and dissolved P contents increased with the extractant concentrations,but the effects on B horizon were relatively weak.Malate solutions had much higher soil-P-release efficiency than that of malic acid at the same concentration,therefore,the mechanisms for malic acid and malate to solublize P should be dominated by reactions of malate anion.The effects of malate anion on P release was found to be cumulative,and the amount of P released was primarily controlled by cumulative malate loading rate.When malate anion was loaded as sodium malate solutions,the regression equation between A1 horizon P release and cumulative malic loading rate was：Y=-0.0005X2＋0.1929X＋1.8192,R2=0.959 3.Merely on a quantitative basis of malate anion leached from forest litter,the increased P release from A1 horizon was estimated to be 3.04 kg/（hm2·a）,accounting for 1/4~1/3 of the annual P absorption in middle-aged forests.The results of natural dark brown forest soils＇ experiments also showed that,malic acid/malate solutions of appropriate concentrations could stimulate soil P release,and were also helpful for P absorption of Fraxinus mandshurica and Larix olgensis seedings.In the processes of P mobilization and absorption,the concentration of 1.0 mmol/L or 5.0 mmol/L had the best function,and malate was better than malic acid.