3种低分子质量有机酸对温带典型林型土壤无机磷组分的影响

【目的】为了使土壤中潜在的无机磷转化为可供植物吸收利用的有效磷,探讨3种低分子质量有机酸对温带典型林型土壤无机磷组分的影响,旨在为温带退化森林生态系统的恢复与重建,以及土壤磷利用率的提高提供基础数据和科学依据。【方法】笔者对温带典型林型土壤采用室内培养法培养120 d,研究了不同浓度(10、25、50 和100 mmol/L)草酸、柠檬酸和乙酸及其对照(CK,蒸馏水)对4种温带典型林型(枫桦红松混交林、白桦天然次生林、红松人工林和落叶松人工林)0～10 cm土层土壤无机磷(Al-P、Fe-P、O-P、Ca-P)含量的影响。【结果】3种低分子质量有机酸均对红松及落叶松人工林内Al-P、Fe-P起活化作用,对O-P、Ca-P起固化作用,3种酸的影响效果为草酸>柠檬酸>乙酸。柠檬酸、草酸使白桦天然次生林O-P含量减少,使其转化为其他形态无机磷。整体来说,低分子质量有机酸处理4种林型土壤后,无机磷向有效性高的Al-P、Fe-P形态转化,从而提高了土壤供磷能力。低分子质量有机酸对土壤无机磷组分变化影响显著(P<0.05),中低浓度有机酸对Al-P、Fe-P、O-P变化影响较大,高浓度有机酸对Ca-P变化影响明显。处理时间对无机磷变化量影响显著(P<0.05),处理时间延长整体使4种林型中Al-P、Fe-P受到的影响加强,O-P、Ca-P受到的影响减弱。各因素对4种林型有显著的交互作用(P<0.05)。土壤中无机磷组分含量变化与无机磷形态、有机酸的种类、培养时间、酸浓度变化及林型等因素均相关。【结论】有机酸对土壤磷的活化是一个既缓慢又持续的综合动态过程,低分子质量有机酸可以通过影响土壤中无机磷的组分,促进难溶性磷酸盐溶解,从而提高土壤磷的有效性。此次研究表明,草酸、柠檬酸、乙酸对4种温带典型林型土壤无机磷组分有一定影响,可以提高土壤无机磷组分的利用率。

Effects of low molecular weight organic acid on inorganic phosphorus fractions of typical temperate forest soils

Abstract: 【Objective】This study explored the effects of low-molecular-weight organic acids on the inorganic phosphorus fractions of typical temperate forest soils in order to test the potential of these acids to convert inorganic phosphorus into phosphorus available to plants. The results obtained can provide data for use in the restoration and reconstruction of degraded temperate forest ecosystems, as well as the improvement of soil phosphorus utilization. 【Method】The effects of different concentrations(10, 25, 50 and 100 mmol/L)of oxalic acid, citric acid, and acetic acid, as well as a control treatment(CK, distilled water)on inorganic phosphorus in the a layer of soil from four types of typical temperate forest(virgin Betula costata-Pinus koriensis forest, natural birch secondary forest, P. koriensis plantation, and larch plantation)were studied by using 120-day indoor incubation methods.【Result】 The three kinds of low-molecular-weight organic acids activated Al-P and Fe-P, and solidified O-P and Ca-P in Pinus koriensis plantation and larch plantation soils, with the effect of the acids ranking oxalic acid > citric acid > acetic acid. Citric acid and oxalic acid reduced the O-P content in natural birch secondary forest, and translated it into other inorganic forms of phosphorus. Overall, after the treatment of the four forest types' soil with low-molecular-weight organic acids, inorganic phosphorus could be transformed into Al-P and Fe-P with high availability, thus improving soil phosphorus supplying capacity to plants. Low-molecular-weight organic acids had significant effects on the change in soil inorganic phosphorus fractions(P < 0.05), and the magnitude of the changes ranked Ca-P > Fe-P > Al-P >O-P. Medium and low concentrations had the greatest impact on variation in Al-P, Fe-P, and O-P, and high concentrations had the greatest impact on variation in Ca-P. The treatment time had a significant influence on the change in inorganic phosphorus(P < 0.05). The effects on Al-P and Fe-P in all four forest types were enhanced with longer treatment time, and the effects for O-P and Ca-P were diminished by prolonged treatment. All the factors examined had significant interactions with forest type(P < 0.05). The transformation of inorganic phosphorus fractions in soil interacted with inorganic phosphorus forms, types of organic acids, the time of culture, acid concentration and forest type. 【Conclusion】The activation of soil phosphorus by organic acids was a slow and continuously dynamic process. Low-molecular-weight organic acids could affect the composition of inorganic phosphorus in the soil, and promote the dissolution of insoluble phosphate, thus improving the availability of soil phosphorus. This study showed that oxalic acid, citric acid and acetic acid affected soil inorganic phosphorus fractions in four different typical temperate forest types, and improved the availability of inorganic phosphorus fractions in the soil.