水曲柳与红松混交对根际P素有效性的影响

用剥落分离法采集水曲柳、红松纯林及其混交林下根际土,并分析了有效P含量特征及其变化机制。结果表明,两树种纯林根际土有效P含量均较非根际土增加,尤以红松纯林较显著。两树种混交后,水曲柳根际土有效P含量较其纯林显著增加。无机P分级结果表明,各林分中红松纯林根际土难利用的闭蓄态P(O-P)比例最低,而较易利用的P源(Fe-P,Al-P)比例最高。混交林中水曲柳根际土O-P比例较其纯林显著下降,而Fe-P、Al-P等松结合态P的比例显著增加。混交林中水曲柳根际土P素有效性的增加,可显著促进混交林中水曲柳对P素的吸收利用,是该混交林增产的主要营养机制之一。

Effect of mixed plantation of Fraxinus mandshurica and Pinus koraiensis on P availability in the rhizosphere soils

The rhizosphere soils were sampled in the pure and mixed plantations of Fraxinus mandshurica and Pinus koraiensis by peeling the adhering soils of roots,and the characteristics of the available P contents were analyzed.The results showed that in the pure plantations the contents of available P in the rhizosphere soil were all higher than in their non-rhizosphere soil,especially in the pure P.koraiensis plantation.After mixed,the content of available P in rhizosphere soil of F.mandshurica was significantly higher than in its pure plantation.Gradation of the inorganic phosphates revealed that the proportion of O-P in the rhizosphere soil of pure P.koraiensis plantation was the lowest and that of Fe-P and Al-P was the highest in different plantation types.After mixed the proportion of O-P in the rhizosphere soil of the F.mandshurica decreased remarkably and the proportion of Fe-P or Al-P increased in contrast with its pure plantation.Increase of the content of available P in the rhizosphere soil of F.mandshurica in the mixed plantation could promote P absorption significantly,which might be one of the mechanisms by which the growth improvement occurred.