不同林龄湿地松土壤养分状况分析

不同林龄（5、10、15及20年生）湿地松人工林土壤养分（铵态氮（NH4^＋-N）、硝态氮（NO3^--N）、有效磷（P）、有机质及pH变化规律的研究结果表明：随林龄增长，土壤速效N（NH4^＋-N＋NO3^--N）含量呈增加趋势；有效P及有机质含量则随林龄增加而降低，但后者在后期略有增加；土壤pH值随林龄增长先上升后降，几种土壤养分的层次差异均较为明显（上层含量高于下层），有必要施入磷肥和石灰进行土壤改良。

Analyse of Soil Nutrients in Pure Pinus elliottii Plantations of Different Stand Ages

The variety of soil NH4^＋ - N, NO3^ - N, available phosphorus （P）, organic matter and pH in Pinus eUiottii plantations of different ages （5, 10, 15 and 20 years -old） were studied. The results showed that the content of available nitrogen （NH4^＋ - N ＋ NO3^- - N） in the soil increased gradually with increase of the stand age of Pinus elliottii plantation. With increase of stand age, the content of available P and organic matter in plantation soil decreased continuously, then organic matter of 20 years old plantation was slightly high than others. The pH increased at first and then declined slowly in soil of Pinus elliottii plantation. The differences of these soil nutrients among different layers were obvious （ the upper content was higher）. It could be suggested that phosphor manure and lime should be applied into the soil of some years old artificial pure Pinus elliottii Engelm. plantation to improve soil nutrient.