水曲柳落叶松纯林与混交林根际土壤氮磷养分特点及变化

测定了水曲柳、落叶松纯林与混交林限际土壤的Ｎ、全Ｐ、有效Ｎ、有效Ｐ及有机质含量。结果表明：水曲柳和 叶松在上述养分含量方面存在互补性。水曲柳根际土的有效磷含量较低，而其余养分含量较高；落叶松则相反，混交林分含量接近甚至超过纯林。总体养分水平水曲柳纯林根际土＞混交林根际土＞非根际土＞落叶松纯林根际土。从春到夏。混交林根际土的有效机下降幅度、全磷量上升幅度均明显大于纯林，全氮量下降幅度则小于相应纯林，混交改善了纯林根际土壤养分状况，使根际氮磷养分例更加均衡合理，促进了养分的吸收和循还，是林木增产的重要原因。

The Characteristics and Variations of N and P Contents of Rhizosphere Soil in Pure Ash or Larch Forests and Mixed Forests

The contents of total N, P and available N. P of rhizosphere soil in pure ash or larch forests and mixed forests in spring and summer were determined. The results showed that there were complementarily between ash and larch in these nutrient contents. The content of available P of ash rhizosphere soil is lower while the others are higher. The result turned out contrary to larch. The nutrient contents of mixed stand tend to even exceed the pure stand in which certain nutrient contents are higher. The general level of nutrient contents decline in the order of pure ash. mixed stand. nonrhizosphere soil. pure larch. From spring to summer. reduction in organic matter content and increase in total P content of rhizosphere soil in mixed stand are greater than those of pure stand, while the reduction in total N content is less. The main reason that the production of mixed stand increase evidently is that its nutrition status in rhizosphere is improved and the proportion of available N to available P is more balanced and reasonable compared with Pure stand. so the nutrition in rhizosphere soil can be utilized fully and efficiently.