冀北山地华北落叶松人工林土壤养分的变化规律

为了解随林龄增长华北落叶松人工林土壤养分含量的变化规律，选择4种不同林龄（9年生、18年生、33年生、43年生）的华北落叶松人工林为研究对象，对林下土壤的养分特征及其空间变化进行了研究。结果表明，土壤的有机质、碱解氮及全氮含量总体上以43年生华北落叶松人工林最高；速效钾及全钾含量有随林分年龄的增加而逐渐降低的趋势；磷元素则随林龄的增加呈现先下降后上升的趋势；同时，各林分土壤有效磷含量均相对偏低。有机质、碱解氮、全氮、速效钾、全钾及全磷的含量都随土层深度的增加逐渐下降，而有效磷含量则表现出先下降后又上升的趋势，拐点在40 cm左右。总体上，人工落叶松林土壤随林分年龄增加未表现出明显的退化趋势。

Changes of Soil Nutrients for Larix principis-rupprechtii Plantation in North Mountain of Hebei

In order to understand the change regulations of soil nutrients in Larix principis-rupprechtii plantation with the forest age,four L.principis-rupprechtii plantations with different ages (9 a,18 a,33 a,43 a) were selected as the research objects,the soil nutrient characteristics and spatial variations were studied .The results showed that the soil organic matter,available nitrogen and total nitrogen were the highest in 43 a plantation.Available calcium and total calcium gradually decreased with stand age,the phosphorus decreased first and then increased with stand age.The content of available phosphorus in the soil was low in each stand.The organic matter,available nitrogen,total nitrogen,available calcium,total calcium and total phosphorus obviously decreased with soil depth.However,the available phosphorus first decreased and then increased with soil depth with a turning point at 40 cm.Generally,with the increase of forests age,there were different trends for various soil nutrient contents in L.principis-rupprechtii plantation,and there were no significant degradation in the soils of L.principis-rupprechtii plantation.