马尾松-火力楠混交林生物量及养分结构特征

对马尾松纯林及其与火力楠的混交林生物量空间格局和养分结构进行了研究。结果表明：马尾松混交林的总生物量为216．41t／hm^2，枝和叶所占比例分别高出纯林3．2％和2．5％；纯林中马尾松的干生物量基本上为金字塔形，枯枝生物量所占比例为1．75％，而混交林中为4．20％。混交林马尾松的粗根主要分布在0～20cm和60cm以下的土层中，细根量则随着土层的加深而减少；纯林中马尾松的粗根生物量和细根都主要分布在40cm以下的土层中。不论是纯林还是混交林，营养元素在树干中的含量最小，在叶中的含量最大（N除外）。火力楠叶中的养分含量大于马尾松，而在根系中P、K、Ca和Mg的含量则为马尾松大于火力楠。N的含量随着马尾松和火力楠根系直径的增大而减小；P、Ca和Mg在马尾松细根中的含量最小，而纯林中则在粗根中含量最小。

Spatial Structure of Biomass and Nutrients in the Mixed Pinus massoniana -Michelia macclurei Plantation

The spatial pattern of biomass and nutrients in the mixed Pinus massoniana-Michelia macclurei plantation and the pure forest of the former were studied.The result showed that the total biomass in the mixed stand was 216.41 t/hm~2,the proportions of branch and leaf was 3.2% and 2.5%,which is greater than those in the pure forest respectively.The stem biomass of Pinus in the pure forest was of pyramid shape and the deadwood biomass accounted for 1.75%,but 4.20% in the mixed forest.The coarse root was mostly distributed in the soil depth of 0~20 cm and 60 cm below and the fine root decreased with the soil depth in the mixed forest.The coarse and fine roots were mostly distributed below the 0~40 cm soil layer in the pure forest. The nutrient content in the stem was the smallest but the content was the largest except N in the leaf.The nutrient of leaf in Michelia macclurei was more than that in Pinus,but P,K,Ca and Mg contents of the root were in reverse.N content decreased with the thick root size of Pinus massoniana and Michelia macclurei.P,Ca and Mg contents of the fine root were the smallest in the mixed forest but that of the coarse root was the smallest in the pure forest.