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.