中文摘要：

为探究“退耕还林（牧）”工程对陕西省子午岭林区的影响，分析3种典型的人工林（刺槐林、油松林和侧柏林）叶片-凋落叶-土壤的C、N、P含量及其生态化学计量特征.结果表明： 3种人工林不同组分中C、N、P含量大小均为叶片〉凋落叶〉土壤，刺槐林叶片N、P含量显著高于油松林和侧柏林.刺槐林、油松林和侧柏林叶片N∶P分别为12.2、5.4和6.1，油松和侧柏较刺槐林存在N亏损，C∶N和C∶P大小均为凋落叶〉叶片〉土壤，N∶P为叶片〉凋落叶〉土壤.油松林叶片C∶N与凋落叶C∶N间存在显著正相关关系.刺槐叶片在生长周期内吸收利用的N和P存在比例关系，且其凋落叶在元素再吸收后N和P的残留量也存在比例关系.与油松和侧柏相比，刺槐是黄土高原南部森林带最适宜的造林树种.

英文摘要：

In order to research into the influence of Grain to Green Project in Ziwuling forest region, this paper took three typical plantations which were Robinia pseudoacacia plantation, Pinus tabuliformis plantation, and Platycladus orientalis plantation in the Ziwuling forest region of Shaanxi Province as research objects and analyzed the carbon, nitrogen and phosphorus contents of leaf, litter and soil among the three plantations. The results showed that the contents of C, N and P in the three plantations were in order of leaf 〉 litter 〉 soil, the contents of N and P in leaf of R. pseudoacacia plantation were significantly higher than that of P. tabuliformis plantation and P. orientalis. Leaf N：P was 12.21, 5.36 and 6.09 in R. pseudoacacia plantation, P. tabuliformis plantation and P. orientalis plantation, respectively. It was indicated that the three species were all subject to N deficiency. C：N and C：P showed the trend of litter 〉 leaf 〉 soil, and N：P demonstrated the trend of leaf 〉 litter 〉 soil. There were highly significant positive relationships in C：N between leaf and litter in P. tabuliformis plantation. N and P in the leaf development process of R. pseudoacacia plantation were proportionally absorbed, and proportionally remained in the litter after N and P resorption. R. pseudoacacia was the better plantation species than P. tabuliformis and P. orientalis in the south fo-rest zone on the Loess Plateau.