中文摘要：

根据在黄土高原丘陵沟壑区具有代表性的安塞县退耕地植被样方的调查资料。利用TWINSPAN对退耕地植物群落的类型及其优势种进行了确定，即退耕地植物群落主要有猪毛蒿（Artemisia scoparia）为优势种的群落、达乌里胡枝子（Lespedeza davurica）和长芒草（Stipabungeana）为优势种的群落、铁杆蒿（Artemisia gmelinii）为优势种的群落和白羊草（Bothriochloa ischaemum）为优势种的群落。典范对应分析（Canonical，Correspondence Analysis ）得出：显著影响黄土高原丘陵沟壑区退耕地物种变化的主要因子为退耕年限、全磷、速效磷和土壤水分。结合物种生活型特征，认为白羊草和达乌里胡枝子在黄土高原丘陵沟壑区具有较强的适应性，可作为退耕地的适宜引种物种，以调控和加速植物群落演替，控制土壤侵蚀。

英文摘要：

Based on observation of vegetation quadrates of abandoned farmlands in Ansai, a loess region of hills and gullies, vegetation communities and their dominant species were ascertained through TWINSPAN. Results show that there are mainly 4 vegetation communities： Artemisia scoparia dominated community, Lespedeza davurica and Stipa bungeana dominated community, Artemisia gmelinii dominated community, and Bothriochloa ischaemum dominated community. The Canonical Correspondence Analysis reveals that the year since abandonment, total phosphorus, exchangeable phosphorus and soil water content are important factors significantly effecting the variation of species in abandoned croplands. Along with the life-form characteristics, it is considered that Bothri- ochloa ischaemurn and Lespedeza davurica have strong ducing species in abandoned croplands to accelerate and sion on the hilly-gullied loess plateau. adaptation to site conditions, and could be the proper introdirect vegetation community succession and control soil ero-sion on the hilly-gullied loess plateau.