Abstract: Using system clustering to divide the secondary successive of the abandoned farmland in the loess hilly regions of northern Shaanxi province,the similarity of lengths of years and standing conditions of the abandoned farmlands were discerned.Combining the above discernment with the quantitative ordination of DCA,the abandoned farmland successive phases and series were affirmed.The successive phases are as follows: annual weeds Artemisia scoparia+other annual weeds association→annual weeds A.scoparia assocaiation→annual weeds A.scoparia Waldstet kit+perennial herbage or undershrub assocaiation→rhizoma grass Agropyron cristatum(L.)association→perennial herbage or tuft grass+annual weeds association→perennial herbage association→undershrub Lespedeza davurica association→perennial herbage + undershrub or thick tuft grass association→short rhizome and thick tuft grass association.

Key words: Loess hilly region, Succession series in abandoned old land, Quantitative analysis

摘要： 用系统聚类法划分陕北黄土丘陵区撂荒地的次生演替阶段,可以定量的认识不同年限、立地条件下撂荒地群落的相似性,结合DCA数量排序确定撂荒地的演替阶段或序列。其撂荒演替的各阶段分别为:一年生杂类草猪毛蒿(Artemisia scoparia)+其它杂类草群丛→一年生杂类草猪毛蒿群丛→一年生杂类草猪毛蒿+多年生草种或小灌木的共优群丛→根茎禾草冰草(Agropyron cristatum)群丛→多年生草本或丛生禾草+一年生杂类草群丛→多年生草本群丛→小灌木达乌里胡枝子(Lespedeza davurica)群丛→多年生草本+小灌木或密丛型禾草群丛→短根茎密丛型禾草白羊草(Bothriochloa ischaemum)群丛。

关键词: 黄土丘陵区, 演替序列, 数量分析