黄土丘陵沟壑区退耕地自然恢复植物群落的分类与排序

采用TWINSPAN分类和CA排序方法，对黄土高原皇随便沟壑区安塞33个退耕地自然恢复植被样方进行了分类与排序。结果表明，在40a的演替过程中，退耕地植被大体上经历了猪毛蒿（Ａrtemisia scoparia）为优势种的群落、达乌里胡枝子（Ｌespedeza davnrica）和长芒草（Ｓtipa bungeana）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，４个群落的物种组成表现出较强的延续性和递进性。排序轴与环境因子的相关分析表明，土壤养分、土壤水分以及地形因子或强或弱地影响着退耕地自然植物群落的变化，其中土壤有机质、氮磷钾、土壤水分以及坡度与植物群落变化之间的关系密切。

Classification and Ranking of the Forae Naturally Recuperating on the Farming-Withdrawn Land in the Hilly and Gully Regions of the Loess Plateau

The two-way indicator species analysis and the correspondence analysis were adopted to classify and rank the forae naturally recuperating on 33 sample sites distributed in Ansai county standing in the hilly and gully regions of the loess plateau.The results revealed that in the forty-year evolution,the vegetations on the farming-withdrawn lands successfully experienced Artemisia scoparia-,Lespedeza davurica-,Stipa bungeana-,Artemisia gmelinii-,Bothriochloa ischaemun- dominated forae which displayed relatively strong continuation and transmission capacities.The correlation analysis between ranking and ambient factors indicated that soil organic matter,nitrogen,phosphorus,potassium and moisture as well as landforms strongly or weakly affected the changes of the forae naturally growing on the farming-withdrawn lands and of these factors,soil organic matter,nitrogen,phosphorus,potassium and moisture,and slopeland gradients closely related to the changes of vegetation forae.