Abstract: Hilly Loess Region is the most fragile and underdeveloped area of the Loess Plateau and vegetative restoration and reconstruction is the first task of ecological enviroment construction in this region.The policy of returning farmland to grassland,grazing ban,and hillside enclosure and so on has been allaround implemented in the northwestern China.Realizing the community characteristics after enclosing hillsides for vegetative restoration in the gully area would help to analyze the direction of vegetative succession in this area and make sure of the mission and objective of vegetative restoration.Investigations were conducted on plant species abundance,species frequency,and species similarity coefficient in plots of two gullies which located in the typical Hilly Loess Region of Ansai County,northern Shaanxi Province.Based on the investigation,81 species belonging to 31 families were found and the families of Gramineae,Compositae,and Leguminoseae accounted for 19.75 %,16.05 %,and 14.81 %,respectively.After 20-year hillside enclosure,vegetative succession has expressed a better succession trend with high abundances and diversity.Herbage was the major community life form,especially perennial herbage,while shrub and arbor also had importance positions.Shrub and arbor showed significant influence on the diversity and structure of plant communities and so on.Patch pattern of vegetative distribution was prominent in the gullies.Differenceswere found in the construction pattern of importance values of shrub and arbor between different direction gullies.We also found that the south-north gully was more even than the west-east gully.There were some differences in species similarity between different gully directions;however,these differences were mainly affected by some coexistence species and unusual species.

Key words: Gully area, Vegetative restoration, Community, Community similarity, Hilly Loess Region

摘要： 对黄土丘陵区2个不同沟向沟谷地植被群落特征进行样方调查,统计分析沟谷地植物物种频度和植物种群相似系数。调查共记录植物81种,隶属31个科,菊科、禾本科和豆科物种分别占物种总数的19.75%、16.05%和14.81%;封禁20年左右的沟谷地植被演替表现出良性演替的趋势;目前该沟谷地植物群落生活型中草本植物仍占主导地位,尤其是多年生草本,而灌乔生活型植物也已占有重要地位。灌乔木树种对植物群落多样性和结构等方面具有重要影响,沟谷地植被分布的斑块格局较为突出,不同沟向沟谷地的灌乔植物种的重要值构成格局存在一定差异,南北沟向较西东沟向分配均匀;沟向不同,沟谷地所形成的植被种群相似性具有一定差异,主要是由于受到一些伴生种和罕见种的影响。此研究对掌握该地形植被演替方向,明确植被恢复任务和目标具有一定意义。

关键词: 沟谷地, 植被恢复, 群落, 群落相似性, 黄土丘陵区