Study On The Habitat Characteristics And Vegetation Succession Of Mined Wastelands In The West Of Beijing

Taking a panoramic view of the domestic and foreign research status, there is no report on the vegetation succession rules in different habitats of mined wastelands in the west of Beijing. Based on the survey and analysis on habitats and vegetation in mined wastelands of Mentougou in the west of Beijing, this paper systematically researched the impact on the ecological environment and the characteristics of number and distribution of mines as well as the characteristics of habitats and vegetation community of mined wastelands (quarry and coal mine), revealing the process of habitats change and vegetation community succession under the condition of natural revegetation. The main results are as follows:(1) Using the methods of on-site inspection combined with geographic information system, the types, mining methods, number, status, floor space and distribution of mines were analyzed. The results showed that the main types of mine are coalmines and quarries with a total number of 267 and floor space of 1799.8hm~2 . The number of coalmine is 154 with floor space of 1501.0hm~2 , 16 of which are operating and 138 closed. The number of quarries is 113 with a total floor space of 298.9hm~2, 46 of which is operating and 67 closed. Coalmines are all underground mining with the two mining methods of tunnel system and incline shaft. According to the mining objects and the way of exploitation of quarries, there are 102 limestone quarries, all opencut mining. Shale quarries are five with more than 80% is underground mining. There are three opencut mining Nylon quarries.In addition, there are three different types of quarries: Iraq Cordero stones, p. Philip Stone and basalt quarries.The former two types are underground mining and basalt is opencut mining. From the distribution perspective, coalmines are mainly located in the southeast and southwest, quarries are mainly located in six towns in the east.Thedistribution of quarries is intensive and the sites in different towns are extremely imbalance.(2) Using the principal component analysis (PCA) to analyze the habitat characteristics of mined wastelands, the result showed that the two dominant habitat factors of elevation and abandoned years could be used as the habitat division basis of vegetation communities for the two mined wastelands.(3) Taking two-way indicator species analysis method (TWINSPAN) to divide the quadrats of mined wastelands, combining the actual situation, the vegetation was dividend into five coenotypes both in quarry and coalmine wastelands, and each coenotype has a habitat type correspondently.(4) Taking a diversity index, β diversity index, growth form, life form, change of species, reduction rate of vegetation coverage and increase rate of soil hardness, the vegetation communities characteristics were analysed.In quarry wastelands with the increment of abandoned years the kind of species rises gradually and the composition of species is becoming more and more similar with the surrounding plant community.But the evenness decreases which shows that individual species takes the position of dominant species with the increment of abandoned years.The species diversity index of each plant community is higher than that of the surrounding plant community which may be caused by the diversification of microhabitat in quarry wastelands.The a diversity index of herbaceous layer is higher than that of shrub layer and tree layer in different abandoned years.With the increment of abandoned years the a diversity index of shrub layer increases obviously while the herbaceous layer and tree layer increase slightly.The α diversity index of tree layer is lower than that of shrub layer and herbaceous layer apparently.In the early stage of natural revegetation annual and biennial herb occpuies the majority.With the increment of abandoned years perennial herb and shrub increases gradually while the annual and biennial herb decreases clearly. Gramineae, Leguminosae, and Compositae are the main species of plant community in different abandoned years.The plant species of surroundings affects the species of natural revegetation conspicuously. Additionally the reduction rate of vegetation coverage and the increase rate of soil hardness both show decrease tendency.With the increment of abandoned years a diversity index of coalmine plant communities rises.The composition of species is becoming more and more similar with the surrounding plant community.After sixteen years the plant community shows the trend to be stable, but the diversity index is lower than the surrounding plant community apparently which explains that the coalmine wastelands has restriction on some plant species. The a diversity index of herbaceous layer is higher than shrublayer and tree layer in different abandoned years. With the increment of abandoned years a diversity index of herbaceous layer and shrub layer increase obviously. When the community reaches stable stage, a diversity index of three layers all decreases to some extent. The change of life form and species are the same with the quarry wastelands.The variation of vegetation coverage and soil hardness are similar with the quarry wastelands.(5) According to the partition result of the plant community and habitat types of quarry and coalmine wastelands with TWINSPAN as well as the characteristics analysis, the different communities are divided into different successional stages. The plant community of quarry wastelands in hilly Piedmont is divided into one succession stage, namely the herb stage.The community type is Assoc. Pharbitis nil- Bidens parviflora.In a shallow mountain there are three successional stages: The first stage is herb community stage. The community type is Assoc. Ulmus pumila - Bidens parviflora; The second stage is the transition phase of herb community to shrub community.The community type is Assoc. Digitalis purpurea- Vitex negundo.The third stage is shrub community stage.The community types are Assoc. Spiraea salicifolia-Vitex negundo and Assoc. Periploca sepium-Vitex negundo.In the coalmine wastelands of Shallow Mountain, the plant communities are divided into two succession stages: The first stage is shrub community stage. The community type is Assoc. Artemisia lavandulaefolia - Vitex negundo.The second stage is tree community stage. The community type is Assoc. Eriophorum gracile - Ailanthus altissima. In the low mountain, the plant communities are divided into two succession stages: The first stage is herb stage. The community type is Assoc. Acalypha australis - Setaria viridis.The second stage is the transition phase of herb community to shrub community. The community type is Assoc. Artemisia mongolica - Bidens parviflora. In mid-mountain, there is only one succession stage, namely the herb community stage. The community type is Assoc. Clematis intricata - Bidens parviflora.