Laws Of Vegetation Community Succession And Plant-diversity In Peatlands

The wetland ecosystem of Jinchuan region, which is located in the middle of Longgang Mountains inwest piedmont of Changbai Mountain, is a special ecosystem in Houhe river basin. The ecosystem comprises many peatlands which were developed from the the typical crater lakes in Changbai Mountain. The peat in this area is herbaceous peat developed in Holocene, which is characterized by continuous development and high deposition rate. In addition, this wetland ecosystem is the typical representative of this region because of its special geographical position and intact peat. At the same time, the succession and development of the vegetation in these peatlands, which are relatively well preserved with rich plant species, have certain regularity. Therefore, the ecosystem has important significance on mire science research. There were lots of studies on changes of species diversity during the process of vegetation succession, but the researches on vegetation succession of the crater lake peatlands in the eastern part of Jilin Province are rarely reported. The research on plant diversity of the typical wetland ecosystem, which developed on the crater lake peatlands, will provide reference for revealing the law of wetland succession. Therefore, the variation of species diversity in the crater lake peatlands was systematically studied in this article on a large, medium and small scale to seek vegetation succession law during the vegetation succession of Jinchuan wetland, and to provide theoretical basis for protection of the wetland.The space-for-time method was applied to analysis vegetation succession law and plant diversity of the crater lake peatlands according to the vegetation characteristics, species diversity and function diversity, physiological and ecological characteristics of dominant species and population pattern of three crater lake peatlands. The conclusion is as follows:(1) The three main sample areas are peatlands with different succession stages. They all developed from crater lakes. They were isolated from each other, then formed biological islands almost without genetic exchanges. Based on the traditional theory of lake succession and existing evidence, the order of swampiness time of these three peatlands from early to late was: Gushantun, Jinchuan and Hanlongwan. The vegetation succession process of these three peatlands is concentric succession(developing from the lake shore to the middle).(2) It is commendable to distinguish these three peatlands which were in different succession stages by using the method of classification and sorting. Overall, the three peatlands have various plant species, containing 39 families, 62 genera and 75 species, and the number of genera in every family is different in floristic composition. Most of the genera, which number is 56, contain only one species, accounting for 91.8% of the total number of genera, and 76.7% of the total number of species. It indicates that the plants of peatlands in this region are characterized by diversity and dispersion.(3) Due to shorter time of succession, community in Hanlongwan is still in the developmental stage, and the succession develops slowly. Therefor, with regard to species diversity index and evenness index, there is no significant difference between the sites of this peatland. By comparison, the number of plant species and species diversity of Jinchuan peatland(with relative longer succession) are significant higher than that of Hanlongwan. In addition, the species diversity of communities in the edge is usually higher than in the center of Jinchuan peatland. Because the evolution history of Gushantun is longer, the peatland inner environment is consistent, and the difference of species composition between every quadrat is not obvious. The results based on the comparative analysis on different plant community functional diversity in Gushantun, Hanlongwan and Jinchuan peatland habitats with different succession stages show that: compared with plant nutrition traits, plant morphological traits were more relevant to the other traits. The mean weight of leaf dry matter content and leaf carbon content of the community in Jinchuan wetland was significantly higher than that in Gushantun and Hanlongwan wetland. This means that leaf nutritional properties of the three peatland are obvious different. Meanwhile, under the condition of water flooded, the functional traits of the communities with different dominant species are similar. As far as one single functional trait is concerned, leaf carbon content could be a representation for functional diversity. Leaf carbon content of different communities in Jinchuan wetland has higher heterogeneity. This phenomenon is similar with species diversity. Changes on functional diversity in habitats explain that natural environments are complex and diverse. The driving effect of one factor always has a relationship with other multiple environmental factors. So it is necessary to consider the mutual effect of many factors together when we examine the relationship between plant functional traits and environment.(4) There are differences in the relationship between species diversity and community productivity in wetlands with different succession stages. Overall, the biomass of communities in three peatlands is obviously different, and the biomass of communities and dominant species shows seasonal dynamics. The biomass of Hanlongwan peatland is the highest and Gushantun peatland is the lowest. The relevance between aboveground biomass and species diversity index of plant communities in Gushantun and Hanlongwan wetlands is linear positive correlation,while it is negative correlation in Jinchuan wetland. One or more functional diversity traits have impact on productivity. Aboveground biomass shows a significant negative correlation with specific leaf area, and also has significant linear correlation with leaf size and plant height. Generally speaking, this study indicates that there is a weak relevance between functional diversity and productivity. The responses of species diversity and functional diversity to environmental factors are often similar but sometimes different in a small minority of cases. Both species diversity and functional diversity showed a significant correlation with soil total phosphorus and total nitrogen. Soil nutrient elements had a greater influence on community functional diversity than nutrient elements in water.(5) In the process of wetland vegetation succession, there was a significant positive correlation between the patterns of Betula ovalifolia and moss mound. Betula ovalifolia population was randomly distributed at the initial invasion to wetlands. With competition for resources and population expanding. Betula ovalifolia seedlings chose the pattern of cluster distribution. Among the environmental factors that impact on communities, available phosphorus is the most important of all, followed by moss height.(6) Water depth of wetlands had a greater influence on the development of dominant plant Carex Schmidtii during the process of vegetation succession. Deeper water level could hinder biomass accumulation of Carex schmidtii, change the distribution of biomass in plants, and slow down the process of wetlands from wet to dry, consequently slow down the process of vegetation succession. On the contrary, shallow water level could speed up the pace of succession. It indicates that water depth is one of the main influence factors for wetland community succession. Overall, plants can adapt to dynamic change in community environment by changing its physiological characteristics. It is fully proved that vegetation community dynamics and physiological ecology characteristics of plants are closely related.