Plant Succession In Deglaciated Terrain On Mt. Yulong

With global climate warming, deglaciated terrain, which is1250m in length, surrounding Baishui No.1Glacier on Mt.Yulong was formed since the late19th century. It provides an ideal place for plant succession in nature. In view of frequent fires and the need to restore ecosystem in Mt. Yulong, as well as fewer reported studies, it has very important theoretic and practical significance in researching ecological succession in this region. Selecting Mt. Yulong in China’s alpine-monsoonal temperate glacier region as the study area, a chronosequence method (substituting space for time) was used to study the community composition and its numerical characteristics, ecological and physiological characteristics of dominant species, the relationship of plant succession and soil nutrition, as well as the connection of plant succession and glacier variation. The major conclusions are as follows:(1)55plots are investigated in total, in which91species have been found, about63species have been identified, which belong to28families and46genera. They are mainly about dicotyledon, contain arbor, shrub and herb three life forms plants on the foreland of Baishui No.1glacier in Mt. Yulong. There are seven types of genus’ distribution. It includes Cosmopolitan, North Temp., Arctic-alpine, North-Temp.&South-Temp., East Asia, Sino-Himalaya and Endemic to China. These plants are mainly composed of North Temp, and Cosmopolitan, and they account for about50%and21.4%.(2) Based on field observation in August,2011and experimental data, plant succession and dispersal mechanism of dominant species was studied by numerical classification and ordination techniques on the foreland of Baishui No.1Glacier at Mt. Yulong. The results indicated a total of50samples were classified into9community types, which were further classified into3successional stages on the glacier foreland at Mt. Yulong. The early succession stage contained Arenaria delavayi+Meconopsishorridula association. Four associations in the middle stage were composed of Arenaria delavayi+Kobresia fragilis, Carexcapilliformis+Polygonummacrophyllum and Carex kansuensis and Pedicularis rupicola. The late stage included Kobresia fragilis+Carexcapilliformis, Kobresia fragilis, Kobresia fragilis+Ligusticumrechingerana and Kobresia fragilis+Ligusticumsikiangense four associations. The general tendency was from nudation to alpine screes sparse vegetation, then to alpine meadow. With increasing terrain age, species diversity, richness, aboveground biomass and vegetation coverage increased clearly during different stages. In addition, there were anemochory, mammalichory and myrmecochory three types of dispersal methods. The change was from anemochory to a mixture of anemochory, zoochory and other dispersal methods to zoochory in dominant species all through the plant succession.(3) According to plant813C, all the dominant species occurring in every succession stages belong to C3phtotsynthesis pathway plants. With the succession went on, the overall trend of plant813C variation among the four C3species was Arenaria delavayi (SUC1), Polygonum macrophyllum (SUC2) and Arenaria delavayi (SUC3)> Kobresia fragilis (SUC5)>Carex capilliformis (SUC4), hence the plant water use efficiency (WUE). According to the results of regression analysis, all these dominant plants δ13C decreased with the increase of soil nutrient content. According to plant nutrient content, its overall trend of plant C or N content was Arenaria delavayi (SUC1)<Polygonum macrophyllum (SUC2) and Arenaria delavayi (SUC3)<Carex capilliformis (SUC4) and Kobresia fragilis (SUC5). While the overall trend of plant C:N was Arenaria delavayi (SUC1), Polygonum macrophyllum (SUC2), Arenaria delavayi (SUC3) and Carex capilliformis (SUC4)<Kobresia fragilis (SUC5). According to the results of regression analysis, among the4dominant plants, the nutrition content of Arenaria delavayi had not remarkable response to soil nutrition, while Polygonum macrophyllum has the remarkable response to soil nutrition. In the4soil nutrition indicators, many dominant plants have remarkable response to soil Total nitrogen content, soil Total carbon content comes second.(4) With the development of plant succession, The content of total nitrogen (TN), total phosphorus (TP), total potassium (TK) and total organic carbon (TOC) in soil increased sharply. Detrended canonical correspondence analysis (DCCA) revealed strong relation between community compositions and environmental factors. Total organic carbon (TOC), total phosphorus (TP) and Elevation (ELE) were important factors which influenced the distribution of plant communities. Elevation influenced the early settlers most, while TOC and TP affect the late succession most. With the increasing content of TOC, the Shannon-Wiener, Richness, vegetation coverage and aboveground biomass were growing remarkably in plant succession.(5) Statistical analysis on species data in different succession reveals the communities composition and its successional law in different aged foreland, namely experienced bare land-herb-shrub-tree3vegetation types on the retreating land of Baishui No.1Glacier during nearly250years. From the aspect of Niche Theory, it is due to the niche and adaptability of different species vary, which leads to various plant communities at different succession stages, and the dominant species which often occupy more wider niche, better adaptability and appear on different succession stages at the same time. In all, vegetation succession is developing which have the tendency of ecological niche differentiation and can utilize resources maximum, moreover, the essence of the species replacement is operated in the course of ecological niche differentiate and close constantly, and the severe interspecific and intraspecific competition.