Growth Characteristics And Ecosystem Services Of Phragmites Australis, A Typical Vegetation In Baiyangdian Lake

As the special habitat formed by the interaction between terra and water area, wetlands are considered one of the world's three majoy ecosystems along with forests and oceans. Wetlands account for approximately 6.4% of the earth's surface, provide habitats for nearly 20% of the known species on the earth, and have irreplaceable ecological functions. As the largest freshwater lake in north China, Baiyangdian Lake plays a significant role in protecting the environmental security of the whole basin and majoy cities. The lake mainly made up of marsh with nutritious soil, is a proper habitat for Phragmites australis. P.australis distributes widely in the wetland, is a typical vegetation and plays an important role in the process of the ecological functions. However, since the 1970's, due to various reasons encountered, the wetland has been shrinking, and the P.australis area has also been fluctuating, at the same time the quality of P.australis has been downtrending and the production of P.australis has also been plummeting. This situation has not only affected the income of local farmers, but also affected the conservation of wetland biodiversity and its ecosystem services.This thesis used P.australis, the typical vegetation in Baiyangdian Lake, as an example to research the growth characteristics, soil physical and chemical parameters of the dominant vegetation in the typical wetlands in north China.The direct and indirect value of P.australis in ecosystem services was estimated, and the suitable harvest time of P.australis was also researched.The study found that the soil water content increased with the increasing depth, the minimum of which was in April and the maximum was in August; the contents of soil organic matter, total nitrogen and total phosphorus decreased with the increasing depth, the maximum of which appeared in the surface layer, and the changing trends in different layers over time are different; soil total nitrogen / total phosphorus ratio decreased with the increasing depth.The density of P.australis populations remained stable over time, showing the adaptation to environmental factors; the height and diameter of P.australis increased over time, and had the fastest growth rate during the main growing period; rhizome with the largest biomass, nitrogen and phosphorus accumulation, and the corresponding parameters of each component increased over time; lamina with high total nitrogen, total phosphorus, and the corresponding parameters of each component decreased over time; the maximum P.australis plant biomass, nitrogen and phosphorus accumulation were respectively in August, August and October, the maximum of corresponding parameters of aboveground were in October, August and June; the total nitrogen / total phosphorus ratio of the aboveground was higher than 16 in growing period, showing that phosphorus was the limiting factor to the growth of P.australis in this period.The P.australis in Baiyangdian Lake had a high biomass(6.48~9.13 kg·m-2, at an average of 7.18 kg·m-2), and carbon storage(2.86~4.04 kg·m-2, at an average of 3.17 kg·m-2). The underground biomass was larger than shoot biomass, and the ratio was over 3(1.90~4.18, at an average of 3.27). Thus underground carbon storage was more than 3 times that of shoot. A typical wetland like Baiyangdian Lake had a strong carbon fixation capacity, 0.69~2.25 kg·m-2·a-1, can be 1.4~4.6 times of the average carbon fixation of terrestrial vegetations in China, and 1.7~5.5 times of that of the world. According to the formula of light efficiency, it was still low, only 0.50%~1.65%. If the light efficiency were improved to be 5.00%~6.00%, the maximum value in theory, the carbon fixation and release oxygen capacity of the vegetation in the wetland would increase 2.03~11.00 times, reach 6.60~8.28 kg·m-2 and 18.70~22.44 kg·m-2 per year, the nitrogen and phosphorus absorption capacity would also increase accordingly, the potential ecosystem services would be huge.The suitable harvest time of P.australis was found to be October and the economic value made by harvest the aboveground parts can reach 389 million yuan(including the P.australis sale income 117 million yuan, emission reduction benefit of carbon fixation 133 million yuan, benefit of release oxygen 124 million yuan, benefit of nitrogen and phosphorus absorption 12 million yuan and 3 million yuan), which was equivalent to 16.34% of the gross national product of Anxin County and 60.78% of the tourism income of the region of Baiyangdian, and brought significant economic and ecological value. We suggest that the research and management of P.australis in Baiyangdian Lake should be reinforced and the P.australis should be put into comprehensive utilization so as to enhance local income and people's living standard. Besides, local government should increase financial assistance to accelerate the ecosystem services of the wetland, promoting socialist rural construction and creating socialist harmonious society, and realizing development of all-round social-economic-natural complex ecosystem.