| As the largest lake of Shandong area, Lake Nansi has a strategic significance because of its locating on the East Route Project of South to North Water Diversion. It plays important role in supporting the economic development and ecologic balance. The wetland is silted up and water is polluted seriously because of human activities and natural changes. The wetland resources are exploited excessively so that the ecosystem structure and diversity of biology are damaged. The functions of wetland retrogress and the ecosystem services are reduced.The author takes part in the project sponsored by natural science fund of Shandong Province (Y2008E13). This paper is supported by the project. By combining the ecosystem objective existence and mankind's needs and using macro and micro methods, the paper researched the structure, functions and services value of Lake Nansi. The conclusions are as follows:(1) Analyzed the landscape pattern of Lake Nansi wetland in 1987~2006 by making use of remote sensing data (SPOT image of 2006 and TM images of 1990, 1997, 2004). The work platforms are ERDAS9.0 and ArcGis9.0. The results show that 1987~2006, Lake Nansi wetland reduced, the manpower's wetland and other field increased. The landscape pattern tends broken. The area of natural wetland descends continuously, from117.63km2 in 1987 to 693.34km2 in 2006. Plaques number and density increased. Average size, perimeter - area fractal dimension and spread index reduced. Diversity index and evenness index increased.1987~2006, Plaques number increased continually from 2917 to 3047 and plaques density increased continually from1.08/km2 to 1.21/km2. Plaques of average size decreased continually from 0.94 km2 to 0.83km2。(2)Analyzed biology and environment of Lake Nansi wetland ecosystem by field survey and data analysis.The ecosystem structure and function of the lake took place a series of varieties. As the shape of Lake Nansi like a shallow dish, precipitation of annual and seasonal changes vary widely, the lake silted up badly and pollution is serious, its ecosystem structure and function took place a series of changes. In 1983 ~ 2006 years, the biomass of Lake Nansi wetland was downward in whole. The aquatic plant biomass reduced was the most and the fastest. Fish biomass in 1983 and 1997 was decreasing, and began to rise in 2004, it exceeded 1983 in 2006. It was drought in 2002. The lake entered into the wet period in 2003, 2004 and water level raised, local management put a lot of fry in batches, and human intervention increased fish stocks. Phytoplankton, Zooplankton and Benthos continued to decline during1983 to 2004, and in 2006 exceeded in 2004, but still below its level in 1997, 1987, and 1983. Lake Nansi aquatic plant biomass changes reflect human reclamation, aquaculture and other activities on lakes and wetlands affected are imperfect from the periphery to the center of the lake. Changes in ecosystem structure caused the material production, water conservation, flood control, water purification, air conditioning, and nutrient cycling functions impaired in varying degrees.(3) Using the theories and methods of Energy established by H.T.Odum, evaluated the structure and function of Lake Nansi wetland ecosystem in overall. Lake Nansi inputs (including the sun, wind and rain) the amount of solar value of 1.11×1021sej/a, output solar value 1.73×1020sej/a, primary productivity is1.61×1020sej/a, non-renewable energy or resources (including sediment and water) is 1.03×1021sej/a. At the same time, Lake Nansi in aquatic vascular plants and fish the ecological benefits is significant. Energy investment ratio is 0.0009. Net energy yield is 165.23 and environmental loading rate is 14.22. The data show that the investment in Lake Nansi is low. High net energy yield and environmental loading rates show that Lake Nansi wetland ecosystem has great contribution to the economy; regional economic development level is low and very depends on the environment.(4) On the basis of the structure and function research, determine the Nansi Lake wetland ecosystem services: basic services and social services. The services values are basic (physical value, process value) and social values. Through effective classification, applies value assessment methods to evaluate the value of wetland ecosystem services. Lake Nansi wetland ecosystem services is 1026.17×107 $ for many years average. The total service value fluctuated in the study period from 1018.51×107 $ in 1983 to 1116.09×107 $ in 1987; then it decreased to 1001.00×107$ in 2004; it increased to 1028.91×107$ in 2006. The total service value was reduced from overall trend and the average annual reduction was 9.43×107 $. Comparison of different periods (1983, 1987, 1997, 2004, 2006) the value of ecosystem services and changes in the composition, the presence value and social value years was average value in many years, the process value was decreasing, the total service value fluctuations was caused by the value of material. It illustrates that outside interference (natural energy input and human activities) directly affects the wetland ecosystem material production. Then, the various functions and services of ecological processes were changed. From the services value composition, the process services value was maximum, accounts for about 71.65% of the total value; followed by the material value, about 17.72%; the presence value and social value were minimum. The data show that the contribution of process of Nansi Lake wetland ecosystem to the local economy was largest; followed by physical function. The presence value and social value were neglected.(5) Analyzing the driving forces caused changes by the Nansi Lake wetland ecosystem structure, function and service values. In addition to the regional precipitation changes, the shape of lake and silts up because of biological decay, the human activities to Nansi Lake is the main reason which disturbances the ecological system. Diversion, reclamation, farming, watershed water pollution is the main form of human interference. It rooted in five aspects: demographic changes, poverty, market and government failure, economic policies and structures, development patterns and preferences. Install reasonablely the water resources, controll pollution, repair wetland ecosystem; develop reasonable policies and systems; establish a perfect market mechanism is expected to effectively control human activities on the Lake Nansi ecosystem disturbance.In the context of global change, changes in the natural environment of Nansi Lake severe, and as the social and economic development, the impact of human activities affect the wetland more comprehensive and deeper. Nansi Lake wetland area decreased; the landscape tended to broken; its ecosystem structure and function were damaged; service value showed a decline of instability. These indicate that Lake Nansi wetland ecology and environmental degradation. Ultimately, humanity obtains the benefits from wetland ecosystem has decreased, affects human survival and quality of life. Lake Nansi Wetland Nature Reserve was established in 2003. The East Route Project of South to North Water Diversion started construction. From then on, the wetland eco-environment management improved. However, due to the wetland ecosystem's feedbacks take longer and socio-economic development has inertia, Lake Nansi wetland eco-environment degradation was controlled but has not been fundamentally improved. Develop reasonable policies and systems; establish a perfect market mechanism is expected to effectively control human activities on the Lake Nansi ecosystem disturbance.The research about Lake Nansi wetland ecosystem structure, function and services enrich the theory of wetland ecosystems. At the same time, it provides a theoretical basis and application of reference for Lake Nansi wetland protection and restoration of ecosystems.
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