| As an important part of urban ecological environment, urban lake wetland is an important wetland type with a significant socio-economic value. With the acceleration of global urbanization, land use has produced a crucial influence on the ecological environment of lake-wetland, and triggered a series of ecological and environmental issues. In order to reveal the relationship between land use patterns and water environment of lake wetland and biodiversity in the process of urbanization further, taking Daqing city as the research area, this study analyzes the change characteristics and driving force of lake wetland landscape pattern in the urbanization process, reveals response of landscape space patterns to water environment of urban lake wetland, illustrates the main influencing factors of habitat fragmentation surrounding the lake wetland on biodiversity formation of urban lake wetland. The main conclusions of this study are shown as follow:1) The formation of the heterogeneous urban landscape has a significant impact on the landscape pattern of lake wetlands in Daqing. From 1979 to 2009, land use structure of urbanization region changed significantly in Daqing. From a perspective of change type of land use area and transfer rule, as the habitats of thousands animals and plants, lake wetlands, vegetation and swamp were severely occupied and destructed. Specifically, the transition between farmland and urban construction land indicate the urban expansion was implemented by extensive arable land occupation, similar with regularity of city expansion. At the same time, the landscape pattern of lake wetlands in Daqing has changed obviously. From 1979 to 1989, influced by the South-to-North and North-to-South policy of water conservancy projects construction, lake-wetland area significantly increased by 27,000 hm2. During 1989 and 2009, a large quantity of lake-wetland changed into urban construction land and bare land, which results in the shrinkage of the lake wetland area by 14,800 hm2 as well as a rapid growth in urban construction land of 68,300 hm2. The massive encroachment on the expansion of urban expansion is the main reason for the decrease of the wetland area of the lake. The policy factors expressed a nonegligible impact on lake wetlands landscape evolution from 1979 to 1989.2) The health status of the topical urban lake-wetlands of Daqing is diagnosed from environmental quality and biological diversity. Daqing lake wetland water was seriously polluted, the water quality index (WQI) is between 24.71% and 63.53%. Mean value was 42.21%, the water environment pollution of Lake wetland is very serious. Water quality determination of the value of the coefficient of variation is too large, may and wetland area of lake, shoreline length and the surrounding land use types and sources of pollution factors.The average contents of Cu, Zn, Pb, Cr and Ni element in lake wetland surface sediment were respectively 2.71,2.10,3.31,1.48 and 1.62 times of its corresponding background value, showing an obvious pollution and enrichment trend. The lake wetland comprehensive pollution index (P) was between 0.85 and 1.98, with a mean of 1.53, indicating that degree of heavy metal contamination in surface sediment belonged to light pollution state. The significant positive correlation (p<0.01) between Cu and Pb as well as Cu and Ni in lake wetland sediment, which demonstrates Cu, Pb and Ni might share common sources of pollution. The results show that total of 305 species of vascular plants were recorded which belonged to 60 families and 170 genera, which accounted for 12.19% of the number of vascular plants in Heilongjiang Province. The number of vascular plant species in 9 lake-wetlands is between 31-112, Margalef index of the species diversity-was between 4.17 and 11.02, Simpson index was between 2.49 and 3.85. Shannon-wiener index was between 0.86 and 0.97. The diversity of vascular plants in different lake wetland was obvious, but the overall level was low; the plant diversity was not related to the wetland area. The theory of island biological geography was no longer applicable, and the main factors that determine the diversity of wetland plants were changed to the degree of disturbance of habitat diversity and human activities. Bird survey totally recorded 71 species in spring, belonging to 10 orders and 27 families. Shannon-wiener index was between 0.501 and 1.012, and the number of bird species was positively correlated with lake wetlands area. The bird species distribution of different habitat patches were shown in a descending order:marsh wetland> meadow> open water> farmland and settlement, indicating that land use type and habitat played significantly impact on the number of bird species and distribution. Maintain habitat types and structure diversity has become a key factor affecting lake-wetland species diversity.3) There is a multi-scale response relationship between the land use composition and the water environment quality in the buffer zone of the lake wetlands. Environmental quality assessment includes two aspects of water quality and the surface sediment. The correlation analysis of buffer zone land utilization type area proportion and heavy metal content revealed that the relationship between the land utilization type area proportion of lake wetlands water quality and heavy metal content was significantly, and had an obvious scale dependency. On the 1000m scale, the land use type such as grassland, land for urban public buildings and facilities, residential area, forest land and water area and other land use types was the key factors influencing the water environmental indicators; On the 500m scale, land for urban public buildings and facilities, impervious area, grassland and bare land and other land use types were the main factors affecting the water environmental indicators. On the 100m scale, swap, grassland, land for urban public buildings and facilities and residential land use type were the critical factors influencing the water environmental indicators. In addition, the correlation between area proportion of different land use type and the heavy metal content in lake-wetland water and sediment present obvious difference. Specifically, on the 1000m scale, area proportion of grassland was significantly negatively correlated with content of NH4, TN, CODMn in water. While the area proportion of land for urban public buildings and facilities was significantly positive correlated with Ni element content in the sediment. Similarly, the area proportion of residential land and water area was highly significantly positively correlated with Pb element content in the sediment. All element content of Cu, Zn, Pb, Cr and Ni showed a positive correlation with the area proportion of forest land. On 500m scale, area proportion of grassland was significantly negatively related to content of NH4, TN, CODMn in water. The area proportion of land for urban public buildings and facilities was significantly positive correlated with Pb element content in the sediment. There was a highly significant positive correlation between the impervious area and Pb, Cr and Ni content in the sediment. The area proportion of bare land has a significantly negative correlation with Pb content in the sediment. Finally, on the 100m scale, there was a significant negative correlation between the area proportion of grassland and content of NH4, TN, CODMn in water. Area proportion of swamp significantly positively correlated with TN. The area proportion of land for urban public buildings and facilities as well as residential land was significantly positive correlated with Cu and Pb content in the sediment.4) Different land use patterns in lakeside has a great impact on plant species richness and diversity of urban wetland. The impact index of Ming lake is the most significant, with a serious data 77.27; Chengfeng lake and Sanyong lake shows less serious data,65.30 and 62.18; The impact indices of Yueliang lake, Dongkaliang lake, Chenjiadayuan lake, Lande lake and Dongjia lake are between 35～55, in a middle class; The impact of Dongfenghu lake is the slightest,32.28; The overall comprehensive impact index is 65.46, in a middle class. The results of evaluation index weight and value generation show that land use types have significant influence on wetland plant species richness and diversity distribution in lake area, the impact of construction land is the most serious, the impact of farmland and bare land on natural habitats and plant diversity cannot be ignored as well.5) Diversity and distribution of the bird species was influenced by the composition of the land use in the buffer zone of the lake wetlands. There is a significantly positive correlation between bird species diversity index H’and grassland area of buffer zone (p<0.01), the number of bird species is positively related to the weight of grassland (p<0.05),which indicates the grassland is the main area of bird habitat and foraging. Through the multiple regression calculation of dominant and common species with environment factors indices of 10 habitats, the results indicates that distribution characteristic of bird species is correlated with environmental factors indices, and different bird species shows significantly different adaptability and selectivity preference on habitat, bird species biodiversity is reducing as urban construction land weight and human interference increasing.In conclusion, the changes of land use pattern led by urbanization process is the key driving force in latest 30 years of Daqing. There are close contact among the water environmental quality, the biodiversity of plants and bird and the surrounding land. Therefore, at the beginning of protecting or restoring the environment of urban lake wetland, adjust the surrounding land constitution in different scale, and increasing the restoring grassland weight are the first steps to implement. |
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