| Urbanization is an important indicator to measure a state’s comprehensive strengthen. Furthermore, urbanization has huge effect on the evolution of urban landscape patterns. There are two major reasons for the evolution. Firstly, the original rain gathering area with strong functions of water storage and purifying, together with functional space of rivers’ banks,have been gradually reduced due to the increasing land demand of human being. Secondly, the consequent large-scale urbanization changed the landscape patterns of suburban and its surrounding regions. In general, urbanization has affected the structure, process and functions of urban and suburban ecological system. Therefore, the contraction between the deterioration of environment brought by urbanization and people’s presure needs of improving the environmenthas become one of the main contradictions in today’s society. As an important resource of the urban ecological environment, water environment has been influenced by the urbanization process more seriously, especially in the form of land use. Under such circumstances, the following questions have become hot issues in academic circles: How can we use and develop urban land reasonably, so as to reduce the negative effects of landscape pattern change caused by urbanization on water environment? How can we explore the best way of urban land use?Guiyang City, the capital of Guizhou Province is listed in the first batch of demonstration areas for building eco-city in China, is also one of the cities with rapid urbanization in West China, ecological advantage is The greatest comparative advantage of Guiyang City. As a result,the change in land use types of its core area and the impact of landscape pattern change on its ecological environment due to urbanization are representative. Hence, it is important in addressing both in theoretical and practical significance to explore characteristics of the urban landscape pattern evolution in Guiyang and its impact on the ecological environment especially on water environment. The generated results could will provide scientific planning and reasonable construction of the construction of ecologically-civilized.In this paper, taking the urban expansion of Guiyang in the context of China’s rapid urbanization as the research line, we applied remote sensing and GIS technology as well as the theory of landscape ecology to set up a spatial-temporal database for the six districts under Guiyang based on land use and cover. By analyzing the change of land use through the land use dynamic index and describing the changes of landscape pattern in these areas through different indexes for landscape “mosaics”and types, we discussed the characteristics of land use, and the spacial differences as well as the natural and human driving forces of typical landscape types in the core area of Guiyang between 2000 and 2014. Based on the research of the integral landscape pattern evolution of these areas, we selected the Nanming River and Maixi River, the typical rivers in the core area, as well as the Aha, Huanxi and Songbaishan reservoirs, typical reservoirs of lakes, as the objects of study to explore the pattern evolution of the landscape surrounding these typical water bodies. Combining with the monitoring data of the water environment for years, we used gray correlativity analysis and SPSS(Statistic Package for Social Science) to conduct cor-relational analysis for the change in the land use, the pattern evolution of landscape and the typical water quality in order to discuss the water environment effect of the landscape pattern evolution surrounding the core area. Taking the urban built-up area in 2010 as the source, we screened ecological resistance factors and put the water bodies and rivers into the rigid constraints for the buffer analysis and grading as well as giving them a value respectively. By doing so, we established the correlation trends of ecological factors after the urban expansion and modification, thus could simulate the expansion direction of the city based on the protection of water environment by using the model of minimum resistance accumulation. The conclusions were as follows: 1. The landscape patterns in the core area of Guiyang City evolve quickly, and the landscape patterns surrounding different typical water bodies have sharp differences.In the areas covered by the research, we focused on 6 land use types including paddy field, dry land, construction land, forest land, water body and garden plot. Among them, the forest land was the dominant landscape in the core area, which accounted for more than 40% of the total area. In addition,the area of construction land was expanding with a increase of 444,997 hm2 in 2014 comparing that in 2000. Within Maixi River basin, the forest land and paddy filed were the main types, but the area of forest land, dry land and paddy field declined year by year, and the ratio of construction land and garden plot increased year by year. The ration of construction land was changed significantly, which was increased from 3.6% to 13.34% with a increase area of 317.73 hm2. Within the Nanming River Basin, the construction land was the main type, and the ration increased gradually. Within the Aha Reservoir, the forest land and paddy filed were the main types,and the area of paddy filed was decreased dramatically while the area of construction land was increased greatly. In the reservoir, the ratio of construction land was increased from 40.99% in 2000 to 52.34% in 2014. Within the Huaxi Reservoir, the forest land was the main type. As the dominant landscape, the ratio of forest land in this reservoir increased from 44.78% in 2000 to 47.47% in 2014. Within the Songbaishan Reservoir, the dry land and forest land were accounted for the most in the total area, but the ratio of construction land was increased year by year, and the other land use types were decreased with the area of dry land having a biggest decline.Moreover, the structure of land use differs in different river basins and reservoirs. In the whole core area, the biggest change was found in the sharp decrease of paddy filed and the large increase of construction land, and the change of land use type in Maixi River stayed the similar with the general trend in the core area. In the Nanming River, its buffer zone ranging from 0 to 500 meters was mainly construction land, and the ratio was increasing. The fist class water protection zones in both Aha and Huaxi reservoirs were mainly forest land, as the area of forest land increased at different degrees. In general, the increasing area of the fist class water protection zones in the Aha Reservoir was mainly construction land, while the forest land in Huaxi reservoirs took the main increasing area. For the pattern evolution of the landscape surrounding the typical water bodies, the biggest increasing range of the plaque density of land use was found in the buffer zone of the Nanming River and the first class water protection zone of the Aha Reservoir over time, while a slight increasing range in the Maixi River basin as well as both the Huaixi and Songbaishan reservoirs. In addition, the trend of landscape diversity enhanced gradually in the buffer zone of the Nanming River, while the same trend decreased in the landscape surrounding the Aha, Huxi and Songbaishan reservoirs, but the change of the trend in the Maixi River basin was not noticeable. The indexes for landscape evenness in the first class water protection zones of the Aha, Huaixi and Songbaishan reservoirs were slightly increased. Furthermore, the indexes for the biggest plaque of forest land in typical water bodies are significantly different. The index for the biggest plaque of forest land in Nanming River was obviously decreased. 2. The spatial differences of land use structure surrounding the typical rivers were also noticeable in the core area of Guiyang.We observe the influence of pattern evolution of landscape surrounding the Nanming River on water environment. The construction land of the buffer zone ranging from 0 to 500 meters of the Nanming River increased in general, and the construction land of the Huaxi Section were mainly transformed from dry land and paddy field. Although the construction land stuffs the internal of the Xinzhuang Section, the area has a little increased. In addition, the landscape change of the other types is not that big. The trend of landscape diversity in all buffer zones of the Huaxi reach rose, and the contagion and plaque connectivity index were decreased, so the agricultural landscape that dominate the whole area shattered gradually. In the Xinzhuang reach, the urban landscape dominates the area, so the level of landscape diversity in this area was weaker than that of the Huaxi reach, and as the increasing ratio of urban construction land, its landscape diversity further weakens. The patterns of landscape in the Huaxi and Xinzhuang reaches show a significant difference, at the same time, the water quality in these two sampling sites displays a marked difference. Obviously, the water quality is related to the land use and landscape patterns in these tow reaches. The water environment in the Xinzhuang reach was worse than that of the Huaxi reach may due to the main landscape featuring construction land in the Xinzhuang reach. Although the Xinzhuang reach has a bigger area of construction land than that of Huanxi reach,ρ(TN) and ρ(TP) of the Xinzhuang reach are on a declining curve, since the Xinzhuang reach carried out the treatment of point source pollution, channel cleaning and artificial wetlands construction.There were duration variability and spatial variation in dry, normal and wet seasons for water quality in this correlation, and different pollutant sorts can change the correlation. No matter for the whole basin or buffer zones, SHDI was an important factor to forecast water quality.We also observe the influence of pattern evolution of landscape surrounding the Maixi River on water environment. The construction land and grassland increased gradually in the Maixi River basin, but the change of the forest land was small, and the area of paddy field and garden plot dropped off. From the upstream to the downstream, as the ecological land such as forest, shrub and herbaceous plant increased, and the diversity of land use strengthened and the evenness index were declined. In addition, the contagion and plaque connectivity index also decreased, so the landscape of dry land and paddy filed that dominate the whole area shattered gradually. From the upstream to the downstream, the nitrogen and phosphorus concentration decreased in general with the significant drop of TP. A slight decline of TN attributed to the fact that the downstream has many paddy fields, cornfields, dry lands with the high TN and TP soil. Thus, the non-point source pollution process is close related to the landscape composition and patterns. Besides, TN and the percentage of agricultural land are correlated in a positive fashion.3. The landscape patterns surrounding typical reservoirs have different correlations with the water quality in the core area of Guiyang City.The level of NH4+-N,TN,TP have different values in the firs class water protection zones of the three reservoirs during the different period. The level of NH4+-N and TP in the Huaxi, Songbaishan reservoirs was lower than the Aha reservoirs. For the influence of the land use change of the first class water protection zones in these three reservoirs on the water quality, the “sink” landscape such as grassland and forest land has a stronger correlation with various pollutant indexes than that of the “source” landscape such as construction land, dry land and forest land, which demonstrates that sink landscape can play a significant role in the retardation of water pollution of urban reservoirs. Based on the correlation between the indexes of landscape surrounding the Aha, Huaxi and Songbaishan reservoirs as well as the pollutant indexes, we can find that higher PD, SHDI landscape indexes mean a stronger correlation with the pollutant indexes, then a stronger impact on the water quality of reservoirs.4.The Landscape surrounding the Nanming River in the main urban area presents a “source” load, while the landscape in the Maixi River in the suburb as well as the Aha, Huaxi and Songbaishan reservoirs presents a “sink” load.Based on the analysis of the characteristics of the surrounding landscape patterns and land use in the typical river(Nanming River) and the typical reservoir(Aha Reservoir) in the main urban area as well as the typical reservoirs in the suburb(the Huaxi and Songbaishan reservoirs), we further analyses the landscape load comparative index of “source and sink” of different buffer zones in typical water bodies of Guiyang and its correlation with the water quality, then makes quantitative analysis for the direct and indirect effects of the various landscape indexes on the water quality so as to reflect the influence of landscape pattern change on the water quality. The result showed that the buffer zone of the Nanming River in the main urban area demonstrated a “source” landscape load, and the landscape contrast index(LCI) increased year by year from 2002 to 2014. the Maixi River in the suburb also presented a “source” landscape load, and the same index declined gradually from 2002 to 2014. At the same time, the first class water protection zones of the Huaxi and Songbaishan reservoirs had a “sink” landscape load, and the LIC decreased year by year from 2002 to 2014. This result can prove that a large area of forest land in the suburb would play a strong role in the ecological restoration and pollutant intercepting, demonstrating an effective capacity to improve the water environment. Through the path analysis, we can find that TP and COD are two important indicators to measure water pollution. In addition, LCI was close related to both TP and COD, and has a strong direct impact on them. Based on this, it’s safe to say TP and COD can tell the situation of non-point source pollutant output, and the change of TP can affect the water quality. Although LCI and TN were correlated in a negative fashion, its direct effect on TN was not significant, and its indirect effect on the concentration of TN was mainly by means of other landscape indexes. Both fragmentation of representation landscape and edge density(ED) of heterogeneity were close related to various indexes for water quality, and then have a strong direct effect on water bodies. To be specific, both the fragmentation and ED have a negative effect on contamination index of water quality. In addition, larger contagion and stronger diversity of landscape can promote a better adhesion of plaque, more reasonable balance of landscape factor allocation and less non-point source pollutant output, and along with the intercepting and transforming of “sink” landscape, guaranteeing the better water quality. Therefore, the landscape pattern change has a certain influence on the water quality, so to allocate landscape patterns properly could control non-point source pollution and improve water quality. 5.Considering the influence of the rigid resistance in the typical water bodies, the core area of Guiyang expands in the direction of low resistance value to form the urban pattern featuring a single center and multiple groups.Taking the urban build-up area in 2010 as the source, we use arcgis9.3 to sort weight of single factors such as land-form, land cover and ecological sensitivity so as to simulate a resistance value panel. It turned out that higher resistance value signifies a bigger constrain force on the urban expansion, and the high resistance value can be found in the Baihua mountain range in the north, the Qianling mountain range in the middle part and the three belts in the southern mountain range. In addition, by applying the logarithmic method, we divide the urban expansion into different ecological adaptable zones, namely, priority zone for development, key zone for development, ecological management zone, restricted development zone as well as forbidden zone for development. Furthermore, we correct ecological resistance factors through the model of MCR, and take main water bodies and rivers as rigid constraints to grade buffer zones with assignment. Based on our research focusing the influence of landscape patterns and their evolution in the Maixi River basin, the buffer zone ranging from 0 to 500 meters in the Nanming River as well as the first class water protection zones of the Aha, Huaxi and Songbaishan reservoirs on the water environment, we divide the rivers and reservoirs into different buffer zones at five levels. By locating the downtown as the midpoint, we can find the level of resistance in the south is higher than that in the north in general, which means a centralized and continuous distribution of the high resistance value in the Huaxi, Songbaishan and Aha reservoirs while a shattered distribution of the high resistance value in the Wangjia Dajing as well as the Baiyun District, Wudang District and South Huaxi District. Besides, a linear distribution of the high resistance value is found along the banks of the Nanming River. Therefore, it’s obvious to notice the research findings is in line with the classification of ecological adaptable zones. By passing the ecological landscapes such as urban water bodies, the least resistance of urban expansion can develop in the direction of low resistance value on the premise that the maximum resistance value for typical urban water bodies was considered fully. In conclusion, the urban expansion for the core area of Guiyang should develop in the east, expand in the north, connect in the west and extend in the south. To be specific, the urban expansion pattern consists of a single center( the old city and the Jinyang New District) and multiple groups(the Shawen High-tech Zone, Xintian group, Longdongbao group and Huaxi group). |
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