Study On Thermal Environment Effect Of Landscape Ecological Pattern In Lanzhou City

At present, the world and China are experiencing rapid urbanization process. From the viewpoint of landscape, urbanization is the spatial evolution of landscape pattern. Spatial configurations and temporal evolution of urban landscape is premise to produce a variety of eco-environmental problems. In the process of physical ecology landscape replaced by artificial ones, urban heat island formed with a series of heat radiation, heat storage and heat transfer as a result of urban surface cover material changed. Therefore, selecting the thermal environment under landscapes as ecology process of landscape pattern, which link the urban landscape ecology with urban environmental problems and introduce the study paradigm of landscape ecology into urban ecology environment successfully, has important signification in theory and practice.Comparing to the plain cities, Lanzhou’s integrated effects include the artificial and original influence factors bringing about the prominent and particular hot island effects. So it is necessary to research on the temporal-spatial characteristics and formation mechanisms of thermal environment in Lanzhou. This thesis, selecting the typical valley basin city in the semi-arid zone——Lanzhou city as an example area, extract urban expansion information and the key ecological factors, retrieve land surface temperature from remote sensing images. Base on GIS and spatial statistic methods, the landscape spatial-temporal pattern and its thermal environment effect at urban scale was studied, and the spatial pattern and the influencing factors of urban thermal environment was analyzed by using a substitute of Multi-Criterion valuation method. This research firstly provides a new paradigm for the study of urban landscape ecology or urban ecology environment in theory, at the same time can perfect or promote the methods and system info landscape ecology, can also support the decision for urban landscape planning, ecological livable city constructing and regional sustainable development in Lanzhou city. The main research works and obtained conclusion in this dissertation are as follows:1. Urban expansion and its heat island response in Lanzhou City. The information of urban construction land was extracted and the land surface temperature was retrieved via mono-window algorithm based on the 1978,1993,2001 and 2010 Landsat/TM and ETM+ images, with the urban heat-island ratio index and the land surface temperature grade maps built. In 1978-2010, the construction land in the central area of Lanzhou City increased from 87.47 km2 to 172.61 km2, and the urban expansion had a spatial consistency with the urban heat island expansion. At the same time of urban expansion, the urban surface temperature increased gradually, and the heat island area had an increasing expansion.2. Thermal environment effect of underlying surface type and pattern in Lanzhou City. The authors put forward a V-I-AP (vegetable-impervious-soil) model, with an attempt to address problems of mixed pixels arising in moderate-resolution remote sensing images. Urban underlying surface was represented by green vegetation and impervious surface generated by linear spectral mixture analysis. Relationship between urban heat island and underlying surface was analyzed based on combining mathematical statistics with spatial statistics. The variance in land surface temperature (LST) and NDVI values associated with different landscape types was studied. Then, the quantitative relationship was acquired by regressive analysis. Shannon Diversity Index (SHDI) and Contagion Index (CONT) were also introduced to analyze the spatial difference between LST and NDVI under the different spatial compound mode of land use. Results suggest that:(1) The vegetation abundance of Lanzhou City decreased significantly during the period from 1999 to 2006. However, the imperious surface abundance increased by 5.32%. A positive spatial autocorrelation exists in the distribution of green vegetation, impervious surface and heat island strength in Lanzhou City.(2) There is an apparent correlativity between LST and NDVI. A significant inverse correlation relationship between LST and NDVI associated with all land use polygons, the same associated with each land type, but correlation coefficients associated with land use types are different. It is more sensitive of LST change on the influence of NDVI in the area of higher CONT or lower SHDI.(3) Water area, green space has a significant cooling function, while the building ground warming effect is obvious. These three kinds of surface area and the average LST of the explored plots are closely related. The effect of selected ecological green space index on LST is in decreasing order of green space coverage, division, average area of patch, cohesion index, shape index, and fractal dimension. There is a positive correlation between fractal dimension and LST, and a negative correlation between LST and other index.3 Spatial scale effect on landscape patterns. Xigu District was selected as a study area for analysis of variation of landscape index with grain size from the landscape level and type level by using 2005 SPOT 5 remote-sensing images. Results demonstrate that 10 m was an intrinsic observation scale for land use landscape of Xigu District. The characteristics of landscape types and landscape patterns of the study area varied significantly with the increase in grain size, reflecting certain scale dependence. Landscape indexes of the townships(towns and neighborhoods) displayed differentiation characteristics of urban-peri-urban-countryside and apparent gradient variation.4. Simulation and analysis of human dimensions of urban thermal environment in Lanzhou City. The author employed Spatial Principal Component Analysis(SPCA) method to analyze the spatial pattern and the influencing factors of urban thermal environment as a substitute of Multi-Criterion valuation (MCE) method. Result indicated that there are four primary factors to influence the density and spatial pattern of urban environment in Lanzhou, which can be generalized as landscape pattern, allocation of industries, urban construction density and types of underlying surface. Landscape pattern is regarded as the most sensitive factors to Lanzhou’s thermal environment among these factors, whose variance contribution was up to 48.42%.