Landscape Ecological Security Evaluation Of Hohhot Urban Spatial Expansion

With the rapid development of China’s economy, growing population, urbanization has become an important phenomenon in today’s society. Urbanization was the most obvious feature in the aspect of urban space expansion, it is a measure of an important symbol of the city. A massive urban space expansion has a dramatic impact on the surrounding landscape, resulted landscape pattern change. Consequent environmental pollution, ecological damage, land degradation, urban heat island and a series of environmental problems, leading to declining regional ecological security, highlighted the growing security risks.Therefore, this paper Hohhot area of the study, between the 1977 with the 2014 year about 6 Remote Sensing Images the RS and GIS technology, in its analysis of urban spatial expansion and temporal variations and the evolution of landscape structure on the basis of characteristics, based on the " pressure - state - response"(PSR) conceptual model for the evaluation of landscape ecological security Hohhot. Which aims at exploring urban space expansion impact on the landscape ecological security, provided the basis for urban land using optimization. Specific results are as follows:(1) Hohhot from 1977--2014 in built-up area expanded,38 years built-up area expanded 195.39km", area increased nearly six-fold expansion speed of the city. Hohhot built-up area located mainly in the direction of increasing the city’s east and south, which is the main direction of urban expansion. Period of five urban expansion, although different in terms of speed and strength, but the overall trend continued to accelerate, growing strength; where, in 2001 2010 City area increased up to the most; 2010--2014 Urban expansion rate the fastest, the intensity of urban sprawl are the strongest.(2) Hohhot city expanded in the early days of space inside is filled with mainly urban compact shape simple rule; external expansion mainly to later period, the rate of expansion continues to accelerate, urban fringe loose structure, the shape of the city increased complex and tortuous. In the urban space and in the process of expanding the city center is also undergoing metastasis; initial study period and mid-city focus shifted to the northeast; the latter part of the city shifted the focus of the study period the southeast. From the entire study period, the overall focus of the city to the southeast transference, the transfer distance of the center of gravity 1529.18m.(3) From the point of view of landscape type change, Hohhot declined arable land, construction land is increasing, there are vary of degrees of reduction of woodland, grassland and waters occupied unused land to be developed. The overall number of plaques in the study area is increasing, especially in construction land and farmland patch number increased up to the landscape as a whole tends to fragmentation and heterogeneity. Waters affected by human activities is relatively small, the most complex and irregular patch shape; arable land affected by human activities intensity of the strongest patch shape tends to be simple and regular; land for construction in a state of irrational expansion patch shape increased complexity.(4) From the point of view of change in landscape pattern, the study area is mainly on patch density, decreased aggregation, separation increasing indicating more plaque fragmentation, heterogeneity and discrete. Dominance index and contagion index declining, explained the benefits of reducing plaque, within the dominant patch connectivity decreased barrier enhanced plaque tending to fragmentation. Diversity index and evenness index continued to rise, indicated that more and more uniform distribution of the different types of plaque, landscape has become increased diverse.(5) From 1977 to 2014 year, the Hohhot landscape ecological security index declining trend in declining security, ecological security of high-level Chinese and decreased to a moderate level. It indicates that the entire study area landscape ecological security is continuing to reduce security risks to increase ecosystem growing insecurity. During the study period (1977-2014), the change rate of comprehensive index about landscape ecological security is different, can be divided into two periods:a period from 1977 to 1990 the comprehensive index of landscape ecological security decreased slowly. The safety level are in the high level; another period is from 1990 to 2014 in landscape ecology comprehensive security index decreased rapidly, the safety level decreased from high level to middle level.