| Ever since the mid 20th century, the world has always been up against daunting environmental challenges resulting from such major global problems as population explosion, environmental pollution, energy and resource shortages. Land use and land cover changes (LUCC) not only impact the sustainable development of a region, but also have a relatively marked influence on global change. The landscape ecological effect caused by some regional land use changes is a hot-spot issue of the ecological study. The study on landscape ecology of LUCC is aimed to discuss the changes of regional landscape pattern in the land use, reveal the regularity lying behind the dynamic changes of land use pattern, the landscape ecological effects and the ecological security. The research contributes enormously to our maintaining regional ecological equilibrium, improving regional ecological environment. In addition, it helps to curb the irrational land use and development so as to achieve the resource and regional sustainable development.Based on the landscape ecology principles, the present study has selected Changde City in Dongting Lake region as the study area. With adopting GIS spatial analysis and comparative approach, the study conducts field research and applies diagnostic model by combining the methods of process analysis, ecological analysis and comprehensive analysis evaluation. In doing so, the current study focuses on the theory and methodology of LUCC and comes to research conclusions as follows.First, in combination with the relevant theory of land use and land cover changes, the study analyzes the characteristics of LUCC pattern in Changde City from the perspectives of the present land use, the dynamic changes of land and the landscape pattern.In Changde City, cultivated land, woodland and unused land are the main land types. The main land uses in combinative structure of land use in Wuling District, Hanshou County, Jinshi City and Li County are all categorized into four types, while Taoyuan County and Shimen County have the fewest types of main land uses.The characteristics of the dynamic LUCC changes include:(1) in terms of the changing quantity of land use, during the period from 1998 to 2007, all of cultivated land, other agricultural land, rural residential land, unused land have been reduced, among which the area of cultivated land has been shrunk most; (2) with regard to spatial variation of land use change, during the period from 1998 to 2007, the inner city cultivated land, other agricultural land, residential land, industrial and mining land have witnessed an decreasing trend, among which cultivated land has the biggest annualized lapse rate as-0.30%; (3) according to the land use change from 1998 to 2007, it is predicted that the inner city cultivated land, other agricultural land and unused land will be reduced during the period from 2008 to 2020 and the unused land will be decreased most by almost 10.77% from 258083.96 hectare in 2007 to 230287.34 hectare in 2020. Meanwhile, construction land and other agricultural land will otherwise take on a trend of augment.Second, the driving mechanism of land use change is revealed. Further study on the relationship between resource, environment and social economy in the regional land use changes. Taking the change process into consideration, the present study has developed the driving assessment indicator system for analyzing regional land use.Land use and land cover changes attribute to natural factors, social economy and policy factors as well. With the increasing population and accelerated urbanization process, the social and economic factors have become the dominant ones causing the regional land use and land cover changes. The industrial restructuring and agricultural population variation are the main driving forces behind the area changes of cultivated land, rural residential land and unused land in Changde City. The variation of economic factors and demographic factors is the main driving force behind the area changes of urban land. The economic growth and variation of general population are the main driving force behind the area changes of independent industrial and mining land. The economic development and technological advance are the main driving force behind the area changes of transportation land.Third, landscape ecological effects of LUCC are analyzed from the perspectives of landscape pattern characteristics, ecological service function and landscape stability. The coupling change relationship between land use pattern and ecological service function demonstrates the impacts of LUCC on ecological service function and reveal the mechanism of effects of land use activities in Changde City on the regional ecological service system.With reference to LUCC landscape pattern, the landscape types of Changde City mainly comprise woodland and cultivated land, each of which takes 36.96% and 25.96% of the overall landscape area respectively. The woodland and cultivated lands are main integral part to adjust landscape pattern of land use and constitute the advantage landscape of the research area. In the next place are unused land, other agricultural land, residential land, industrial and mining land and grassland. The cultivated land patches are relatively even, and the transportation land patch pattern is the most complex. On the whole landscape, cultivated land has advantages and relatively greater influence on the overall landscape spatial pattern. From the view of whole research region, the landscape features greater diversity, abundance, more advantages, greater evenness and higher heterogeneity of the overall spatial pattern.Referring to the current situation of land use and land cover in Changde City and considering the present research results both at home and abroad, the paper has readjusted the value coefficients of ecological service function and assessed the variation of ecological service value. Besides, landscape ecological effects of land use and land cover structure is also discussed in the study. On the analysis of value variation of ecological sub-function, the functions of water saving take the primary position in the single annual service function of the research area ecological system in the years of 1998,2003 and 2007, which are 21.54%,25.49% and 25.58%. The land use of Changde City is at present at the period of adjustment, during which the ecological values of cultivated land and grassland decreased and that of woodland and water increased, while that of residential land and industrial and mining land also increased. In all, the ecological service value has risen by 3252.55×106 yuan.The landscape stability of Changde City displays a marked difference on the whole. Taoyuan County enjoys the highest landscape stability, the index of which is 3.9723. In the next place are Shimen County, Li County, Dingcheng County and Hanshou County in proper sequence. The landscape stability of land use in Wuling District is the lowest with the comprehensive index of 0.8435. The common features are small landscape area and patches, little diversity of patches, unitary landscape type and simple landscape spatial pattern. There exists sharp correlation between the ecological service function value and LUCC landscape stability. The land use changes have direct influence on the land ecological service value. In adjusting the land structure, the variation of various land ecological service value will make the ecological service value and rational land use have a reference value.Fourth, based on the ecological footprint model, the paper analyzes the situation of ecological security in Changde City and presents suggestions on ecological security. (1) During the period from 2003 to 2007, the ecological footprint takes on an increasing trend from the perspective of overall ecological footprint. In 2003, it is 12154041 hm2. In 2007, it is 15230029 hm2. The absolute volume of increase is 3075988 hm2. The ecological pressure index increases from 2.27 in 2003 to 2.89 in 2007 with the ecological pressure increasing by 0.62. Changde City has been in the situation of ecological deficit for strait five years. The conflict between population and land deteriorated and even became more and more worsened year by year, which poses a threat to the sustainable land use. (2) The regional ecological security index fluctuates between-0.1923—3.255 in the five years. The ecological security of all of the counties and districts of Changde City are in an extremely unsafe situation. Wuling District takes on the fastest decline of ecological security index dropping from-0.5672 in 2003 to-3.255 in 2007. (3) The efficiency of utilizing land resource is improved continuously by Changde City. Nevertheless, the per capita ecological footprint during the research period surpasses the per capita ecological carrying capacity. The land ecological system is always in the excess load situation and even in dangerous one, which can be shown in the aspects of ecological deficit of cultivated land, water and fossil fuel land in particular.
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