Influence Of Land Use/Land Cover Change On Land Surface Temperature In Chongqing Center District

Bearing a close relation to sustainable development, Land Use/Land Cover Change(LUCC), a key component and a primary cause of global change, has been attracting increasingly worldwide attention from all countries and international organizations. As an important type of land use coverage, urban land has become one of the focus contents in LUCC research. With the rapid development of society and economic, process of urbanization is accelerating. As the place influenced by human drastically and completely, no main character is kept by urban ecosystem except large climate character and topography features. This leads to fragility and instability of urban ecosystem, so series of problems appear during city expansion. Since "Urban Heat Island" phenomena were proposed by Lake Howard in 1833, more and more attention on thermal environment in city were paid.Chongqing is built against mountains at the junction of the Yangtze River and the Chialing. So Chongqing is a typical Mountainous City and water-city combining mountain with water everywhere. It displays its important position during the period of historic transition in the Western Development. As a Mountainous City, Chongqing has a little great difference about Land-Use from any other city, regardless it is from the aspect of social economy or ecological environment. Therefore, the researches of the Land-Use and Land-Cover have practical value. In this dissertation, the author selects Chongqing center district where is economy highly developed and human activity frequently as study area. Base on the TM/ETM images of 1986, 1995, 2000 and 2007, the author analyzed the land use and land cover change (LUCC), the spatial characteristic of land surface temperature and the relationship between land surface temperature and characteristic of land cover. This paper exposes the characteristic of land cover impacts on urban thermal environment, and provides scientific bases for reducing extend of the thermal environment deteriorating. The conclusions can be draw as follows:1 .Research of the land use/land cover change in Chongqing center districtThe land use types of the case study area can be classified into woodland, grassland, cultivated land, urban land, water body and rural residential area, according to the interpretation to the satellite images of 1986, 1995, 2000 and 2007 with reference to the historical maps and GPS positioning survey data on-the-spot. Based on the classification, transfer matrixes of LUCC from 1986 to 1995, 1995 to 2000 and from 2000 to 2007 were made and the features of LUCC were analyzed. The general trends of LUCC in the study area from the matrix show: The research on land use/land coverage change demonstrates the phenomenon of "one increase and two decreases", the former refers to urban land squares significantly increases by 18.02% in 2007 from 11.54% in 1986, expanding 130.76km in net increasing squares .The latter refers to squares of dry land and paddy fields significantly decrease which includes dry land's decrease by 490.33km~2 in 2007 from 581.15km~2 in 1986 ,with the aggregate decrease of 90.82km~2.and paddy land's decrease by 19.17% in 2007 from 20.10%,with the aggregate decrease of 44.64km~2.The land use change in Chongqing's main districts existed deliberate differentiations. Urban land scatters in plain areas along the bank of river, and woodlands and dry lands mainly scatter in hilly areas. Before 1995, woodlands in hilly areas were seriously destroyed and dry lands and paddy lands slowly decreased. After 1995, dry lands and paddy lands dramatically decreased and urban expansion land fast increases which expands from banks of river to hilly areas nearby. During the whole study periods, the interactive change of varied lands is apparently clearer in late period than that in the beginning of the period. The change of varied lands is mainly due to Chongqing was directly administered by central government in 1997.2. Dynamic analysis of urban expansion land in center districtsIn order to study urban expansion land in center districts in Chongqing, the paper uses a series of theory which includes gridding analysis, concentric circle theory of GIS, to study varied ingredients about the change of land use. The paper concludes: the urban appearance of center districts in Chongqing is different according their geographical characteristics. Its evolution law is concluded as below: In recent 20 years , the standard differentiation of varied lands in center districts in Chongqing city gradually have decreased which shows center districts in Chongqing have a trend of self-organization optimization. Residential land expansion intensity in center districts in Chongqing changes in different periods. Its speed and intensity is much more different in the 1997 period. From 1986 to 1995, the expansion intensity gradually increases and the expansion speed and intensity goes up to maximum position, however, the expansion speed and intensity gradually decrease from 2000 to 2007, almost one tenth compared with the former. From 1986 to 2007, industry lands increase from 18.0391km~2 to 64.4700km~2 in studied area. Its net increasing areas are 49.4039km~2 and its annual expansion speed is 13.05%. Its source is mainly paddy land and dry land, with the proportion of 23.99% in paddy land and 39.14% in dry land. Land for commercial use in center districts in Chongqing city not only takes an insignificant proportion, but its distribution is not reasonable. According to our research towards international metropolis, with the development of urbanization, the optimal location of commerce is within 5 km away from the center of city, and the proportion is 15%.Transmission process of urban appearance described by remote sensing image in recent 20 years in Chongqing city, mainly demonstrates urban railway's influence. If the municipal transportation is well, urban land expands along the transportation route axis (2007), and the condition is not favorable, it expands near the urban land.3. Space-time analysis of land surface's temperature in center districtThe dissertation calculates the land surface temperature id varied land cover type in center districts as well as varied urban lands in constructed area in the year 1986 and 2007, and then concludes that urban land's surface temperature is higher. (305.16K in 1986 and 305.33K in 2007).The expansion of urban space makes land use coverage types changes, especially in the changed urban land area, the temperature increases apparently. It also changes underlying surface, especially urban land's increase which increases regional land surface temperature. In the studied period, the land surface temperature of greenbelt maintains in the minimum status and the land surface temperature of industry land is highest among all the investigated land types. The standard deviation is not so high in respective sample; it shows that the change extent of land for single use is steady in the inner part of the city. With the contrast of data in 1986 and 2007, we find land surface temperature of urban land conform an order: industrial use land, residential land, commercial use land, garden greenbelt and protection greenbelt. Generally speaking, industrial use land's surface temperature is highest, and residential land's surface temperature is near to commercial use land's temperature, and garden greenbelt and protection greenbelt's temperature are lowest.4. Quantities analysis on land use /coverage change's influence on surface temperatureThe dissertation prudentially analyzes the inner relationship of plant coverage and surface temperature, with a respective overprinting analysis of underlying surface on land coverage and land surface temperature. After the comparison land surface temperature of varied underlying surface and plant coverage average result and standard deviation, the consequence shows in studied period, woodland has a highest plant coverage degree (58.70%-50.95%); urban land's plant coverage degree is reluctantly higher than water area. (19.07% and 17.77%), correspondingly, average temperature of woodland's surface is lowest and urban land's surface temperature is highest. We select industrial use land, commercial use land residential land, garden greenbelt and protection greenbelt to paint maps which include varied land use type's plant coverage degree of center districts. The paper thinks in the research duration, garden greenbelt's plant coverage degree is always at the highest status and industrial use land's plant coverage is at the lowest status. Each plant coverage degree's standard deviation in calculated region is relatively higher and it formulates the plant coverage degree of land for single use in the city changes significantly. Through a correlative analysis of plant coverage degree and land surface temperature, index of plant coverage degree is negatively correlated with land surface temperature. According to slope of plant coverage degree and land surface temperature, it is divided into two parts: 0-35% and 35-75%, the former's slope is more than 0.2 and the latter's slope is within 0.05-0.1.The dissertation finally concludes the land coverage change's influence on land surface temperature. With the change of land use on plain, hilly areas in Chongqing's main districts, the plant coverage degree accordingly changes and then affects the land surface temperature. In the region which land coverage types change, totally speaking, the plant coverage degree decreases 10%, and the land surface temperature increases 0.49K.