| The change of land use is not only one of the biggest factors of carbon cycle in land ecological system, but also the main human activity that making CO2emissions has increased dramatically than the burning of fossil fuels. The city is the area of human activities most actively and the area of dense population, high energy consumption and more concentrated artificial carbon emissions. In recent years, CO2emissions control has gradually turned to a level of urban regional scale. carbon source, carbon sinks and carbon cycle process caused by urban land use change and its ecological environment effects have been a hot spot of land science and global variation science.With the Construction of Guanzhong-Tianshui Economic Zone and International Metropolis Construction in Xi’an, energy consumption is growing fast and land use is been an important development while a great increase of population and a rapid development of economy. The proportion of construction land has shown a trend of substantial growth, and the violent change of land use structure will have important influence to ecological environment and carbon cycle process. For the time being, to have a study on urban carbon sink change and its carbon sink enhancement effect of a driven by land use changes in process of Xi’an urbanization, to understand correctly spatial-temporal characteristics of change in land use in Xi’an and to present ways and alternative policies of carbon sink enhancement have direction and lesson affect for development of low carbon city and low carbon economy in Xi’an, urban development, land use and ecological spatial planning.Being set in regional of Xi’an and aimed at exploring ways of carbon sink enhancement, the research supported by RS and GIS technology, dissect land use change characters in Xi’an from1997to2007and analyze relationship between urban land use change and carbon sources and sinks, then dissect carbon sink enhancement characters in Xi’an and present alternative policies and ways of land use in Xi’an and carbon sink enhancement. The conclusions are drawn as follows:(1) There is a great relationship between the dynamic change of land use and the total amount of carbon sink. The land use dynamic characteristics in Xi’an from1997to 2007:quantitatively, the cultivated field has a highest dynamic degree of land use that reach up to-0.77%; structurally, cultivated field changed into woodland and building land; in degree, as a whole, the degree index of land use had a ascend trend, Xi’an bordered by2001and2003is on the development period, adjustment period and development period in order; characteristics of spatial pattern change in Xi’an city area is peripheral extension and interior filling. The total amount of carbon sink characteristics:as a whole, curve is choppy conspicuously in a W-type rising trend which is in complete accord with woodland, so carbon sinks change of cultivated field and woodland determined the total amount and structure of carbon sink; the more the rate of cultivated field, garden, woodland and grassland is, the higher the total amount of carbon sink is, especially with woodland. Generally speaking, there is a great relationship between the dynamic of land use change and the total amount of carbon sinks; the change of carbon sinks was remarkably influenced by the area change of cultivated field, garden, woodland and grassland.(2)The two main carbon sinks were woodland and cultivated field. Woodland and cultivated field whose annual carbon fixation account for more than90%of total carbon sinks in Xi’an from1997to2007; carbon sinks of woodland per unit area is the biggest, which is3.23times of cultivated field.(3) There is a regional difference of carbon sinks in Xi’an. There is a definite relation between urban spatial growth and carbon sinks that regional development intensity was inversely related to carbon sinks. As the urban space is splayed out gradually, carbon sinks of Xi’an urban area is now tapering off. Generally speaking, there is a regional difference of carbon sinks in Xian, and its total characteristic is that high in the south, low in the north and none in the central.(4) The carbon sink enhancement of Xi’an was on the decrease. The most apparent change in quantity and structure of carbon source is construction land in Xi’an from1997to2007; there is a growing tendency for carbon source and carbon sinks of Xi’an, and the growth of carbon sink is less than the growth of carbon source, though the carbon sink enhancement of Xi’an was on the decrease.(5)A relevant solution is sought to carbon sink enhancement by increasing carbon absorption and reducing carbon emissions. With interrelated analysis, present alternative policies and ways of carbon sink enhancement in the process of urbanization:increased urban carbon sink by strengthening forest land conservation and increasing crop yield prediction; control and reduce urban carbon sink by adjusting the structure of industrial land, increasing the energy efficiency, readjusting energy mix and controlling urban land use sprawl. |
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