| Abstract: Leaf area index (LAI) is an important ecological parameter. In this paper, LandsatTM/ETM data were used to retrieve canopy reflectivity of Xi'an in 1988 1998 2000 and 2003 by 6S model respectively. By correlation analysis of canopy reflectivity and vegetation index (VI) obtained from remote sensing data in 2003 and its field data, a reasonable retrieval model for LAI was established. Based on the retrieval model, we got maps of LAI distributions in different time, considering natural and human activity factors to analysis the spatio-temporal distribution of LAI and its evolvement.The study has led to the following findings and conclusions:(1) By correlation analysis of Landsat TM/ETM band SRVI NDVI RSR and LAI, it profounded that the correlation between LAI and NDVI behaved a good relativity in this paper, that is: LAI = 7.0895 * NDVI + 0.197, R~2=0.7205.(2) LAI values are corresponding to the spatio-temporal distribution in the area, and the spacial distribution of LAI present circle character, the values increased from Xi'an city to outskirt. Also the spacial distribution of LAI is accordant to the Landuse status.(3) The policies such as adjusting agro-structure, strengthening construction power to the town and so on, affected LAI and its distribution.Taking Qin mountain as the typical area, to analysis the respondence between seasons and LAI changes. The climate factors of temperature precipitation and sunlight time affect LAI obviously.Because of the field measured data and parameters used in the paper are dedicated to the special environment of the study area, the regressing models provided in this study can not be universally applied elsewhere. And also the natural and social status should be analysed based on the study area.
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