Change Research Of Cropping System In China Based On Time Series Data Of NDVI

Climate warming have an impact on China’s production and life, especially onagriculture. Although the change of cropping systems in China is result of severalnatural, social and economic conditions, the main is climatic factors. Analyzing thedistribution and change of cropping system in China through remote sensing not onlyunderstand and evaluate the crop production and production potential timely andaccurately，but also benefit agriculture-related departments to draw up effectiveagricultural policies.Pathfinder AVHRR NDVI data, SPOT VEGETATION NDVI data and climatedata are used in this study. Two extraction methods of cropping systems: twicedifference algorithm and fourier transform are investigated based on NDVI data of2000. The changes of cropping systems are analysed using twice difference algorithmin recent years (1986-2006). Then the impact of temperature and precipitation oncropping systems are researched by≥0℃Annual accumulated temperature andannual precipitation data. Main research conclusions are received as follows:1. The results of cropping system using twice difference algorithm and fouriertransform are basically compatible with the distribution regularity of China’sagricultural cropping system: The more south, the more complex. But they are nottotally the same. After comparison and verification, the precision of twice differencealgorithm is nearly77.5%, The Kappa Index is0.64. While the precision of fouriertransform is71.1%, The Kappa Index is0.55. As the result, both methods could beused to extract the distribution of cropping system in China. But, it’s more accurate oftwice difference algorithm.2. The changes of cropping system in nearly20years are analysed afterextracting the distributions of cropping system in1986,1996and2006. The boundarybetween single and double crop rotations is broadening northward and westward. Themaximum northward distance is160km. The boundary between double crop rotationsand triple crop rotations is expanding northward. Considering the cropping area, thearea of single crop rotations decrease by nearly8percentage. The areas of double croprotations and triple crop rotations increase of7.2%and1.3%of the total cultivatedarea, respectively. While the mutual conversions between cropping systems are alsocomplex, especially the mideast of China. Single crop rotation turns into double croprotations mainly in Hebei, Jiangsu and Shanghai area, Anhui, Jiangsu and so on.While a part of double crop rotations become single cropped mainly in Hebei, easternof Gansu and Sichuan.3. From the climate data, the change of boundary with cropping system isconsistent with the change of boundary with accumulated temperature, especially inthe north-south line. Temperature is the most direct and important factor of croppingsystem northward. But the real boundary of cropping system is more to south than theboundary of temperature. In recent20years, the trend of precipitation is increased, leading to the west boundary of double cropped moving westward. Precipitation isone of the reasons for cropping system westward.