Temporal and Spatial Difference in Carbon Footprint of Regional Farmland Ecosystem--Taking Jiangsu Province as a Case

In this paper,the dynamic changes and spatial distribution characters of carbon absorption,carbon emission,and carbon footprint of farmland ecosystem were estimated based on the statistical data of consumption amount of chemical fertilizer,pesticide,plastic film,fuel used by agricultural machine,and irrigated area,arable land area,and crop yield from 1995 to 2009 in Jiangsu Province and different regions.The results showed that the dynamic of crop carbon absorption amount shaped like a "V",decreased first and then increased in last 15 years,changing from 2 933.6×104 t·a-1 to 3 896.9 ×104 t·a-1.Carbon absorption intensity varied in the range of 6.04 t·hm-2·a-1 to 7.71 t·hm-2·a-1.During the period,both of total carbon emission amount and emission intensity from agricultural inputs showed the rising trends from 727.2×104 t·a-1 up to 882.7×104 t·a-1 and from 1.43 t·hm-2·a-1 up to 1.88 t·hm-2·a-1,respectively.And the carbon emissions from chemical fertilizer had been the most important carbon emission source in all agricultural inputs,but the carbon emission from agricultural machine kept a fastest growing.Carbon footprint of farmland ecosystem increased slowly with a fluctuation range of 13.68×105 hm2·a-1 to 17.56×105 hm2·a-1,accounting for 27.0% to 36.1% of cultivated land area,while carbon ecological surplus showed a trend of decrease during the period.There were obvious differences between the regions in Jiangsu,and the spatial distribution appeared that the southern regions were usually less than the north regions.The estimates presented here are based on limited evidence and parameters,and have an uncertainty associated with them,further studies are need.