【摘 要】
：
The Songhua River,the third largest river in China in terms of discharge,drains the well-known organic-rich black soil region in Northeast China.Over the last century,the Songhua basin has undergone m
【机 构】
：
Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,P.R.China
【出 处】
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The 6th International Symposium on Larger Asian River(第六届亚洲大
论文部分内容阅读
The Songhua River,the third largest river in China in terms of discharge,drains the well-known organic-rich black soil region in Northeast China.Over the last century,the Songhua basin has undergone more significant land cover change than any other region in China owing to intensive migration and cultivation activities.However,there are also some meso-or small-scale sub-basins remaining less-exploited or even still in a wild state covered by natural forest.This provides an opportunity to evaluate the impacts of the conversion from forest to cropland on the riverine organic carbon through spatial analysis.This study has for the first time examined the riverine organic carbon and its controlling factors in the Songhua basin.The mean DOC and POC are 7.0mg/L and 1.8mg/L,respectively.POC accounts for 4.7% of TSS in average.Stable isotope and C/N ratio indicate that the organic carbon is mainly derived from terrestrial and autochthonous fraction accounts for about 26% of POC.The fluxes of DOC and POC are estimated to be 0.76 t/km2/yr and 0.20 t/km2/yr,respectively.It is found that spatial variation of cropland cover is negatively correlated with DOC flux,while positively with POC flux.Conversion of forest to cropland may increase the riverine organic carbon concentrations particularly for POC through soil erosion,but on the other hand irrigation may ultimately reduce the carbon flux particularly for DOC by returning river water to soil-crop system.
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