加速侵蚀对土壤腐殖酸动态变化的影响

土壤腐殖酸的流失是土壤退化的标志之一。林地被开垦破坏后，土壤腐殖酸的流失程度在坡面上的空间分布与侵蚀方式和侵蚀强度相对应，坡面中部和中下部浅沟沟槽处最为严重，细沟侵蚀区次之，梁峁上部片蚀区相对最弱。侵蚀土壤中的腐殖酸总碳、胡敏酸碳和富啡酸碳含量随开垦年限的增加呈指数减少，其减少程度受侵蚀强度和侵蚀方式的影响。腐殖酸的流失程度与加速侵蚀造成的土壤剖面破坏密切相关。恢复植被可使土壤腐殖酸逐渐增加，土壤肥力得到恢复，土壤退化过程得到逆转。

IMPACT OF ACCELERATED EROSION ON DYNAMICS OF SOIL HUMIC ACIDS

Soil humic acid loss is one of the signs of soil degradation.After vegetation removal,the spatial distribution of soil humic acid loss rate responds to types and intensity of soil erosion at the hillslope and gully slope.The most severe location of soil humid acid loss is the ditch of shallow gully erosion area at the middle and lower part of the hillslope,the second one is rill erosion area and the sheet erosion on the upper part of slope is not as severe as the other two.The contents of soil humic acid,humin acid and fulvic acid in eroded soil are decreased exponentially with reclaimed years and their loss rate is affected by erosion intensity and types.The loss rate of soil humic acids has a close relationship to the soil profile damage by accelerated erosion.Vegetation restoration can make soil humic acids gradually increase,soil fertility be restored and soil degradation process be reversed as a result.