退耕还湖后安庆沿江湿地土壤颗粒分形特征

以安庆沿江不同退耕还湖方式(白荡湖区,低坝高网式养鱼;菜子湖区,自然恢复湿地)和不同历史利用方式(水耕和旱耕)的湿地土壤为研究对象,分析退耕还湖后湿地土壤的颗粒分形特征变化。结果表明,退耕还湖后白荡湖区湿地土壤颗粒分形维数和<0.01 mm粒径颗粒含量降低,且历史水耕湿地土壤颗粒分形维数降幅小于历史旱耕湿地;菜子湖区湿地土壤颗粒分形维数和<0.01 mm粒径颗粒含量升高,且历史水耕湿地土壤颗粒分形维数增幅大于历史旱耕湿地。2个湖区湿地土壤颗粒分形维数与土壤细黏粒、粗黏粒和细粉粒含量呈显著正相关(P<0.01),与粗粉粒、细砂粒和粗砂粒含量呈显著负相关(P<0.01),与土壤有机质、全磷和有效氮含量呈显著正相关(P<0.05),土壤颗粒分形维数和土壤养分含量的聚类分析结果总体相似。土壤颗粒分形维数可作为评价退耕还湖后湿地生态恢复过程中土壤演变状况的重要参考指标。

Fractal Features of Soil Particles of Riverain Wetlands Recovered From Farmlands in Anqing, Anhui Province

Soils of recovered wetlands different in land use history(paddy and upland farming) and in mode(low dam and high net aquaculture in Baidang Lake and naturally recovered wetland in Caizi Lake) in Anqing were sampled for study of changes in fractal feature of soil particles after returning farmland to lake(RFL).Results show that in Baidang Lake area the fractal dimension of soil particles and the content of <0.01 mm particles decreased after RFL,and the change of the former was less significant in wetlands that used to be paddy fields than in wetlands that used to be upland fields,while in Caizi Lake area,the fractal dimension of soil particles and the content of <0.01 mm particles increased after RFL,and the changes of the former was more significant in wetlands that used to be paddy fields than in wetlands that used to be upland fields.The fractal dimension of soil particles of the wetlands in these two areas were significantly and positively related to the contents of fine clay,coarse clay,and fine silt(P<0.01) and to the contents of soil organic matter,total P and available N(P<0.05),but negatively to the contents of coarse silt,fine sand and coarse sand(P<0.01).On the whole,the fractal dimension of soil particles of the wetlands is quite similar to the result of clustering analysis of soil nutrient contents.It is,therefore,suggested that fractal dimension of soil particles be used as a comprehensively quantitative index to evaluate changes in soil of the wetlands after RFL.