甘家湖湿地边缘带土地荒漠化演变中土壤颗粒分形特征

The Soil Fractal Dimension Characteristics in Desertification Process on the Edge of Wetland in Ganjiahu

采用分形理论,研究了甘家湖湿地边缘带不同景观变化类型土壤颗粒体积分形维数的特征。结果表明,(1)从芦苇湿地边缘、胡杨林土、梭梭灌木林土、芦苇湿地、耕地周边、耕地到盐化草甸土的土壤粒径变化可以看出:湿地边缘带土壤荒漠化演变中砂粒含量在逐渐上升,粉粒、粘粒含量逐渐下降。这表明湿地边缘带人为的放牧、开垦、牛羊践踏对土壤产生了一定影响,使得土壤的细粒物质流失而发生粗粒化的演变。(2)体积分形维数的变化反映出:随着甘家湖湿地边缘带土壤荒漠化程度加剧,分形维数减小。分形维数由高到低依次为:芦苇湿地边缘、胡杨林土、梭梭灌木林土、芦苇湿地、耕地周边、耕地、盐化草甸土。在垂直剖面上耕地周边、耕地、盐化草甸土的土壤分形维数变化不大,而芦苇湿地边缘、胡杨林土、梭梭灌木林土、芦苇湿地土壤表层的分形维数大于中层和底层,说明放牧、牛羊践踏加速了土壤颗粒的分解,造成土壤表层粘粒含量较中层、底层的多。(3)体积分形维数与砂粒、粉粒和粘粒含量表现出不同的相关性。

This paper uses the fractal theory which has studied different types of the soil volume fractal dimension characteristics on the edge of wetland in Ganjiahu.The result indicates that：（1）The soil particle size is changing from the edge of reed wetland,Populus diversifolia forests soil,the ammodendron bush soil,the reed wetland,the cultivated land surrounding,cultivated land to the salt meadow soil.This shows that the sand content is rising gradually in the soil desertification process of the edge of wetland,while the silt clay content is decreasing gradually.The changing of the edge of reed wetland,Populus diversifolia soil,the ammodendron bush soil,the reed wetland,the cultivated land surrounding,cultivated land to the salt meadow soil shows that the sand content is raising gradually on the soil desertification of the edge of wetland,while the silt clay content is decreasing gradually.This indicates that the artificial grazing,cultivating,cattle and sheep trampling on the edge of wetland has had certain influence on the soil.This makes the fine soil materials occur coarse-grained evolution.（2）The volume fractal dimension＇s change reflects： the desertification degree is increasing with the soil fractal dimension decreasing on the edge of wetland in Ganjiahu.The desertification degree from high to low orderly is the edge of reed wetland,Populus diversifolia soil,the ammodendron bush soil,the reed wetland,the cultivated land surrounding,cultivated land to the salt meadow soil.The soil fractal dimension in vertical profile changes little on the cultivated land surrounding,cultivated land and the salt meadow soil,while the soil surface fractal dimension is greater than the middle and bottom on the edge of reed wetland,Populus diversifolia soil,the ammodendron bush soil,reed wetlands.This means grazing and cattle and sheep trampling accelerate the decomposition of soil which resulting in the surface soil clay content is larger than the middle and bottom.（3）There are different relativities between volume fractal dimension with the clay,silt and sand content.