不同巨桉人工林土壤分形特征及抗蚀性分析

为探讨耕地退耕成人工巨桉林后对土壤团粒结构及土壤抗蚀性能产生的影响,在野外调查与室内分析的基础上,选择4.5年生巨桉纯林、巨桉+果树、巨桉+粮食作物土壤作为研究对象,农耕地作为对照,研究了不同巨桉人工林下水稳性团聚体分形维数的变化特征,分析了分形维数与土壤养分状况、土壤结构稳定性以及土壤抗蚀性能的关系。结果表明,4种模式土壤分形维数介于2.142~2.296;在0~15 cm土层分形维数表现为耕地林果林粮纯林,纯林和农耕地之间差异显著,其他3种模式之间差异不显著;在15~30 cm土层分形维数表现为耕地纯林林粮林果,4种模式之间差异不显著。分形维数与土壤有机质含量、大团聚体含量呈显著和极显著负相关;与土壤平均重量直径、水稳性指数有负相关趋势;与土壤体积质量、微团聚体含量呈极显著正相关。说明土壤分形维数越小,土壤有机质、大团聚体含量越高,土壤平均重量直径、水稳性指数越大,土壤体积质量、微团聚体含量越低,土壤结构越稳定,抗蚀力越强。因此,团聚体的分形维数值能反映土壤性质的变化,通过对土壤分形维数特征的研究可以定量揭示不同巨桉模式下土壤抗侵蚀的能力。

Study on Soil Fractal Features and Anti-erodibility of Soil Water-stable Aggregates Under Different Eucalyptus grandis Plantations Styles

In order to explore the impacts of eco-environment changes on the soil structure and anti-erodibility in the conversion of farmlands to Eucalyptus grandis plantations, soil samples of 4.5-year Eucalyptus grandis plantations such as pure Eucalyptus grandis, Eucalyptus grandis+grain crops, Eucalyptus grandis+fruits were chosen as researching materials and farmlands as comparison, the fractal characteristics of soil water-stable aggregates and the relationship among soil nutrient, soil stability and anti-erodibility were carried out based on the field investigation and lab analysis. The results showed that the different patterns had different fractal characteristics, the fractal dimension was between 2.142 to 2.296. In the soil depth of 0-15 cm, the order of fractal dimension was farmland > Eucalyptus grandis+fruits > Eucalyptus grandis+grain crops > pure Eucalyptus grandis. There was a significant difference between the farmland and pure Eucalyptus grandis, instead of the other 3 types. In the soil depth of 15-30 cm, the order of fractal dimension was farmland > pure Eucalyptus grandis > Eucalyptus grandis+grain crops > Eucalyptus grandis+fruits, and there was no significant difference among 4 types. The fractal dimension had a significant negative linear correlation with organic matter, big soil water-stable aggregate, and a negative linear correlation with mean weight diameter of water stable aggregate and water stable index. On the contrary, it had a significant positive linear correlation with soil bulk density and micro-aggregate. Furthermore, the smaller the fractal dimension was, the higher the content of organic matter and the big soil water-stable aggregate, the bigger the mean weight diameter of water stable aggregate and the water stable index, the lower the soil bulk density and the micro-aggregate, and the stronger the anti-erodibility of soil water-stable aggregate. In the other word, the fractal dimension can be used as an important parameter for characterizing the soil structures and properties, also can be used as an indicator of soil anti-erodibility of the different Eucalyptus grandis plantations.