巨桉人工林下土壤团聚体稳定性及分形特征

Soil Aggregates and Fractal Features Under Different Styles of Eucalyptus grandis Plantations

选择3年生巨桉纯林、巨桉+粮食作物、巨桉+果树土壤作为研究对象,农耕地作为对照,运用标准化平均质量直径及分形理论,分析不同巨桉人工林下的土壤团聚体稳定性及分形维数特征。结果表明,不同林地模式下,水稳性团聚体平均质量直径的变化顺序为农耕地>林粮>巨桉纯林>林果,农耕地与不同林地模式下水稳性团聚体平均质量直径差异显著,农耕地在退耕成巨桉人工林后不利于土壤大团聚体的形成;3种林地模式与农耕地比较有效磷、容重差异显著,土壤有机质、碱解氮、有效钾含量差异不显著,说明林地覆盖增强了土壤的紧实度;相关分析表明,影响土壤稳定性的最重要因素为大团聚体的含量,而其他因素影响不显著;分形维数与<0.25mm团聚体含量、容重呈显著、极显著正相关,与1～2mm团聚体含量、平均质量直径呈极显著负相关,说明土壤团聚体的分形维数越小,土壤大团聚体含量越高,土壤团聚体稳定性越强;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质量的特点。

By using normal mean mass diameter and fractal theory,choosing soil of 3-year Eucalyptus grandis plantations such as pure Eucalyptus grandis,Eucalyptus grandis＋grain crops,Eucalyptus grandis＋fruits as researching materials,and farmlands as comparison,the stability of soil aggregates and the fractal characteristics as well as between both relationships were discussed.The results showed that the order of normal mean mass diameter was farmlands〉 Eucalyptus grandis＋grain crops pure〉 Eucalyptus grandis Eucalyptus grandis＋fruits.To normal mean mass diameter,there was significant difference between farmlands and Eucalyptus grandis plantations,furthermore,it was harmful to form bigger soil aggregates after farmlands into Eucalyptus grandis plantations.There was no significant difference of soil organic matter,available nitrogen,available potassium,contrary to available phosphorus,bulk density,it showed that the forest cover enhanced the soil compactness.The analysis of correlation indicated that bigger aggregate content was main factor that influenced the stability of soils.Fractal dimension had a significant linear positive correlation to the content of soil aggregates size 〈0.25 mm,bulk density,on the contrary of the content of soil aggregates size of 1~2 mm and normal mean mass diameter.In the other word,the smaller soil particle fractal dimension was,the better stability of soil aggregates was.According to the results,fractal value can reflect the change of soil properties,and the same time,it can quantitatively reveal soil quality characteristics of different Eucalyptus grandis plantations.