大渡河干热河谷区核桃林下种植模式对土壤团粒结构分形特征的影响

以大渡河干热河谷区不同种植模式（包括:农耕地对照(NCK)，核桃对照(HCK)，核桃+甘蓝+甘蓝(HLL)、核桃+甘蓝+马铃薯(HLT)、核桃+大白菜+大豆(HDD)）为对象，研究了不同种植模式对干筛和湿筛条件下团聚体组成、结构体破坏率和团粒结构分形维数的影响，探讨了团粒结构分形维数综合值与土壤理化性质综合值的关系。结果表明，农耕地转变为核桃林和发展核桃林下种植对促进土壤团聚体形成，提高结构稳定性，降低结构体破坏率和团粒结构分形维数，以及改善土壤理化性质具有较好作用。干筛和湿筛条件下团粒结构分形维数分别随干筛和湿筛条件下>0.25 mm团聚体含量的增加而降低。土壤团粒结构分形维数综合值HCK＞NCK＞HDD＞HLT＞HLL，土壤理化性质综合值HLL＞HLT＞HDD＞NCK＞HCK。干筛和湿筛条件下团粒结构分形维数均与有机质含量、容重、非毛管孔隙、毛管孔隙、总孔隙、通气度、自然含水量、最大持水量、毛管持水量和田间持水量呈显著相关；土壤团粒结构分形维数综合值与土壤理化性质综合值呈显著相关。土壤团粒结构分形维数能较好表征大渡河干热河谷区农耕地转变成核桃林和发展核桃林下种植对土壤理化综合性质的影响。

Effects of Under-forest Planting Patterns on Fractal Features of Soil Aggregate Structure in the Dry-hot Valley of Dadu River

The dry-and wet-sieved soil aggregate composition,percentage of construction damage(PCD),and fractal dimension of aggregate structure(D) were determined under different planting patterns(including farmland control(NCK),walnut control(HCK),walnut+cabbage+cabbage(HLL),walnut+cabbage+potato(HLT),and walnut+Chinese cabbage+soybean(HDD)) in the dry-hot valley of Dadu River,and the relationships between the synthetic values of D(SFD) and soil physical and chemical properties(SPC) were analyzed.The results showed that both conversion of farmland to walnut plantation and planting under walnut plantation were beneficial to promote soil aggregates formation,enhance structure stability,decrease PCD and D,as well as improve soil physical and chemical properties.The dry-and wet-sieved D values decreased with the increase of the contents of >0.25 mm dry-and wet-sieved aggregates.The SFD ranked as HCK>NCK>HDD>HLT>HLL,while the SPC ranked as HLL>HLT>HDD>NCK>HCK.The dry-and wet-sieved D values were significantly correlated with soil organic matter content,bulk density,non-capillary porosity,capillary porosity,total porosity,aeration porosity,natural water content,maximum water-holding capacity,capillary water-holding capacity,and field water-holding capacity.The SFD was significantly correlated with the SPC.These findings indicated that the D could be considered as an useful index to comprehensively evaluate soil physical and chemical properties when converting farmland to walnut plantation and planting under walnut plantation in the dry-hot valley of Dadu River.