人工草地种植模式对沙化土壤团聚体及有机质含量的影响

通过连续6年定位试验，研究了紫花苜蓿（Medicago sativa）单播、多年生黑麦草（Lolium perenne）单播、紫花苜蓿/多年生黑麦草混播3种种植模式对豫北地区土壤团聚体及其有机碳和土壤有机质的影响，并利用分形维数对土壤团聚体特性进行了量化研究。结果表明：沙化裸地和3种种植模式下土壤机械稳定性团聚体以5~3 mm和3~2 mm粒径为主，土壤水稳性团聚体以<0.25 mm粒径为主；与沙化裸地相比，3种种植模式下5~3 mm和3~2 mm 粒径土壤机械稳定性团聚体含量显著增加，而土壤水稳性团聚体的变化主要表现为<0.25 mm粒径显著减少，3~2 mm和2~0.5 mm粒径显著增加，同时≥2 mm粒径的土壤机械稳定性和水稳性团聚体有机碳含量明显增加；与沙化裸地相比，3种种植模式下土壤有机质含量均不同程度地增加，紫花苜蓿/多年生黑麦草混播 > 紫花苜蓿单播 > 多年生黑麦草单播，且随土层的加深而降低，呈现表聚性特征；无论机械稳定性还是水稳性团聚体，土壤质量分形维数（D_m）沙化裸地 > 多年生黑麦草单播 > 紫花苜蓿单播 > 紫花苜蓿/多年生黑麦草混播；5~3 mm和3~2 mm粒径的土壤机械稳定性和水稳性团聚体与有机碳含量极显著正相关（P<0.01），与土壤有机质含量极显著相关（P<0.01）。相对于沙化裸地，豫北地区人工草地建植6年后能够有效改善土壤团聚体特性，优化土壤主要理化性状，其中又以紫花苜蓿/多年生黑麦草混播为最佳的种植模式。

Effects of Planting Patterns on Soil Aggregates and Organic Matter Characteristics of Sandy Soil

Through six consecutive years of positioning test in northern Henan province, compared with sandy bare land, the effect of three kinds of planting patterns(alfalfa single-sowing, perennial ryegrass single-sowing, alfalfa/perennial ryegrass mixed-sowing) on soil aggregates and its organic carbon and soil organic matter were studied, and the soil aggregates characteristics were quantified by fractal dimension. Results showed that the soil mechanical-stable aggregates were mainly composed of particles with sizes 5-3 mm and 3-2 mm under sandy bare land and three kinds of planting patterns, while the soil water-stable aggregates were mainly composed of particles with size <0.25 mm; compared with sandy bare land, the content of mechanical-stable aggregates(5-3 mm and 2-3 mm) under three kinds of planting patterns were significantly increased, while the content of water-stable aggregates(<0.25 mm) decreased significantly, and the content of water-stable aggregates(3-2 mm and 2-0.5 mm) increased significantly. At the same time, the organic carbon content of soil mechanical-stable and water-stable aggregates(≥ 2 mm) increased obviously; compared with sandy bare land, the contents of soil organic matter under three kinds of planting patterns were incresed, the order was as follows:alfalfa/perennial ryegrass mixed-sowing > alfalfa single-sowing > perennial ryegrass single-sowing, and the contents decreased with the deepening of the soil layer, that is, surface aggregation features were presented; both soil mechanical-stable aggregates and water-stable aggregates, the order of fractal dimension(D_m) was:sandy bare land > perennial ryegrass single-sowing > alfalfa single-sowing > alfalfa/perennial ryegrass mixed-sowing; Pearson bilateral test showed that it had significantly positive correlation between the content of mechanical-stable and water-stable aggregates(5-3 mm and 3-2 mm) and their organic carbon(P<0.01), and it also showed significant correlation associated with soil organic matter(P<0.01). Conclusion:compared with sandy bare land, it showed that the soil aggregate characteristics and physiochemical properties of artificial planting grassland after six years were improved effectively in northern Henan province, which the alfalfa/perennial ryegrass mixed-sowing was the best planting pattern.