粤东北山区不同土地利用类型红壤团聚体及其有机碳分布特征

Red Soil Aggregate and Its Organic Carbon Distribution under Different Land Use in Mountain Area of Northeast Guangdong

以天然常绿阔叶林地、柚果园、茶园、人工桉树林地和旱地为研究对象，采用野外调查和室内实验分析相结合的方法，研究了粤东北山区红壤团聚体及其有机碳的分布特征。结果表明：①研究区5种土地利用类型红壤各级风干团聚体占总团聚体的比例均为粒径〉5mm的最大，阔叶林地各级风干团聚体含量基本上高于其他土地利用类型。湿筛后，阔叶林地和果园土壤团聚体水稳性较好，表土层粒径〉0．25mm的水稳性团聚体含量均在70％以上；而茶园、桉树林和旱地各土层土壤水稳性团聚体明显减少，结构体破坏率高。②不同粒级红壤团聚体有机碳含量在不同土地类型有明显差异，总体上表现为阔叶林地最高，果园次之，旱地与桉树林地最低。随土层增加团聚体有机碳含量呈逐渐减小趋势，阔叶林地团聚体有机碳含量垂直变化最大，减幅达46．25％；桉树林地和旱地减幅最小，分别为29．58％和12．54％。③不同粒径团聚体的百分含量与其有机碳含量之间存在线形关系，阔叶林地和果园土壤〉5Him、5-2mm团聚体与其有机碳含量之间呈高度或显著正相关。茶园、桉树林地和旱地则较小粒径的团聚体与其有机碳含量之间呈高度或显著正相关。地带性森林植被的营造和保护有利于土壤团聚体的形成以及土壤有机碳的积累与稳定。

By using the research method of field investigation and laboratory analysis, the aggregate composition and organic carbon distribution of red soils sampled under different land use types （natural evergreen broad-leaved forest, orchard land, tea plantation, artificial eucalyptus forest and dry farm land ） in Northeast Guangdong are studied in this paper. The results show that： （1） For dry sieve, the content of the red soil aggregates in grain size 〉 5mm under five land use types is the largest, the content of the aggregates in different grain diameters in evergreen broad-leaved forest is larger than those under other land use types. For wet sieve, the water-stable aggregates of grain size 〉 0.25mm in surface layer of evergreen broad-leaved forest and orchard land are more than 70%, but the soil aggregates of tea plantation, artificial eucalyptus forest and dry farm land decrease obviously, and the destruction rates of soil structure are high. （2） The organic carbon contents of soil aggregates in different grain diameters under five land use types are different significantly. The organic carbon content of the aggregates in evergreen broad-leaved forest is the largest, while those in eucalyptus forest and dry farm land the smallest. Carbon contents of soil aggregates organic generally decreased with depth, and decrease range in broad-leaved forest is the largest （46.25%） , while those in eucalyptus forest and dry farm land the smallest （29.58% and 12.54% ） . （3） A linearly positive correlation is found between soil aggregates and their organic carbon contents. The correlation between the soil aggregates of grain size 〉 5mm as well as 5-2 mm and organic carbon content in broad-leaved forest and orchard land is extremely significant, and that between the soil aggregates in smaller grain diameter and organic carbon content in tea plantation, eucalyptus forest and dry farm land is significant. It is proved that construction and protection of natural forest vegetation would promote soil aggregate formation and would be favorable for the accumulation and stability of organic carbon.