石灰岩发育的乔木林下土壤团聚体形成的影响因素

将采集的喀斯特地区纯石灰岩发育的林下土壤,全部进行干筛分为>5、5—2、2—1、1—0.5、0.5—0.25 mm五个粒级,再将五个粒级的土壤分别湿筛,烘干后收集为>5、5—2、2—1、1—0.5、0.5—0.25 mm五个粒级。对五个粒级的土壤分别进行碳水化合物、胡敏酸、游离氧化铁铝、非晶质氧化铁铝和钙、镁的提取和测定,迅速将提取过胶体的土壤进行湿筛测定分解的各级团聚体含量,以此来分析土壤团聚体稳定性与各因子间的关系。研究结果表明:土壤经干筛后,团聚体含量高,团聚体以大粒径为主,小粒级含量低;土壤经湿筛后,团聚体含量减少不是很明显,组成也是以大粒径为主;胡敏酸对<2 mm粒级的团聚体的稳定性作用最大,游离氧化铁、铝对大团聚体(>5 mm)稳定性的作用最大;0—5cm土层土壤团聚体稳定性总体上好于5—20 cm土壤层;有机胶体对小粒级团聚体稳定性的影响很大。

Affecting Factors for Forming Soil Aggregates under Trees Developed from Limestone Weathering

The paper screens all the collected soil of limestone under trees in karst area,which is developed into five levels of >5 mm,5～2 mm,2～1 mm,1～0.5 mm and 0.5～0.25 mm by dry sieving method.Then wets the soil of the five levels respectively and collects five levels of >5 mm,5～2 mm,2～1 mm,1～0.5 mm and 0.5～0.25 mm after drying.It extracts and tests on carbohydrate,humic acid,free iron-aluminum oxides,non-crystalline iron-aluminum oxides,calcium and magnesium of the five-level soil respectively and quickly wet screens and tests the contents of soil aggregate of each level that has extracted colloid for analyzing the relationship between stability of soil aggregates and each factor.The outcomes show that: a) the content of aggregates is high after dry screening and the composition is mainly large grain size and less small grain size;b) the reduction of aggregate is not remarkable after wet screening and the composition is large grain size as the main;c) the influence of humic acid to the stability function of aggregate(<2 mm) is the maximum and the influence of free iron-aluminum oxides to the stability function of large aggregate(>5 mm) is the maximum;d) the stability of soil aggregate at 0～5 cm soil layer is better than that of 5～20 cm soil layer and;e) the influence of organic colloid to the stability of small grain size aggregate is great.