humusn.腐殖质humus podzolic soil腐殖质灰化土humus fractionation腐殖质分级humus-clay complex腐殖质粘土复合体humus eluvial horizo腐殖淋溶层humus siallitization腐殖质粘土化过程humus carbonate soil黑色石灰土humus carbonatic soil腐殖质碳酸盐土humus eluvial horizon腐殖淋溶层humus organic material腐熟有机物humus enriched horizon腐殖质富集层