真菌和细菌生物量在土壤团聚体中的分布和耕作响应

Distribution patterns of,and the effects of tillage type on,bacterial and fungal biomass within soil water-stable aggregates

首次报道亚热带紫色水稻土中土壤真菌和细菌生物量在不同粒径水稳性团聚体中的分布及耕作的影响。实验样品采自16年的国家紫色土长期定位试验站的垄作免耕（Combining Ridge and No-tillage,NT）、冬水稻田（Flooded Paddy Field,FPF）和常规平作（Conventional Tillage,CT）土壤。表层土样（0~20cm）通过湿筛法分别得到〉4.76 mm、2.0~4.76 mm、1.0~2.0 mm、0.25~1.0 mm、0.053~0.25 mm、〈0.053mm粒径的土壤团聚体。采用麦角固醇和胞壁酸标记法测定各级团聚体中真菌和细菌的生物量。结果显示在垄作免耕、冬水稻田、常规平作土样中,真菌生物量与细菌生物量在〈0.053 mm的粘粒中含量最低;在0.053~0.25 mm的土壤微团聚体中最高;在大于0.25 mm的大团聚体中真菌和细菌生物量随粒径的增大而增多,但细菌和真菌生物量在不同耕作方式的土样中的变化模式有一定的差异。3种耕作方式相比较,垄作免耕的土壤真菌和细菌的生物量在3种耕作方式中最高,冬水稻田次之,常规平作最低。真菌生物量与细菌生物量的比率分布模式在不同耕作方式的土样中差异较大,垄作免耕的真菌生物量与细菌生物量的比率在3种耕作方式中最高,冬水稻田次之,常规平作最低,但除了在0.25~1.0 mm、2.0~4.76 mm的团聚体之间有明显差异外（P〈0.05）,其余粒径之间均无明显差异（P〉0.05）。这表明土壤真菌生物量和细菌生物量在亚热带紫色水稻土水稳定性团聚体中的分布模式与团聚体的粒径和耕作方式有关,3种耕作方式中垄作免耕对真菌和细菌生物量分布的响应最为明显。

The distribution patterns of bacteria and fungi in different water-stable aggregates（WSA）,and the effects of tillage methods on bacterial and fungal biomass,were investigated in a long-term field experiment.Tillage treatments examined in this study included Conventional Tillage（CT）,Flooded Paddy Field（FPF）,Combining Ridge and No-tillage（NT）.A wet sieving method was used to separate soil aggregates into six groups based on particle diameter： 4.76 mm,2.0-4.76 mm,1.0-2.0 mm,0.25-1.0 mm,0.053-0.25 mm and 0.053 mm.Fungal and bacterial biomass were estimated by measuring the amount of ergosterol and muramic acid,respectively,in the samples.Both bacterial and fungal biomass were lowest in the smallest soil particles（0.053 mm） and highest in the 0.053-0.25 mm fraction.As the size of the soil micro-aggregate increased,the associated bacterial or fungal biomass also rose,however,there were notable response differences between the two taxonomic groups.Of the three tillage methods examined,maximum bacterial and fungal biomass was found in the Combining Ridge and No-tillage（NT） treatment;minimum biomass occurred under Conventional Tillage（CT）.There were significant（P0.05） differences in fungal and bacterial biomass in the 0.25-1.0 mm and 2.0-4.76 mm particle-size groups among the three tillage methods;there were no significant differences（P0.05） in the remaining size groups.The results of this study indicate that both fungal and bacterial biomass in the soil are related to the particle size of the soil aggregates as well as to the tillage method.The Combining Ridge and No-tillage（NT） treatment yielded the highest fungal and bacterial biomass associated with WSA,which suggests soil health is maximized when soil disturbance is kept to a minimum.