Soil aggregates can be considered massive microbial incubators. Thus, the study of the bacteria and fungi colonizing different soil aggregate fractions helps to elucidate the factors influencing the associations between microhabitats in soil aggregates and microbial functioning. The main objective of this study was to evaluate the total bacterial and total fungal abundances and soil quality‐related parameters of four aggregate size fractions (>2 mm, 2–0.25 mm, 0.25–0.053 mm and <0.053 mm) at two depths (0–5 cm and 7–12 cm) under three different management regimes (no cultivation, direct seeding [DS] and traditional tillage [TT]). We analysed the pH, electrical conductivity and organic carbon (OC) and nitrogen (N) concentrations in both bulk soil samples and aggregate fractions. For DNA extracted from each aggregate fraction,we performed qPCR analysis of 16S rRNA (an estimate of bacterial abundance) and internal transcribed spacer (an estimate of fungal abundance). The TT decreased the proportion of macroaggregates (>2 mm), which constituted only 16.7% (with 0.17 OC/100 g soil) under this treatment at 0–5‐cm depth, compared with 50.7% (with 1.34 g OC/100 g soil) in uncultivated soil. The abundances of bacteria and fungi exhibited contrasting responses to soil management across aggregate fractions, which differed by depth. The abundance of bacteria, but not fungi, was closely related to OC and N concentrations, with higher values in macroaggregates than in microaggregates for TT and DS at 0–5 cm depth. Uncultivated soil showed no OC differences across aggregate fractions and the bacteria were distributed uniformly among them. Fungal abundance was higher in microaggregates, mainly in DS, concurrent with lower bacterial abundance. Therefore, bacteria and fungi responded differently to changes in properties at the aggregate scale induced by soil management within the soil surface horizon.

中文翻译：

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不同管理方式下不同大小土壤团聚体中细菌和真菌的不同反应

土壤聚集体可以认为是大型微生物培养箱。因此，对细菌和真菌定殖在不同土壤团聚体组分中的研究有助于阐明影响土壤团聚体中微生境与微生物功能之间关联的因素。这项研究的主要目的是评估两个深度（> 2 mm，2-–0.25 mm，0.25-0.053 mm和<0.053 mm）的四个骨料级分的总细菌和总真菌丰度以及与土壤质量相关的参数。 0–5 cm和7–12 cm）在三种不同的管理方式下（不种植，直接播种[DS]和传统耕作[TT]）。我们分析了散装土壤样品和集料部分的pH，电导率以及有机碳（OC）和氮（N）的浓度。对于从每个聚集部分提取的DNA，我们对16S rRNA（估计细菌丰度）和内部转录间隔区（估计真菌丰度）进行了qPCR分析。TT降低了大骨料的比例（> 2 mm），在这种处理下，深度为0-5 cm时仅占16.7％（0.17 OC / 100 g土壤），而50.7％（1.34 g OC / 100 g土壤）土壤）。丰富的细菌和真菌在不同的骨料级分中表现出不同的土壤管理响应，深度不同。细菌和真菌的丰度与OC和N浓度密切相关，在0-5 cm深度处，大型聚集体的值高于微聚集体的TT和DS值。未经耕种的土壤在各个骨料组分之间均没有OC差异，并且细菌在它们之间均匀分布。微聚集体中的真菌丰度较高，主要在DS中，而细菌丰度较低。因此，细菌和真菌对土壤表层范围内土壤管理引起的总尺度性质变化的反应不同。