Spatial distribution of microbial biomass in microaggregates of a silty-loam soil and the relation with the resistance of microorganisms to soil drying
Spatial distribution of microbial biomass in microaggregates of a silty-loam soil and the relation with the resistance of microorganisms to soil drying
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DOI：
10.1016/0038-0717(95)00192-1
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发表时间：
1996-04
影响因子：
9.7
通讯作者：
M. V. Gestel;R. Merckx;K. Vlassak
中科院分区：
文献类型：
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作者：
M. V. Gestel;R. Merckx;K. Vlassak
为了表明决定微生物在土壤结构中的位置的因素，将粉质壤土湿润和干燥后的样品在温和分散（在水中摇动16小时）后分离成颗粒大小的组分。测定土壤各组分微生物量C和总有机C、总氮含量。通过组分的织构分析确定了各粒径组分中微团聚体的存在。总土壤微生物生物量C含量的50%以上和土壤有机C含量的37%与团聚粘土（20-2 μm）和粘土粒径（<2 μm）组分有关。它们分别占土壤总重量的19%和5%，分别占整个土壤中粘土大小颗粒的40%和23%。粗粉粒（50 ~ 20 μm）颗粒以非团聚矿物颗粒为主，占土壤总重的38%，土壤微生物总生物量C和土壤总有机C均仅占7%。多元线性回归表明，颗粒间生物量C含量的差异几乎完全（R2= 0.99）由其粘土和有机C含量解释。如果微孔隙率决定了微生物在土壤结构中的位置，就不会观察到这种密切的关系，因为在微聚集方面，分数是非常不均匀的。因此，研究结果表明，微团聚体本身对土壤中微生物在大小分数上的分布没有影响。讨论了其他因素的影响，如衬底可利用性。与湿润土壤相比，土壤干燥和再湿润使未分步土壤的微生物生物量C含量降低了36%。比较了干土粒度组分（单位土重、粒重、有机碳和粘土）与湿土的微生物生物量。结果表明，20-2 μm粒径颗粒中的微生物细胞比其他粒径颗粒中的微生物细胞更容易干燥。这个部分含有相对最多的粘土，这表明粘土的存在并没有为土壤生物提供额外的保护，防止土壤严重干燥。
To indicate factors determining the location of microorganisms in the soil structure, moist and dried-remoistened samples of a silty-loam soil were separated into particle-size fractions after gentle dispersion (shaking in water for 16 h). Microbial biomass C and total organic C and N contents of soil fractions were measured. The presence of microaggregates in each size fraction was determined by texture analysis of fractions. More than 50% of the microbial biomass C content of the total soil and 37% of the soil organic C content were associated with the aggregated clay (20-2 μm) and the clay-size (<2 μm) fraction. These represented respectively 19 and 5% of the total soil weight and contained respectively 40 and 23% of clay-size particles present in the whole soil. The coarse silt-size (50-20 μm) fraction, consisting mainly of non-aggregated mineral particles, contributed 38% of the total soil weight and contained only 7% of both total soil microbial biomass C and of total soil organic C. Multiple linear regression showed that the variation in biomass C content between size fractions was almost completely (R2= 0.99) explained by its clay and organic C content. Such a close relationship would not have been observed if microporosity had determined the location of microorganisms in the soil structure, as fractions were very heterogeneous in respect to microaggregation. Thus, the results indicate that microaggregation per se had no effect in this soil on the microbial distribution in size fractions. The effects of other factors, such as substrate availability, are discussed. Soil drying and rewetting reduced the microbial biomass C content of unfractionated soil by 36% compared to moist soil. Microbial biomass concentrations of size fractions from dried soil (expressed per unit of soil weight, fraction weight, organic C and clays) were compared with those of moist soil. The results indicated that microbial cells associated with the 20-2 μm size fraction were more susceptible to desiccation than those residing in other size fractions. This fraction contained relatively the most clay, suggesting that the presence of clay does not provide extra protection for soil organisms against severe soil drying.