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Impact of common sample pre-treatments on key soil microbial properties
Soil Biology and Biochemistry ( IF 9.7 ) Pub Date : 2021-06-01 , DOI: 10.1016/j.soilbio.2021.108321
Julia Schroeder , Lisa Kammann , Mirjam Helfrich , Christoph C. Tebbe , Christopher Poeplau

Pre-treatment of soil samples prior to analysis is acknowledged to affect microbial activity and community parameters, but recommendations are diverging and there are no best-practice or standardised laboratory protocols. For the microbial carbon use efficiency (CUE) as a ratio parameter of C allocated to anabolism over total metabolised C, the effects of sample pre-treatment are unpredictable because the underlying parameters of microbial metabolism may be affected differently. In treatment or land use comparisons, it is important to know whether soils are affected in a similar way by pre-treatment. Based on five different paired sites (each with cropland and forest), the effects of six common pre-treatments were evaluated on 18O-CUE and associated parameters, i.e. respiration rate, soil microbial biomass C, total DNA extracted, and estimated abundances of fungi, bacteria and archaea. The six common pre-treatments were: (i) immediate analysis of field-fresh soil samples, and analysis following 14 d pre-incubation of soil samples that were (ii) field-fresh, (iii) air-dried, (iv) oven-dried (40 °C), (v) frozen at −20 °C and (vi) frozen in-situ (dry ice and subsequently liquid N2). The experiment revealed two main findings. The first was that pre-incubation of 14 d had the most pronounced effect and reduced microbial respiration rate, growth rate and microbial biomass C by between 28% and 63% on average compared with field-fresh samples, suggesting an impact of the reduction in readily available substrates on microbial activity. The second finding was that even after 14 days of pre-incubation, drying & rewetting caused an increase in the microbial respiration rate in forest soil samples of 64 ± 53% (air-drying) and 86 ± 65% (oven-drying), known as the Birch effect. However, CUE as a ratio parameter was found to be unaffected by sample pre-treatment, with only minor changes after 14 d of pre-incubation. Pre-treatment (including pre-incubation) affected cropland and forest samples similarly, with one exception: the estimated abundance of fungi increased only with drying & rewetting in forest soils. This suggests that dried cropland soils could potentially yield appropriate community data, while forest soils respond to soil drying in a more complex way. It was concluded that CUE values can be derived from soil samples regardless of whether they were dried & rewetted, frozen & thawed, or stored fresh.



中文翻译:

常见样品预处理对关键土壤微生物特性的影响

在分析之前对土壤样品进行预处理被认为会影响微生物活动和群落参数,但建议存在分歧,并且没有最佳实践或标准化实验室协议。对于作为分配给合成代谢的 C 与总代谢 C 的比率参数的微生物碳利用效率 (CUE),样品预处理的影响是不可预测的,因为微生物代谢的潜在参数可能会受到不同的影响。在处理或土地利用比较中,重要的是要知道土壤是否以类似的方式受到预处理的影响。基于五个不同的配对站点(每个站点都有农田和森林),评估了 6 种常见预处理对18O-CUE 和相关参数,即呼吸速率、土壤微生物生物量 C、提取的总 DNA,以及估计的真菌、细菌和古细菌丰度。六种常见的预处理是:(i) 现场新鲜土壤样品的即时分析,以及 (ii) 现场新鲜土壤样品,(iii) 风干,(iv) 土壤样品预培养 14 天后的分析烘箱干燥(40℃),(v)冷冻于冷冻-20℃和(vi)-原位(干冰并随后液氮2)。该实验揭示了两个主要发现。首先是预培养 14 d 效果最显着,与田间新鲜样品相比,微生物呼吸速率、生长速率和微生物生物量 C 平均降低了 28% 至 63%,表明减少的影响容易获得的微生物活性底物。第二个发现是,即使经过 14 天的预孵化,干燥和再润湿导致森林土壤样品中微生物呼吸率增加 64 ± 53%(风干)和 86 ± 65%(烘箱干燥),被称为伯奇效应。然而,发现作为比率参数的 CUE 不受样品预处理的影响,在预孵育 14 天后只有微小的变化。预处理(包括预孵化)对农田和森林样本的影响类似,但有一个例外:真菌的估计丰度仅随着森林土壤中的干燥和再润湿而增加。这表明干燥的农田土壤可能会产生适当的群落数据,而森林土壤以更复杂的方式响应土壤干燥。得出的结论是,无论土壤样品是干燥和再润湿、冷冻和解冻,还是新鲜储存,都可以从土壤样品中得出 CUE 值。

更新日期:2021-06-07
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