The location of microorganisms and substrates within soil pore networks plays a crucial role in organic carbon (C) processing, and its microbial utilization and turnover, and has direct consequences for C and nutrient cycling. An optimal approach to quantify responses to new C inputs from microorganisms residing in specific pores is the addition of new C to pores of target sizes in undisturbed soil cores. We used the matric potential approach to add ¹⁴C‐labelled glucose to small (< 40 μm, root free) or large (60–180 μm, potentially inhabited by roots) pores of undisturbed soil cores. Localization of glucose‐derived C via ¹⁴C imaging was related to pore size distributions and connectivity, characterized via X‐ray computed microtomography (μCT), and to β‐glucosidase activity, characterized via zymography. After 2‐week incubations, 1.3 times more glucose was mineralized (¹⁴CO₂) when it was added to the large pores; however, more ¹⁴C remained in microbial biomass when glucose was added to the small pores. Consequently, although utilizing the same amounts of easily available C, the microorganisms localized in the large pores had faster turnover compared to microorganisms in small pores. Stronger associations between β‐glucosidase activity and glucose‐derived C were observed when glucose was added to the large pores. We conclude that (a) the matric potential approach allows placing, albeit not exactly, of soluble substrates into pores of target diameter range, and (b) microorganisms localized in large pores respond to new C inputs with faster turnover, greater growth and more intensive enzyme production compared to those inhabiting the small pores.

中文翻译：

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微生物周转率的孔尺度视图：在特定大小的土壤孔隙中添加可溶性碳后，结合14C成像，μCT和酶谱分析

微生物和基质在土壤孔隙网络中的位置在有机碳（C）的加工及其微生物利用和周转中起着至关重要的作用，并直接影响碳和养分循环。量化居住在特定孔隙中的微生物对新碳输入的响应的最佳方法是将新碳添加到原状土壤核中目标尺寸的孔中。我们使用基质势方法将¹⁴ C标记的葡萄糖添加到未受扰动的土壤核心的小孔（<40μm，无根）或大孔（60-180μm，可能被根部居住）中。通过¹⁴定位葡萄糖衍生的CC成像与通过X射线计算机断层扫描（μCT）表征的孔径分布和连通性有关，并与通过酶谱表征的β-葡萄糖苷酶活性有关。孵育2周后，将葡萄糖添加到大孔中后，其矿化的葡萄糖（¹⁴ CO ₂）多了1.3倍。但是，更多¹⁴当将葡萄糖添加到小孔中时，C残留在微生物生物量中。因此，尽管利用了相同数量的容易获得的C，但是与小孔中的微生物相比，位于大孔中的微生物具有更快的周转率。当将葡萄糖添加到大孔中时，观察到β-葡萄糖苷酶活性与葡萄糖衍生的C之间更强的关联。我们得出的结论是：（a）潜在的基质方法允许将可溶性底物（尽管不完全准确）放置在目标直径范围的孔中，并且（b）定位在大孔中的微生物以更快的周转，更大的生长和更密集的方式对新的碳输入做出响应与那些居住在小孔的人相比，酶的产生。