Soil organic matter is composed of a variety of carbon (C) forms. However, not all forms are equally accessible to soil microorganisms. Deprivation of C inputs will cause changes in the physical and microbial community structures of soils; yet the trajectories of such changes are not clear. We assessed microbial communities using phospholipid fatty acid profiling, metabarcoding, CO₂ emissions, and functional gene microarrays in a decade-long C deprivation field experiment. We also assessed changes in a range of soil physicochemical properties, including using X-ray Computed Tomography imaging to assess differences in soil structure. Two sets of soils were deprived of C inputs by removing plant inputs for 10 years and 1 year, respectively. We found a reduction in diversity measures, after 10 years of C deprivation, which was unexpected based on previous research. Fungi appeared to be most impacted, likely due to competition for scarce resources after exhausting the available plant material. This suggestion was supported by evidence of bioindicator taxa in non-vegetated soils that may directly compete with or consume fungi. There was also a reduction in copies of most functional genes after 10 years of C deprivation, though gene copies increased for phytase and some genes involved in decomposing recalcitrant C and methanogenesis. Additionally, soils under C deprivation displayed expected reductions in pH, organic C, nitrogen, and biomass as well as reduced mean pore size, especially in larger pores. However, pore connectivity increased after 10 years of C deprivation contrary to expectations. Our results highlight concurrent collapse of soil structure and biodiversity following long-term C deprivation. Overall, this study shows the negative trajectory of continuous C deprivation and loss of organic matter on a wide range of soil quality indicators and microorganisms.

土壤有机质由多种碳（C）形式组成。然而，并非所有形式都可以平等地被土壤微生物利用。碳投入的剥夺会导致土壤物理和微生物群落结构的变化；然而，这种变化的轨迹尚不清楚。我们使用磷脂脂肪酸分析、元条形码、CO ₂评估微生物群落排放和功能基因微阵列在长达十年的 C 剥夺现场实验中。我们还评估了一系列土壤理化特性的变化，包括使用 X 射线计算机断层扫描成像来评估土壤结构的差异。通过分别去除植物输入 10 年和 1 年，两组土壤被剥夺了 C 输入。我们发现在 C 剥夺 10 年后，多样性措施有所减少，这在之前的研究中是出乎意料的。真菌似乎受到的影响最大，可能是由于在耗尽可用植物材料后争夺稀缺资源。这一建议得到了可能直接与真菌竞争或消耗真菌的非植被土壤中生物指示类群的证据的支持。在 C 剥夺 10 年后，大多数功能基因的拷贝也减少了，尽管植酸酶和一些参与分解顽固性 C 和产甲烷的基因的基因拷贝增加。此外，碳剥夺下的土壤显示出预期的 pH 值、有机碳、氮和生物量降低以及平均孔径减小，尤其是在较大的孔隙中。然而，在 10 年的 C 剥夺后，孔隙连通性增加，与预期相反。我们的结果突出了长期碳剥夺后土壤结构和生物多样性的同时崩溃。总体而言，这项研究表明，在广泛的土壤质量指标和微生物上，持续碳剥夺和有机质流失的负面轨迹。氮和生物量以及减少的平均孔径，尤其是在较大的孔中。然而，在 10 年的 C 剥夺后，孔隙连通性增加，与预期相反。我们的结果突出了长期碳剥夺后土壤结构和生物多样性的同时崩溃。总体而言，这项研究表明，在广泛的土壤质量指标和微生物上，持续碳剥夺和有机质流失的负面轨迹。氮和生物量以及减少的平均孔径，尤其是在较大的孔中。然而，在 10 年的 C 剥夺后，孔隙连通性增加，与预期相反。我们的结果突出了长期碳剥夺后土壤结构和生物多样性的同时崩溃。总体而言，这项研究表明，在广泛的土壤质量指标和微生物上，持续碳剥夺和有机质流失的负面轨迹。