Hummocky landscapes are naturally susceptible to erosion by water and tillage. Downslope movement of material results in the accumulation of soil in depositional positions and exposed sub-soils at the surface of eroded positions, affecting landscape-scale C cycling and productivity. Prolonged or extreme erosion can create inverted soil profiles with deeply buried C-rich surface material. The susceptibility of this C to decomposition is largely controlled by the potential of microorganisms to degrade it with long-term implications for C dynamics in agroecosystems. Our objective in this study was to evaluate whether the redistribution of soil along eroded hill slopes creates differences in the structure of the soil microbial community, both laterally across the landscape and vertically through the soil profile. Using phospholipid fatty acid analysis (PLFA) and high-throughput DNA sequencing, we investigated the abundance, diversity and community structure of microbial communities along an eroded landscape. Microbial abundance and community structure were found to be strongly influenced by a depth gradient at the near-surface (0-20 cm). In a depositional backslope position, viable microbial biomass was detected to the depth of the A horizon (85 cm), with a C-rich buried layer that contained substantial viable biomass (10.1 -18.8 mu g PLFA g(-1) soil). Soil organic carbon (SOC) concentration was significantly correlated (r = 0.40; p < 0.001) with PLFA concentration at all positions, indicating microbial abundance is determined by C availability. In contrast, community structure was related to the origin of the soil in the landscape, and may be regulated more strongly by SOC composition. Pyrosequencing of bacterial and fungal DNA showed that genetic diversity was largely maintained in former surface soils. Our work demonstrates that abundant microbial biomass is supported in C-rich buried soils while SOC is largely preserved for decades. The presence of an abundant and diverse community suggests that there is potential for enhanced C loss under changing conditions such as climate change or modified land-use
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机译：丘陵景观自然容易受到水和耕作的侵蚀。材料的下坡运动导致土壤堆积在沉积位置，而裸露的次土壤在侵蚀位置的表面堆积，从而影响景观尺度的C循环和生产力。长期或极端的侵蚀会造成深埋的富含C的表面材料的土壤形态倒转。碳的分解敏感性在很大程度上受微生物降解的潜力控制，这对农业生态系统中的碳动力学具有长期影响。我们在这项研究中的目的是评估沿侵蚀的山坡土壤的重新分布是否在土壤微生物群落的结构上产生了差异，无论是横向穿过景观还是垂直穿过土壤剖面。使用磷脂脂肪酸分析（PLFA）和高通量DNA测序，我们调查了受侵蚀景观中微生物群落的丰度，多样性和群落结构。发现微生物的丰度和群落结构受近地表（0-20厘米）深度梯度的强烈影响。在沉积后坡位置，可检测到的微生物生物量达到A层深度（85厘米），其中富含C的埋层含有大量的可行生物量（10.1 -18.8μgPLFA g（-1）土壤）。土壤有机碳（SOC）浓度与所有位置的PLFA浓度均显着相关（r = 0.40; p <0.001），表明微生物的丰度由C的有效性决定。相反，群落结构与景观中土壤的起源有关，并且可能受SOC组成的影响更大。细菌和真菌DNA的焦磷酸测序表明，遗传多样性在以前的表层土壤中得到了很大的维持。我们的工作表明，富含碳的埋藏土壤中支持了丰富的微生物生物量，而SOC可以保存数十年。丰富多样的社区的存在表明，在气候变化或土地利用改变等条件变化的情况下，碳损失可能会增加
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