Kramer Susanne, Dibbern Dörte, Moll Julia, Huenninghaus Maike, Koller Robert, Krueger Dirk, Marhan Sven, Urich Tim, Wubet Tesfaye, Bonkowski Michael, Buscot François, Lueders Tillmann, Kandeler Ellen
Institute of Soil Science and Land Evaluation, University of Hohenheim Stuttgart, Germany.
Institute of Groundwater Ecology, Helmholtz Zentrum München - German Research Center for Environmental Health Neuherberg, Germany.
Front Microbiol. 2016 Sep 26;7:1524. doi: 10.3389/fmicb.2016.01524. eCollection 2016.
The flow of plant-derived carbon in soil is a key component of global carbon cycling. Conceptual models of trophic carbon fluxes in soil have assumed separate bacterial and fungal energy channels in the detritusphere, controlled by both substrate complexity and recalcitrance. However, detailed understanding of the key populations involved and niche-partitioning between them is limited. Here, a microcosm experiment was performed to trace the flow of detritusphere C from substrate analogs (glucose, cellulose) and plant biomass amendments (maize leaves, roots) in an agricultural soil. Carbon flow was traced by rRNA stable isotope probing and amplicon sequencing across three microbial kingdoms. Distinct lineages within the as well as were identified as important primary substrate consumers. A dynamic succession of primary consumers was observed especially in the cellulose treatments, but also in plant amendments over time. While intra-kingdom niche partitioning was clearly observed, distinct bacterial and fungal energy channels were not apparent. Furthermore, while the diversity of primary substrate consumers did not notably increase with substrate complexity, consumer succession and secondary trophic links to bacterivorous and fungivorous microbes resulted in increased food web complexity in the more recalcitrant substrates. This suggests that rather than substrate-defined energy channels, consumer succession as well as intra- and inter-kingdom cross-feeding should be considered as mechanisms supporting food web complexity in the detritusphere.
土壤中植物源碳的流动是全球碳循环的关键组成部分。土壤中营养碳通量的概念模型假定在碎屑圈内细菌和真菌的能量通道是分开的，这受到底物复杂性和难降解性的控制。然而，对于其中涉及的关键种群及其生态位划分的详细了解仍然有限。在此，进行了一项微观实验，以追踪农业土壤中碎屑圈碳从底物类似物（葡萄糖、纤维素）和植物生物量添加物（玉米叶、根）的流动情况。通过rRNA稳定同位素探针和跨三个微生物界的扩增子测序来追踪碳流。在细菌和真菌中均鉴定出不同的谱系是重要的初级底物消费者。尤其在纤维素处理中，但随着时间推移在植物添加物中也观察到了初级消费者的动态演替。虽然明显观察到了界内生态位划分，但不同的细菌和真菌能量通道并不明显。此外，虽然初级底物消费者的多样性并未随着底物复杂性显著增加，但消费者演替以及与食细菌和食真菌微生物的次级营养联系导致在更难降解的底物中食物网复杂性增加。这表明，应将消费者演替以及界内和界间交叉取食视为支持碎屑圈食物网复杂性的机制，而非底物定义的能量通道。
