Biological Regulation of Subsoil C-cycling under Field Conditions

在第一阶段进行的两个土壤转移实验提供了证据的深度特定的碳掺入纤维素或根衍生的碳到不同的土壤微生物组。真菌丰度在底土中受到限制，但真菌在表层和底土中比细菌吸收更多的碳。因此，我们需要更好地了解特定土壤微生物群体的碳释放以及土壤剖面中微生物残留物的运输，以充分模拟土壤剖面中微生物介导的碳途径。来自两个联合实验（观测站和DOC注入）的数据将与不同深度的标记细菌和真菌的暴露相结合（见任务1和2），从而有可能在两个不同的分辨率水平（时间尺度：周或年，空间尺度：厘米或米）下表征群体特定的周转时间以及微生物残留物的迁移。由于我们已经了解到底土中的真菌生活受到限制，并且将较深的底土转移到较浅的底土会刺激真菌丰度，因此我们需要进一步探索底土中真菌群落的动态和驱动因素。利用下一代真菌内部转录间隔区（ITS）测序，我们将根据其主要来源的C定义真菌公会;腐解真菌是那些从死亡的有机物质中获得C的真菌，根相关真菌是那些直接从宿主植物中获得C的真菌。我们将涉及真菌的关键球员生产特定的酶，并确定他们要么saprotrophs（生产水解和氧化酶）或分解（只生产氧化酶）。在研究单位的背景下，我们的数据将阐明细菌和真菌驱动的底土中有机物质稳定的重要性，并提供更好地了解森林生态系统中的长期碳储存。

Two soil transfer experiments done in the first phase provided evidence of depth specific carbon incorporation of either cellulose or root derived carbon into different groups of soil microorganisms. Fungal abundance was restricted in subsoils, but fungi incorporated more carbon than bacteria in both surface and subsoils. Consequently, we need to better understand the release of carbon from specific groups of soil microorganisms as well as the transport of microbial residues within the soil profile to adequately model microbially mediated C pathways in soil profiles. Data from the two joint experiments (observatories and DOC injection) will be combined with the exposure of labelled bacteria and fungi at different depths (see Task 1 and 2), making it possible to characterize group specific turnover times as well as transport of microbial residues at two different levels of resolution (temporal scale: either weeks or years, spatial scale: centimeters or meters). Since we have learned that fungal life in subsoils is restricted and that transfer of deeper subsoil into shallower subsoil stimulates fungal abundance, we need to explore further the dynamics and drivers of fungal communities in subsoils. Using next generation sequencing of fungal internal transcribed spacers (ITS) we will define fungal guilds based on their main source of C; saprotrophic fungi are those that gain C from dead organic material, and root-associated fungi are those that gain C directly from their host plant. We will relate fungal key players to the production of specific enzymes and identify them as either saprotrophs (producing hydrolytic and oxidative enzymes) or decomposers (producing oxidative enzymes only). In the context of the research unit, our data will clarify the importance of bacterially and fungally driven stabilisation of organic substances in subsoils and provide a better understanding of long-term carbon storage in forest ecosystems.