Deadwood in the final decay class: Shifts in functions, processes and active microbial communities (Woodstock II)

枯木(原木)代表着许多生物的栖息地和底物，这些生物通过几个阶段的腐烂转变为腐殖质。腐殖质的转化对于依赖于枯木的特定腐烂阶段的生物体和森林中长期的碳(C)储存至关重要。了解腐烂原木的过程、微生物群落结构和功能是困难的，因为几个腐烂类别通常是并行存在的。在这项建议中，我们将研究BELLong Dead实验中13个树种的原木中平行存在(以下称为整体)腐烂类、最终腐烂类和死木腐殖质的平均水平。我们的主要假设是，枯木作为微生物的栖息地和底物的功能在从散装到腐殖质的转变过程中发生了变化。这些变化与底物质量、微生物群落结构和过程速率的变化有关，并因树种、区域或样地以及森林管理强度的不同而不同，从而导致森林中腐殖质和碳的不同积累。这些物理分离的枯木组分的底物质量和活性细菌和真菌群落成员将分别通过化学/光谱分析和新形成的DNA标记和扩增序列进行评估。树种特性和样地枯木部分基质质量的具体差异将与微生物过程速率和活跃的微生物群落成员联系在一起。过程速率包括呼吸作用、生物固氮、微生物碳利用效率、微生物生长、微生物生物量和身体周转。我们预计真菌对腐殖质的贡献将减少，细菌功能的多样性将增加对腐殖质的贡献。此外，我们预计确定性过程以及活跃微生物群落的专家也将增加对枯木腐殖质的研究。综合专业知识将使我们能够重新评估微生物多样性、微生物过程和最终腐烂类枯木和木生生物体腐殖质之间的联系。通过致力于跨区域的协调和完全重复的实验，我们期待着对森林生态系统中的枯木管理具有很高的科学影响和好处的稳健结果。

Lying deadwood (logs) represents a habitat and substrate for many organisms that is transformed to humus through several stages of decay. The transformation to humus is critical for organisms that rely on specific decay stages of deadwood and for long-term carbon (C) storage in forests. Understanding processes, microbial community structures and functions of decaying logs is difficult because several decay classes typically exist in parallel. In this proposal, we will study an average of parallel existing (hereafter bulk) decay classes, the final decay class and deadwood humus from logs of 13 tree species in the BELongDead experiment. Our overarching hypothesis is that the function of deadwood as habitat and substrate for microorganisms changes in the transition from bulk to humus. These changes are related to shifts in the substrate quality, microbial community structure and process rates and differ among tree species, regions or plots, and forest management intensity, and result into different humus and C accumulation in forests. The substrate quality and active bacterial and fungal community members of these physically separated deadwood fractions will be assessed by chemical/spectroscopic analyses and by labelling of newly formed DNA and amplicon sequencing, respectively. Tree species identity and plot specific differences in substrate quality of deadwood fractions will be linked to microbial process rates and active microbial community members. Process rates include respiration, biological N2 fixation, microbial carbon use efficiency, microbial growth, microbial biomass and necromass turnover. We expect that the fungal saprotrophic contribution will decrease and the diversity of bacterial functions will increase towards deadwood humus. Further, we expect that deterministic processes as well as specialists of the active microbial communities will also increase towards deadwood humus. Combined expertise will allow us to reappraise the relevance of the link between microbial diversity, microbial processes and substrate quality of deadwood in the final decay class and humus for wood-inhabiting organisms. By working on a coordinated and full replicated experiment across regions, we expect robust results with high scientific impact and benefits for deadwood management in forest ecosystems.