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

躺着的枯木（原木）代表了许多生物的栖息地和基质，这些生物通过几个腐烂阶段转化为腐殖质。向腐殖质的转变对依赖枯木特定腐烂阶段的生物和森林中长期碳(C)储存至关重要。由于几种典型的衰变类型是并行存在的，因此很难理解腐朽木材的过程、微生物群落结构和功能。在本提案中，我们将研究BELongDead实验中13种树种原木的平行现有（以下简称散装）腐烂类，最终腐烂类和枯木腐殖质的平均值。我们的总体假设是，枯木作为微生物的栖息地和基质的功能在从散装到腐殖质的转变过程中发生了变化。这些变化与基质质量、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、森林经营强度的不同而不同，从而导致森林中腐殖质和碳积累的差异。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/光谱分析和标记新形成的DNA和扩增子测序来评估。树种鉴定和枯木组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有关。过程速率包括呼吸作用、生物固氮作用、微生物碳利用效率、微生物生长、微生物生物量和坏死块周转率。我们预计真菌腐坏贡献将会减少，细菌功能的多样性将会增加。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。综合的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的基质质量之间的相关性，以及栖息在木材上的生物的腐殖质。通过开展跨区域协调和全面复制的实验，我们期望获得具有高科学影响和效益的可靠结果，用于森林生态系统的枯木管理。

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.