Impact of deadwood on functional diversity and biogeochemical traits in underlying forest soils

腐烂的枯木为许多特殊的生物提供了栖息地。它们大多是森林生态系统中能量丰富而营养贫乏的资源。原木在养分含量和可用性方面与土壤不同，但与下层土壤的生物和化学相互作用在很大程度上是未知的，因此关于枯木对森林土壤功能和生物多样性的影响的知识存在空白。真菌菌丝有能力在两种栖息地之间架起桥梁，并在枯木和土壤之间重新分配营养。在生物多样性实验区，受森林经营的影响，在BeLongDead实验中暴露的13种树种原木和不同土壤中，通过不同的养分浓度存在养分梯度。了解养分转运的关键机制对于预测养分梯度对木-土界面微生物群落结构和功能、细根性状和土壤化学性质的影响至关重要。提出的项目的目的之一是阐明不同土壤真菌群落在探索森林中发生的营养转运的潜力在一个控制的实验室实验。在BeLongDead实验中，另一个目的是研究长达9年的原木分解对下层土壤的长期影响。我们的总体假设是，营养贫乏和营养丰富的土壤对原木的养分梯度的反应不同，而养分梯度因树种而异。对于营养贫乏的土壤，我们假设原木养分对(1)养分向土壤的转运，(2)腐养真菌的功能多样性，(3)细根密度，外生菌根短根和外生菌根真菌的多样性，以及(4)微生物生物量和活性的积极影响越来越大。对于营养丰富的土壤，我们预计相反的反应（1和2），没有影响(3)和类似的效果(4)。为了验证这些假设，我们将结合创新和既定的方法，以及实地工作和实验室实验。菌丝营养易位将根据15N和33P标记以及元转录组测序进行评估。化学和微生物土壤参数以及根系性状将与真菌群落结构和活性联系起来，通过下一代测序方法进行评估。综合专业知识将使我们能够评估真菌多样性与生态系统过程中原木以下土壤特性的相关性。通过在营养梯度上进行协调和完全重复的实验，我们期望得到具有高科学影响和林业效益的可靠结果。

Decomposing deadwood logs serve as habitat for many specialized organisms. They mostly represent an energy-rich and nutrient-poor resource in forest ecosystems. Logs differ from soils in nutrient content and availability, but the biological and chemical interactions with underlying soil are largely unknown, leaving a gap of knowledge concerning the implications of deadwood for functions and biodiversity in forest soils. Fungal hyphae have the capability to bridge the two habitats and to redistribute nutrients between deadwood and soil. In the Biodiversity Exploratories, nutrient gradients exists through different nutrient concentrations in logs of 13 tree species, exposed in the BeLongDead experiment, and different soils, influenced by forest management. Understanding nutrient translocation as key mechanism is crucial for predicting the impact of nutrient gradients as driver of microbial community structure and function, fine root traits and chemical soil properties at the wood-soil interface. One aim of the proposed project is to elucidate the potential of nutrient translocation by different soil fungal communities occurring in the Exploratory forests in a controlled laboratory experiment. Another aim is to study the long-term effects of yet 9 years decomposing logs on underlying soils in the BeLongDead experiment. Our overarching hypothesis is that nutrient-poor and nutrient-rich soils respond differently to nutrient gradients to logs, which vary among tree species. For nutrient-poor soils, we hypothesize increasingly positive effects of log nutrients on (1) nutrient translocation towards soil, (2) functional diversity of saprotrophic fungi, (3) fine root density, ectomycorrhizal short roots and diversity of ectomycorrhizal fungi, and (4) microbial biomass and activity. For nutrient-rich soils, we expect opposite responses (1 and 2), no impact (3) and a similar effect (4), respectively. To test the hypotheses, we will combine innovative and established methods as well as field work and laboratory experiments. Hyphal nutrient translocation will be assessed based on 15N and 33P labelling accompanied by metatranscriptome sequencing. Chemical and microbial soil parameters as well as root traits will be linked to fungal community structure and activity assessed by Next-Generation-Sequencing approaches. Combined expertise will allow us to evaluate the relevance of fungal diversity and soil properties below logs for ecosystem processes. By working on a coordinated and full replicated experiment across nutrient gradients, we expect robust results with high scientific impact and benefits for forestry.