Collaborative Research: Impact of microbial and termite communities on transfer of decaying wood to stable and protected mineral soil carbon pools

随着森林的老化，树木的死亡增加了森林地面上的枯木。即使在较年轻的森林中，强风事件、虫害暴发、火灾和森林管理都可能导致枯木积累。枯木可以储存碳，但长期储存多少是不确定的。木材中的大部分碳在分解过程中以二氧化碳的形式缓慢地返回大气。然而，其中一些也会进入土壤，在那里可以储存几十年到几个世纪。2011年，松树、白杨和桦木原木被放置在美国的9个森林中，以帮助确定气候、木材类型、白蚁和真菌的存在等因素如何影响木材分解率。所使用的木材具有独特的碳同位素特征，使研究小组能够在其进入土壤时进行追踪，并测量碳在分解过程中损失或作为土壤碳储存的速度。这一知识将提高对森林碳循环的理解，并使人们能够更好地预测气候变化或森林扰动导致的树木死亡增加如何改变森林中的碳储量。这项研究将有助于确定森林在长期尺度上是大气二氧化碳的碳汇还是碳源。该项目还将使初高中学生有机会亲身体验科学研究，并提高四个研究地点附近农村学校对STEM主题的认识。项目科学家将与教师合作，让学生在附近的田野现场参与基于研究的发现和分析，并将与生态学和土壤科学相关的项目主题纳入学校课程，为提高学生对科学和工程职业的兴趣奠定基础。主导木材分解的真菌和无脊椎动物群落沿着白腐到褐腐连续体有不同的木质素和碳水化合物分解途径，这些途径改变了转移到矿物土壤的碳量。本研究的具体目标是评估不同真菌/细菌群落和白蚁对三种木材木质素和碳水化合物衰变途径的作用，并确定这如何影响木材碳向不稳定和受保护的矿物土壤碳库的运动。这需要：1)使用标记木材的13C特征来评估分解者群落功能对木材腐烂途径、质量损失和木材碳向矿物土壤移动的作用；2)利用一系列独特的白蚁排除样地，确定白蚁活动对真菌腐木群落组成、腐木途径和木材碳入矿土的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

As forests age, the death of trees adds dead wood to the forest floor. Even in younger forests, strong wind events, insect outbreaks, fire and forest management all can result in accumulation of dead wood. Dead wood stores carbon, but how much in the long-term is uncertain. Much of the carbon in wood is slowly returned to the atmosphere as CO2 during decomposition. Some, however, also enters the soil, where it can be stored for decades to centuries. In 2011, pine, aspen and birch logs were placed in nine forests across the U.S. to help determine how factors such as climate, wood type, presence of termites and fungi affect wood decomposition rate. The wood used had a unique carbon isotopic signature that allows the research team to trace it as it enters the soil, and to measure how fast carbon is either lost to decomposition or stored as soil carbon. This knowledge will improve understanding of carbon cycling in forests and allow better prediction of how a changing climate or increased tree death from forest disturbance could alter carbon storage in forests. This research will help to determine if forests will be carbon sinks or sources for atmospheric CO2 over long time scales. The project will also give middle and high school students a chance to experience scientific research first-hand, and increase awareness of STEM topics in rural schools near four of the research sites. Project scientists will work with teachers to involve students in research-based discovery and analysis at a nearby field site and incorporate project topics related to ecology and soil science in school curricula, providing a foundation for increasing student interest in science and engineering careers.The fungal and invertebrate communities that dominate wood decomposition have distinct lignin and carbohydrate decomposition pathways along a white- to brown-rot continuum, and these alter the amount of carbon diverted to the mineral soil. This study's specific objectives are to assess the role of different fungal/bacterial communities and termites on lignin- and carbohydrate-decay pathways for the three wood types and determine how this affects wood carbon movement into labile and protected mineral soil carbon pools. This entails: 1) using the 13C signature of labelled wood to assess the role of decomposer community function on wood-decay pathways, mass loss, and wood carbon movement into mineral soil; and 2) using a unique series of termite-exclusion plots to determine the effect of termite activity on fungal wood-decay community composition, wood-decay pathways, and incorporation of wood carbon into the mineral soil.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.