SG: Understanding local controls on wood decomposition in a regional context

森林碳平衡的一个关键决定因素是枯木腐烂的速度。这是由枯木形成的速度和它分解或分解的速度决定的。枯木也是其他营养物质积累的热点，是许多动物、植物和微生物的家园。因为树木含有大量的碳，我们对碳循环可能发生的变化的理解需要更好地理解木材的分解过程。考虑到这一点，该项目将分解美国五种常见树种的原木，横跨美国东北部到东南部的温带森林。对木材腐解率的潜在控制将通过实验进行控制，例如枯木的密度和原木上生长的木材分解真菌的类型。将监测其他因素，如土壤养分含量、温度和湿度。在野外腐烂一年后，树木原木将被收集并带到实验室，以评估它们的分解程度和相关的木材腐烂真菌。然后对数据进行分析，以确定不同条件下的木材分解率。该项目的信息将用于改进对碳循环变化和环境变化对森林的影响的预测。研究结果还将为林业行业管理森林中的死木库存提供指导。通过与皮博迪自然历史博物馆的合作，将传播天然木材腐烂的重要性，为公众展示和用于教育来访的中学生。该项目还将对研究生和本科生进行研究方面的培训，并将与高中暑期实习生合作，这些实习生来自科学领域代表性不足的学生群体。了解枯木分解过程对森林管理至关重要，特别是对于减轻枯木储量下降对森林生产力、生物多样性和碳储存的负面影响。对凋落物分解的控制得到了更好的解决，气候和凋落物质量被认为是全球和区域尺度上分解速率的主要调节因素。这些因素也控制着死木的分解，但额外的不明控制意味着，很难合理确定地预测区域范围内的木材腐解率。这项工作的目标是确定重要的额外控制，然后可以用来制定和参数化碳循环模型，其中木材分解是一个关键的不确定性。在单点研究中，影响木材分解速率的主要因素似乎是真菌群落结构。事实上，木腐菌的种类、菌株和相互作用是腐烂率的重要决定因素。特别是，那些将菌丝聚集成厚厚的菌丝索的真菌被认为是主要的分解因素。这些菌丝聚集的真菌被称为非单位限制真菌，因为它们的菌丝体增殖并将离散的木片相互连接。这种连通性提供了强大的竞争优势，使真菌能够通过获得广泛的营养来源来迅速在枯木上定居。因此，我们项目的工作假设是：当非单位限制的木腐菌能够有效地定植时，倒下的枯木的分解迅速进行。对定殖率和真菌介导的分解速率的主要控制是粗木质材料(CWM)的接近和丰富。这一工作假说将通过横跨美国东部温带森林地区气候梯度的五个地点的观测横断面和共同花园实验来验证。样带研究将评估五个树种的原木的分解情况，这些树种跨越明显的小气候梯度，要么靠近自然的CWM，要么远离自然的CWM。每个地点的四个普通花园将包括零水平、中等水平和高水平的CWM，与使用塑料边缘的复制杂交，以扰乱非单位限制真菌的觅食。解释观察到的分解模式的相互竞争的假设将通过估计非生物因素和分解者群落的功能能力的现场和实验室分析来进行评估。该项目将通过一个实习项目吸引高中生，有大学录取机会攻读STEM专业的应届毕业生，以及来自高等教育代表性不足的背景的学生，将寻求一个带薪的暑期研究职位。目标是帮助纠正这一群体的低大学录取率(10%)。该项目还将涉及研究生和本科生的培训。最后，将与皮博迪自然历史博物馆合作开发面向六年级学生的公共宣传，以扩大他们的学校访问计划的教育工具包，并促进公众对真菌、水煤浆和分解的兴趣。

A critical determinant of the carbon balance of forests is the rate at which dead wood decays. This is determined by the rate at which dead wood is formed and the rate at which it breaks down, or decomposes. Dead wood is also a hotspot for other nutrients to accumulate and it is a home for many species of animals, plants and microbes. Because trees contain a lot of carbon, our understanding of how the carbon cycle might be changing requires a better understanding of the wood decomposition process. With that in mind, this project will decompose logs from five common US tree species across a gradient spanning northeastern to southeastern US temperate forests. Potential controls on wood decomposition rates will be manipulated experimentally, such as the density of dead wood and the types of wood-decomposing fungi growing on the logs. Other factors, such as soil nutrient content, temperature and moisture will be monitored. The tree logs will be collected after a year of decay in the field and brought into the laboratory to assess their decomposition extent and associated wood-decaying fungi. The data will then be analyzed to determine wood decomposition rates under the different conditions. Information from this project will be used to refine predictions of carbon-cycle changes and the effects of environmental change on forests. The results will also provide guidance to the forest industry on management of dead wood stocks in forest.The importance of natural wood decay will be communicated through a collaborative effort with the Peabody Museum of Natural History, by creating "living" dead wood exhibits for public display and use in educating visiting middle-school students. The project will also train both graduate and undergraduate students in research, and will work with high-school summer interns from groups of students that are underrepresented in science. Understanding the processes governing the decomposition of dead wood is essential for forest management, especially to mitigate negative effects of declining dead wood stocks on forest productivity, biodiversity and carbon storage. Controls on decomposition of leaf litter are better resolved, with climate and litter quality considered predominant regulators of decomposition rates at global and regional scales. These factors also regulate decomposition of dead wood, but additional unidentified controls mean that wood decomposition rates at regional scales are hard to predict with reasonable certainty. The objective of this work is to identify important, additional controls, which can then be used to formulate and parameterize carbon cycle models, where wood decomposition is a critical uncertainty. In single site studies, the primary factor affecting wood decomposition rates appears to be fungal community structure. Indeed, the species, strain and interactions of wood-rot fungi are strong determinants of decay rates. In particular, those fungi that aggregate their hyphae into thick mycelial cords are considered dominant agents of decomposition. These hyphal-aggregating fungi are termed non-unit-restricted fungi because their mycelia proliferate and interconnect discrete pieces of wood. The connectivity confers a strong competitive advantage, allowing fungi to rapidly colonize dead wood by accessing a broad suite of nutrient sources. As such, the working hypothesis of our project is: The decomposition of downed dead wood proceeds rapidly when non-unit restricted wood-rot fungi can colonize efficiently. A primary control on colonization, and hence fungal-mediated decomposition rates, is the proximity and abundance of coarse woody material (CWM). The working hypothesis will be tested with observational transects and common-garden experiments across five sites spanning a regional climate gradient in eastern US temperate forests. Transect studies will assess the decomposition of logs of five tree species, across pronounced microclimate gradients, either next to or away from natural CWM. Four common gardens at each site will comprise zero, medium and high levels of CWM, crossed with replicates that use plastic edging to disrupt foraging by non-unit restricted fungi. Competing hypotheses to explain the observed patterns of decomposition will be evaluated using field and laboratory assays estimating abiotic factors and the functional abilities of the decomposer communities. The project will engage high school students through an internship program, where graduating students who have college offers to pursue STEM majors, and who are from backgrounds under-represented in higher education, will pursue a paid, summer research position. The goal is to help redress the low (10%) college matriculation rate of this group. The project will also involve training at the graduate and undergraduate levels. Lastly, public outreach to 6th graders will be developed in collaboration with the Peabody Museum of Natural History, to expand their educational toolkit for school-visit programs, and to promote public interest in fungi, CWM and decomposition.