Dissertation Research: Winter soil respiration in southeast Wyoming

在季节性积雪地区，土壤中活根和微生物在冬季的代谢可能是陆地生态系统每年向大气转移二氧化碳总量的重要组成部分。该项目将测量怀俄明州东南部冬季土壤呼吸，并确定控制它的因素。从短草草原到亚高山森林的一系列生态系统已经建立了测量地块，这些生态系统经历了各种各样的冬季天气条件。海拔最高的地方，大约1万英尺，是一个亚高山森林，在深达10英尺的地方，积雪覆盖了八个多月。海拔最低的地方，5400英尺，只有四个月的积雪，而且是浅而不完整的。这导致了隆冬土壤环境的对比。在高海拔地区，雪提供了一个很深的绝缘层，有效地将土壤与极冷的空气温度隔绝开来，防止土壤冻结。相反，在海拔最低的地方，土壤经常直接暴露在空气中，在隆冬经常冻结。这就产生了一个违反直觉的结果，即在海拔最高的最冷、雪最多的生态系统中，土壤实际上是隆冬时最温暖的。负责土壤呼吸的生物，主要是细菌、真菌和植物根系，依靠液态水的存在来发挥生物活性。因此，预计在冬季，海拔最高的地点比海拔最低的地点有更高的土壤呼吸速率。将对不同研究地点的土壤呼吸进行测量，以确定来自微生物和根系的相对量。将进行实验室实验以确定在低温下对呼吸的控制。一年多来，从陆地进入大气的二氧化碳比燃烧化石燃料释放的二氧化碳多很多倍。在地球上，大部分释放的碳被植物吸收。但是相对释放和吸收速率的微小变化会对大气中的二氧化碳浓度产生很大的影响。目前的计算机模型通常对土壤过程以及它们如何对气候变化做出反应（尤其是在低温下）的描述过于简单。因此，了解控制这些过程的相互作用的生物和物理因素非常重要。除了解决与社会相关的全球气候变化问题外，该项目还将通过雇用一名本科生研究助理，帮助教育和培训新一代科学家。

In seasonally snow covered regions, the metabolism of living roots and microorganisms in the soil over the winter may be an important part of the total annual transfer of carbon dioxide from ecosystems on land into the atmosphere. This project will measure wintertime soil respiration in southeast Wyoming and determine the factors that control it. Measurement plots have been established across a range of ecosystems from short grass prairies to subalpine forests that experience a wide range of winter weather conditions. The highest elevation site, at about 10,000 feet, is a subalpine forest that has snow cover for more than eight months at depths up to ten feet. The lowest elevation site, at 5400 feet, has only four months of snow that is shallow and patchy. This results in contrasting midwinter soil environments. At the high elevation site, snow provides a deep insulating layer that effectively insulates the soil from extremely cold air temperatures and prevents soil freezing. In contrast, soils at the lowest elevation site are often directly exposed to the air and often freeze in midwinter. This has the counterintuitive result that soils in the coldest, snowiest ecosystems at the highest elevations are actually the warmest in midwinter. The organisms responsible for soil respiration, mainly bacteria, fungi and plant roots, rely on the presence of liquid water to be biologically active. Therefore, it is expected that the highest elevation sites will have higher rates of soil respiration during the winter than the lowest elevation sites. Measurements will be made of soil respiration at the different study sites in ways that will enable the relative amounts coming from microbes and roots to be determined. Laboratory experiments will be done to determine the controls over respiration at cold temperatures. Over a year the flux of carbon dioxide from the land into the atmosphere is many times greater than the amount released by the burning of fossil fuels. Over the earth, most of the released carbon is taken back up by plants. But small shifts in the relative rates of release and uptake can have a large impact on atmospheric concentrations of carbon dioxide. Current computer models generally contain overly simple descriptions of soil processes and how they may respond to climate change, particularly at cold temperatures. Therefore, it is important to learn about the interacting biological and physical factors that control these processes. In addition to addressing the socially relevant issue of global climate change, this project will help educate and train a new generation of scientists through the employment of an undergraduate research assistant.