The effect of disturbance on the biogeochemical cycling of carbon in northern forest soils

森林采伐和野火以根本不同的方式扰乱了北方森林土壤中的碳循环。在收获过程中，机械干扰会将有机层中的有机物物理地混合到矿物土壤中，而有机层在火灾中的燃烧会在化学上转化有机物，并产生灰烬和焦炭，从而提高pH值并释放养分。尽管火灾和收割广泛发生，但比较火灾和收割对土壤碳循环影响的研究很少，考虑整个土壤剖面的更少。少数现有研究的结果表明，森林采伐后储存在30厘米以下的SOC在受到干扰后的几年内显著增加，并随着时间的推移而下降。这些碳是以什么形式、以什么速率从地表运来的？它是原地矿化还是从系统中出口？在受火灾影响的森林中，表层有机物的运输似乎仅限于A层，A层是表层的，通常很薄。为什么？ 在接下来的五年里，我的研究计划将集中于研究和比较森林和北方混交林中有机碳的转化和运输，具体目标是：1.在剖面中量化有机碳的运移速率，2.通过剖面识别有机碳稳定和失稳的机制，以及3.评估掩埋和焚烧的有机碳储存的生物有效性。 满足我的计划的短期目标将继续是我的职业目标：1.提高我们对环境扰动对陆地系统中有机碳生物地球化学循环的影响的理解；2)结合更经典的生物地球化学方法(如物理分馏)，促进碳同位素和新的分子技术的使用。 这项研究直接补充了我的省和国家政府同事正在进行的工作，将有助于指导有关气候变化和用于生物能源的生物质的碳和森林管理政策问题。我的研究计划将训练学生生物地球化学的尖端和经典方法，并发展在C生物地球化学循环中提出和回答关键问题的技能。学生、政府科学家和学者之间的互动将加强学生对研究在政策和管理中的相关性和应用的理解和体验。

Forest harvesting and wildfire disturb the carbon cycle in the soils of the boreal forest in fundamentally different ways. During harvesting mechanical disturbance physically mixes organic matter from the organic layer into the mineral soil while combustion of the organic layer in a fire chemically transforms organic matter and produces ash and char that increases the pH and releases nutrients. Despite the widespread occurrence of fire and harvesting, there are few investigations comparing the effects of fire and harvesting on the carbon cycle in the soil, and fewer still that consider the entire soil profile. Findings from the few available studies indicate that SOC stored below 30 cm in harvested forests increases significantly in the years immediately following disturbance and declines through time. Is this carbon transported from the surface, in what form and at what rate? Is it mineralized in situ or does it get exported from the system? In fire affected forests, transport of surface organic matter appears to be limited to the A horizon, which is surficial and typically thin. Why? Over the next five years my research program will focus on examining and comparing the transformation and transport of SOC in wildfire and harvested mixed wood boreal forests with the specific objectives of: 1. quantifying rates of transport of SOC in the profile, 2. identifying mechanisms of SOC stabilization and destabilization through the profile, and 3. assessing the bioavailability of buried and burned SOC stores Meeting the short term objectives of my program will continue to my career goals of: 1. improving our understanding of the effects of environmental perturbation on the biogeochemical cycling of SOC in terrestrial systems and 2) advancing the use C isotopes and novel molecular techniques, in conjunction with more classical biogeochemical approaches (e.g. physical fractionation). Directly complementing work underway by my provincial and national governmental colleagues, this research will assist in guiding carbon and forest management policy issues around climate change and biomass for bioenergy. My research program will train students in cutting edge and classical methods in biogeochemistry and develop skills in asking and answering critical questions in the biogeochemical cycling of C. The interaction between students, government scientists and academics will enhance student understanding of and experience with the relevance and applications of research in policy and management.