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

土壤有机质是陆地上最大的有机碳(OC)储存库，其分解导致每年约75pg的碳(C)以二氧化碳(CO2)的形式释放到大气中。其中超过70%的排放来自一小部分(占总碳的1%)新近加入(1年)的有机物质，其余的排放来自更稳定的土壤有机碳库(SOC)。这种稳定的SOC池分解较慢，因为它在物理上、化学上和/或生物上受到保护，不会分解。尽管我们对小型、快速循环的SOC池如何应对环境变化有合理的理解，但我们对更稳定的SOC池的稳定/不稳定过程的了解还不够深入。随着气候变化，预计北部森林的森林火灾将变得更加频繁，随着北部地区气温上升，农业扩张的机会正在出现。与此同时，人们对利用生物质燃烧产生的生物能源越来越感兴趣，生物质燃烧产生的木灰是碱性的，可以用作土壤改良剂来提高场地生产力。火灾和土地管理，以及气候的变化，改变了土壤环境的物理、化学和生物特性，这可能导致“稳定”碳库的变化(S)。在接下来的五年里，我的研究计划将研究添加灰分对SOC转化和运输的影响，具体目标是：1.量化Ca、Fe和Al在酸性北方土壤中对SOC稳定的作用；2.评估pH和Ca增加的潜力，以增强酸性土壤中矿物伴生有机碳的稳定能力；3.确定添加灰分是否影响SOC在土壤剖面中更深层次的转化和运输。完成我的计划的短期目标将有助于我的职业目标：1.提高我们对环境变化对北方土壤中有机碳生物地球化学循环的影响的理解；2.促进碳同位素和有机碳分馏技术在生物地球化学研究中的应用。这些目标将通过同时进行的学生主导项目来实现。

Soil organic matter is the largest terrestrial reservoir of organic carbon (OC) and its decomposition is responsible for the annual release of an estimated 75 Pg carbon (C) into the atmosphere as carbon dioxide (CO2). Over 70% of these emissions are derived from a small pool (<1% of total C) of recently incorporated (<1 yr) organic matter, with the remaining emissions being derived from a more stable pool of soil organic carbon (SOC). This stable pool of SOC is slower to decompose because it is protected from decomposition physically, chemically and/or biologically. Though we have a reasonable understanding of how the small, fast cycling pool of SOC responds to environmental change, our knowledge of the process of stabilization/destabilization of the more stable pool of SOC is not as well developed. As climate changes, forest fires are expected to become more frequent in northern forests and opportunities for agricultural expansion are emerging with increases in growing degree days in northern regions. In tandem, there has been increasing interest in bioenergy generation using the combustion of biomass which generates wood ash that is alkaline and may be used as a soil amendment to improve site productivity. Fires and land management, alongside changes in climate, alter the soil environment physically, chemically, and biologically which may lead to changes in the pool(s) of "stable" carbon. Over the next five years my research program will investigate the effects of ash addition on the transformation and transport of SOC with the specific objectives of: 1. quantifying the role of Ca, alongside Fe and Al, on stabilization of SOC in acidic northern soils, 2. assessing the potential for increases in pH and Ca to enhance the stabilization capacity of mineral associated organic carbon in acidic soils, and 3. determining if the amount of ash added affects the transformation and transport of SOC deeper into the soil profile. Meeting the short-term objectives of my program will contribute to my career goals of 1. Improving our understanding of the effects of environmental changes on the biogeochemical cycling of SOC in northern soils and 2. Advancing the use of C isotopes and SOC fractionation techniques in biogeochemical investigations. These objectives will be met through concurrent student led projects.