Land Use and Carbon Sequestration in Eastern Deciduous Forests: Complex Interactions Between Human Activities and Ecosystem Processes

地球表面观测到的变暖引起了人们对全球环境中二氧化碳增加的影响的关注，了解森林作为潜在碳汇的作用正在成为国家和全球的优先事项。该项目的目的是调查北美东部落叶林最近的过去，现在和未来的土地利用变化对碳动态的作用。东部落叶林在过去的二氧化碳吸收中可能发挥了重要作用，这是由于在世纪之交的大规模砍伐后的再生长。东部落叶林目前的木材采伐率很高，因此未来的土地利用和覆盖变化可能再次影响碳循环。这些森林是在一套不同的公共和私人管理制度下管理的，每个群体都有不同的土地管理动机，对经济刺激的反应也可能不同。该项目的研究问题涉及西弗吉尼亚州温带落叶林中人类活动（森林管理）和生态系统过程（碳固存）之间的相互作用：1）不同土地利用方式的森林之间的碳储量有何不同？2)土地管理的变化（1989-2000年）如何影响碳储存，这种土地利用变化的人为驱动因素是什么？3)在未来的条件下，中央阔叶林储存碳的能力会如何变化？为了解决这些研究问题，生态系统模型（Pnet-CN）将在两个空间尺度（流域和国家）进行校准和验证。在流域一级，将针对四种管理处理方式对PnET-CN进行校准：成熟林、幼龄林和两种直径限制采伐。在州一级，PnET-CN将于1989年和2000年在美国农业部林务局、森林资源调查和分析（FIA）地块位置运行，这些地块位置按管理策略分类，以与实验流域的位置相匹配。这一生产力模型将与一个计量经济学模型相联系，该模型利用FIA地块数据，结合地块可达性、管理制度和当地硬木木材价格等信息，调查土地利用/土地管理类别及其潜在驱动因素之间的相关性。计量经济学模型将与生态系统模型相结合，进行情景分析，将土地利用和覆盖变化驱动因素的变化与碳储存的变化联系起来。还将制定土地利用和覆被变化驱动因素固定但气候参数变化的情景。鉴于大气中二氧化碳水平升高，了解土地利用和覆盖变化的人为原因及其对碳循环的影响至关重要。该研究通过将木材采伐的经济原因与森林生物量和生产力的细节直接联系起来，解决了土地利用变化，陆地生态系统和碳平衡驱动因素之间的重要相互作用。该项目的成果将有助于州和国家机构在未来经济和气候变化的背景下管理温带落叶林。这项研究还将通过在科学期刊和会议上广泛传播研究结果，通过研究生研究助理、本科生实地助理的支持，以及通过开发研究生和本科生教学模块，提高对落叶林在碳循环中作用的科学认识。

ABSTRACTObserved warming at the Earth's surface has raised concerns about the effects of increased carbon dioxide in the global environment, and understanding the role of forests as potential carbon sinks is becoming a national and global priority. The objective of this project is to investigate the role of recent past, current, and future land use change on carbon dynamics in eastern deciduous forests of North America. Eastern deciduous forests may have played a major role in past carbon dioxide uptake due to regrowth following major cutting at the turn of the century. Current rates of timber harvest in eastern deciduous forests are high, so future land use and cover changes may again affect carbon cycling. These forests are managed under a diverse set of public and private management regimes, with each group possessing different motivations for land management and potentially responding differently to economic incentives. The project's research questions address the interactions between human activities (forest management) and an ecosystem process (carbon sequestration) in temperate deciduous forests of West Virginia: 1) How do carbon stocks differ between forests with different land use practices? 2) How have changes in land management (1989-2000) affected carbon stocks, and what were the human drivers of this land use change? 3) How might the ability of central hardwood forests to store carbon change under future conditions? To address these research questions, an ecosystem model (Pnet-CN) will be calibrated and validated at two spatial scales (watershed and state). At the watershed level, PnET-CN will be calibrated for four management treatments: mature forest, young forest, and two types of diameter limit cuts. At the state level, PnET-CN will be run for 1989 and 2000 at USDA Forest Service, Forest Inventory and Analysis (FIA) plot locations classified by management strategy to match those of the experimental watersheds. This model of productivity will be linked to an econometric model that investigates correlations between land-use/land-management categories and their potential drivers, using FIA plot data combined with information on plot accessibility, management regime, and local hardwood timber prices. The econometric model will be coupled with the ecosystem model to conduct scenario analysis linking changes in drivers of land use and cover change to changes in carbon storage. Scenarios holding drivers of land use and cover change fixed, but varying climate parameters, will also be developed. Understanding the human causes of land use and cover change and their consequences for the carbon cycle is critical given elevated levels of carbon dioxide in the atmosphere. This research addresses the important interaction between drivers of land use change, terrestrial ecosystems, and carbon balance by directly linking economic causes of timber harvest to details of forest biomass and productivity. Results from this project will help state and national agencies manage temperate deciduous forests in the context of future economic and climatic changes. This research will also enhance scientific understanding of the role of deciduous forests in the carbon cycle through broad dissemination of results in scientific journals and conferences, through the support of graduate research assistants, undergraduate field assistants, and through the development of graduate and undergraduate teaching modules.