The Dynamics of Change in Alaska's Boreal Forests: Resilience and Vulnerability in Response to Climate Warming

Bonanza Creek（BNZ）LTER研究的基石是状态因子方法，该方法允许基于独立控制（如气候，母质，地形，潜在生物区系和时间）和交互控制（即，生态系统内部的过程，既影响生态系统过程，又对生态系统过程作出反应。拟议研究的智力价值涉及扩展这一理论框架，以解决生态系统恢复力和脆弱性的基础过程。我们的目标是确定缓冲系统从结构和功能的根本变化（弹性）的因素与可能加速变化到替代状态（脆弱性）的因素。这就需要超越稳态动力学的假设，去问在什么条件下驱动因素的变化可能引发北方生态系统性质的根本变化。我们研究的中心问题是：北方生态系统如何对气候变暖做出反应，包括逐渐和突然的反应，以及正在出现什么新的景观模式？我们分几个步骤研究变化的动态。(1)物理和生物过程对环境时间变化的气候敏感性，它确定了生态系统对气候变化的恢复力的限度：（2）由气候和干扰状况的变化引起的演替动态的变化，它确定了生态系统最易受变化影响的干扰和恢复的适应循环点;（3）可能导致北方森林以一种新的方式发挥作用的阈值变化;整合和综合，我们在多个时间和空间尺度上整合这些气候响应模式，并探索其社会后果。研究设计结合长期观测，长期实验，和过程研究，以确定生态变化和文件控制生态系统的过程和演替动态在三个景观单元：洪泛平原，高地，和湿地。我们通过操纵选择的交互控制来测试关于控制生态系统动态的假设。这些地块级的研究扩展到更大的空间尺度（流域，地区和阿拉斯加州）的分层研究设计，使用广泛的测量，遥感和建模。研究的时间尺度跨越小时（天气）、年（生长、人口）、演替周期（林龄重建）和千年（植被和气候重建）。我们通过确定北方森林在当地提供的生态系统服务的过去和潜在未来变化来探索社会后果（例如，生存资源）和全球（例如，碳封存）。参与LTER跨站点比较使我们能够在更广泛的背景下理解北方过程。为了使这些信息对更广泛的社区可用和有用，我们与学校、社区外展计划、更广泛的科学界和资源管理人员密切合作，通过合作、外展和基于网络的数据管理。信息管理强调我们收集的信息的安全存档，促进其综合使用，并开发基于网络的数据库，以促进科学界的使用。

The cornerstone of the Bonanza Creek (BNZ) LTER research has been the state factorapproach, which allows prediction of ecosystem properties based on independent controls suchas climate, parent material, topography, potential biota, and time and interactive controls, i.e.,processes internal to ecosystems that both affect and respond to ecosystem processes. Theintellectual merit of the proposed research involves expansion of this theoretical framework toaddress processes underlying ecosystem resilience and vulnerability. Our objective is to identifyfactors that buffer systems from radical changes in structure and functioning (resilience) vs.factors that might precipitate changes to alternative states (vulnerability). This requires anextension beyond the assumptions of steady state dynamics to ask under what conditions changesin drivers might trigger a fundamental change in the nature of boreal ecosystems. The centralquestion of our research is: How are boreal ecosystems responding, both gradually andabruptly, to climate warming, and what new landscape patterns are emerging?We study the dynamics of change in several steps. (1) Climate sensitivity of physicaland biological processes to temporal variation in the environment, which defines the limits ofresilience to climate change; (2) changes in the successional dynamics caused by changes inclimate and disturbance regime, which define the points in the adaptive cycle of disturbance andrecovery at which ecosystems are most vulnerable to change; (3) threshold changes that arelikely to cause the boreal forest to function in a qualitatively new way and (4) integration andsynthesis in which we integrate these modes of climate response across multiple temporal andspatial scales and explore their societal consequences.The research design combines long-term observations, long-term experiments, andprocess studies to identify ecological changes and to document controls over ecosystemprocesses and successional dynamics in three landscape units: floodplains, uplands, andwetlands. We test hypotheses about controls over ecosystem dynamics by manipulating selectedinteractive controls. These plot-level studies are extended to larger spatial scales (watersheds,regions, and the state of Alaska) in a hierarchical research design, using extensive measurements,remote sensing, and modeling. Temporal scales of the research span hours (weather), years(growth, populations), successional cycles (stand-age reconstructions), and millennia (vegetationand climate reconstructions).We explore societal consequences by identifying past and potential future changes inecosystem services that boreal forests provide both locally (e.g., subsistence resources) andglobally (e.g., carbon sequestration). Involvement in LTER cross-site comparisons enables us tounderstand boreal processes in a broader context. To make this information available and usefulto a broader community, we work closely with schools, community outreach programs, thebroader scientific community, and resource managers through collaborations, outreach, and webbaseddata management. Information management emphasizes secure archival of the informationwe have collected, promotion of its use in synthesis, and development of web-based databases tofacilitate its use by the scientific community.