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

点击翻译按钮获取中文摘要

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.