Study Sites & Design: Overview
Our research is conducted in a number of sites that encompass a variety of landscape types, and times since disturbance:
The Bonanza Creek Experimental Forest (BCEF), located approximately 20 km southwest of Fairbanks, Alaska, was established in 1963 with about 3360 ha (8,300 acres) of upland, interior Alaska boreal forest. In 1969, the experimental forest was enlarged to 5053 ha (12,487 acres) to include representative floodplain forests along the Tanana River. The Forest is within the Tanana Valley State Forest, a unit managed by the Division of Forestry, State of Alaska. In 1987 the Bonanza Creek Long-Term Ecological Research program was established, with BCEF as its primary research site.
The Bonanza Creek LTER research program at Bonanza Creek Experimental Forest is designed to study ecosystem structure and function through examination of controls over successional processes in taiga forests of interior Alaska. This study tests hypotheses regarding the controls on ecosystem succession with study plots located in different successional stages of primary succession on the floodplain of the Tanana River, and in different stages of succession following wildfire.
The Caribou-Poker Creeks Research Watershed (CPCRW) is a relatively pristine 104 km2 basin north of Fairbanks, Alaska. The watershed is reserved for ecological, hydrological, and climatic research, and is owned jointly by the State of Alaska and the University of Alaska Fairbanks. Climate and hydrology data have been collected since 1969, as well as ecological studies on a more sporadic schedule. The CPCRW is the only research watershed in the United States located in the zone of discontinuous permafrost, which comprises a large portion of the state of Alaska, including most of interior Alaska. The watershed is fairly representative of upland headwater stream basins in subarctic Alaska. Hydro-biological research in CPCRW has several major emphases: to assess the role of disturbance in the terrestrial landscape (e.g. wildfire, herbivory, logging) on subarctic stream ecosystems, and to assess the influence of discontinuous permafrost on fresh water ecology.
As the BNZ LTER expanded its focus to understand regional effects of climate change and in particular, climate-disturbance interactions (including fire, permafrost thaw, and insect/pathogen outbreaks), we expanding our core measurements to an extensive, regional set of sites chosen to specifically address variations in site conditions driving divergence of successional pathways. This regional site network focuses on black spruce, which is the most extensive forest type in interior Alaska and is experiencing radical disturbance-driven changes in successional dynamics. The regional site network incorporates sites located in three major ecoregion of interior Alaska, which are defined by geographical zones in surficial geology, parent material, climate, and local flora. These three ecoregions are the Ray Mountains, the Tanana-Kuskokwim Lowlands, and the Yukon-Tanana Uplands. All three ecoregions have a strongly continental climate with cold winters and warm summers, discontinuous permafrost, and prevalent forest fires. There are, however, differences in the permafrost temperatures, summer moisture, and dominance of forest fires across these ecoregions.
The Eight Mile Lake study area (EML) is upland tundra located in the northern foothills of the Alaska range about 14 km west of Healy, Alaska (63º 52' 42”N, 149º15' 12”W). The site is situated on moist acidic tundra on a relatively well-drained gentle northeast-facing slope. Permafrost temperature in this region are currently ~ -1°C and therefore susceptible to thaw. Research at EML is focused on a permafrost thaw gradient, and in a permafrost heating experiment. The thaw gradient has three sites with minimal, moderate, and extensive thaw determined by the amount of vegetation change, active layer thickening, and thermokarst formation they have undergone. The soil warming experiment has been conducted using snow fences to trap insulating layers of snow. Core measurements at EML include monitoring of soil temperature and moisture, thaw depth, water table depth, and carbon dioxide fluxes. We also measure plant productivity and phenology, soil and plant nutrient status, methane fluxes, and stable and radioactive carbon isotopes in plants and soils.
The Alaska Peatland Experiment (APEX) is located in a moderate rich fen adjacent to the Bonanza Creek Experimental Forest and consists of three water table manipulations (control plot, drought or lowered water table treatment, flooded or raised water table treatment). Two soil warming treatments are replicated within each water table plot. Since 2005, we have measured greenhouse gas, vegetation, and hydrological responses to these hydrologic manipulations. In 2007, we began expanding our experiment into two new sites in the BCEF, including a forested peat plateau underlain by permafrost as well as a collapse scar bog formed after permafrost thaw and thermokarst occurred several decades ago. The APEX project is continuing to expand by testing other large-scale experimental approaches to studying controls on peatland carbon cycling, including rain-out shelters to mimic drought, as well as snow fences and snow removal/addition to alter snowpack dynamics.