About Bonanza Creek LTER

The Bonanza Creek Long-Term Ecological Research program (BNZ LTER) is located in the boreal forest of interior Alaska, USA. BNZ LTER was established as part of the National Science Foundation's Long Term Ecological Research Network in 1987. The program is jointly managed by the University of Alaska Fairbanks and the Boreal Ecology Cooperative Research Unit, the northernmost outpost of the USDA Forest Service Pacific Northwest Research Station. BNZ LTER research is concentrated in two sites near Fairbanks, Alaska: the Bonanza Creek Experimental Forest and the Caribou Poker Creeks Research Watershed.

The Boreal Forest of Interior Alaska

The boreal forest is the second most extensive biome on Earth, covering 17 million km2 of the Northern Hemisphere, and accounting for approximately one third of Earth's total forest area. Globally, the northern and southern boundaries of the boreal forest are associated with the Arctic air mass, which extends southerly in wintertime to define the southern most extent of the boreal forest, and shrinks northward during summer to delineate the boundary between boreal forest and tundra.

In Alaska, boreal forest occupies some 60-70% of the land area, with tundra and coastal coniferous forest making up the remainder. Approximately 32%, or 42.8 million ha, of the total 137 million ha that make up the interior Alaska boreal ecoregion is forested, of which >60% is dominated by black spruce (Picea mariana). The remainder is complex mosaic of grasslands, shrublands, bog and fen meadows, shrub and sedge tundra, and open water, with rock outcrops, snow and ice at high elevations.

Climate is ultimately the factor that differentiates the boreal forest from other biomes. Within interior Alaska, climate is a consequence of the northerly latitude of the region and the presence of the Alaska and Brooks Ranges, which block maritime and polar influences, yielding a dry continental climate with cold winters and warm summers.

The cold climate slows most soil-forming and biogeochemical processes and leads to the formation of permafrost, soil which remains frozen year round. The interior Alaskan boreal forest is underlain by discontinuous permafrost, which serves as a barrier to roots and water percolation, promoting anaerobic conditions.

The potential biota of the boreal forest is also limited by the constraints of climate. The vegetation and animals that dominate here are well adapted to the harsh environment. The mosaic of vegetation found within the boreal forest results from variation in environmental conditions and from past disturbances, such as fire, insect and pathogen outbreaks, and flooding.

Changing Climate and Disturbance Regimes

The boreal forest is also a land undergoing rapid environmental change. During the last third of the twentieth century, many areas of the boreal forest have warmed more rapidly than any other region on Earth. This pattern is consistent with projections of general circulation models, which predict that human-induced increases in greenhouse gases will cause the global climate to warm, with warming occurring most rapidly at high latitudes.

The ecological characteristics of the boreal forest render it vulnerable to the direct and indirect effects warming and other global changes. Organisms and properties of the boreal forest are sensitive to changes in climate, permafrost, and fire regime, so climatically-induced changes are likely to propagate through most ecological processes.

Changes in the boreal forest will certainly affect its human residents through modifications to the biota, permafrost distribution, soil stability, hydrologic regime, forest productivity, fire regime, insect outbreaks, and many ecosystem goods and services. These changes could in turn influence non-boreal residents through positive and negative feedbacks to Earth's climate system.

• see Summary of Findings from Prior Research

Research Overview

The Bonanza Creek Long-Term Ecological Research program (BNZ LTER) focuses on improving our understanding of the long-term consequences of changing climate and disturbance regimes in the Alaskan boreal forest. The central question of our research is: How are boreal ecosystems responding, both gradually and abruptly, to climate warming, and what new landscape patterns are emerging? Our overall objective is to identify factors that buffer systems from radical changes in structure and functioning (resilience) vs. factors that might precipitate changes to alternative states (vulnerability). This requires an extension beyond the assumptions of steady state dynamics to ask under what conditions changes in drivers might trigger a fundamental change in the nature of boreal ecosystems.

Resilience theory provides a logical basis for organizing our research on the dynamics of change into four sections:

(1) Climate sensitivity of physical and biological processes to temporal variation in the environment, which defines the limits of resilience to climate change;

(2) Changes in the successional dynamics caused by changes in climate and disturbance regime, which define the points in the adaptive cycle of disturbance and recovery at which ecosystems are most vulnerable to change;

(3) Threshold changes that are likely to cause the boreal forest to function in a qualitatively new way, and;

(4) Integration and synthesis in which we integrate these modes of climate response across multiple temporal and spatial scales and explore their societal consequences. 

Study Design

Our study design recognizes three landscape units that differ in their environmental controls and likely response to climatic change:

• Uplands
• Floodplains
• Wetlands

The uplands and floodplains have been the focus of previous BNZ LTER research while wetlands, which are widespread in the boreal region, have not been intensively studied in Alaska. Alaska contains more than half the wetlands in the U.S., but the response of permafrost to complex interactions among topography, surface and ground water, soil properties, vegetation, and precipitation is changing the distribution and functioning of boreal wetlands and tundra.

Our research is concentrated at two intensive study areas that contain representative sites of each landscape unit:

• At Bonanza Creek Experimental Forest (BCEF), we maintain permanent plots in primary floodplain succession and secondary post-fire succession (3-5 successional stages x 3 replicate sites/stage). BCEF also includes a forest-wetland gradient study where we are experimentally manipulating water-table height and summer air temperature.
• At the Caribou-Poker Creek Research Watersheds (CPCRW), we maintain four intensive watersheds, two of which are unmanipulated (low vs. high % permafrost) and two of which have burned recently (a low-severity experimental burn in 1999 and a high-severity natural wildfire in 2004).

For selected variables, we extend observations from intensive studies at BCEF and CPCRW to the Tanana Valley, the watershed in which our intensive sites are situated and which drains the northern flanks of the Alaska Range. The Tanana Valley contains both pristine glacial and non-glacial watersheds and the major areas of agricultural and forestry development in interior Alaska, providing opportunities to examine social-ecological interactions. Where available, we maintain databases of climatic and ecological variables for all of interior Alaska as a basis for modeling and synthesis. Our research design thus gives us a hierarchical study design from plots/watersheds to all of interior Alaska.

Long-Term Monitoring

The BNZ research program has two intensive research sites: The Bonanza Creek Experimental Forest (BCEF) is within the Tanana Valley State Forest and is managed by the Boreal Ecology Research Unit (i.e., the FS component of the LTER) through a renewable 50- year lease to the US Forest Service (renewable in 2018). The Caribou-Poker Creek Research Watersheds (CPCRW) includes lands under the jurisdiction of the University of Alaska and the Alaska Department of Natural Resources. The BNZ LTER manages BCEF and CPCRW, with the Interagency Hydrology Committee, which represents agency interests in Alaskan hydrology, acting as an external advisory committee. We have close working relationships with both the Tanana State Forest and the Alaska Division of Natural Resources. The Alaska Legislature recently passed legislation to transfer the BCEF and CPCRW from the State of Alaska to the University of Alaska to be managed by the BNZ LTER, enhancing the long-term site security. The BNZ site manager (Jamie Hollingsworth) is responsible for managing LTER research in the two research sites, including permitting, transportation, and the planning and implementation of the core research program. Recent improvements in site management include automation and wireless radio communication with climate and microclimate stations, improved coordination of field work, improved boat communication and safety, and improved methods and assessment of statistical power and required sample sizes for long-term vegetation measurements. These efforts have substantially improved the quality, continuity, efficiency, and safety of data collection, releasing time to undertake new activities.

Our core research includes monitoring of climate, hydrology, vegetation, and other essential long-term site measurements:

Parameters measured by BNZ LTER monitoring program:

                  *Jamie Hollingsworth (site manager) is responsible for the BNZ LTER climate monitoring program

                  †Monitoring network includes sites throughout interior Alaska