Greening of the Boreal Forest

Regions: Dehcho Region, North Slave Region, South Slave Region

Tags: climatology, forestry, climate, vegetation growth, moisture

Principal Investigator: Bunn, Andy G (1)
Licence Number: 14532
Organization: Western Washington University
Licensed Year(s): 2009
Issued: Jun 08, 2009
Project Team: Andrea Lloyd (CO-I, Middlebury College), Logan Berner (Research Associate, Western Washington Univ), Chris Robertson (Research Assistant, Western Washington Univ)

Objective(s): The goal of this research is to understand the effects of temperature and moisture variability on growth of forest vegetation in the southern Arctic, and to use the relationship between temperature/moisture and tree growth to construct a model of patterns of greening and browning in the forest and forest-tundra regions in the southern Arctic.

Project Description: This licence is being issued for the scientific research application No.1089.

The overarching goal of this research is to understand the effects of temperature and moisture variability on growth of forest vegetation in the southern Arctic, and to use the relationship between temperature/moisture and tree growth to construct a model of patterns of greening and browning in the forest and forest-tundra regions in the southern Arctic. The researchers will test three hypotheses: 1. Trends in satellite growth are consistent with those of tree growth: browning (negative response) prevail in regions exhibiting threshold temperature responses and declining tree growth over the last 2 decades; 2.Non-linear or threshold responses of tree growth to temperature result from temperature-induced drought stress and are thus:
a. more common in regions of the boreal forest that experience frequent summer drought and/or in which precipitation has declined over the last several decades and b. more common in drought-sensitive species (white and black spruce) than drought-tolerant species (aspen);
3. the magnitude and direction of future changes carbon cycling of vegetation in the southern Arctic will be dependent on both temperature and precipitation, with precipitation acting as a major limit on temperature-induced increases in growth.

The field work that comprises this application deals with the first two research objectives described above and is part of a large, global effort to characterize tree growth in the high latitudes through the compilation of a large circumboreal database of tree-ring chronologies (timelines) using existing and new data. The database will have all available tree-ring chronologies that extend from at least 1900 representing the major tree species that occur in the Arctic and all major boreal geographic regions (eastern and western North America, Russia, Fennoscandia). Existing data will be accessed from the International Tree-Ring Data Bank (ITRDB), hosted by NOAA’s World Center for Paleoclimatology.

At each of six sites, the researchers will obtain increment cores from a minimum of 20 living trees. Increment cores (5.15 mm diameter) will be taken close to ground level above the root collar and placed in paper straws for transport back to the laboratory. An increment core is a narrow cross section of the tree extracted by a hollow drill bit and allows the researcher to determine the tree age and growth pattern in the annual rings. Taking a core from a tree does not harm them. The diameter of each tree will be measured and other observational data will be recorded (e.g., evidence of insects, cone production, canopy density, etc.). Cores will be processed, measured, and crossdated using standard dendrochronological (study of trees) procedures methods, to correct for missing rings.

Researchers will also use raw ring-widths to construct a ring-width chronology (a time series representing average tree growth) for each site. All tree-ring data will be made publicly available as this work progresses.

The researchers will make the data and publications from this project available to individuals and communities in the NWT. If there is interest, they will be happy to discuss our research this summer via community meeting either before or after sampling. Upon completion of the project, they will be developing educational materials using these data to use in classrooms. These materials (e.g., lessons, assignments, data sets) will be made available to communities in the NWT.

The fieldwork for this study will be conducted in areas on a 200 km radius around Great Slave Lake, from July 1 to 31, 2009. A detailed map is available by contacting the researcher, or the Aurora Research Institute.