Base de données de recherche des TNO

Régions: North Slave Region

étiquettes: Dendrochronology, climate change, jack pine, tree rings

Objectif(s): The primary objective of this study is to use dendrochronology to analyze jack pine tree-ring records in the Yellowknife region to reconstruct past climate variability and assess the impacts of recent climate change on the boreal forest ecosystem.

Description du projet: This licence has been issued for the scientific research application No. 6168. The primary objective of this study is to use dendrochronology to analyze jack pine tree-ring records in the Yellowknife region to reconstruct past climate variability and assess the impacts of recent climate change on the boreal forest ecosystem. This research aims to extend historical climate records beyond the instrumental period and provide insights into long-term climate trends, variability, and ecosystem responses in the Northwest Territories. Specific Objectives: 1. Reconstruct historical climate conditions: • Develop high-resolution temperature and moisture reconstructions using tree-ring width measurements and quantitative wood anatomy (measurements of cell wall thickness and lumen area). • Identify long-term climate trends and variability in the Yellowknife region over the past 100–200 years. 2. Assess the sensitivity of jack pine growth to climate variables: • Determine the relationship between tree growth, temperature, and precipitation using statistical climate-growth analyses. • Assess the impact of warming temperatures, drought stress, and changing growing seasons on jack pine growth patterns. 3. Examine the impact of recent climate change on the boreal forest: • Identify changes in tree growth trends in response to increasing temperatures and altered moisture regimes. • Detect climate-induced growth suppression or enhancement, particularly in response to recent warming trends. • Provide long-term climate data to supplement short instrumental climate records in the Yellowknife area. This study will utilize dendrochronological methods to analyze ring width and qualitative wood anatomy of jack pine trees in the Yellowknife area to assess climate-growth relationships and the impacts of climate change. The methodology will follow established dendrochronological techniques, including tree core sampling, laboratory processing, tree-ring measurement, climate correlation analysis, and wood anatomical examination. In addition to tree-ring width measurements, this study will incorporate quantitative wood anatomy techniques to analyze lumen area and cell wall thickness to better understand the physiological responses of trees to climate variability. These anatomical parameters will provide additional information about how climate stressors, such as drought, temperature, and moisture availability, influence tree growth and wood structure. 1. Site Selection and Sampling Strategy We have identified several sites along the Ingraham Trail to collect tree core samples from. We will sample mature and old-growth jack pine trees (>80 years old) to develop long tree-ring records to reconstruct past climatic conditions. Trees affected by fire damage, insect outbreaks, or localized human disturbance will be avoided to minimize non-climatic growth influences. At each site we will collect increment cores from 30–50 trees using a Haglöf increment borer with an internal diameter of ~5mm. Two cores will be collected from each tree, taken at breast height (1.3 m above ground) and at perpendicular directions to minimize reaction wood effects. Sample Preparation and Processing Cores will be mounted on grooved wooden holders for stabilization and sanded using progressively finer sandpaper (100–400 grit) to enhance visibility of annual ring boundaries. Cores are cross-dated using visual cross-matching to identify missing or false rings and cross-dating is confirmed using COFECHA software to statistically verify cross-dating accuracy and ensure chronological integrity. Each core is scanned and measurements of tree-ring widths are made using the CooRecoder program (0.001 mm precision). After measuring, we will develop site-specific ring-width chronologies by standardizing raw ring-width measurements using ARSTAN software to remove non-climatic growth trends (e.g., tree aging effects) and create detrended chronologies emphasizing climate-related growth variability. Climate-Growth Correlation Analysis Climate data (temperature, precipitation, and drought indices) will be obtained from Environment and Climate Change Canada (ECCC) weather stations in Yellowknife. Statistical relationships between tree-ring width and climate variables will be assessed using Pearson correlation analysis and response function analysis. To communicate our research results to the nearby communities, we will submit all thesis and publications to the library at the Aurora Research Institute. We will also communicate our results via northern meetings such as the Geoscience Forum and the Cumulative Impacts Monitoring Program Results Workshop. As always, we are happy to give community presentations in any of the local communities while we are in town. Additionally, we would be honored to work with school children or college students to educate them more about our research on jack pine and climate change within the Yellowknife region. We have done similar research sampling previously in Yellowknife, Inuvik, Old Crow and Fort Smith. The fieldwork for this study will be conducted from: July 01 - September 01, 2025