NWT RESEARCH DATABASE

Tags: physical sciences, climate change, dendrochronology

Objective(s): To determine the growth and recruitment responses of trees and shrubs to changing climate conditions near the tree line and improve understanding of the drivers of shrub patch expansion on the tundra.

Project Description: The objective is to determine the growth and recruitment responses of trees and shrubs to changing climate conditions near tree line and improve our understanding of the drivers of shrub patch expansion on the tundra. Understanding the drivers of shrub distribution and shrub patch expansion on the tundra: Ten shrub patches were selected for measurement and paired permanent monitoring plots were established at each patch; one plot was centred on the patch of interest, the other on the adjacent tundra controlling for topography. These plots will form the focus of ongoing measurements during the summer of 2016 as follows: - Within-plot replicated measurements of soil moisture and thaw depth will be repeated though the growing season to assess the effect of tall shrubs on active layer conditions. - As previously mentioned, the preliminary analysis suggests that soil moisture may be a key constraint on shrub patch expansion. To directly test this possibility, the research team will quantify shrub growth, water use (measured with sap flow sensors), and water stress in relation to local soil moisture and topographic position within these plots. - To complement vegetation work that was completed last summer, the research team will install leaf litter bags to quantify decomposition rates in the plots described above. These litter bags will be harvested periodically to assess mass loss. This will allow the team to test the hypothesis that decomposition is enhanced within shrub patches thereby acceleration productivity. - The research team will use experimental methods to test the roles of ground cover (moss vs. lichen) and snow depth on shrub seedling establishment and shrub patch expansion. Characterizing the changing treeline: The research team will employ tree ring studies to characterize changes in the tree line between Inuvik and Trail Valley Creek. Along this transect, plots will be established (with plot size varying to account for stem density). All trees and saplings in each plot will be mapped, tagged and measured for height and diameter. Increment cores will be collected close to root crowns (age estimation) and at breast height (growth rate determination) in adults. The age of small individuals will be determined by counting stem internodes and a random subset of small individuals will be harvested for tree ring measurements. Samples will be analyzed using standard dendrochronological methods. Data from the Inuvik weather station will be used to relate forest dynamic data to climate. The research team plan to employ a number of methods for communicating results. Both graduate students involved in the project have expressed a keen desire to be involved in direct communication of results to neighbouring communities and as such the research team will work with the Aurora Research Institute to identify opportunities to achieve this through presentations at schools, or engagement of Aurora College in Inuvik. The ArcticNet funding has resources allocated to a community event at which research results will be communicated. Finally, the team will identify opportunities to communicate the results through different forms of media. An example of this is a contribution to a forthcoming issue of the Tusaayaksat Magazine. The fieldwork for this study will be conducted from June 1, 2016 to September 1, 2016.