Quantifying permafrost dynamics via dendrochronology

Project keywords: 

Tree ring analysis, climate reconstruction, discontinuous permafrost; permafrost degradation, permafrost aggradation, linking climate with permafrost dynamics

Name of project lead: Jennifer Baltzer

Project team/partners: For each collaborator please specify: Team member name, role, organization and contact information
J. Baltzer (WLU; PI), A. Sniderhan (WLU; MSc Student); M. Turetsky (Collaborator; peat core analysis), T. Lakusta (Collaborator)

Status: In progress

Location: Scotty Creek (61°18’N, 121°18’W)

Year and month project started: May 2012

Anticipated completion year of project? 2014

Executive year of project (example, year 1 or 2 or 3…) 2

Brief project description:

Background: Understanding conditions that promote permafrost aggradation or degradation is critical for predicting warming-related changes in boreal forest distribution and function in the zone of discontinuous permafrost where permafrost provides the physical substrate for tree establishment and growth. As permafrost degrades, forests will become more fragmented and reduced in area. At Scotty Creek, rapid permafrost degradation has been documented but corresponding rates of aggradation are unknown and quantification of this important process has not been attempted elsewhere in the zone of discontinuous permafrost. Although it is clear that permafrost is degrading rapidly, detailed temporal patterns of change are not known and historical aerial images provide evidence that degradation processes are not equally affecting all plateaus. Detailed temporal and spatial records of degradation would thus greatly enhance our understanding of these processes and underlying mechanisms. Tree rings provide a long-term record of past conditions in far northern ecosystems and may thus prove to be a valuable tool for assessing permafrost dynamics and forecasting future changes under climate warming. Trees growing in temperate climates form annual growth rings. Tree ring analysis (dendrochronology) is a reliable method for quantifying various geomorphic processes.

Objective: To enhance our understanding of discontinuous permafrost dynamics, we are conducting large-scale dendrochronological sampling paired with peat sampling at the Scotty Creek site.

Methods: Using available high-resolution imagery, plateaus with a variety of characteristics were selected. On each plateau, all trees > 7cm diameter at breast height were cored. Cross sections were taken from all dead stems along each grid transect to ensure an adequate sample for estimating degradation. Samples are being analyzed using standard procedures including ring width measurement using a tree-ring increment measuring system and cross-dating. A master chronology will be developed and related to climate data collected on site and in neighbouring Fort Simpson with a view to hind casting climate at Scotty to relate climatic conditions to permafrost dynamics, quantified by kriged mapping of tree establishment dates across grids (past aggradation), and by dating initiation and duration of tree lean (using reaction wood; ongoing degradation). Small-scale collapse scar dynamics will be examined using a combination of tree ring and peat core analysis.

Significance of the results (rationale): / project linkages

What are the key contributions to science/our knowledge base of northern environments

This work will enhance our understanding of local permafrost dynamics within peatland ecosystems on discontinuous permafrost and the linkages of this with climatic factors. This knowledge will contribute to improved predictive tools for the system.

What are the key contributions to cumulative effects monitoring in the NWT?

Understanding the natural dynamics of permafrost aggradation and degradation in response to climate is a critical first step in enhancing our knowledge of cumulative impacts of direct and indirect anthropogenic influences on permafrost integrity.

What is the relevance to decision-makers?

Establishing relationships linking permafrost dynamics and climatic conditions will facilitate projections of the rates and extents of land cover change in areas underlain by discontinuous permafrost. Have predictive tools for such processes is critical for adaptation planning in light of a rapidly changing climate.

Which decision-makers will likely be impacted by / interested in results?

ENR, community leaders, decision makers responsible for infrastructure development decisions

What is the relevance to communities?

Having knowledge of the range of conditions that will be faced as climate warming progresses is critical for planning purposes within communities. Further, the processes described above are resulting in net forest loss, which will have implications for availability of wildlife.

What are the project milestones? (including beginning date and anticipated end-date)

August 2011: Preliminary sampling to assess utility of method. Preliminary sampling at Scotty validates the use of dead trees: intact cross-sections and cores have been measured from pith to existing bark and support the use of reaction wood for estimating the duration of perturbation prior to death.

August 2012: Extensive tree core sampling at Scotty Creek (A. Sniderhan) September-November 2012: Preparation of cores for analysis
December 2012-July 2013: Analysis and cross-dating of cores, data analysis, paper preparation August 2013: Additional tree coring at Scotty Creek and peat core sampling September-December 2013: Completion of tree and peat core analysis
January– June 2014: Preparation of thesis and associated papers by Sniderhan

On-going dissemination of findings to the NWT and scientific community

Key deliverables and reporting: Link to needs of NWT

1. The proposed work will result in at least 2 peer reviewed publications and presentations at international conferences

2. The proposed research will be reported to the Science Committee and appropriate GNWT agencies in the form of a manuscript/thesis/report

Engagement, training and capacity building

Baltzer or Sniderhan will offer a community workshop/presentation on permafrost dynamics in the area, predicted changes based on climate models and the implications for ecosystem function relevant to communities. This will include a demonstration of the methodology and opportunity to ‘date’ degradation processes on appropriate cores/cookies and associate peat characteristics.

At the Scotty Creek site, we have a good working relationship with a number of communities, meeting regularly with them and keeping them informed and engaged in work at the site. 
-

Project progress.

Links to WSIPlan and NWT Science Agenda

2.1D Develop and implement collaborative ecosystem-based research and monitoring programs. 2- develop collaborative partnerships that can enhance ecosystem-based water stewardship in the NWT.

2.1.I Develop and implement collaborative research and monitoring programs for environmental stressors that can contribute to cumulative effects on NWT watersheds. 3- implement cumulative effects research and monitoring programs.

Key project tasks for next year (work plan pieces – research)

Complete tree coring and peat coring at Scotty Creek

Complete sample preparation and analysis

Present research at international meeting

Preparation of at least one publication for peer review

Key project tasks for next year (work plan pieces – engagement, training and capacity building)

Plain language presentations at community meetings in Fort Simpson, Jean Marie, and/or Trout Lake with demonstration material showing the utility of the tree ring and peat core records for assessing and predicting change

Published Papers