NWT RESEARCH DATABASE

Tags: physical sciences, vegetation, climate change, caribou, cumulative effects, remote sensing, habitat

Objective(s): To map changes in vegetation productivity on an annual basis across the Bathurst caribou herd’s range using satellite imagery obtained from NASA’s MODIS sensor (available since 2000) and analyze these data to identify where the most significant changes have occurred.

Project Description: The two main objectives are: to map changes in vegetation productivity on an annual basis across the Bathurst caribou herd’s range using satellite imagery obtained from NASA’s MODIS sensor (available since 2000) and analyze these data to identify where the most significant changes have occurred; and to collect and analyze data on the growth, establishment, and mortality of shrubs and trees over the last two decades by establishing vegetation plots and conducting tree and shrub ring sampling at some of the most significant locations of change identified under objective 1. Satellite image ground-truthing will allow the team to relate the observed satellite signal to conditions on the ground. The collected data is important for interpreting what the satellite trends in vegetation productivity actually represent. The research team propose establishing two parallel transects at each site, each measuring 100 metres long and separated by a distance of 50 metres. These dimensions will allow for measurements to be obtained across a large portion of the area covered by a single MODIS pixel. Plant species will be recorded at 5m intervals along each transect and their heights will be measured. A 0.25 m2 quadrat will be placed at 25 m intervals along each transect. All species inside the quadrat will be identified and then a photograph of each plot will be obtained from a standard height (1.5 m) for reference purposes. All aboveground vegetation inside the quadrat will then be clipped and weighed to obtain a measurement of fresh biomass in three functional groupings: nonvascular (lichens and mosses), woody plants, and herbaceous plants. The totals from all quadrats will be averaged to yield a mean value that will later be compared to satellite imagery obtained on approximately the same date as sampling. The relationship between plant biomass and satellite measurements at the sampling locations will be used to model ecosystem productivity across the herd's range. The research team will undertake sampling of shrubs at the 20 sites chosen for image ground-truthing. Shrubs will be sampled for the purpose of counting and measuring annual growth rings under a microscope. Counting of rings will provide an indication of shrub age, and measurement of rings will provide an indication of the plant’s growth during its lifetime. These two pieces of information are important for assessing the nature of ecosystem change at sampling locations over the past several decades. If the majority of shrubs are young and there are few dead individuals on the landscape, then there is good evidence that these areas have been colonized by shrubs only recently. In a similar manner, if ring widths have increased in recent years then there is evidence that the growth of these shrubs is increasing. One or both of these could be the mechanism responsible for the observed changes in productivity indicated in the satellite signal. Shrubs will be sampled along the transects established for image ground-truthing with the aim of sampling 30 individuals at each site. For each shrub, a count of the number of living and dead stems will first be made and measurements of heights and diameters will be obtained. Pruning shears will then be used to obtain a cross-section from 3 living stems both at ground level and at 20 cm above ground level. Finally, the root crown of the shrub will be dug up using a shovel so that a single cross section can be obtained from the progenerate or ‘parent’ stem. The research team would welcome local participation in helping to ground-truth the satellite imagery. This would be as straightforward as having individuals collect several photographs of vegetation at any given site in the herd’s range and obtaining a corresponding GPS point. These two pieces of data could be submitted to the research team for cross-reference with the satellite imagery and would be very useful in helping determine what types of vegetation have experienced the most or least amount of change. If there was interest the team would be eager to work with various communities or individuals to develop a protocol that individuals could follow for collecting and submitting this information. In February of this year, the researcher travelled to Yellowknife to present results of the initial satellite image analysis to staff of the Territorial Government (ENR), the Tlicho Government, and the Wek’èezhìi Renewable Resources Board. Staff of the Yellowknives Dene First Nation (Land & Environment) were not available to meet in person but an interim report was sent to them for review. The team plan to repeat this outreach and communications trip again later this year and will be presenting at the Cumulative Impacts Monitoring Program (CIMP) territorial results meeting. The research team also hope to be able to meet with these groups when in the Territory this summer. Interim reports as well as a final report are required components of our CIMP project. These will continue to be distributed to GNWT and First Nations Governments as they are completed. The teams are also currently building a website which will be online soon. It will provide regular updates on project results. The team will also be developing a brochure and poster to send to communities and the GNWT for spring 2019 that will highlight our results to date. A second poster will be distributed in spring 2020. The fieldwork for this study will be conducted from July 15, 2018 to August 24, 2018.