NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: biology, plant distribution, caribou, vegetation monitoring, caribou habitat

Objective(s): To map and analyze changes in vegetation productivity and phenology across the range of the Bathurst caribou herd.

Project Description: This licence has been issued for the scientific research application No. 5610. The purpose of this project is to map and analyze changes in vegetation productivity and phenology across the range of the Bathurst caribou herd. The project is rooted in two basic objectives: 1) Map changes in vegetation productivity on an annual basis across the 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. Completion of this objective will allow the team to determine how vegetation productivity and phenology (seasonal timing) have changed across the Bathurst caribou herd’s range over the last two decades. 2) Collect and analyze data on the growth, establishment, and mortality of shrubs over the last two decades by establishing vegetation plots and conducting shrub ring sampling at some of the most significant locations of change identified under Objective 1. Completion of this objective will allow the team to determine the extent to which increases or decreases in woody plant growth and abundance have contributed to greening trends on the Bathurst herd's range. Previous Sampling and Analysis: the research team has completed most aspects related to mapping of vegetation change across the Bathurst range (Objective 1). The team generated maps of change for five metrics over the period 2000-2021. The team’s results show that large portions of the Bathurst range have experienced an increase in plant productivity since 2000 due to progressively longer growing seasons that lead to increased plant growth. However, there is much variability in the patterns of this change, and they do not appear to vary in relation to one particular variable. These results are published in an open access paper and have been reported to governments and communities in the NWT. Field sampling allows the team to relate the observed satellite signal to conditions on the ground and is important for interpreting what the satellite trends represent. Prior to the COVID pandemic, the research team conducted two seasons of fieldwork related to Objective 2. The team measured the composition of vegetation at sites where significant change was detected in the satellite imagery and compared it to sites where no change was detected. The team collected samples at each site to determine the age and growth rate of tall shrubs. Results have just recently been published in an open access paper. In summary, the age of shrubs did not differ between the different sites, indicating that the greening signal is not a result of increased shrub establishment. However, canopy cover and the number of living stems was greater at greening sites, suggesting that differences in leaf growth and survival were responsible. Sampling in 2023 will occur on a different part of the herd’s range to determine if these results are consistent elsewhere. The research team also wishes to collect a new canopy cover measurement which will allow the team to quantify differences more accurately in leaf areas between site types. The team propose the same measurement protocol used in previous years whereby four parallel transects are established at a site, each measuring 100 metres long and separated by a distance of 50 metres. These dimensions allow for measurements to be obtained across a large portion of the area covered by a single MODIS pixel. Plant species are recorded at 10 m intervals along each transect and their heights are measured. In 2023 the research team plans to add a measurement of shrub leaf area index (LAI) at each point obtained with a LiCOR 2000 plant canopy analyzer. This is a nondestructive method of measuring the amount of foliage at a location. In addition to the point inventory and measurements, a 50 x 50 cm quadrat will be placed at the middle and end points of each transect. All species inside the quadrat will be identified and then a photograph of the quadrat be obtained for reference purposes. All aboveground vegetation inside half of 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 each quadrat 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 the satellite signal at the sampling locations will be used to calibrate a map of ecosystem productivity. A sample will be retained from the largest tall shrub stem clipped within each of the 12 quadrats. These will be returned to the team’s lab in Kingston 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. The project is funded by the NWT Cumulative Impact Monitoring Program and the research team has regularly communicated the results to managers and decision makers (GNWT, Tlicho Government, Wek'éezhìi Renewable Resources Board), as well as the general public. The research team will continue this for the duration of the research. To date the team has delivered several public presentations to groups in northern Canada and southern Canada (e.g. Ecology North, CARC, Rotary Club, etc.) and at meetings of government and Indigenous staff and citizens in the NWT (e.g. CIMP results meetings, "Eye on Environment" speaker series, etc.). The team has also produced an outreach video, a briefing note and a website. The team plans to produce a second video and two more briefing notes in the coming year and are planning for a results dissemination trip in December to meet with individuals in Yellowknife and Behchoko. The fieldwork for this study will be conducted from August 3, 2023 to August 31, 2023.