Using the past to inform the future: A paleoecological perspective of the impacts of drought and fire on lakes, permafrost and forests

Regions: Dehcho Region, North Slave Region, South Slave Region

Tags: physical sciences, water quality, climate change, paleolimnology, sediment quality, paleontology, wildfire

Principal Investigator: Pisaric, Michael FJ (18)
Licence Number: 16212
Organization: Department of Geography, Brock University
Licensed Year(s): 2019 2018 2017 2016
Issued: Jan 24, 2018

Objective(s): To examine the frequency and severity of past wildfire and drought (drought-like) conditions in the southern Northwest Territories.

Project Description: The objectives of this research are to examine the frequency and severity of past wildfire and drought (drought-like) conditions in the southern Northwest Territories. Specifically, the research team will examine the following questions: 1) how frequent and severe have fires been in the past; 2) are fires becoming more frequent/severe due to the impacts of climate change; 3) what impact does wildfire have on water quality in streams and small lakes impacted by severe fires in 2014/2015; 4) how frequent and severe has drought or drought-like conditions been in the North Slave region in the past; and, 5) are the recent drought-like conditions experienced in 2014/2015 in the North Slave region anomalous in the context of the past 2-3 centuries or even thousands of years?

Lake sediment/paleolimnology sampling
The lake sediment sampling will occur during the late winter/early spring season and during mid-summer each year. The late winter/early spring field work (late April - early May) will occur while the lakes are still ice covered. The research team will target small lakes to recover long sediment records spanning most of the Holocene (past 10,000 years). The team anticipate these cores to range in length from 1.5 - 3.0 m. Using the ice cover as the coring platform the research team will use a Livingstone piston corer to recover longer sediment profiles from these lakes. The piston coring system allow the team to collect several metres of sediment from lakes with depths varying from a few metres to 10-15 metres. The research team will use a gas powered ice auger to cut through the ice cover and will carry a spill clean up kit at all times. The cores will be examined for their sub-fossil diatom assemblages, charcoal and oxygen and carbon isotopes. Surface sediment cores from the bottom of each lake will also be obtained. A Glew gravity coring system will be used to recover undisturbed sediment profiles from the lake bottom. None of the coring systems used in this study will cause any significant disturbance to the lake bottom sediments. At each lake the research team will also collect water samples to analyze for water chemistry. 10-15 lakes will be sampled. Lakes that have recently experienced forest fires or those that have burned in the past 50 years or so will be targeted. These known fire events can be used to confirm that lake sediment charcoal records do in fact capture local wildfire events.

Tree/dendrochronology sampling
The other aspect of the research activities will focus on the examination of tree growth at several sites in the Snare and Yellowknife river basins. Sites will be visited in the Snare and Yellowknife River systems to develop long tree ring records for these regions. At each site, approximately 30-50 trees will be sampled. A small core (~4.3 mm in diameter) is removed from each tree. If dead snags or old logs are present on the ground, the team will cut a 1-inch thick cookie from these samples. In the case of dead standing snags the team will not disturb trees that appear to be nesting sites for any birds. The research team anticipate visiting approximately 15-30 sites in each river basin during the tenure of this research licence.

Understanding the modern controls on tree growth is critical to accurately interpret tree ring records and climate in the past. To gain a better understanding of the current climatic controls on tree growth, the research team will also use dendrometers and micro cores in the dendrochronological research. Dendrometers are high precision instruments that measure expansion of the tree stem as the tree grows during the summer season. The dendrometer is relatively small and is attached to the tree via two screws. A small rod is held in place against the outside surface of the tree by tension and measurements are recorded every half hour or hour throughout the growing season. As the tree grows and the stem expands, pressure is exerted on the rod touching the tree surface and growth is recorded. The dendrometers will be put on the trees in May of each year and removed in September. They should have no lasting impact on the health of the trees. The research team hope to deploy 8 dendrometers on individual jack pine trees at a site near River Lake, north of Yellowknife.

CABIN protocols
To determine the impacts of wildfires on stream health, the research team will sample assemblages of macroinvertebrate populations living in small streams that were impacted by fires in 2014 and 2015. Stream macroinvertebrates are bugs that live in water, have no backbone and can be seen with the naked eye. Many macroinvertebrates make their homes in the rocks, leaves and sediment found in the stream bed. Some of these insects and non-insects spend their entire lives in water and therefore any changes in the water chemistry of the water can have significant impacts on the survival and health of their populations. in the coming summers, the research team will target several streams (Baker, Boundary, Mosquito Creeks and others along Highway Three within the Mackenzie Bison Sanctuary) to sample stream benthic macroinvertebrate communities and water chemistry. Away from the highways, the team will use helicopter support from Polar Continental Shelf to target stream systems deep within some of the most severe burn areas from 2014. Two types of stream systems will be targeted,: 1) those that were directly impacted by wildfires in summer 2014 and 2015, and 2) control systems that have not experienced recent wildfire activity. The research team will follow standard CABIN protocols for sampling macroinvertebrate communities. At each stream crossing, kick-net samples will be collected from representative stream habitats along a predetermined stream reach following the protocols of the Canadian Aquatic Biomonitoring Network (CABIN). Samples will then be screened to remove large pieces of organic material and to separate macroinvertebrates. Macroinvertebrates will be preserved and then identified using various identification books and materials supplied by the CABIN. A number of species diversity indices will be calculated to enable comparisons between impacted and non-impacted stream systems.

Water samples to examine changes in water chemistry between impacted and non-impacted stream systems, including measurements of nutrients, metals, conductivity and DOC (dissolved organic carbon). A YSI multiparameter sonde will be taken into the field to measure stream pH, salinity, DO (dissolved oxygen) and temperature. Water chemistry data will be analysed using multivariate statistics.

To communicate the research results to the nearby communities, the research team will submit all theses and publications to the library at the Aurora Research Institute. The team will also communicate results via northern meetings such as the Geoscience Forum and the Cumulative Impacts Monitoring Program Results Workshop. As always, the research team are happy to give community presentations in any of the local communities. Additionally, the team are happy to work with school children or college students to teach them more about the work.

The fieldwork for this study will be conducted from April 15, 2018 to November 1, 2018.