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, sediment, paleontology, wildfire

Principal Investigator: Pisaric, Michael FJ (15)
Licence Number: 15838
Organization: Department of Geography, Brock University
Licenced Year(s): 2017 2016
Issued: Feb 10, 2016
Project Team: Dr. Kevin Turner (Co-Investigator, Brock University), Dr. Katrina Moser (Co-Investigator, Western University), Dr. Steven Kokelj (Co-Investigator, Government of Northwest Territories), Caitlin Garner (Graduate student, Brock University), Dana Harris (Undergraduate student, Brock University), Krista Chin (Co-Investigator, Government of Northwest Territories)

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 team will target small lakes to recover long sediment records spanning most of the Holocene (past 10,000 years). 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 allows us to collect several metres of sediment from lakes with depths varying from a few metres to 10-15 metres. A gas powered ice auger will be used to cut through the ice cover and a spill clean up kit will be carried at all times. The research team will fuel the auger up at the helicopter base in Yellowknife to reduce the possibility of any accidental spills at the field sites. The sediment 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 water samples will be collected to analyze for water chemistry. 10-15 lakes will be sampled. The research team will target lakes that have recently experienced forest fires or those that have burned in the past 50 years or so. These known fire events can be used to confirm the lake sediment charcoal records do in fact capture local wildfire events.

Tree/dendrochronology sampling
The research team will examine 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 research team will not disturb trees that appear to be nesting sites for any birds. The research team will visit approximately 15-30 sites in each river basin.

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 use dendrometers and micro cores for 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 should have no lasting impact on the health of the trees.

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. The research team will target several streams to sample stream benthic macroinvertebrate communities and water chemistry. 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). 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 will be collected 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.

To communicate the research results to the communities, all theses and publications will be submitted to the library at the Aurora Research Institute. Results will also be communicated 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 while in town. Additionally, the team are happy to work with school children or college students to teach them more about this work. The research team will volunteer to visit local schools in Yellowknife and discuss the research on jack pine and climate change around Yellowknife.

The fieldwork for this study will be conducted from May 1, 2016 to September 30, 2016.