Elephant Hills Case Study
CLIENT
Province of BC
SERVICES
Full-phase Silviculture
In 2017, the Elephant Hills Wildfire near Ashcroft, British Columbia grew to an incredible 192,000 hectares over the course of 75 days Burning from early July to late September.
Compare this to the previous significant wildfire seasons in 2003 of the McLure fire near Barriere, and the Okanagan Mountain Park fire near Kelowna which were both 26,000 hectares. Since the Elephant Hills Fire, the significant 2021 wildfire season saw the most significant fires of note: Lytton Creek or White Rock Lake fires of 83,000 hectares or Sparks Lake of 96,000 hectares.
PRE-FIRE CONDITIONS
2017 was an interesting year as this was one of the wettest springs on record. This seems to be counter-intuitive that the largest fire in the history of the Thompson Okanagan Natural Resource Region would start following one of the wettest springs. The snowpacks were so great that when they did melt there was a great deal of road washouts downslope to the point where communities throughout the Thompson Okanagan region were endangered, roads blown out and bridges washed away.
Silviculturists expect rains in late May and early June as well as cooler weather. In most years, this weather event can be counted on and is described as June-uary. This mid spring rain event did not happen in 2017. Soil moisture levels continued to drop throughout May, June, August and into September without any significant rain events.
The extremely wet spring caused the native grass species to grow extremely tall and create a significant fuel hazard. This fire started in the grasslands and grew much larger in the dry interior Douglas-fir forests. This is how the wettest spring in recent memories helped create conditions for the largest fire year on record.
PROACTIVE PLANNING
Forsite was asked by the Province of BC to manage the silviculture activities for this fire using Forest Carbon Initiative funding. Communications were coordinated by the Thompson Rivers Natural Resources Region between all stakeholders in the area. All activities from helicopter recces, surveys, planting prescriptions, planting planning, tendering contracts to tree planters, implementing planting programs and following up with survival surveys were covered by the provincial funding.
Forsite has a long history of silviculture surveying in and adjacent to the affected area of the Elephant Hills fire. Chris Durnin, RPF is the main survey forester for West Fraser, Ainsworth Lumber, BCTS, and the Ministry of Forests all operating within the fire area. Her intimate knowledge of the landbase was crucial to decision making during and after the fire.
Chris Durnin (Silviculture Specialist – Surveys) and Colin Hegan (Silviculture Specialist – Planting) conceived and created the Natural Regeneration Matrix that prioritized stands for survey and planting post fire. This Natural Regeneration Matrix was adopted into the province’s direction for Guidance: Post-Wildfire Recce/Survey Report Summary and Treatment Prescription.
This tool triaged different types of stand and ecologies in an attempt to determine which stands would reforest naturally and which stands would remain free of young conifers.
Within the first year after the 2017 fire Forsite’s team noticed a significant difference between the responses of competing vegetation, particularly pinegrass. In the first years after the fire, focus was on surveying and reforesting the sites with the greatest fire mortality. Today, we are still surveying and learning about sites with lower fire intensities.
OLDER STAND RECOVERY
Older stands, including those stands that had a large volume of mature trees prior to the fire, had an obviously delayed response of competing vegetation. These are forests and plantations that had high fire intensity (number of trees that were killed) as well as high burn severity (how deeply into the soil the fire burned).
Pinegrass regrowth in these stands appeared very weak and scattered. This pinegrass appeared to be growing from wind scattered seed. The roots of the pinegrass appeared to have been fully killed off because the fire burnt deep into the ground, killing the roots of the pinegrass. Because of the intense burn severity on these stands, there is an extended time window to reforest these stands by underplanting them without mechanical site preparation. We are also able to significantly increase the percentage of Douglas-fir in these planting treatments.
The success of Douglas-fir survival in the 2019 and 2020 planting years has been excellent – averaging 90% survival.
YOUNGER STAND RECOVERY
Younger plantations that burnt had an immediate pinegrass response that would compete with planted trees, particularly putting Douglas-fir seedlings at risk. These are plantations that had high fire intensity (number of trees that were killed) but low burn severity (how deeply into the soil the fire burned).
The pinegrass response immediately after the fire appeared to be a regrowth of the plants that were there prior to the fire. The fire appeared to have increase the virility of this pinegrass. These stands did not burn very hot because the fuel load on these sites was not high.
We are paying very close attention to the vegetation competition on these sites. Some of these sites will need to have mechanical site preparation such as disc trenching, excavator screefing or ripper plow treatments. These mechanical site preparation treatments will be essential to seedling survival where the vegetation response has been extreme.
REPLANTING
The success of underplanting into severely burnt stands matches up with the findings of the 2019 report “Reforesting Dry Sites in the Thompson Okanagan Natural Resource Region”. An obvious trend on extremely dry and very dry sites was that the success of planting treatments relied primarily on the intensity of disturbance as well as the presence of shade (amongst a host of other lesser factors).
The 2017 drought event had significant mortality in the Thompson Okanagan Region. In this drought year, trees planted into very aggressive soil disturbances, such as burn piles and road rehabilitation, survived. Trees planted into mechanical site preparation treated areas survived only where the disturbance was greatest. Raw planting or weaker site preparation treatments had significant mortality.
These findings matched up with our observations in the Elephant Hills fire. The planting treatments that did the best were stands that had a combination of high burn severity (fire burnt deeply into the roots), as well as retained dead conifers that provided shade to the planted trees. This combination protected the young seedlings from competing pinegrass as well as the scalding sun.
Reforesting Dry Sites in the Thompson Okanagan Natural Resource Region. Colin Hegan- Forsite.
WHAT’S NEXT
Lessons learned from the 2017 Elephant Hill and other wildfires in the area are educating decisions being made for the recovery of the severe 2021 wildfire season. Silviculture Specialists like Forsite’s Chris Durin, RPF and Colin Hegan, RPF continue their work to develop drought resistant stands and procedures to reforest dry sites. Colin completed a review on the underplanting in the previous 15 years that helps the decision making process’ for the entire province’s reforestation efforts.
Forsite fire behaviour specialists believe that the fire hazard is low in previously burnt stands which poses low risk to the planted trees. Planting quality trees in strategic locations to offer the best chances of survival before the overstory collapses, will continue to create safe environments for planters while providing the lowest tree mortality possible.
We will continue to learn as fire seasons progress and tools are developed for recovering land bases post wildfire.
