Fall Followup Observations on Increasing the Wildfire Resilience of our Regen Stands

I worked on a wildfire this summer then spent the fall doing layout for salvage harvest and assisting with the fire rehab. It gave me a chance to revisit the area mentioned in my Aug. 4 post (link below) and add to my observations on improving the wildfire resilience of our regenerated stands.

Don’t Neglect the Value of Crown Closure to Improve Wildfire Resilience and Wood Quality

We are planting trees to produce a marketable product at some point in the future. We rely on selling logs to pay for all the other management objectives in our plans. The planted trees represent a substantial initial cost to the Licensee and potential future income to the taxpayers. Losing a plantation to fire is a major set back, especially to small area based tenures such as Woodlots and Community Forests. Almost inevitably the taxpayer will be out of pocket.

The Fire

This fire occurred predominantly in the MSdm2. The main drainage that burned was a North running valley with steep side slopes that varied from 0 to 70%. The drainage had experienced substantial harvesting since the 1970’s with plantations being predominantly Pl and  ranging from 1 year old to 50+ years. The site was productive. The  50 year old planted trees had reached merchantable size with a volume of 175 to 200 m3 per ha. I may have planted some of these trees.

A wide riparian reserve ran the length of the drainage containing an extremely heavy fuel load of large diameter standing (200sph) and down dead Sx and Bl. There were substantial reserves in the valley due to adjacency standards and inoperable ground.

Here are my additional fall observations:

1. Reducing the surface fuels is the key to protecting our regen.

This isn’t new but how much we have to remove may surprise folks especially to protect the regen in the first 5 to 10 years. It is very susceptible to mortality with even a smoldering ground fire.

When I started my tree-planting career in the 70’s every block we planted had been burned. Sometimes they were still burning.

We lost broadcast burning as a tool about 30 years ago. So it appears that any regen stands older than 30 years, that were burned prior to planting, have a far higher chance of survival with minimal damage. Stands younger than 30 years old are far more susceptible to fire damage.

Other methods (excavator rake, pile and burn) of post-harvest fuel reduction appear to be almost as successful at reducing losses. See previous blog below.

Post Harvest Fuel Reduction as a Silviculture Tool

Stumpage will need to be adjusted to reflect the added costs of all these treatments.

2. Adjacent fuels loads affect regen survival. Riparian reseves and wildlife tree patches increase the fire intensity and appear to contribute to damage to adjacent stands of regen. As the flavor of the day moves to higher retention in harvest areas foresters should consider the possble effects of the elevated fuels loads on future fire behavior and related damage to the young planted trees.

A very wide riparian reserve ran the length of the main drainage and numerous retained and reserved areas had been established.

Pictured is typical fuel load in the reserved and retained areas before the fire. Over mature Sx Bl – 200 sph standing dead with heavy load of deadfall.

Note the severe damage to regen adjacent to WTP in the background and decreasing damage further away.

The intense Rank 5 fire in the WTP and associated convective column are the culprit.

The convective column can carry heat far greater distances than previously thought (up to 2.5 km) Google new US Forest Service Safe Zone guidelines.

On this fire it appears that the heavy fuel load in the riparian reserves and leave patches created, or at least contributed to, the fire storm (Rank 5/6) that consumed everything in the drainage.

3. Site prep (trenching, mounding) doesn’t appear to reduce fire behavior or associated damage noticeably.

4. Crown closure appeared to reduce damage from wildfire. Stands with closed crowns have higher RH, lower temperature and reduced wind speed than adjacent openings. Crown closure limits sunlight available for ingress of grass and brush under the canopy and initiates self-pruning.  (Limiting surface and ladder fuels). There is a trend for lower stocking standards in fuel modification projects. This needs more research. Increased planting density may actually be a better choice for wildfire resilience and wood quality.

+/- 10 year old stand before. Wide spacing, branches to the ground, lots of sun for grass and brush. Surface fuels heat up substantially.

Reduced chance of survival in a wider range of weather conditions

Extreme early crown closure in fire origin Pl. Generally these stands are naturally able to survive all but the most extreme fire behavior. We lost some of these in the Heat Dome as they basically were tall grass.

Note: This picture is from another fire and used as an example only. An approching fire did slow and drop in intensity when it hit this stand.

I couldn’t come to any definitive conclusion on how the age that the crown closure occurs affects survival. It appears that resiliency improves if crowns close in the 5-to-10-year range. This is rough field observations and is an opportunity for detailed research.

50 year old stand with crown closure. Cooler, moister, calmer. Adjacent fire in reserves was Rank 5 but dropped to Rank 2 when it hit this stand.

5. Some BCWS supervisors may not be aware of the potential costs associated with the loss of regen. Licensee’s should make sure BCWS supervisors and planners are fully aware of these costs and push for agressive action when priorities allow or be prepared to take action on their own.

Regen blocks (mid-frame) still burning a month after the fire was “under control”. These hot spots were well inside the fire perimeter and posed little threat of escape. Logically, and as per BC Emergency Management System priorities,  crews were sent to other higher priority incidents.

Licensee may have to be prepared to take action on their own to protect assets.

Initial stages of the blowup that nuked the drainage pictured above.

Order some more seedlings.

6. During intense fire activity we are going to incur losses. Minimizing the damage may be the only option.

These are rough field observations and may not apply to other sites but I think we have opportunities to better protect our investments and future forests.

Doug