Post Harvest Fuel Reduction as a Silviculture Tool

Introduction

It is great to see so much work and interest in Landscape Level Fuel Management especially regarding post harvest fuel loads. The “boutique” small scale fuel modification that has been done adjacent to communities and other high value assets is very beneficial however, it is too costly to do large scale projects in this manner.

I am worried that reliance on government grants will not allow this critical work to be sustainable if/when political priorities change. Cost efficiencies have to be found to encourage land managers to undertake post harvest fuel reduction on a continuous, long term basis as part of their regular responsibilities.  

Licensee’s have a variety of methods of assessing and dealing with post harvest fuels with variable results.

Treeplanter view of post harvest fuel loads

I am not a scientist or forest professional but have worked in forestry for 47 years. I am sure most silviculture foresters are aware of the information below but I thought I would share for those not in the business of growing trees.

The post harvest treatment portion of a large fuel reduction project in my area produced many benefits. The work decreased silviculture costs, increased the value and volume of the next stand of timber growing on the site , protected that regenerating stand from fire for a considerable time all while meeting the main objective of protecting adjacent values.

Background

In 1967 my family helped develop a recreational business and community in the southern interior of BC. I have worked and played in the area consistently since then. The area is surrounded by a 2500 ha Recreational Reserve that, other than the exclusion of fire, has progressed through the successional process with minimal human influence. I have watched this forest progress from post fire young regen to mature timber for almost 60 years.

After being involved in the 2017 wildfire response I recognized how invaluable Firesmart and fuel modification were in protecting communities and other high value assets.  I presented the idea of constructing a fuel break to the Community Association and the business owner and they bought in with only minimal reservations. They also initiated the process of becoming a Firesmart Community.

The Community Association worked with FESBC, the business owner, various Ministries and local First Nations. They hired a Professional to do the assessments and develop a prescription and operational plan and started work in 2018.

Site Description

The area of the fuel break is a typical high elevation southern interior forest. The project is a 400m. wide by 2.5 km long U-shaped block directly below the village on Crown land and immediately abutting private property. It is located between 1600m. and 1800m. elevation in the ESSF dc2 and MSdm1. Slope range is 0 to 45% with generally southerly aspects ranging from east to west. Soil and moisture range from shallow, dry rocky outcrops through to rich, wet moisture receiving areas. The majority of the project area had rich, moist soils and a duff layer that averaged 10 cm thick. The area is a fire prone landscape with regular periods of prolonged hot, dry windy weather.

History, Timber Type and Fuel Load

The area where the recreational business and community are located burned in the 1930’s in a large wildfire.

Area of project in 1967. +/- 30 years since the fire

Timber types ranged from small diameter dense Pl on the dry rocky sites to large diameter Sx and Bl on the wet sites. The majority of the work area consisted of 60 to 80 year old Pl with a diameter of 20 cm and a height of 20 m. Due to being high density fire origin there were very few lower branches, small knots, little taper and only 20% live crown. Density ranged from 600 to 1500 stems per ha with volumes ranging from 250 m3/ha to 425 m3/ha.

Example of Timber in the project areas.

Mod to heavy surface fuel load due to self- spacing in Pl stand.

Note the high quality timber (few branches, tight grain, little taper, <20% live crown) due to being a high density fire origin stand.

Almost all lumber milled from this project graded as MSR = the highest value product suited for engineered wood products.

The Work

The area was harvested in 2018. Post harvest fuel reduction took place in 2019. Chipping and hauling were investigated but access difficulties and time constraints made piling and burning the best choice. Broadcast burning was ruled out due to the proximity to the community and large number of leave trees and leave patches. Local residents also preferred piling and burning.

A combination of excavators with a rake or clam attachment and a D7 with brush blade were utilized. Cost was $800 per ha. and production was +/- 2 ha/day. On suitable ground the dozer pushed the slash to the hoe which built beehive piles. This minimized site disturbance by reducing the amount the dozer had to turn and created clean piles that would ignite easily and burn cleanly and completely. Where the ground exceeded the dozer slope limits the hoe raked and piled. Approximately 3 to 4 piles per ha. were created. Two people burned the piles in two days in the fall.

We used the US Forest Service Photoload Sampling Technique for estimating pre and post raking fuel loads.

Conventional Roadside Harvest activities.

Post- harvest fuel load +/- 250-350 tonnes/ha.

Post treatment rake and pile +/- 5 to 10 tonnes/ha

Followup

I have walked the work area at least once per year since the work was completed. In 2020 I observed 10, 000 to 100,000 Pl, Lw and some Sx/Bl germinates coming in. The regen is fairly evenly distributed around the site even in the deeper duff areas. In 2021, as the area is on Crown Land with stocking obligations the Licensee did plant about 150 sph of Larch and Pine to ensure minimum stocking standards were met.

Pl and Lw germinates 2020

Pl germs 2020

2023 natural regeneration

2023 natural regeneration (taller Lw are the planted stock)

Conclusions

In 2021 a large wildfire got to within 400 meters of the resort. A fire behavior specialist viewed the treated area with the intent of improving it to protect the community. He decided it would be an effective control line as is with no more work required.

The post harvest fuel reduction by raking and piling exposed mineral soil and distributed cones. The resulting high volume of germination eliminated the need for tree planting. The planting that was conducted helped raise the number of Lw regen but wasn’t necessary to reach regular stocking standards.

For $800 per ha it was possible to protect the next stand of trees and other adjacent values. For that $800 investment it was also possible to eliminate planting costs. The resulting high density naturally regenerated stand will produce a high volume of very high quality logs that mimic those from fire origin stands. On blocks with better access it may be possible to market the piles for chips or hog fuel instead of burning. With commercial thinning this site may produce logs in 60 years.

Fire origin high density Pl stand – producing very high volumes and high quality logs. Little taper, tight grain, no or small knots, < 20% live crown

Pl planted at low density – short and tapered, live crown to ground, long branches and large knots, producing very low quality logs and lumber

Most silviculture foresters already have the decision making skills in their tool box regarding dragging, mounding or trenching. Fuel reduction by raking and transporting or burning may be another option that makes the fuel reduction more economical.

In order to re-introduce widespread use of this treatment there will likely have to be some stumpage adjustments and possibly some adjustments to the regen delay requirements.

Let me know what you think and if you ever want a look at the project or want some more info.

Talk soon.

Doug