Stepping inside the Valley Fire burn zone: Our Boggs Mountain field trip

A Pepperwood Fire Mitigation and Forest Health Initiative update.

By Lisa Micheli, PhD, President & CEO

Team Pepperwood at Boggs Mountain rocking the hard hats:
Michael Gillogly, Lisa Micheli, and Sophia Porter 

When Michael and Sophia and I finally reached the severe burn zone, it was kind of like stepping in to the cartoon world of Tim Burton’s Nightmare Before Christmas, with slender ebony black branchless trunks clawing at the sky.  The foresters tried to break us in easy on this Boggs State Research Forest tour, including Nick Kent of CalFire and Fred Euphrat who is an instructor at Santa Rosa Jr. College and currently advising Pepperwood on our forest management planning process. 

We met at the Boggs Mountain CalFire forest station, which had been an island of firefighting activity during the onset of the Valley Fire less than two months ago, before the guys who worked there put up their “white flags” and had to get helicoptered out.  The station itself survived and was in a zone of relatively low burn severity. While some of the trees showed sign of char from the flames, the ground itself was covered with recently dropped pine needles which draped a soft looking sepia carpet over whatever scorched soils lay beneath.  

Field map of burn zone, fire severity, Boggs boundary,
and remaining live trees.

At the station they showed us a map of the burn zone marked in pink to dark reds, with the darker the red showing increasingly greater burn intensity.  Green dots showed the survivors, living trees the foresters hoped would provide some of the seed needed for forest regeneration.  But right now the urgency is on identifying the dead trees, and getting them out of the forest for a couple of reasons—to reduce future fuel loads, to make way for new plantings, and perhaps even to help fund restoration.  They do leave 5% of the dead trees behind for habitat, with dead wood known as excellent habitat for cavity-nesting birds and other critters.

Forester showing how to expose cambium and
example of healthy indicators despite scorched bark.

The way the foresters can tell whether a tree is alive or dead is by taking an axe to its base and taking off about 1 inch or more of the bark in order to expose the cambium* underneath. The cambium seemed rather akin to our own fatty layer, lying just beneath the skin of the tree, and containing cells that are in charge of growth (see the more technical definition below).  We learned that if it is white and firm that’s an indicator of life, but if it’s gooey and caramel colored, the tree is likely a goner.  So this has been a big focus of the immediate post-fire efforts on the state forest, to identify live and dead trees in order to cull out the dead.

Don Lindsay of California’s Geologic Survey showed us the water quality/sediment runoff study sites that are being installed at multiple locations to measure how much soil erodes this winter off of the forest floor.  This is really important given we are in an El Niño season that could bring heavy rains! Will the more severely burned areas shed more soil than the less severely burned areas?  Lindsay’s study (in partnership with university researchers) will create controlled study sites where literally all of the sediment coming out of a small drainage (1-2 acres) uphill will be captured and measured.  They will also measure the amount of incoming rain and water coming off the sites using a rain gauge plus a small dam and water depth measurement setup. (See photo below). It’s exciting to know they are collecting this critical data and it’s also clearly a lot of work.  Don has been hustling to get the sediment traps installed before the onset of the rainy season.

Don Lindsay of Cal Geological Survey showing a water quality
monitoring setup.

Eerie shape left where a living tree stump used to be.

When they finally took us into the severely burned area, it was like stepping into a charcoal landscape.  The trees were shiny and metallic, with their bark looking in some ways more like stone then wood. The stones that were burned were shedding their fried outer layers (called spalling**).  There were shadows of branches where all that was left was oxidized rust colored minerals streaked across the black earth.  We found more than one reverse tree stump, where the earth was essentially sculpted by the negative space of a tree vaporized by the heat (see photo below).  Where the soils have experienced great heat, often at the intersection of rock or root, Fred showed us how hydrophobic*** (or water repellent) the soils were by pouring water out from a drinking bottle to show us how it pooled up and refused to sink in.  This means even though the soils are extremely stressed by drought, one of the lasting effects of the fire will be to cause more runoff than normal for at least this winter. 

Someone in our group started to observe that beetle activity was already evident on the burned trees, including tiny little piercings on the bark surface and some kind of extruded waste collecting at the bottom of the tree which was oddly a light pink-orange color.  With the threat of bug infestations helping to take out what’s left, starting next spring the foresters will focus intently on planting new trees, and apparently a range of planting techniques will be designed and tested at Boggs Mountain State Forest.  On the way out we saw many signs of miraculous life coming back on its own: a bracken fern that had pushed up through the charcoal soils, and this fresh oak shoot coming off a fried stump. I thank Nick and Fred for hosting us and I look forward to visiting again next spring to help track the recovery of the site!

Oak re-sprout—life carries on!

*The vascular cambium is a plant tissue located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards to the bark). It is a cylinder of unspecialized meristem cells that divide to give new cells which then specialize to form secondary vascular tissues.

** Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms. Spalling and spallation both describe the process of surface failure in which spall is shed.


*** Hydrophobic is repelling, tending not to combine with, or incapable of dissolving in water.