After Fire in the North State Garden – McConnell Arboretum and Gardens at Turtle Bay Exploration Park - Redding
( If you are reading this anywhere but my blog, you can find the original post here. )
Recently I visited the McConnell Arboretum and Garden at Turtle Bay Exploration Park in Redding. In a North State Garden last toured the park with Lisa Endicott, Horticulture Manager, in February of this year when she talked to us about the history, layout and mission of the mature 20-acre cultivated display garden and 200-acre arboretum. This time, however, I was talking to Lisa about the damage caused to the gardens by a wildfire that started in the City of Redding and ran through the Arboretum and Gardens on August 26th.
The fire started in town and ran swiftly through untended green belts. Heavy winds of up to 30 or 40 miles an hour that day, coupled with extreme summer heat and dry conditions, allowed the the fire to rapidly burn more than 130 acres in downtown Redding. The area of the McConnell Arboretum and Gardens most affected was on the sundial side of the Sundial Bridge but across the main walkway running perpendicular to the bridge.”
Fire is devastating and destructive. The 2008 Northern California fires burned many acres and homes and negatively affected much of our region. If a silver lining can be found in the fire at the McConnell Arboretum and Gardens, it is in the fact that with the fire here also comes the opportunity to learn: to observe and draw conclusions about the nature of fire in a garden setting and how most efficiently and effectively to respond and go about with restoration. “Oh yes, the fire presents us with an opportunity for research we wouldn’t otherwise have had,” says Lisa, with something of an ironic laugh. “This is the first fire we’ve had since I’ve worked on the grounds (more than 10 years now) and we will be collecting information about various plants’ response to the event – short and long term. For instance how did the Mediterranean plants fare versus the native plants? How did the well-established fare compared to the juvenile or young plants?”
“About a quarter to a third of the Arboretum’s Savannah area was damaged,” Lisa explains, “as well as about 20% of the outer rim of the intensely planted display gardens.” While the entirety of Turtle Bay Exploration Park was efficiently evacuated, “wonderful fire crews and staff armed with hoses and shovels - and the irrigation system - worked to control the fire and safe-guard the gardens. We expect that oaks (primarily Blue Oaks - Quercus douglasii) and many other native plants should regenerate – the pines and manzanitas are more of a question.” As we walk around the garden – from the nursery down the main pathway towards the Sundial Bridge, the fire damage runs along the northern perimeter of the garden on our left. The area dedicated to South African plants took the hardest hit, and “one prize South African Restio was lost,” Lisa tells me sadly. Burned and blackened tree trunks and desiccated shrub forms are ghostly reminders of the event. But in the ashes, and dried leaf-littered walkways are signs of hope: “The oaks are doing just what the Fire Ecologist Carl Skinner, told us they should do. They dropped their leaves in order to slough their fire damage.” Already – just weeks later at the time of my walk-through – small green leaves are emerging at the ends of many of the oak’s bare branches. It’s amazing to see. And is a reminder that fire is historically an integral part of our native habitat – and the oaks are built to deal with it better than we are, for sure.
Fire Ecology as a scientific field of study (a branch of Ecology), especially in the American West, makes strides with every fire season in better understanding the role that fire has played and continues to play in the health and well-fare of any ecosystem or bioregion. Philosophies on fire management have evolved significantly over the past few decades, moving from a school of total fire suppression to a belief that fire is an “inherent and integral part of our dynamic landscape.” Long-term fire management strategies need to try to accommodate a fire cycle, work to understand and respond to mitigating factors such as climate change or multi-year weather patterns like El Nino and drought, and try to diminish loss to public and private property. No mean feat. And just as theories on how to control fire have changed, so too have theories on how to respond following a fire.
“When fire strikes, in residential or native landscapes – people want to rush in and fix it – clear and re-plant or re-seed,” says Lisa. “The forest Ecologists assured us that the wait and see approach was painful for us, but much better for the Arboretum and Gardens. Nature has a cycle. And the cycle includes letting the plants come out of shock from the trauma. Let them slough their leaves – which then mulches and protects the vulnerable exposed soil beneath. Allow the plants and soil and microorganisms to start healing. Allow yourself, the gardener, to see which plants have suffered irreparable damage and which may yet survive.”
This careful approach is actually perfectly in keeping with the Arboretum and Garden’s high standard of “offering insight about plants with thoughtful emphasis on making selections in harmony with the climate, either native species or from the same type of climate zones elsewhere in the world.”
In the McConnell gardens some plants – it is already clear – are gone – from the fire or simply the plants’ proximity to intense heat. But Lisa and crew won’t dig out the root balls of a lot of the larger shrubs or trees until spring. They may cut the questionables back to the ground, but for many of even these they will still wait for the small chance that plants’ root balls could send out fresh growth in the spring. Leaf drop will be left on the ground as mulch and more mulch may be laid down in order to reduce erosion and keep top-soil in place in the event of heavy wind or rain. Some restoration planting or seeding may take place late this Fall or early this coming winter, but for the most part, the McConnell Arboretum and Gardens will let Nature take her course.
And they - the gardeners - will take careful notes.
Volunteer hours and dollars are always welcome for restoration and maintenance at the McConnell Arboretum and Gardens. For information on giving time or other resources, visit: www.turtlebay.org.
For more information on Fire Ecology and recommendations for working with a landscape damaged by fire, try the following websites:
The Association for Fire Ecology: www.fireecology.net.
The California Chaparral Institute: www.californiachaparral.com/
The Association for Outdoor Education: aeoe.org/resources/fire/index.html
Below is a paper on assessing native oaks after fire damage. It was sent to me by Glenn Nader, Natural Resources Advisor at the University of California County Extension program, and reprinted with his permission:
Cooperative Extension
University of California
Doug McCreary
Natural Resource Specialist
U.C. Sierra Research and Extension Center
(530) 639-8807
BURNED OAKS - WHICH ONES WILL SURVIVE?
Each year fires burn thousands of acres where the predominant vegetation is oak trees. Where fires burn
intensely, trees can be totally consumed. In other places, leaves on trees can be scorched, but the trees
remain standing. Where fires burn only the surface vegetation, many trees appear relatively unaffected,
except for some blackening of the bark near the ground. The question arises, which of these trees will
survive?
The purpose of this paper is to provide some information about how to assess the damage to burned oak
trees and to provide guidelines for determining whether trees should be cut down or saved. Unfortunately,
it’s difficult to predict the degree of damage accurately from the outward appearance of trees. Several
factors discussed below influence how much injury has occurred including tree species.
STEM DAMAGE
The most important variable influencing the degree of injury is whether or not the cambium, or tissue
directly beneath the bark, has been killed. If it has been killed all the way around the stem, then the top of
the tree will eventually die, though this may take several years. However, even if a small portion of the
circumference of the cambium remains alive (as little as 10%), then the tree will likely survive, though the
overall vigor could be reduced considerably.
Some species of oaks have thicker bark, which helps protect their cambium from injury. Since interior live
oaks generally have thinner bark than either blue or black oaks, their stems are more sensitive to heat.
Tree size also influences the degree of susceptibility to fire. Since larger trees have thicker bark, they are
more resistant to fire damage. Therefore, smaller trees exposed to the same intensity of fire are more likely
to be killed or severely damaged.
How do you tell if the cambium of a tree ahs been killed? There is a greater chance of lethal cambium
damage if the bark has been severely blackened and charring has reduced bark thickness. If the bark has
been cracked or separated from the wood, the cambium is almost certainly dead. One can determine the
degree of damage most accurately, however, by actually cutting away a portion of the bark to observe the
cambium beneath. If the cambium is dark or yellowish, it’s probably dead. If it is white or pink, on the
other hand, it is most likely alive. Since such injury may take some time to show up, assessments of
cambium injury should be made several weeks after the fire has occurred.
LEAF INJURY
In general, leaf injury is much less damaging to the tree than stem injury. Trees that have had most or all of
their foliage burned off will likely recover if the cambium is intact. Both deciduous and live oaks produce
some new foliage each year. Thus, if the only apparent damage to the trees is scorched leaves, they will
likely leaf out and grow normally next spring.
RECOMMENDATIONS FOR HARVESTING FIRE DAMAGED TREES
As mentioned previously, it is difficult to accurately assess the degree of fire damage or to make general
recommendations based upon what the tree looks like. If you have a valuable tree, consult a professional
forester or arborist to help determine the degree of injury. If possible, it’s also desirable to let at least one,
and preferably three, growing seasons pass before making a final decision to cut large, valuable trees whose
crown survival is uncertain. Below are some general recommendations about which trees to cut and which
trees to save, gleaned from an USDA pamphlet on post fire management of five southern California Oaks*:
Cut trees if:
• They are less that 6” in diameter and have been scorched all the way around their base
• They are 6-12” in diameter and have continuous charring around their base, with reductions in bark
thickness.
• They are greater than 12” in diameter, have continuous charring, pronounced reductions in bark
thickness, and occasional exposure of underlying wood.
• They have basal wounds on 50% or more of their trunks and are located in residential or recreational
areas that present a mechanical risk. (They could fall on people or structures).
Leave trees if:
• They have lost all of their foliage, but sustained only minor stem damage.
• They have only spotty scorching around their base, with at least 10% of their cambium alive.
• They are over 12” in diameter and are scorched all the way around their base, but have no reduction in
bark thickness.
SPROUTING FROM KILLED TREES
Even if the trunks of trees have been killed and they are cut down, many oaks will sprout from their
stumps. Sprouting is especially vigorous for live oaks. However, it also occurs on almost all other oak
species as well. In the spring, sprouts originating from the stump or roots will start to grow. There can
eventually grow into mature trees. Sprouts generally grow much faster than shoots originating from acorns.
However, they also produce multiple stem trees. If the sprouts are pruned back to one or two dominant
ones, these will grow more rapidly and the tendency for multiple branching will be reduced.
*T.R. Plumb and A.P. Gomez. 1983. Five Southern California Oaks: Identification and Post-fire
Management. Pacific Southwest Forest and Range Experiment Station. Gen. Tech. Report PSW-71.