The Theory & Practice Of Redwood
by Bruce Anderson, March 2, 2016
Long before wine grapes and marijuana, family farms were Mendocino County's dominant feature. Timber sustained several thousand families who were able to take home enough money from the woods and the mills to create the stable communities that lasted here until the early 1970s. Many people called the family ranch home while they went off to work in the woods, worked in the schools, fished, raised a few chickens and cows and generally did a little bit of everything to pay the taxes on the old home place.
There aren't many family homesteads anymore, but Comptche's Hollister Ranch, George and Cindy Hollister, proprietors, is a step back into a life earned from the careful cultivation of a small timber holding.
The Hollisters have two sons. Paul is in the Air Force, Victor is a student at Cal Poly SLO. Mom and Pop hope the boys will eventually come home to make their way where Hollisters have been a fixture for nearly a hundred years.
Cindy and George have carefully managed their four hundred-plus acres of redwoods into a steady income for themselves, although the bland verb “manage” disguises an awful lot of hard physical work rooting out non-marketable tree species to create the lush redwood forest that now covers most of the Hollister's modest property. They're justly proud that their redwoods have been cultivated to where redwood growth has increased to roughly four percent a year. “We're constantly thinning to enhance growth of redwood, and the money some years is good and some years not so good,” the Comptche logger says with the fated shrug he shares with farmers everywhere.
George Hollister has lots of hard earned opinions about how to do timber. A man of many parts, he's not only logged his own trees, he's worked for his mammoth neighbor, Mendocino Redwood Company back to when it was the Masonite Corporation. Hollister says he agrees with the application of chemicals to root out fir, madrone and tan oak so redwood can flourish. “Try getting them out by hand!” he says, going on to point out that way back fires burned out the undergrowth and cows grew fat munching on the weed-like new growth of scrub oak and madrone.
As we drove up the ridge and into the forest, George noted the charred evidence of the great Mendocino fire of 1931 that burned all the way from the coast to Ukiah. That big fire's blackened stamp still marks the larger redwoods for miles around. “A lot of people think because we're so close to the ocean that fire isn't that big a danger,” the logger observes. “Not true. We have a lot of hot fire days, and all of us in this area worry about it.” George cites the fast-moving fire of 2008 caused by downed power lines behind the Comptche Fire Station. “This whole county can go up anytime. It's a big worry.”
”I went to UC Berkeley and Humboldt State,” the long, lean son of the soil begins the statement of his inspirations and bona fides. “Professor Bill McBride was the most influential teacher I had.” But the Hollisters, through years of hands-on toil, have come to their own theories pegged to the centrality of soil moisture as the key to restoring healthy redwood stands. “A lot of foresters emphasize sunlight,” he says, “but you've got to have soil moisture, that and you thin constantly to get the redwood growing. The thing that I do that is different from what most people do is I always cut the smaller redwood trees, and yes, I do a lot of it myself. High quality redwood is what has always driven the industry in Mendocino County.”
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The following is a crash course by the Hollisters called ‘Soil Moisture and Tree Growth’…
What I have seen suggests, in older undisturbed redwood forests, soil moisture is the limiting factor to forest growth. In younger or logged in forests, sunlight is the growth limiting factor.
To see this, the 1977 drought is a good place to start. The 1977 drought was more severe than any one of the drought years we are currently experiencing. In the 1977 drought we did not get enough rain for the grass to turn green. In all of the current drought years, it appears that at some point during the growing season the forest soil profile has been saturated.My experience has been that in areas uncut shortly before the 1977 drought, a much narrower drought growth ring can be seen. This can be observed by looking at growth rings from borings taken from standing trees with an increment borer, or, much easier, from stumps.
But not all redwoods that were growing during the 1977 drought show the effects of the drought. The young trees in clearcuts harvested a few years before the drought, and older trees in heavily thinned stands harvested in years immediately before the drough,t appear unaffected by the 1977 drought.
The Lindquist thinning plots in Jackson Demonstration Forest, with various basal area retentions, are a good example. The plots that were thinned don't show the 1977 drought, the control plots do. I believe these commercial thinning plots were done in 1973. This suggests that in uncut older forests, the available soil moisture is mostly depleted every year by transpiration. In young forests, or thinned forests, annual transpiration is quite a bit less than what the available soil moisture is.
Tan oak control in a redwood forest is a second example. If one takes an older, uncut stand of tan oak and redwood, let's say 50 years old, and only removes the tan oak, there is a positive growth response seen the following year in the remaining redwoods. Because these redwoods have been existing as co-dominant in the stand before the tan oak is removed, there does not appear to be a significant change in the amount of sunlight hitting the photosynthetic part of the redwood tree. This suggests the competition between tan oak and redwood is for soil moisture.Sometimes the growth response in redwoods from removing tan oak is dramatic. There is a larger positive growth response after two years. The larger response after two years suggests there is an expansion of the redwood trees' root system because the increase in sunlight hitting the photosynthetic surface area of the tree due to removing tan oak appears minimal and not proportionate to the increase in the redwood tree growth rate.
The third example is in thinning from below which means thinning that leaves the tallest and biggest trees of a given page. When thinning older pure redwood stands or redwood clumps surrounded by grass, the Redwood Road systems are assumed to be fully developed. The redwood trees that are left have a positive growth response the following year after thinning and there is less discernible two year secondary response.
Again, since thinning is being done from below, the change in sunlight hitting a photosynthetic surface of individual leave trees appears relatively unchanged the year following thinning. There are shady needles that transition to sun needles, but the part of the leave three that has been in full sunlight appears to be getting close to the amount to the same amount of sunlight as before thinning.,I emphasize from below because most thinning currently done is from above where the taller and larger trees of the same age are removed and the results could be different.
Something of added interest: I was looking at redwood growth rings in an older second growth stand on the river flat across from Paul Dimmick State Park on land owned by Mendocino Redwood Company. I was not expecting to see the 1977 drought in these redwoods because of the proximity to the Navarro River and due to the river having some flow during the 1977 drought. But I did see a very definite drought ring for 1977.
This supports the view that the moisture in the soil that is being transpired and in the root zone is separate from the water flowing under the surface and in waterways. But there appears to be a definite influence on water available for transpiration due to the interface between where the root zone is and where water is flowing. We see this in more vigorous growing redwoods seen along streams and near springs. It reminds me of redwood roots that plug up septic leach lines. The roots tend to do fine in the leach line but don't venture very far into the septic tank.
These suggestions, based on observations, result in conclusions and questions. One conclusion is that since a measurement for transpiration potentially closely fits a measurement for photosynthesis potential because both depend on needle surface area and older, an older closed canopy stand is "overstocked." In a typical growing season an older, undisturbed redwood forest will show growth due to water stress, not due to a reduction in seasonal sunlight. The question is, Why do older redwood forests that have openings in their canopies still show droughts from the past?
It is a given that redwoods need some light or they don't grow and any tree that is blocking sunlight from a redwood is competing with that redwood. But a redwood forest manager is more importantly managing soil moisture, not sunlight. Redwood forestry is, in effect, dry land farming. The concepts of dry land farming and thinning from below apply to all redwood forest management regardless of whether the application is commercial or otherwise. Park managers and groups like Save the Redwoods League would benefit. The need to control hardwoods in a managed redwood forest becomes obvious as do the implications for managing redwoods for drought conditions. Managing a redwood forest with less than a closed canopy means sunlight will be hitting the forest floor providing a constant opportunity for other tree competition to develop and also the constant need to control these competitors. Fire and grazing were the popular means to control this competition in the past. Herbicides are commonly used today.
For your information, Douglas fir responds differently to thinning than redwood does, and a lot of what I am saying above does not apply to Douglas fir.