Old-Growth in the Sierra Nevadas
A Report on the Sierra Nevada Ecosystem Project by Jerry Franklin
From the Environmental Review Newsletter
Volume Three Number Ten, October 1996
Foresters have traditionally viewed old-growth timber as decadent; allegedly disease prone, it grows
slowly, and provides poor habitat for favored game species, primarily deer. However, timber companies
value old-growth timber for its fine grained, strong wood and high return per tree. As a result, most old-growth forests throughout the West have been replaced by young, fast-growing stands of timber.
Professor Jerry Franklin of the University of Washington has described the structural components of old-growth forests: they include large diameter trees, standing and down large timber (snags and nurse logs), and a multilayered forest canopy. Professor Franklin has helped provide the groundwork for the realization that mature forests are an important part of a biologically diverse, healthy, forest ecosystem.
Professor Franklin received bachelor's and master's degrees from Oregon State University and a Ph.D. in botany from Washington State University in 1966. He worked as a research forester for the U.S. Forest Service for fourteen years; then was director of the ecosystem studies program for the National Science Foundation for two years. After eleven years as a professor at Oregon State University, he moved to the University of Washington as a professor in the College of Forest Resources. Professor Franklin has many scientific publications on the form and function of forest ecosystems, the application of ecological principles to the management of natural resources, and on the theory and practical applications of landscape ecology.
In recent years Jerry Franklin has been involved in trying to reconcile resource management disputes such as the northern spotted owl controversy, using scientific knowledge to inform political/economic disputes.
The following report on the status of old-growth and late successional forests in the Sierra Nevada Mountains of California is excerpted from a talk given by Professor Franklin before the University of Washington Botany Department in April, 1996.
The Sierra Nevada Ecosystem Project
I have spent the last five years more involved in using applied science to resolve natural resource issues than in primary research activity. I got involved, initially reluctantly, with congressional testimony, then subsequent to that, I was part of the Gang of Four. The Gang of Four - also called the Scientific Committee on Late-Successional Forest Ecosystems - were four forest scientists who were brought together to help three congressional committees define the issues and resolve the problems associated with spotted owls and old-growth timber management on the national forests. I then subsequently became involved with the Forest Ecosystem Management Assessment Team (FEMAT) effort put together by President Clinton to give him some options and some advice, which ultimately led to the northwest forest plan. These efforts to get scientists involved in defining and resolving resource issues has expanded in the last five years. In addition to these efforts in the Northwest, I worked for the provincial government of British Columbia on the scientific panel on forest practices on Clayoquot Sound.
Now I am involved in a project that was initially proposed by Congress after the Gang of Four effort. Congressman George Miller of California was impressed enough with the notion of getting a relatively succinct analysis of the forest and watershed situation by the FEMAT effort that he wanted the same thing done for the Sierras. Subsequently in 1992, Congress gave the Sierra Nevada Ecosystem Project (SNEP) $7 million and two-and-a-half years to assess the conditions in the Sierra Nevada ecosystem - meaning the entire Sierra Nevada with a focus on the federal lands, but also looking at the private lands - to assess the conditions of the resources, and also provide some scenarios for the state to consider for alternative ways to resolve conflicts. This effort ended December 31, 1995.
My assignment as part of the SNEP team was to figure out how we could assess late-successional forest conditions in the Sierra Nevada and then lay out for Congress various considerations they needed to resolve issues of sustaining late-successional forests and related species in the Sierra Nevada. We emphasized the structural features we thought were associated with high quality, late-successional forests; large diameter living trees; the large standing dead trees or snags; large down logs, all elements that are important structural attributes of old forests and also important to many late-successional species as well as other attributes such as canopy density.
I broadened my assignment from old-growth forests because old-growth forests are only a part of the set of forests we are interested in conserving from the standpoint of biological diversity. There is a lot of what you might call mature forests, forests in the category of 100 to 250 years that play important roles as well. So in the Gang of Four effort and again in the Sierra Nevada effort, we looked at late-successional forests; meaning nearly all forests beyond their youth. There were some problems in assessing forests in the Sierras because the Sierra Nevada did not have a history of catastrophic disturbances that wiped out stands, that created whole new age classes of forests. The history of forest disturbance in much of the Sierra Nevada was light-to-moderate intensity fires at relatively frequent intervals that resulted in much of the forest having a very complex structure in which you had old trees and young trees all linked together in a fine scale mosaic. It was a different situation than in the Northwest where you can go out and find a 500 year old stand and be pretty confident that a disturbance happened there 500 years ago, but not much has happened since that time. You cannot do that in the Sierra.
Another complication in the Sierra Nevada was a history there of partial cutting. Even in the old days when there wasn't really any industrial forestry at all, loggers tended to leave many trees behind; they tended to log a stand selectively. Even when industry and the Forest Service began to do timber management, they also tended to be selective rather than practice clearcutting. For that reason much of the forest in the Sierra
Nevada has been logged, but not heavily. This means you cannot simply divide the forests into natural and unnatural forests. There is a gradient of conditions and many of our best remaining late-successional forests in the Sierra Nevada have had significant human activity, including timber harvest. So identifying and defining late-successional conditions in the Sierras and then trying to provide an overall assessment was difficult.
The classic Sierra forest which occupies the primary forest zone in the Sierra Nevada is a mixed conifer forest: a mixture of sugar pine; a yellow pine, which can be either ponderosa pine or jefferey pine; white components of fir, incense cedar, and Douglas fir. There are also some unusual communities in the Sierra Nevada; for instance, the giant sequoia, which is a variant of the mixed conifer forests.
The Sierra Nevada has been heavily impacted by human activity. Post-settlement activities of western man entered the region in significant numbers in the 17th century and we begin to get significant activity in the Sierra Nevada towards the middle of the 19th century associated with the Goldrush. Today the most populous state in the Union lives adjacent to the Sierra Nevada system. Many of the human impacts come as a result of transportation, and development within the Sierra Nevada itself.
We have also had a lot of timber management activity within the Sierra Nevada, although it got started on the national forest lands at a much slower pace than it did in the Pacific Northwest. Patch clearcutting has come only relatively recently to the Sierra Nevada, even though timber harvest has been carried out for the last 150 years.
We have had many consequences as a result of our fire control programs. The Sierra Nevada region experienced a lot of fire under natural conditions. Light-to-moderate fires were a frequent part of the forest environment in the Sierra Nevada. And with the fire control programs that were instituted early in this century, we now have developed high stand densities in many regions where traditionally the stands were kept relatively open by fire. Some of these areas have a serious problem where these stands have become over-dense and can undergo catastrophic mortality when you enter into one of the drought periods such as the one California is in now. Catastrophic fires are a major concern in the Sierra Nevada. The more typical situation is where low intensity ground fires crept around the forest floor for days on end. The other extreme is the kind of catastrophic fire that burns thousands of acres; which nobody wants to see and is increasingly a problem in the Sierras, not only because of the increased fuels, but also because human developments have become more intricately interwoven with the forest fabric.
We have pollution impacts in the Sierra Nevada as well; pollution problems associated with the central valley of California where ozone and air pollutants move up into the Sierra Nevada. The SNEP study has shown - this was a shock to me - that in Giant Forest, one of our greatest concentrations of giant sequoias, the air quality at 7,000 feet elevation is poorer than it is at Visalia or Fresno in the central valley.
My responsibility in SNEP was to deal with the late-successional forests, which includes the old-growth forests. But the forests in the Sierra Nevada have a variety of forms, depending upon site conditions and the kinds of disturbances. We felt we could not define old-growth forests on the basis of the age of the trees alone. There are many stands that have been disturbed in various ways, but they still have some very old trees. Similarly, there may be stands which have a lot of structural complexity, a lot of habitat potential for late-successional organisms and yet are not particularly old in terms of the oldest trees present. So we decided we were going to use a variety of structural criteria for defining late-successional habitat. We did that because the forest structure provides a good surrogate for many species and processes we are interested in. We also used forest structure because ultimately we had to assess the entire Sierra Nevada in a year and a half. We had to work with what we could see on aerial photographs and satellite images. Given the constraints, forest structure was all we could work with.
The kinds of structural features we used to define late-successional conditions included a lot of things having to do with structural complexity; the appearance of multiple canopy layers. We recognized that some of the high quality forests would be in this kind of structural condition, with a lot of smaller size material as well as larger old trees. But some of the better old-growth forests were going to be those park-like stands which did not have the same level of structural diversity as some of
the closed stands. We also had to be sensitive to the fact that there were stands that had been logged which provided high-quality old-growth conditions. One reason for that is that some of the forests in the Sierra can grow rapidly.
We developed a scale from zero to five, recognizing the degree to which a forest was going to contribute to late-successional or old-growth function in the Sierra Nevada ecosystem. A stand that had low late-successional attributes would get a zero rating; one that had a lot of complexity, particularly some of these with high canopy densities as well as a lot of large diameter trees would get a high rating.
The other problem we had in the Sierra Nevada has to do with the complex patchwork of most of the forest in the Sierra Nevada. You don't see great big patches of homogenous or uniform forests in the Sierra Nevada like we do in the Pacific Northwest; which has to do with the Sierra's history of low intensity disturbance. So you often find in the Sierra Nevada these mosaics where you have an intermixed patchwork of older forests and younger forests. So we are dealing in many parts of the Sierran landscape with this fine scale pattern. It is not only fine scale but it is a low contrast patchwork, which means it is difficult to define in many cases where one kind of patch ends and another begins. In other parts of the Sierra Nevada there are fine scale patchworks with different kinds of habitat conditions, but they are intricate mosaics which would take a great deal of time to map individually. We also have fine-to-medium landscape mosaics with high contrast; we have created some of those high contrast
landscapes through our forest practices.
How were we going to deal with these fine scale patchworks? We could not map them easily and even if we could map them, it would be difficult to analyze a million or more individual units. We could not deal with that at this scale of policy analysis. We had to find some way to aggregate these forest patches. So we decided to map larger landscape-level units which we call polygons, which often represented mosaics of different kinds of patches. For example, a polygon might be a mixture of intact forest and clearcut areas, but that polygon you might say is uniformly heterogenous in the mix of patches that existed there. That is how we approached the job of mapping the Sierra Nevada, which is fundamentally the same way we mapped old-growth forest in the Northwest as part of the Gang of Four exercise.
I brought about 150 resource specialists into one location for a long week in which we all sat in the same large room and as teams, mapped all of the federal lands in the Sierra Nevada into polygons based primarily on orthophotos. The mappers were resource specialists who knew the ground. They drew these outlines - polygons - then characterized them as to the kinds of patches that occurred within them and gave those polygons ratings from zero to five, depending on the level of structural complexity. Through that process we created a map of the entire Sierra Nevada with a total of about 2,800 polygons. For each of those polygons we have information on the kinds of patches, on the kinds of forest structural conditions, and an overall rating of late-successional structural quality.
The initial mapping was done two years ago. During subsequent summers members of the SNEP team went out to see how well the mappers portrayed the forest conditions, and how well they had rated them with particular concern that there was good consistency among the various mapping teams. We have also had an independent team do a validation on a small subset of the mapping.
Over that time, I had the good fortune of being able to visit every polygon in the Sierra Nevada that was rated as a four or five. Naturally I took a look at a cross section of all the different polygons from very low rated to very high rated, but I made it a point to look at all those high-rated polygons.
Fives have the highest levels of structural complexity, but the fours are also very good forest, and often from an ecological point of view, they may be even better than the fives, because they more approach that open, park-like condition that was so characteristic of much of the mixed conifer forest before we began our fire control programs. It surprised us that some of the high ranked polygons were out on the western boundary of the national forests. I would have thought the remaining good, old-growth forest in the Sierra Nevada would be in the backcountry, but a significant amount of the remaining old-growth was associated with canyons. This is because the topography was so steep no one had been able to get in and log it. That is good because it gives you a better distribution of remaining old-growth forests. But it is also a problem because those forests are potentially at substantial risk of fires because many of them
are at the urban-forest boundary.
Forest Types in the Sierra Nevada
A very common foothill, pine-oak type of forest has a lot of
grey pine, what we used to call digger pine. Generally these
forests do not get very high structural ratings because of their
fire history and because of their low productivity. They simply
don't have the ability in many cases to develop complex
conditions. In the mixed conifer zone a pine plantation would
generally have a zero rating based on structural complexity; it
doesn't do anything for late-successional organisms. A young
forest would have a rating of one for the structural attributes
on which we rate old-growth quality. A classic mixed conifer
stand would have a structural rating of four; it would be a
relatively open stand. The understory in these is often bear
clover which helps carry ground fires and maintains these stands
in an open condition.
A high quality, class five mixed conifer stand can have some very fine sugar pines with much of the canopy closure the result of white fir in the stand. Reproduction of all of the mixed conifer species in the Sierra Nevada is a part of a high quality, late-successional forest stand. In the Sierra Nevada, especially if you reintroduce fire, you see the small openings in the forest that are needed for regeneration.
A class five could be a structurally rich old-growth red fir stand with a lot of large diameter trees, large snags and down logs. Whereas, a beautiful, pristine stand of jefferey pine can have low productivity, low levels of structural complexity.
But even a species like jefferey pine can produce a complex stand.
Lodgepole pine is one of the major sub-alpine forest types. As you move into the sub-alpine you see lower productivity; you can have old forests but many of them do not provide the structural richness you need for species like the California spotted owl. So sub-alpine forests, even though many of them are old, even though many of them are botanically very important, do not get that high a rating in terms of this structural standard. Because of that we developed an alternative system for rating late-successional structural complexity that was based on a type-by-type comparison rather than using a single standard. But since most of the issues in the Sierra Nevada have to do with commercial forest types, we focussed our analytic effort there.
On the east side of the Sierra you get into a yellow pine type forest; it can be either jefferey pine or Ponderosa pine. Many of those forests are in very poor condition. All of the large diameter trees have been cut out; all that is left is understory.
First of all, the most impacted ecosystems in the Sierra Nevada are not forests; they are the aquatic ecosystems. There are essentially no aquatic ecosystems that remain biologically intact, and very few that are physically intact after the last 200 years of human activity. Streams were placer mined, they have been grazed continuously, they have been logged over, they have been diverted, they have been dammed. The stream and river systems are an extremely altered set of ecosystems. This is equally true of the ponds and lakes. Probably no more than five percent of the Sierran high lakes had fish at the time of white settlement. Now there are probably five percent of the lakes that do not have fish; all as a consequence of our fish planting program. So it is the aquatic ecosystems of the Sierra Nevada and the associated organisms, that are the most altered, the most at risk; with significant numbers in danger of extinction.
The other ecosystem that has been extraordinarily impacted is the foothill ecosystem: that zone of pine and oak; the grey pine, and oaks associated with the central valley, the foothills of the Sierra Nevada. These systems have been dramatically impacted by human activity, most recently by urban development. There is no question that it is in this part of the Sierra Nevada that we find more elements of biological diversity at risk than in any other, and in which we have the least amount of federal land available to try to resolve those issues.
In regards to the late-successional forest - the old-growth forest - we find there is very little high quality, late-successional forest left in the Sierra Nevada. Depending upon the forest type you are looking at, we found about sixteen percent of the mixed conifer forest was rated as a four or five; that is the good, remaining, mixed-conifer old-growth forest.
The situation on the east side of the Sierra Nevada is much worse than it is in the mixed conifer forests on the west side, because the topography is gentle on the east side. Because the timber resource is so much more limited on the east side, essentially all of the yellow pine forests east of the Sierra Nevada have been heavily cut over, and about one-and-a-half percent of the yellow pine type was given a rating of four or five. There is almost no remaining high quality old-growth forest left on the east side; just a few remnants. On the east side there is so little good pine forest left that there is not enough left to begin building a conservation strategy around, which is not the case on the west side.
If you read many of the news accounts of the Sierra Nevada you may have the image of a forest ecosystem in collapse, you may have this notion that the forests there are falling apart. Certainly there are some areas, on the east side for example, where there are large parts of the Sierra Nevada where there is a significant problem with forest health. But over the two years of the study, I flew all of the Sierra Nevada at least twice, and catastrophic stand collapse - high levels of tree mortality - are very localized in the Sierra Nevada. Over most of the Sierra Nevada, the forest appeared to be in a good condition. Furthermore because there is relatively little history of clearcutting, there is a much higher level of forest continuity in the Sierra Nevada than there is in the Cascades or east of the Cascades. The Blue Mountains for example, are in a much more highly fragmented condition than the Sierra Nevada as a whole. So
forest health is actually good over much of the Sierra Nevada. Forest continuity is good, but structural complexity of these forests is low as a result of the partial cutting practices that have gone on. Furthermore, we have a problem in that the forests have significantly increased their density, which means an increased potential for fire to move through. The increase in forest density is a result of both fire control and active efforts to increase stand densities to increase production.
As a part of a conservation strategy for old-growth in the
Sierra Nevada we are going to have to preserve the remaining high
quality forest in the Sierra Nevada: save what is left of the
best. Secondly, we can develop a reserve-based strategy. We need
to identify the areas in the Sierras we want to manage for late-successional forests; and the primary active thing we need to do
is to return fire to those areas. If we actively manage them so
as to try to reduce the potential for catastrophic fire, and re-introduce a more frequent light-to-moderate fire regime - as has
been done in the national parks - we will have a more stable
We have developed a variety of conservation strategies: One of them is called the ALSE strategy - the area of late-successional emphasis strategy - in which we lay out larger, multi-polygon areas based on the fours and fives and use those as central elements in creating larger landscape units which we then can manage to reduce the potential for catastrophic fire and to reintroduce fire. The idea is to create and maintain the kinds of features within these landscapes which maintain a low density stand of large diameter trees; and through frequent burning prevent the development of ladder fuels, which would allow fire to get from the ground to the crown.
Another important part of any conservation strategy that we are going to propose for the Sierra Nevada is a major effort at riparian [streamside] protection. And the path that is going to be taken in the Sierras is not to view the riparian forest as something that protects the stream, but instead the notion that the riparian forest is an ecosystem in and of itself that deserves to be recognized and protected. So instead of being a buffer for the stream, we have the concept of a riparian zone and then a buffer beyond that to protect the riparian habitat. You can imagine that in a drier range such as the Sierra Nevada, the riparian forests are very important for many elements of biological diversity, including many invertebrates. We are talking about no entry zones at least comparable to the scale we are talking about in the Northwest Forest Plan, which would provide a variety of functions for the stream including the provision of large woody debris.
Reserves by themselves would be insufficient to provide for the conservation of biological diversity in the Sierra Nevada. There is no way that you can have enough reserve areas in enough locations to achieve your objectives. This is true here in the Northwest as well. The other major part of upland terrestrial strategy has to do with managing the matrix, the managed landscape; that is, the part of the landscape in which we are extracting wood products, so as to conserve biological diversity there as well. In the Sierra Nevada it is clear that the key to the matrix is in restoring and maintaining a significant population of large diameter trees through essentially all of the upland landscape. Over the years even while forest cover has been maintained, structural complexity has greatly decreased. So the major part of the matrix strategy is one of restoring and maintaining a population of large diameter trees, and the derivatives of those trees which are the large snags, and the large down logs. This means managing forests to maintain a population of six to ten large diameter trees per acre. We are beginning to see some management in the Sierra Nevada that follows that already, following the interim guidelines for timber management for the California spotted owl. Basically those timber management guidelines call for cutting no trees over a certain diameter. You can take the small trees, you can take the medium-sized trees, but you leave all of the big trees behind. Many elements of Sierran biological diversity, including the California spotted owl, seem to be tied mostly to some of these structural elements, not to having a totally pristine area. Again of course, structural diversity begins to match some of the natural disturbance events in the Sierra Nevada.
I am continually telling both students and foresters: Catastrophic (stand altering) fire is not like clearcutting at all; nature kills trees, but it does not remove the carcasses. There were certainly catastrophic fires in the Sierra Nevada historically. One of the biggest debates we had in the SNEP team is whether catastrophic fires were important or not important in the Sierra Nevada. I happen to think they were infrequent but important.
A final word with regards to animals. We cannot come up with biota that clearly need either totally intact, late-successional forest, or large tracts of late-successional forests in the Sierra Nevada. In the Sierra Nevada we cannot tie our conservation wagon to something like the California spotted owl the same way that we can do it with intact old-growth forests here in the Cascades. It is not clear with the marten, the fisher and even the wolverine, whether it matters to them whether they have large, pristine tracts of late-successional forest. Nevertheless, we have argued that any conservation strategy should have large blocks of late-successional forest because prior to human settlement, that was the condition in the Sierra Nevada. If you look at late-successional conditions in the national parks, it is easy to construct a scenario that eighty to ninety percent of the mixed conifer and the east side pine forests were in high quality, structurally complex, late-successional forest condition as a part of the pre-settlement landscape. That was a conclusion I did not expect to come to. I thought in a high disturbance kind of landscape there would be less good, old-growth forest. In fact, almost the entire landscape was covered with it because old-growth forest was in a dynamic equilibrium with a light-to-moderate fire regime; unlike the Northwest woods where there was an infrequent catastrophic disturbance cycle.
Question: How does the east side of the Cascades in Oregon and Washington compare to the Sierra Nevada?
JF: Much worse. A problem I think, has to do with the fact that the eastside of Oregon and Washington within Region Six, was part of the biggest timber region in the Forest Service. And so the whole timber mentality of the westside spilled over into the eastside forests. When you fly the Blue Mountains or the Wallowas in eastern Oregon, the forests are as fragmented as anything you ever saw on the westside. They have done a tremendous amount of clearcutting over there. On the Sierras they have no tradition of that. In fact some of the forests were only coming on line with clearcutting in the early 1980s, just in time to get shut down. Sure, some forests did a fair amount of clearcutting, but flying the Sierra Nevada is a totally different experience than flying the Wallowa, Whitman, Umatilla, the Ochoco national forests, totally different. Clearcutting is largely due to the mentality of the management agency.
Question: Are the Sierras and the Cascades similar enough ecologically that they should receive similar management?
JF: Absolutely. I think what we have learned out of the Sierra experience should be very relevant to the experience here. But I have to warn you first of all, the Forest Service in its Columbia Basin assessment has not wanted to assess old-growth at all. They have absolutely refused to map it. Secondly, you have a significant group of people, led by some of the people in our forestry department at the University of Washington, who want you to believe that there is no way you can manage for old-growth, or that you can reserve old-growth areas and manage them to maintain those structures and values. So we are swimming upstream much more on the eastside than we are in the Sierra Nevada.
Question: When you rate the large granite basins that are up in the sub-alpine zones low because of structural diversity, emphasizing diameter; those may be thousand-year-old trees and the system may be typical of sub-alpine. Does that cause problems with your rating system? Does that open those areas up to select cutting because of their low rating and they are not spotted owl habitat? It seems like the plant underestimates the relative position of those types of forests. Those are very rich forest in their position in the sub-alpine zone.
JF: This is one of the big controversies during the first year of the SNEP project. Clearly, if you use a single structural standard as I have been presenting to you, bristle cone pine forests in the White mountains don't get a very good rating: it is not a closed canopy forest, its trees are not big. Many people were pulling their hair thinking those forests were not going to get a good rating as old-growth forests. First of all, I was not too concerned about it because the controversies all revolved around the commercial forest types; most of the high elevation types are already conserved in parks and wilderness. However a number of members of the team were concerned, so we developed ratings where sub-alpine pine types were rated against each other. So if you were the best you could be in that type, you were a five. Also in the report we said that even though these are not habitat for many late-successional organisms, botanically, environmentally, aesthetically, some of these are extraordinarily important. The bristlecone pine is a good example of that. We have focussed on the commercial forest types, but we have covered our bases on the sub-alpine.
Question: You mentioned the lack of charismatic megafauna like grizzlies or wolves. Is that due to the extirpation of these animals? Do they require pristine habitat?
JF: Probably not. The big, wide-ranging predators and herbivores do not require one habitat condition like old-growth forest; they tend to work a variety of conditions. What they tend to need is remoteness from human beings, not so much a particular stage of forest succession. I think we would have a hard time coming up with a poster child for the Sierra Nevada. If I had to pick a poster child it would be the big, old, sugar pines; those are magnificent trees and they once truly dominated the Sierran mixed conifer forests. They have been picked and plucked for a hundred and fifty years. <
Question: Did the SNEP team recommend preservation of the overly dense condition. How do you protect that from catastrophic fire?
JF: Dense stands are going to be there. All this talk about the Sierra Nevada all being parklike, all of it being subjected to light-to-moderate intensity fire, is baloney. Those mixed conifer landscapes are mosaics and always have been, which included some portions of the landscape that did not burn very often and carried relatively high densities. Similarly, parts of that landscape were always pretty parklike and had a lot of light, frequent firing. You had a complex landscape pre-settlement, you still do today. If we adopt one of these conservation strategies, we are not going to end up with park-like pine stands everywhere, but we are going to end up with complex stand mixtures.
Question: What is the longevity of old-growth trees and is there any prospect of regeneration of old-growth over time?
JF: First of all, in regards to existing high quality old-growth, I would say almost categorically there is no problem with maintaining it in perpetuity. All you have to do is re-introduce an approximation of the original fire cycle for that landscape and you will be able to maintain the populations of large diameter trees.
Where you do not have high quality forests, we've got to do two things: first of all, we have to grow back some of the large diameter components. I think of it as an escapement of trees into
a larger diameter class where they are safe; you don't bother them anymore, and when they die, not salvaging them but leaving the standing and down dead material so there is that large structural component. That is one thing: restore and maintain the large diameter component. The second thing is to restore fire to the system, or if you are not going to restore fire, some kind of silvicutural system that does not allow you to build up catastrophic levels of fuel.
Copyright 1996 Environmental Review