What is Urban Old Growth?

Discussions of Urban Forests and trees in general, including their growth, care, and impact on society. Discussions of specific trees, parks or forests in urban areas should be included in the proper forum of the Trip Reports and Site Descriptin category of this BBS.

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Urban Old Growth

Post by edfrank » Sun Jun 19, 2011 7:14 pm

This a repost of an older topic from the Website/Google List
urban.JPG
Subject: [ENTS] What is Urban Old Growth?
Date: Sun, 4 Oct 2009 17:56:11 -0400

What is Urban Old Growth?
Edward Frank, (revision 10-04-09)


It can be, and has been, argued that the term “old growth” is simply a human construct that has no scientific basis. It is a concept that can be defined to suit the purposes of whoever is using the term to manipulate the situation to his or her benefit. People who are in favor of exploiting a resource or developing a property on a forest site may use a restrictive definition that allows them to discount the site as old growth. They can then log the patch of forest and develop the property as it suits them without destroying “old growth.” People who are in favor of preservation may use a broader definition that would restrict the cutting of the forest in order to preserve it for themselves and future generations.

This cavalier dismissal of the term old growth is a cynical argument that must logically be rejected. Simply because a term can be and has been misused by people or groups with a specific agenda, does not prove that the term old growth is not a viable concept. This idea can be likened to the idea of art. Different people have different ideas of what are the boundaries and characteristics of art, and may disagree in any specific case, while all accepting that art exists. Similarly a person would need to be extremely insensitive not to recognize that old growth forests do exist. It is simply a matter of how to describe or define them.

There have been hundreds of definitions of old growth proposed and applied. Many are based on minimum age requirements and/or other arbitrary boundaries for demarcating what is or is not an old growth forest. A detailed review of each of these definitions does not really advance the discussion very far. Rather than dealing with specific numerical boundaries, what is needed is an understanding of the core concepts implicit to defining old growth and how they apply in particular situations.

In a world that had been untouched by man, all of the forested land would be covered in “primary forest.” This category of forest can be explicitly defined: "Primary forest or natural heritage forest: Forest with a continuous heritage of natural disturbance and regeneration. In North America this usually means that the forest was not cleared for agriculture or otherwise used for timber by either Native Americans or by European settlers. (Frelich and Reich, 2003) Even when trying to apply this primary forest definition there are additional considerations that need to be made. “There is still some subjectivity here, since in some regions all forests had at least some selective cutting, and you still have to come up with a subjective criterion for the amount of human disturbance that disqualifies a stand from the category of primary forest. Also, primary forest includes stands dominated by young early succession forest, old early succession forest, young late succession forest, and old late succession forest." (Frelich, Sept 30, 2004, ENTS post)

In this ideal untouched world, old growth forests would be those in the late stages of succession and development and would include patches of younger trees filling canopy openings created by small scale disturbances of various ages. “"Primary old growth forests or natural heritage old growth forests are primary forest stands that are in late stages of succession and development... The natural-heritage criterion for delimiting old growth makes it clear that natural disturbance is an integral part of the old-growth ecosystem and ensures that old forest will continue to include species in all stages of succession and development that have undergone genetic selection by natural processes, rather than harvesting and high-grading." (Frelich and Reich, 2003)

We do not live in an ideal world. In most of the eastern United States virtually all of the forests have been impacted to some degree by human activities. Native Americans set fires to drive game and clear land. Early European settlers if they did not clear areas of land outright typically would harvest at least some trees for their own use. Commercial logging in the late 1800’s and early 1900’s clear-cut vast areas and essentially denuded much of the eastern United States. Even if the trees in an area were never cut, they have been impacted by human activities. In the 1920’s and 30’s chestnut blight devastated the American chestnut population. It was a species that in some places represented 90% of the basal area of the forest.

More recently we have had the gypsy moth, emerald ash borer, and hemlock wooly adelgid all exotic invasive species, all introduced by human activities that are killing large numbers of trees and in some cases threatening to destroy entire species of trees and their related ecosystems. Other introduced species of plants and animals are displacing native populations. Large areas of land are continuing to be logged. Vast areas of land are being cleared for residential and commercial development. The effects of acid rain can be seen across the eastern seaboard. So if the criterion for defining old growth forest is just this ideally pristine, totally unaffected forest, then we do not have any old growth forest.

A pragmatic/practical approach would be to evaluate a particular forested site to determine what characteristics it retains of this idealized primary old growth forest and to balance those findings against a baseline of how much impact is acceptable for a forest to be considered old growth. Since there is a wide variation in the degree to which forests have been impacted across the eastern United States, this baseline needs to be developed in the context of forests in the local region. In urban areas this baseline should be developed with respect to the other forests in the same urban area.

Secondly there should be an evaluation of the potential to enhance the old growth characteristics of these patches through removal of invasive species, reintroduction of native species, and similar rehabilitation efforts that includes both active and passive management techniques. These efforts have proven to be effective by many local conservation groups in patches of forest they are striving to preserve. The document The Gradient of Old-Growth Restoration Practices – Mass Woods http://www.masswoods.net/index.php/oldgrowth states: “There is no one specific "old-growth condition" to aim for as an objective and therefore no one way to create it. Instead, it is more valuable to consider increasing the amount of old-growth characteristics in your woods in a way that matches your objectives.”

If considering whether an area should be preserved or not, a third criterion is also appropriate. The question to ask is whether this particular patch of forest is in some way biologically significant. A patch of old growth can be fairly judged significant it is a rare forest type in the eastern landscape. Other significant characteristics might include the presence of an unusual assemblage of flora, the presence of rare or threatened species of plants or animals, the existence of an unusual ecosystem based around a specialized local environmental condition, a population which contains a concentration of individuals an atypical or uncommon genetic makeup, or similar special circumstances.

As a starting point for a discussion, the following generalized definition is offered: “The primary characteristic of an old-growth forest is that it contains a substantial percentage of old trees in a setting that exhibits only limited human impact. These forests are generally characterized as populated with late-succession species for the particular regional or environmental regime. Canopy openings formed by natural processes, such as wind throw and fire, and populated by younger trees are often found contained within the larger old-growth forest.” (after Edward Frank, Sept. 2006, ENTS Post) This definition has no hard edges for this discussion to catch on as it proceeds.

In a suburban or urban setting, the prospects for finding and retaining old growth forests are dire. In a wooded area, a patch of old-growth forest can be buffered by surrounding younger forests, which protect the old-growth from compromise due to edge effects. The younger forest buffers may serve to limit other adverse impacts to the area of old growth as well. Over time, as the surrounding forest ages, species dependant on old-growth forest to survive can spread out from the core area of old growth into the surrounding forest. Some species require a large, contiguous area of forest to thrive. These can do well where a core of old growth forest is surrounded by large tracts of younger forest. In an urban setting however the forest segments are often heavily dissected by roadways and developments. Often edge effects may extend across the entire area of a particular patch. With a greater edge to area ratio, these forests are more susceptible to the establishment of invasive species of plants and animals. Human utilization of these areas is also increased and the impacts of foot traffic, bicycles, trash and similar effects are higher than occurs in more isolated areas. In cases of urban old growth, I do not think more traditional old growth ecosystem concepts apply. Certainly most of the sites in urban areas are far along on the more heavily impacted end of the spectrum.

I also don’t think a minimum area approach is appropriate. A tiny site that has special qualities is significant; a larger site that has these qualities is, likewise, significant. A mediocre site that is large is still a mediocre site. If you were looking at broad scale management issues, for example some species of animals require a large block of contiguous forest to maintain a viable population, and then the size of the area would be a primary consideration. However, in an urban setting most of the forest patches are already small. Setting a minimal size for something to be considered worthwhile would only further limit the already small number of sites that should be considered for protection. As a practical matter, if there were a minimum area, then in controversial situations, you can bet that a contested site would be subdivided into sections smaller than the minimum, through whatever arbitrary means that could be thought of, so that none of original area would meet the minimum size criteria. A comparable strategy has been used in the west to bypass the limits on water usage by larger commercial farms.

Similarly, I do not see how an old growth ecosystem concept can be adequately applied because how could you generate a numerical evaluation of where on the spectrum of old growth a particular urban site would lie? This an especially difficult problem when you are looking at different size parcels, with different starting forest ecosystems, with different human impact histories, and different degrees of impacts by different types of invasive species? Once a problem become too complex without any concrete way to assign values, then basically any result you desire can be created in an evaluation.

I think there must be a reasonable approach taken at the smaller scale level at which people often must deal. This is certainly the case for urban parks and properties that are too small to form completely self-contained native forest ecosystems. Cogs and pieces of the theoretical ecosystem will be lost through happenstance. The constituent forest patches will be heavily impacted by invasive species and other human impacts. Still, from a big picture view, the separate forest patches may constitute or support some kind of ecosystem. It just will not be the type of fully functioning ecosystem that is most desirable. But looked at from the smaller end of the scale, these incomplete systems are worth saving and can be maintained with some minimal degree of management.

The cores of these incomplete systems are the old trees and the other native species that are still hanging on in the face of the invasive species and human impacts. Perhaps the result will be a simplified form of a native forest system with some old growth, but that is still a rare to uncommon feature in an urban setting.

Considering that most forests in the immediate vicinity of urban zones have typically been cut at least several times in their history, any forest section that contains some old-growth characteristics is extremely rare and should be considered valuable. It is within this conceptual framework that any evaluation of a particular patch of urban or suburban forest should be conducted.

Most of the impacts considered above are indirect impacts. The key consideration in most cases is whether or not old trees are present. If there are any 150-year-old trees on a parcel, this demonstrates that the forest has not been completely cleared for at least that length of time. In an urban setting if more than a handful of old trees are present, those areas should be considered to be urban old growth and managed as such. Because urban old growth areas are so rare, they should be preserved and a management strategy should be developed that will enhance their old growth forest characteristics. These efforts will likely include removal of non-native planted and invasive species, treatment of trees and plants to protect them from invasive insects, removal of trash and debris from the site, efforts at limiting the impacts of human utilization, replanting and restoration of native tree and plant populations, and protection and restoration of natural water features.

Bibliography:
Frank, Edward. Old Growth Definitions, Sept. 12, 2006, ENTS Post http://www.nativetreesociety.org/oldgro ... debate.htm

Frelich, L. E. and Reich, P. B. Environ. Rev. Vol. 11 (Suppl. 1), 2003. Perspectives on development of definitions and values related to old-growth forests.

http://groups.google.com/group/entstree ... 0835807fe&


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"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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edfrank
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What is Urban Old Growth?

Post by edfrank » Sun Feb 24, 2013 1:04 am

DON BERTOLETTE
10/5/09
Ed-
I was in travel status when your treatise below came out, and it wouldn't download into my iPhone...briefly at home before returning to travel status, I've just read your post and it's clear that you've thought about this alot, and had a chance to refine it for presentation. Well done!
Comments? Do a search and find 'rehabilitation', replace it with 'restoration'. Why? If the site has gotten to the point of rehab (I use this phrase for strip mines, which can get rehabbed and in a reasonable period of time get revegetated, perhaps with some species reforested), then it is too far along that path to be restored to old-growth 'status'. As we have discussed before, resilience is the key issue..."if it ain't got that swang, it don't mean a thang, do wap do wap..."
Off to Eastern California for the rest of the month (I'll probably include the bristlecone pine forest!), have a wonderful leaf-peeping Fall!
-Don
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Don
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Re: What is Urban Old Growth?

Post by Don » Sun Feb 24, 2013 2:41 am

Ed-
Surprised to see this com up under active topics, but it was a good read, and I think I'd only add one thought to what we said already. I think the two words that I'd probably bring to bear would be 'resiliency', and 'disturbance'. While I understand your focus on the lower end of the 'area' scale, the old-growth stand (trying to stay away from the word ecosystem for your benefit) lasts ONLY if it has enough resilience to sustain itself through the natural disturbance regime its location has. That resilience isn't QUITE magic, but it involves an assemblage of species that has over the years provided the moisture storage, nutritional systems (eg, soil critters, symbionts, etc.), seed banks, pH buffers that sustained the stand through previous disturbances.
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
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Joe

Re: What is Urban Old Growth?

Post by Joe » Sun Feb 24, 2013 7:32 am

wow, I'll have to print out this thread- a lot to digest!
Joe

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Re: What is Urban Old Growth?

Post by edfrank » Sun Feb 24, 2013 11:26 am

Don,

This came out three years ago. The topic came up on another website, and I thought maybe I should repost it here again. Since its first introduction we have gained new people that likely have not read it, and longer term members might have some new thoughts on the subject. This article appeared in the Bulletin of the Eastern Native Tree Society, Volume 4, Issue 4, Fall 2009, p. 3-5. http://www.nativetreesociety.org/bullet ... v04_04.pdf
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Don
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Re: What is Urban Old Growth?

Post by Don » Sun Feb 24, 2013 3:26 pm

Ed-
I don't know either where the bottom limits are on acreage for 'stands of significance', but if they're to have any kind of permanence, it will be the vegetative (and yes, human) community that it's in, that succors it.
Another consideration where the climate or environment provides cyclic disturbance regimes (for example, in New England, wind events; in the Southwest US, wildfire) it will be the frequency and/or intensity that drives ecosystem response, presence or absence of 'old-growth' characteristics in a stand...: > }
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
http://www.akbigtreelist.org

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Re: What is Urban Old Growth?

Post by edfrank » Sun Feb 24, 2013 4:19 pm

Don,

I agree with you. At the lower limits the "Urban Old Growth" is not self sustaining without human community intervention and their persistence is dependent on the period of the disturbance regimes - many of which can also be affected by the actions of the human community.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

Joe

Re: What is Urban Old Growth?

Post by Joe » Sun Feb 24, 2013 6:04 pm

edfrank wrote:People who are in favor of preservation may use a broader definition that would restrict the cutting of the forest in order to preserve it for themselves and future generations.
Of course "cutting" could be destructive or very constructive if done right- good forest mgt. is a lot closer to preservation than any sort of land development- which is why, I suggest that those who push for more preservation and those who want more and better mgt. ought to be allies, though they seldom are. The foresters tend to despise those who want to "lock up the land" and the preservationists tend to despise "logging" as if it was all bad. It's all so unfortunate. There's enough land to do lots of both- especially if we tame the developers, who ought to be redeveloping land abused in the past.
Joe

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Re: What is Urban Old Growth?

Post by edfrank » Sun Feb 24, 2013 6:24 pm

Joe,

I don't really disagree with you, but I was characterizing the end points in the alternative positions.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Re: What is Urban Old Growth?

Post by jamesrobertsmith » Sun Feb 24, 2013 7:25 pm

I encounter lots of big trees here in Charlotte. Sometimes even little groves of them. Old growth, though...not sure. As you say, it depends on the definition.

http://tilthelasthemlockdies.blogspot.c ... green.html

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