Primary and Old Growth Forest - Archive of Older Posts

"The population of trees that live to be old is a very small, and selective, subset of original seedlings."
 Dr. Robert Van Pelt, Sept. 24, 2007 

Old Growth and Primary Forests

On March 14, 2010 The Eastern Native Tree Society and Western Native Tree Society switched from discussion lists on Google Groups to a new discussion list in a Bulletin Board format at:  Posts made since the inception of the BBS on march 14, 2010 will be sorted and archived on the BBS. Click on the link above to go to the equivalent section on the new BBS. This website will continue to serve as a front end for the ENTS and WNTS groups. It will continue to serve as a repository of older posts, and will serve as the host site for special projects and features that are not well suited for a BBS format. Please visit the BBs for the latest information and trip reports.

Primary and Old Growth Forest

by Edward Forrest Frank

Old growth forest is a term that everyone has heard. It refers to forest stands that have a large number of old trees. Defining the specifics of what is an old growth forest is a much more complicated proposition. The terms "primary forest" or "natural heritage forest" may be more appropriate terms for management and study purposes because their definitions recognize that forests are part of a dynamic system that are affected by natural disturbances and regrowth.
cottonwoodgroves.jpg (25299 bytes)

The Minnesota Department of Natural Resources  defines old growth as follows: "Old-growth forests are natural forests that have developed over a long period of time, generally at least 120 years (DNR definition and consistent with definitions for the eastern United States), without experiencing severe, stand-replacing disturbance--a fire, windstorm, or logging. Old-growth forests may be dominated by species such as sugar maple, white spruce, or white cedar that are capable of reproducing under a shaded canopy. These old-growth forests can persist indefinitely.  Old-growth forest may also be dominated by species such as red pine, white pine, or red oak that do not reproduce as well under shade and that require disturbance to open the canopy. These old-growth forests will eventually be replaced by the more shade tolerant tree species in the absence of disturbance."

The attempt to define old growth is a mire of different viewpoints, perspectives, motivations, terminology. A simple all-encompassing definition doesn’t exist as the characteristics of an old growth forest varies from locality to locality and from forest type to forest type.  Maurice Schwartz found ninety-eight separate definitions of old growth with an internet search. The above definition has problems itself. Some forest types are dominated by trees with a lifespan of less than 120 years. These forests otherwise may have all of the characteristics of old growth but are excluded by the time criteria stated above. The definition is also ambiguous with respect to how much disturbance is severe disturbance.  Regulators want a strict definition that can be applied without compromise, dynamicists want a definition based upon processes that are taking place in the evolution of the forest, environmentalists want a more encompassing definition to include areas peripheral to the oldest forest which are essential to maintaining ecosystem integrity, lumbering interests want a limited definition that says that very little forest is old growth because of potential public opposition to timbering old growth forest.

Old Growth Forest can also be defined (after Frelich 2002): Forest that meets a threshold determined by some political and (or) scientific process.  Often officials working for public land management agencies will propose a threshold and then get feedback from elected officials and the public to develop a final threshold. These thresholds can vary considerably and could include one or more of the following: a minimum stand age; minimum age of trees, either absolute age or relative to their potential maximum age; minimum size of trees (either absolute or relative to maximum potential for the site); stage of development and succession; and degree of naturalness, such as the historic lack of logging.

 Remnants of 200 year old jack pine, red pine and birch forest on Three Mile Island, Seagull Lake, blown down July 4, 1999 and burned Sept. 2002. Note young paper birch and red pine regeneration 2 feet tall.

Under many definitions an old growth forest that has suffered a fire, blowdown, or other natural disturbance would cease to be old growth with the loss of old trees. Lee Frelich (Sept 30, 2004, ENTS post) wrote: "There is not and never will be a biological definition of old growth. Since old growth is a human construct, it is what people say it is, and that varies among political jurisdictions. However, if you want a simple inclusive definition for outlining forests on the ground for preservation, then use primary forests (forests that have not been logged). 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 amount of human disturbance that disqualifies a stand from the category of primary forest. Also, primary forest includes a stands dominated by young early successional forest, old early successional forest, young late successional forest, and old late successional forest."

"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 heavily logged for timber by Native Americans or by European settlers. Historical records and paleoecological evidence can often be used to establish the existence of primary forest; in many parts of North America large-scale logging is a recent phenomenon and stand ages greater than the dates of first logging can be used to establish primary status." (Frelich and Reich, 2003)

"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 highgrading." (Frelich and Reich, 2003).

"The old-growth forest that blows down, whether 25%, 50%, or all of it, is still primary forest and has the potential to recover to a developmental stage with large old trees. Since all forests are created by disturbance, this is part of the natural cycle. The most important function of reserved old-growth forests is to see how they respond to and recover from disturbance." (Lee Frelich, ENTS post Oct 2, 2004) 

The challenge is to refocus the debate over natural forests to "primary" rather than "old growth", which is simply a snapshot in the life of the primary (and autopoietic) forest. The danger in continuing to focus on "old growth forests" is that as these forests undergo natural disturbance policymakers could legally (and quite logically) take them out of protection. (Gary Beluzo, ENTS post Oct. 3, 2004)

Most people are impressed by large old trees. They are more motivated to visit and protect these stands of ancient forest. A relatively young, early successional forest, may be a primary forest. Lee Frelich (ENTS post, Oct. 4, 2004) argues: "Most tree populations in the northeastern U.S. that have not been logged go back 3000-5000 years. That usually interests most people, especially when you tell them that the young post-disturbance forest is carrying on a 5000 year heritage." An educational goal would be to make people aware of the long history of these primary forests.

sedonacanyon001.jpg (109728 bytes) Old Growth forest in Sedona Canyon, Arizona

Can other plant communities can be called old growth or primary growth? Yes, without any doubt,  a threshold for level of human disturbance that disqualifies a community from being primary can be developed analogous to the criteria for primary forests. For example, a savanna that did not have the trees cut, was never plowed, and can be restored and maintained by prescribed fires would qualify.  Lee Frelich (ENTS Post Feb 10, 2004) wrote:  "Minnesota Department of Natural Resources recently switched to natural community-based definition for forest and other vegetation. They used ordinations including trees, shrubs and understory plants to separate communities within each region of the state. The ordinations were based on thousands of plots where all trees and plants were identified by Natural Heritage Ecologists. Those plots that fell together in clusters in multi-dimensional ordination space defined a natural community, and the characteristics of those plots were used in the descriptions that have now been published." 

The PA Bureau of Forestry,  has an
discussion of the term old growth: "Finally, it is also important to include representatives of different ecosystems in old growth, not only the typical hemlock-white pine or hemlock-beech associations of the well-known Cook Forest and Heart's Content. It is for those reasons that places are included in this tour such as Bear Meadows (a large ancient bog) and Cranberry Swamp, giving visitors a broader vision of the varied components of the entire macro-system. While it is true sometimes that "we can't see the forest for the trees," it is just as true that we should not confuse the forest with the trees. In other words, while we speak of old-growth forests in terms of the major tree species found there, old-growth is really a term describing entire ecosystems. The other plants and animals who live within the tree-defined framework are vital to the whole."

Clearly the Eastern Native Tree Society needs to be on the forefront of these issues. We need to characterize not just big trees, but areas of primary forest as well. We need to consider old growth or primary growth not just in terms of the trees present, but as part of a wider ecosystem. We should not ignore the cactus forests, the prairie grasslands, and the tundra as part of the whole.

Frelich, L. E. 2002. Forest dynamics and disturbance regimes, studies from temperate evergreen-deciduous forests. Cambridge University Press, Cambridge, U.K.

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.
-  Edward Frank, October 26, 2004 Gary Beluzo, Professor, Holyoke Community College, wrote on Sept.23, 2007, concerning management of forest systems: 

"A natural system is ... "a complex autopoietic system is regulated internally; the sum total of all genomes present. This is not to imply anything teleological.   Complex systems can spontaneously order without "purpose" and begin to show some characteristics of what we call "Life". A very simple example would be a hurricane. But, a better example would be what are called "dissipative structures", chemical reactions that maintain themselves as long as the reactants are available. So, natural systems are complex because there is no single cause and effect, no single causative pathway. In fact, the "control" is comprised of multiple positive and negative feedback loops that operate on "auto pilot" without consciousness. These systems have evolved over time through trail and error resulting in adaptations that WORK. Natural systems should NOT be managed because they are already a "perfect world"   I believe that management is appropriate for anthropogenically disturbed/maintained systems. In this case, a single species has consciously altered a system and is managing it for utilitarian purposes. The natural trajectory has been altered; the system has been taken off "auto pilot" and is now evolving according to the desire/purpose of one species, one genome. The system is greatly simplified, particularly in the causative control of that system. It is linear, less resilience, less capacity to adapt."



Orwig, D.A. and A. D'Amato. 2007. Southern New England old-growth forests: how much is left and can they help inform management decisions? pp. 10-11 in Old Growth in the Northeast. New England Society of American Foresters Quarterly

Pederson, N., A. W. D�Amato, and D. A. Orwig. 2007. Natural History from Dendrochronology: Maximum Ages and Canopy Persistence of Rarely Studied Hardwood Species. In: Proceedings of the 15th Central Hardwood Forest Conference. Knoxville, TN.

D'Amato, A.W., D. A. Orwig, and D. R. Foster. 2006. New Estimates of Massachusetts Old-growth Forests: Useful Data for Regional Conservation and Forest Reserve Planning. New England Naturalist. 13(4):495�506
  • Lund, H. Gyde. 2005. Definitions of old growth, pristine, climax, ancient forests, degradation, desertification, forest fragmentation, and similar terms. [Online publication], Gainesville, VA: Forest Information Services. Misc. pagination.  

© Copyright 2002, 2003 Eastern Native Tree Society