"How Can I Tell if My Woods are Old Growth?"

Discussions of the nature and definition of old growth and primary forests.

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Joe

"How Can I Tell if My Woods are Old Growth?"

Post by Joe » Tue May 29, 2012 6:56 am

http://northernwoodlands.org/articles/a ... old-growth
by Michael Snyder | April 10th 2012


Old-growth forests, sometimes simply called “old growth,” are just that: really old woods. Accordingly, they are marked by the presence of exceptionally old, typically large-diameter trees that are living, dying, and dead. For most forest types in our region, this likely means there are trees exceeding 150 years old and some may be as old as 200 (white pine), 250 (sugar maple), or 400 years (hemlock).

If you do have an old growth forest, consider yourself very lucky indeed, as truly old forests are exceedingly rare in the northeast. Most of our forests have been cleared for agriculture and cutover one or more times over the last few centuries. And although much has re-grown, and despite a strong history of conservation and good management since, trees in the secondary forests we see today are much younger and therefore significantly different from those that existed previously.

By most accounts, less than 0.5 percent of the current forestland in the northeast is old growth and no region in the eastern deciduous and mixed forest zone has more than 1.1 percent old growth. With a couple of notable exceptions in northern New Hampshire and Maine, most of the last remaining northeastern old-growth forests are small and isolated, restricted mostly to inaccessible steep land and wetlands. Still, if you have some particularly large-diameter trees in your woods, say, in excess of 25–30 inches, and there is little evidence of human intervention or large-scale natural disturbance, they just might qualify.

Because tree growth rates vary so much by species and growing conditions, diameters can be misleading. Thus, there is no good substitute for measuring the actual age of a tree. Fortunately, you do not have to cut down your prized old tree to determine its age by counting the annual growth rings on its stump. You can instead count the rings in a cross-section of the stem extracted as a pencil-sized core from the standing tree using a forester’s tool known as an increment borer. Ask any second-grader who’s had a visit from a local forester and they’ll confirm that it works like magic.

Except when it doesn’t. No, it is not foolproof. In very large, very old trees, the innermost rings of wood tend to be decayed and this makes an accurate estimate of the tree’s age impossible. But fear not. Even without an increment borer you can judge whether your woods are old growth by other means. In fact, the alternative approach involves a more complete understanding of the characteristics of old forests – most of which can be observed while simply walking through your woods and requiring no specialized equipment.

First, accept that old forests comprise trees of many ages and sizes. Sure, to be actual old growth, there must be some exceptionally old ones, but even the oldest woods contain many more young and middleaged trees than old ones. If you’ve got a range of tree diameters and at least a few lunkers in the mix, keep walking and looking, you might be on to something special. Next, look up at the canopy. Truly old forests have an uneven canopy with many scattered, small gaps owing to tree crowns breaking and falling here and there over an extended period of time. Young forests tend to have fewer large trees and fewer canopy gaps.

If your woods are truly old-growth, you will also notice an abundance of dead trees, both standing as “snags” and on the ground as “woody debris.” Importantly, in old growth this accumulated dead wood exists in many sizes and in varying stages of decay, reflecting the full range of ages and sizes of the living trees accumulated on the site over many years. This diversity of dead wood provides habitat for a wide range of animals – from insects to salamanders – as well as critical germination seedbeds and nutrient cycling for forest regeneration. In old growth you will also notice a greater abundance and diversity of herbs, lichens, and fungi, all of which support life forms and processes under-represented in younger forests.

Lastly, truly old forests will exhibit “pit and mound” microtopography, which reflects where trees were toppled by windthrow long ago but have decomposed, leaving only the pit, where the trees used to be rooted and mounds of soil that used to contain the roots.

Beyond all the good ecological science describing them, chances are you’ll just know it when you’re in an old-growth forest. All of those attributes add up to make a very different kind of forest, and when you’re in one, it is a difference you can feel.


Michael Snyder, a forester, is Commissioner of the Vermont Department of Forests, Parks and Recreation

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edfrank
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Re: "How Can I Tell if My Woods are Old Growth?"

Post by edfrank » Tue May 29, 2012 8:48 am

Joe,

Excellent! Thank you for posting this.

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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dbhguru
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Re: "How Can I Tell if My Woods are Old Growth?"

Post by dbhguru » Tue May 29, 2012 10:12 am

NTS,

Michael Snyder's description is pretty good, but needs amplification. So, I am presenting observations on some important points based on my own participation in old-growth research that began in the mid-1980s.

The New York Adirondacks have, by far, the largest old growth reserves in the Northeast. The only larger region in the eastern biome is the upper Mid-west, and northern Minnesota in particular. The southern Appalachians rank third. New Hampshire's and Maine's old growth is miniscule by comparison. My advice to anyone in the northeastern region who has the time and wants to see class-A old growth in abundance, visit the Dacks. For the East as a whole, Dr. Mary Byrd Davis's "Old Growth in the East" is still the most complete listing of old-growth sites that we have. "Eastern Old-Growth Forests - Prospects for Rediscovery and Recovery" by Island Press is still the most readable book about eastern old growth ecosystems and covers the subject from soup to nuts. I can list sources that cover the topic if desired. In time Dr. Joan Maloof's inventory as a result of her old-growth forest network will be an important source of information.

In terms of old-growth characteristics, the pit and mound micro-topography fits some forest types better than others. In particular, pits and mounds fit the forests that Michael Snyder is talking about, but mid-western oak-dominated old growth seldom exhibits this feature to any significant extent. There are reasons for it that I won't go into here.

Much of the surviving old growth in the East does not exhibit big trees because the growing conditions are too austere, and the sites are steep and rather inaccessible. The Cross-timbers in Arkansas, Oklahoma, Texas, and Kansas is a prime example. Small, gnarled post oaks and eastern red cedar reach advanced ages, yet most people who pass through those woodlands think of them as just scrubby and unimportant. The tops of rocky ridges in both the northern and southern Appalachians harbor old growth that has until recently gone unnoticed.

Contrary to the belief of some, there is an abundance of research on eastern old growth out there in the literature that dates to the early 1900s. It is just very scattered. Our own Dr. Lee Frelich, NTS VP, is one of the foremost experts on eastern old-growth forests on the planet. He is a source of infinite depth and experience. And we have others. Dr. Neil Pederson has seen and studied more than his share of old-growth sites. Then there is Dr. Dave Stahle, whose credentials are known around the world, and let's not forget Dr. Don Bragg. The list doesn't end there. Will Blozan has seen as much old growth as any of us, and often from up in the canopy. The list goes on. I mention these names because if there is a desire to discuss eastern old growth, we have no better place to turn than to the efforts of some current members of NTS.

One of our biggest challenges today is to decide where we come down on hands-off policies versus some form of management of sites identified as old growth. Today, our forests are faced by the invasives that threaten to eliminate important species. A strict hands-off policy makes little sense. Neither does turning over these sites to conventional forestry - a prescription for their elimination. Important old growth sites need multi-disciplinary scientific committees to oversee them and make the hard decisions to protect species from extirpation from sources that we humans introduced. This is basically the game plan for the forest reserves here in Massachusetts.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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