The Stand – Is This Basic Management Unit Still Relevant in Variable Density Prescriptions?

The stand is the basic unit of forest management and one of the first concepts taught new forestry students taking a silviculture class. And this concept and term is probably one of the first used and defined by any forester providing management suggestions to family forest landowners. Helms (1998) in the Dictionary of Forestry[1] defined stand as: A contiguous group of trees sufficiently uniform in age-class distribution, composition, and structure, and growing on a site of sufficiently uniform quality to be a distinguishable unit. In my opinion, the key words here are uniform and distinguishable.

Ponderosa pine stand.
Ponderosa pine stand. Photo: Chris Schnepf, University of Idaho, Bugwood.org

We use this term, stand, to describe the basic silvicultural unit for planning and implementing management activities because thinking of the entire forest is way too complex. We therefore break the forest into management units called ‘stands’ for efficiency. Obviously, you would manage a red alder stand differently than a Douglas-fir/hemlock stand, and so.

In Washington State we find pure stands, such as Douglas-fir stands and ponderosa pine stands; mixed conifer stands, such as Douglas-fir/hemlock and hemlock/cedar stands; and even-aged, mixed conifer stands, such as a 15-year-old western larch and grand fir stand. There are many others, but mostly they have uniformity in species mixes, tree density, and tree ages. They also suggest that there is uniformity in forest floor vegetation such as the shrub/grass/herbaceous layer, often ignored in the past. As management for non-timber products and forest floor dwelling animals and reptiles becomes more important we must bring these stand attributes into the discussion as well. Traditionally the stand has remained a constant throughout time – at least during one rotation. For example a 25-year-old Douglas-fir stand will have trees that remain cohorts throughout their lifetime progressing from this aged stand to a 50, 60 70 age-stand etc. The collection of stands across your ownership defines your forest holdings. Traditionally, variability within the forest is thus achieved by variability between forest stands. This variability is often welcomed by family forest landowners who are interested in multiple ownership objectives from annual flowers to wildlife to timber harvesting. I have often told landowners in the past your forest is composed of a number of even-aged aggregates that taken as a whole define your forest. And these stands are often defined by past management actions such as logging or thinning or natural disturbances such as wind storms or wild fires.

The Conundrum with Variable Density Prescriptions

In a September 2013 Journal of Forestry article, The Stand: Revising a Central Concept in Forestry, Professors O’Hara and Nagel question the stand as a traditional basic concept.[2] They question the use of traditional stand attributes (species, ages, structures) when applying new management scenarios such as variable retention regeneration methods, or variable density thinning amongst others. Under these options, land managers and owners will be increasing within or intra-stand variability. Will then the traditional definition of a stand still be applicable? Will the original stand boundaries move over time? Will maps and other planning documents need to be redone? Will a new term be coined to address these stands under variable density management? These are heady questions for those thinking way into the future and contemplating management actions to achieve personal goals.

variable retention demonstration
Green tree variable retention demonstration treatment. Dog Prairie, Umpqu National Forest, Oregon. Photo: Doug Maguire, Oregon State University, Bugwood.org,

For example, you implement a variable density thinning in a portion of a pure Douglas-fir plantation that is 15-years-old on a good site, in the hopes of increasing the habitat diversity for aesthetics and song birds. Professors O’Hara and Nagel maintain that the original stand boundaries and other attributes will change ecologically over time. I agree, but I do not see the need to rewrite management plans and eliminate the original predetermined stands. Older stands and newer stands can overlap in management planning and can be illustrated on plan maps.

I do not feel that the introduction of variable density stands or variable retention harvests are a major stumbling block in planning future management options. Document these management changes in your activities diaries and plans. Or simply draw on your management maps the area of the overlapping stands. Yes, you may call them something new, but also record the original names and stand attributes, just like you would if a wildfire burned a portion of your forest creating new stands, for example: burned Douglas-fir plantation and unburned DF plantation. In another example, maybe you apply a variable density thin to a portion of a pure 20-year-old ponderosa pine stand and that splits it into two new stands; one called the 20-year-old PP variable density stand and the other retains the original name. The key here is to maintain good data records and or photo-points to document the changes from your variable density actions.

Two adjacent stands managed under a common variable retention harvesting scenario may also result in a larger combined stand that would simplify future data keeping. For example, one stand was harvested using a group selection cut and is adjacent to one that was harvested using variable retention. Over time in the following rotation, these stands boundaries are apt to coalesce into a single larger stand. Once again, record keeping is important here for future references, especially so younger generations know what the intent was with the initial stand entries.

I agree with O’Hara and Nagel that we do not need to invent a new term for stands managed under these new variable density scenarios, but simply need to document what has been done and change the boundaries as needed over time.

Therefore I believe the stand will remain the cornerstone of silvicultural prescriptions. However under modern alternatives the ecological and management history documentation will be paramount. I encourage you to read the article by O’Hara and Nagel and learn more about this new trend in stand nomenclature and impact. [3]

By Donald Hanley, WSU Extension Forester Emeritus

NOTES:
[1] Helms, John A. (editor) 1998.The Dictionary of Forestry. ISBN 0-939970-73-2. Society of American Foresters.

[2] Journal of Forestry 111(5):335-340.

[3] SAF restricts access to this article unless you are a SAF member or wish to pay for it. If interested, see the SAF website at www.safnet.org. Or better yet, borrow a copy from a SAF member.