What Happened to the Trees?
by David Bakke, Forest Silviculturist
In your trips into the woods, many of you have been exposed to a variety of forest management methods and tools. However, you have likely only been truly aware of one harvest method, clear cutting. This is unfortunate although understandable; clear cutting is an intensive management tool that is easily discernable. But forest management can and does involve so much more than clear cutting. This article will try to place clear cutting in its management context and also try to describe the other commonly used harvest methods employed by professional foresters in the central Sierras.
To begin with, why are clearcuts so obvious to you? Because they appear so obtrusive in the landscape. A grove, or stand, of trees that you might be familiar with is harvested, and in its place is a dramatically different opening. You may wonder why this was done. There is a biological reason for clearcuts, as there is with the other harvest methods that foresters use. In part, the method that a forester uses is based upon the characteristics of the tree species that are being managed. This is a special field of forestry known as silviculture (from the Latin, meaning the cultivation of trees or groups of trees). The other part of forestry that may help determine the harvest methods are the objectives of management. Is the landowner interested in maintaining the highest financial return from the property, or more interested in growing the biggest trees?
Even-aged and Uneven-aged Management
There are two basic management systems used in the Sierras that landowners employ if they are interested in long term forest management. These two systems are often referred to as even-aged management and uneven-aged management. In the past these two systems' were easily distinguished from each other, although these days there is often some blurring between the two. These two management systems have been developed over about the last 100 years. As traditionally taught in forestry schools, even-aged management refers to a system where a stand of trees is maintained over time as single-aged, and eventually are harvested all at once, in a regeneration harvest. After this regeneration harvest, a new stand of trees is established, either through planting or relying on natural seeding, so that another single-aged stand is begun. Uneven-aged management does not maintain this single-aged stand, but rather, as the name implies, within the area of management there will be several different age groups present. At no point in time is the entire management area regenerated and a continuous cover of trees is maintained.
The management of an even-aged stand may begin as a plantation of newly planted seedlings. We start out with lots of seedlings with the intention of thinning them out over time as they grow and compete with each other. Thinning is a technique of removing certain trees to provide growing room to those desirable trees that remain. Over the life of a stand, it may be thinned four or five times, with fewer and fewer trees taken out over time. At a determined age, the stand is harvested for the final time (known as a regeneration harvest). This time of final harvest can be determined economically, biologically, or based upon a desired tree size. In even-aged systems, the regeneration harvest is where the clearcut comes into play. This is one method of conducting the regeneration harvest. There are others, such as a shelterwood, where several trees (S to 15 per acre typically) are left to provide seed and shelter for the developing stand; or a seedtree cut, where trees are left (3 to 7 per acre) to provide seed for the developing stand. The decision to use a particular method is often based upon the species being managed. Species such as ponderosa pine are often managed through clear cutting, since they are very tolerant of full sun; whereas species like red fir may be managed through shelterwoods, since they need some protection as seedlings. It is in fact the misapplication of this regeneration harvest that often leads to the problems we see with this system. Clearcuts are appropriate for regeneration of species such as ponderosa pine, but if used in the red fir type, this can present management problems. The scale of the final harvest can also provide some problems; a ten acre clearcut has much less impact than a one hundred acre clearcut.
An uneven-aged stand really has no beginning or end, although portions of it may. This probably needs some explanation. In order for uneven-aged management to work as a long term system, there must be provision made for the establishment of new seedlings, so that all age classes that are desired are maintained, over time. In order to provide this opportunity, an opening must be created. The size of the opening created is used to describe the two methods normally applied. The first method is called group selection, and as the name implies, a small area is cut, normally 1/2 to 2 acres in size. This has the appearance of a very small clearcut. This method is used when sun loving species such as ponderosa pine are part of the desired species mix. The second method is called single-tree selection, which as its name implies involves the removal of a single tree, creating a very small opening, normally less than a quarter acre. This method is used where sun loving species are not part of the desired species mix; because the size of the opening is often too small to allow such species to grow. The group selection method may involve planting of seedlings or relying on natural seedling establishment; the individual tree selection method relies on natural regeneration.
So what type of management is practiced on the Eldorado National Forest? The 1989 Land and Resource Management Plan called for rather intensive even-aged management utilizing clear cutting as the main regeneration harvest method. This method of management was chosen because of the high level of production that could be sustained over time, with rather minimal investment in time and money. But because of some shortcomings in this management method, based on visual concerns, effects to biodiversity and ecosystem functioning, clear cutting in particular, and traditional even-aged management in general is not the current management direction on the Eldorado, or any national forest in California. We are in an age of transition and uncertainty as to our future direction. It would be easy to say that we are moving towards uneven aged management, but that is not entirely true either. The management of the Eldorado will likely be a blending of traditional methods, adapting these methods to fit the realities of today.
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