by John W. Monroe, Owner, Monroe Timberland Consultants, and Quality Vegetation Management Certified Advisor
For most landowners, the first thinning of a pine stand generates a gross income of about $125 to $225 per acre. While that may not seem like much, the benefits of thinning can reap a much greater return in the long run. Thinning selected timber prior to a pine stand's final harvest is an important pine management technique. Although it provides some income through the sale of pulpwood, the primary reason for thinning is to create a better growing environment for the remaining dominant crop trees — the straightest, largest diameter trees with little or no defects — which translates to more valuable sawtimber at final harvest. The theory behind thinning is simple: to counteract natural mortality and maximize land use. Most Southern pine stands are established by planting more trees than the land can accommodate long term. For example, a stand established with 400-plus pine seedlings per acre may accommodate the trees' vigorous growth only for 12 to 15 years before running out of room for healthy growth. Thinning creates space for pines to add impressive diameter growth and reach their potential for sawtimber size sooner. In addition, thinning opens the forest canopy. Sunlight can then reach the forest floor, encouraging growth of native grasses and legumes that benefit wildlife. Unfortunately, this additional sunlight also encourages the growth of understory hardwoods, which negatively affects pine growth by competing for available water and nutrients. Applying herbicide and conducting controlled burns are probably the most important management techniques following thinning. They help maintain an open understory, better browse for wildlife, and easier access for hunting and recreation. Of course, the pines will grow faster, too, with no hardwood competition.
First, consider the age and size of the trees. A first thinning generally should occur when pines are about 16 years old. It could be earlier or later than that, depending on a number of factors, including the number of trees per acre, genetics, soil quality and the amount of competing vegetation. Pine stands on land previously used for row crops, for instance, may be ready for a first thinning at 12 years due to higher soil fertility and lack of hardwood competition. To account for these factors, use the trees' average diameter at breast height (dbh) to determine timing. Generally, the optimum time for a pulpwood thinning is when the average dbh of pines is about 6 inches and tree height is at least 40 feet. Another rule of thumb is to maintain 30 percent or more of total height in live crown in the dominant trees. Before proceeding, obtain an accurate inventory of the stand. This usually involves your consulting forester cruising the timber to estimate the number of trees per acre, average dbh, tree height, basal area, site index and growth rates. Growth rates are determined using an increment borer to gauge recent radial growth of dominant trees. If the distance between rings in the outer inch is narrowing, it indicates growth is slowing. Your consultant can then evaluate the information to determine whether the stand is ready for thinning, and to estimate the volume and type of forest products to remove. The data can also be used to project future timber volumes and timber sale revenues.
The Right Approach
The most commonly recommended thinning method is cutting every fifth row in a pine stand. While fourth-row and even third-row thinnings also are used, the latter removes too many trees. I prefer to keep row thinning to a minimum. Fifth-row thinning leaves groups of four rows that can be thinned from the side. On properties where rows aren't evident, have the logger cut a straight line about every 40 feet to create corridors, and then thin between the corridors. Most importantly, do what is right for your stand to improve its future value. Avoid cutting the best trees during the first thinning. Those crop trees fetch the best price at final harvest. The more crop trees a property has after a first thinning, the better.
Finding a Logger/Buyer
Seek the advice of your Quality Vegetation Management™ (QVM) Certified Advisor or consulting forester to choose a reputable logging company. Hiring loggers who do a professional job is just as important, if not more so, as getting the highest price. Most consultants open their projects for bidding to reputable logging crews to ensure that they contract a competitive price. The consultant also will supervise the thinning to ensure conditions of the contract are met. Many logging contracts include a 12-month cutting period for completing the project. To avoid getting caught without a logger, advertise for bids early. It might take a year to get a logging crew in to complete the thinning.
Consultants know the buyers and have worked with them in the past. They also know the current market rate for timber. Thorough experience with the bidding process gives consultants the background and knowledge to determine whether a bid is acceptable. The consultant's most vital role is to keep the best interests of the landowner (client) in mind.
Following a first thinning, I usually recommend leaving the stand alone for about one growing season. You may notice that hardwood competition will start to sprout during this first year. To eliminate these competing hardwoods, use Arsenal® herbicide Applicators Concentrate (Arsenal AC) at mid-rotation to promote growth of the crop trees. Perform this “release” treatment in the late summer or early fall, during the first growing season after thinning. The following winter, perform a controlled burn to reduce limbs and debris left after thinning, and to further control any undesirable vegetation. Depending on your objectives, controlled burning can be repeated every two to four years to maintain the open understory.
About John Monroe, ACF
John W. Monroe, a consulting forester and QVM Certified Advisor, opened Monroe Timberland Consultants in 1994. Based in Raleigh, N.C., the company serves private landowners in North Carolina and Virginia with a multitude of services, including forestland management planning, timber appraisal and timber sales assistance. In addition, Monroe is a licensed real estate broker and a certified arborist.
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