May 26, 2017, 8:56 pm
Thinning Southern Pine Stands

Sustainable forest management takes in to account the long-term health of the forest ecosystem while providing present and future generations with environmental, economic, and recreational opportunities. Southern pine stands demand full sunlight to combine with adequate soil nutrients and water for healthy growth. When the individual trees within a stand become crowded the competition for available sunlight, nutrients, and moisture hinder growth. Removal of some of the individuals in the stand is necessary so that the remaining trees may grow and remain healthy. Thinning allows the factors of growth to be reallocated to the remaining individuals in the stand. The benefits of thinning in southern pine stands are well documented to include an increase in stand health, revenue generation, and enhanced wildlife habitat.

Due to nature’s pre-disposition to competition, a pine stand left unmanaged will start to experience inter-tree competition for vital resources such as nutrients and light as both individual tree and stand canopy density increase. This can affect tree shape and height, two primary factors in determining the value of the stand. Once the initial period of free growth is complete and the forest has filled in, growth stagnates and quickly begins to change as the trees either attempt to gain more light or as they are crippled by lack of nutrients. This can lead to diseased and unstable trees that are more susceptible to invasive pests and wind damage. Under prolonged competition for resources, smaller trees will eventually die. While this natural process is known as “self-thinning,” it is not an option for those wishing to optimize growth patterns. Unbalanced tree proportions resulting from limited nutrients and affecting the tree’s carbohydrate balance lead to increased mortality. Without a live crown ratio of 30-40%, southern pine trees are thought to have too little foliage density to respire effectively for optimal growth.

 

 

If a pine stand is thinned to maximize tree health and profitability, the stand will not reach the crowded “self-thinning” stage. Instead, trees that grow at a desired rate and maintain optimal crown and carbohydrate ratios will be retained, thus yielding a higher-quality product. Additionally, in our carbon conscious time, it allows a greater amount of carbon to be sequestered per acre over the life of the stand.

It is important to understand the options available when thinning to determine how it will affect any particular stand. Two common thinning methods used on planted southern pine stands are selective thinning (removal of smaller or poor quality trees) and row thinning. Used in conjunction, these methods produce the best biological benefit to the stand while providing supplemental income early in the rotation. It is widely accepted that southern pines are most responsive to thinning at young ages (10-15 years). Thinning is not a “one and done” land management practice. Since it can take 30 or more years for a stand to reach maturity, thinning should be a consistent land management tool until the stand has matured. The first thinning typically removes about half of the trees and a third of the basal area of a stand while each subsequent thinning is done on a maintenance basis to remove small and diseased or poorly formed trees whose live crown ratios have dropped below 30%.

The benefits of thinning a southern pine stand are numerous. Thinning helps to keep the stand in optimal health by allowing adequate water, nutrients and light for the stand. When these important resources are limited, growth slows and portions of the stand may die. By removing competing trees, the growth is concentrated to fewer, faster growing trees which helps to reduce the time required to reach harvestable size. Once at a harvestable size, a thinned stand will generally have trees with a larger diameter. Trees with an increased diameter can be used for chip-n-saw logs or sawtimber as opposed to pulpwood bringing in higher revenues for the landowner. Although prices may seasonally and geographically fluctuate, current prices for pulpwood stand around $13/ton, chip-n-saw prices are around $17-19/ton, and sawtimber prices are around $32/ton. By properly managing pine stands, there is a greater probability for the client to receive higher monetary yields for individual trees during the thinning process and at final harvest. Wildlife habitat is favorably impacted by thinning of southern pine stands. Openings within the forest allow movement through the landscape. Deer and small mammals, turkey and ground nesting birds benefit from the native grasses and increased browse which develop with sunlight penetration.

Revenue generation, stand health, improved wildlife habitat, and an increase in stand value are all benefits of choosing to responsibly manage southern pine stands by periodically thinning. Not only does thinning provide a more optimal environment for the trees by limiting competition to water, light and nutrients by removing poor quality trees but it also provides the land owner with supplemental income as they wait for the pine stand to mature. Land owners have various options when it comes to thinning and should work with forestry professional to create a schedule that is economically and biologically fit for their pine stands.