Most forest landowners will harvest timber at some time to generate revenue. There are three primary wood products that can be harvested during the life of a stand: pulpwood, chip-n-saw, and sawtimber. Pulpwood has the smallest diameter trees and the lowest monetary value. Larger diameter trees produce sawtimber for lumber and sometimes poles. Sawtimber and poles have the highest monetary value. Medium diameter trees produce chip-n-saw that can be used for both pulpwood and sawtimber. Several factors, including site characteristics, economics, and landowner goals in the management plan, influence the forest products produced over the life of the stand. When establishing or regenerating a forest, determining the planting density or spacing of trees is essential for future profits from the forest.
For southern pine stands, density has often been as high as 680 TPA (trees per acre) or 8’ X 8’ spacing. At this density, the hope is to do a first thinning of all pulpwood, a second thinning of chip-n-saw, and a final harvest of sawtimber with a possible third harvest of poles. Poles will require 40 or more years. However, the prevailing economics should be considered so that the profit at final harvest or first thinning exceeds the money invested in planting. If the demand and price for pulpwood are low, it may be better to plant at lower densities. Lower-density pine planting can allow landowners to harvest chip-n-saw at the first thinning instead of pulpwood. This will result in greater revenue at the first thinning, a final harvest of sawtimber for the landowner, and a more attractive harvest to potential loggers. A registered forester can help you understand your area’s forest product markets and advise on planting densities.
Lower density planting also offers other advantages. Due to the fewer number of thinnings, the likelihood of soil compaction and residual tree damage is reduced because heavy equipment enters the forest less often. The trees are more vigorous with higher growth rates due to lower competition from surrounding trees. The more vigorous trees will be more resistant to insects and diseases. The wider spacing can also provide for wildlife forage and the possibility of mixed pine hardwood stands. Spacings of 14’ or more between rows reduce road and trail building because machinery can move between the rows. A table with spacing and TPA can be found at Pine Stand Thinning – Clemson Extension Forestry and Wildlife.
Regardless of the spacing strategy implemented, landowners need to plant seedlings with superior genetics and growth rates. There are now loblolly seedlings with genetics that will produce high-quality wood even when grown at wide spacings. Ask a registered forester for assistance finding the best seedlings that suit your site quality and spacing choice. Mass control pollinated (MCP) seedlings typically have the best genetics, although open-pollinated (OP) seedlings are a viable option.
Spacing Considerations
Spacing for pulpwood and biomass production
Planting just to harvest biomass or pulpwood would require densities of 680 TPA or higher and higher planting costs. The competition between trees caused by the dense planting will eventually lead to growth stagnation due to light competition and poor root and crown development. The final harvest is typically when growth begins to stagnate. This strategy will produce lower profits in a shorter period of time (often 12 years).
Spacing for two thinnings and a final sawtimber harvest
The first thinning would be pulpwood while the second thinning would primarily be chip-n-saw. This would require an optimal planting density of 570 TPA but could be as high as 680 TPA. This could produce three cash flow opportunities, but pulpwood prices may not be profitable.
Spacing for one chip-n-saw thinning and final harvest
Another approach is to plant at wider spacing to lower planting costs and skip the first thinning for pulpwood. The first thinning would be for chip-n-saw, followed by a final harvest of sawtimber. This option offers some flexibility to adjust to the market. If pulpwood prices increase, you could do a first thin for pulpwood at an earlier age, but the chip-n-saw option is still an option at a later age. A spacing of 8’ X 12’ (454 TPA) or 10’ X 10’ (436 TPA) may delay diameter growth stagnation, lowering the chances of wind or ice damage, and providing trees with greater diameter and height at first thinning. The wider spacing can also provide enough sunlight for wildlife forage and wildflowers for pollinators.
Spacing for final harvest only at age 25-30
All thinning can be skipped with just a final harvest for sawtimber. Planting density should be 175 to 303 TPA. A 12’ X 12’ planting spacing can yield nearly twice the sawtimber volume as 8’ X 12’ spacing when harvested at age 25. This may be a good option for parcels less than 20 acres to provide an economically attractive product (sawtimber) to wood buyers or in areas with poor pulpwood markets. Due to the wide spacing, this strategy could also provide forage for wildlife and wildflowers for pollinators.
References:
Amateis, R.L. and A.E. Burkhart. 2021. Rotation-age results from a loblolly pine spacing trial. Southern Journal of applied Forestry 36: 11-18.
Cartner, T. 2018. “Are You Dense? Science-based Loblolly Pine Planting Density Recommendations.” https://www.forestryandland.com/post/are-you-dense-science-based-loblolly-pine-planting-density-recommendations
Hiesel, P. and J. Steele. 2022. Pine Stand Thinning. Clemson Cooperative Extension, Clemson, SC. Pine Stand Thinning – Clemson Extension Forestry and Wildlife.
VanderSchaaf, C.T. 2023. Loblolly pine planting densities for landowners in areas with poor pulpwood markets: some considerations. Journal of Forestry 121: 383-390.
Wayne Bowman, James W. Garner, John Scrivani, James Starr, and Tim Tigner. 2005. Virginia Department of Forestry. Forestry Topics FT0003. Facts About Low-Density Plantings of Loblolly Pine: Advantages of Planting Fewer Trees Per Acre.
Author(s)
Robert Carter, Cooperative Extension, Forestry and Wildlife Agent
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