Summer 2010

Volume 19 No. 2

Maximizing future timber through forest improvement today

by Ron Rathfon & Mike Saunders

Forest improvement includes implementing practices that protect and sustain forest health and achieve landowner goals. It may simply involve fencing livestock out of the forest or preventing wildfires. Commonly, however, forest improvement includes timber stand improvement (TSI). Timber stand improvement focuses on increasing timber value of a forest through: 1) increasing the proportion of valuable timber tree species in a forest stand; 2) increasing the proportion of trees that have good timber form, high quality, and defect-free wood volume (i.e., crop trees); and 3) reducing the time it takes for crop trees to grow to maturity by increasing growth rates. Timber stand improvement may also improve wildlife habitat, control invasive species, and enhance environmental, scenic, and recreational values of the forest. Forest improvement is an investment in the future of your forest and should be a part of any written forest management plan.

According to Dr. William Hoover, Professor of Forest Economics at Purdue University, it is not uncommon for annual rates of return from a forest improvement operation on average to high-quality sites to exceed 10-15%. Reinvesting a small percentage of timber sale income back into the forest as forest improvement work makes good business sense. Forest improvement practices range from simply cutting grapevines to the very complex task of marking trees for an improvement harvest or a commercial thinning. Often, more than one of these practices is done in a single operation. With a little instruction, landowners can control vines and prune young crop trees. However, many landowners will want the assistance of a forester for doing most other forest improvement practices.

Pruning - This practice removes side branches from the lower trunk of a tree in order to produce clear, knot-free, and hence higher- valued wood. Do not prune species that self-prune naturally, such as tulip poplar.

Grapevine control - Wild grapevines should be controlled in areas where trees are being grown for timber, particularly on highly productive sites, and in areas soon to be harvested and regenerated under full sunlight. Grapevines can be controlled at any stage of development.

Invasive plant control - Following a disturbance in the forest, such as a timber harvest, invasive plants capitalize on the new open space and quickly spread into the disturbed area. Many invasive plants threaten forest regeneration, while others can destroy existing native trees (e.g., kudzu vine). If invasive plants are present in the stand or in adjoining stands or areas, their management and control should be included in the forest management plan. 

Cull tree removal - Severely damaged, excessively branchy, deformed, and disea sed trees often have little or no current or future commercial timber value. Depending on the tree species (e.g., oaks), you may retain these cull trees for wildlife food and cover, or as a seed source for future forest regeneration. Leave 4 to 6 cull trees per acre at least 11 inches in diameter for wildlife.

Preparing for forest regeneration - To regenerate a forest stand, older, mature trees are harvested from an area to create favorable light conditions on the forest floor for a new generation of sun loving tree seedlings to get established. Harvest, kill, or coppice all trees in the area to be regenerated, including the unmarketable ones.

Thinning - This practice removes selected trees from a stand to reduce compe tition and favor the growth, health and development of remaining trees in the stand. Timely thinning keeps crop trees healthy and growing to their full potential. Thinning can be done at any stage of stand development following crown closure, or when individual tree crowns begin to interlock and significantly reduce the amount of sunlight reaching the forest floor, and prior to stand maturity.


With a little instruction, landowners can control vines and prune young crop trees. However, many landowners will want the assistance of a forester for doing most other forest improvement practices. Federal and state cost share programs may be available to help pay for this work. A district forester can help identify and enroll properties in cost share programs, assuming funding is available. Visit for more contact information.

For more in depth information on forest improvement, see the Forest Improvement Handbook, FNR-IDNR-414 (28 pgs). Printed copies and web only versions are available from Purdue University Extension (

Ron Rathfon is an Extension Forester with Purdue University’s Department of Forestry and Natural Resources. Mike Saunders is an Assistant Professor of Silviculture in the Department of Forestry and Natural Resources at Purdue University.