Long-Term Selection Cutting Study

Photo Credit

USDA Forest Service photo by Christel Kern

Height plot used to remeasure tree quality variables (2017). 

Early Findings 

In the 1960s, early analyses from the Cutting Methods Study found that medium selection produced the best balance of tree growth, timber yield, regrowth of new trees, and tree death. As a result, for more than 50 years, regional forest plans and forest management guides have often recommended variations of medium selection cutting. Medium selection means removing a moderate amount of trees so that a remaining standing crop of forest is stocked at about 75 square feet per acre of tree basal area remain.

Alternative selectio

n cutting approaches are light selection and heavy selection, which leave the residual growing stocks or basal area around 90 square feet and 60 square feet per acre, respectively. Early data analysis from the study found that light selection led to high quality trees remaining in the forest and poor regeneration of new trees. Heavy selection led to greater growth and high economic returns and lower quality trees remaining in the forest. Finally, medium selection produced the highest economic return in term of marketable timber.

Analysis Today

Today, data collection from the Cutting Methods Study and analysis of the historic dataset continues through collaborations between the research team from the Forest Service and universities.

Recent analysis has reaffirmed some study findings from the 1950s while uncovering new insights. Single-tree selection methods, particularly those that involve heavier cutting, are more financially rewarding and beneficial for forest growth. However, it is essential to strike a balance between cutting too much and leaving too many trees standing. This analysis also highlights the importance of long-term monitoring in forest management. While heavy selection can accelerate desired outcomes, it requires careful observation over many years to ensure sustainability.

Photo Credit

USDA Forest Service photo by Christel Kern

Forester T. Strong assists with tree size measurements in permanent plots on the Argonne Experimental Forest (2016). 

The original goal of selection cutting was to establish a balanced arrangement in forests with trees of various ages and sizes: many small trees, some medium-sized ones, and a few high-quality large sawlog trees. The idea was to harvest trees from all size classes gradually, allowing the stand to regenerate and maintain its original structure. However, a study published in 2019 found that this method hasn’t yet created a balanced uneven-aged stand. Instead of maintaining a varied age structure (uneven-aged), some forests continue to show characteristics of even-aged stands. This suggests that selection cuttings might take a long time to stabilize forests that are initially even-aged. At the same time, forests that were already uneven-aged the selection cutting method seemed to work well and kept the structure stable.

The Cutting Methods study’s focus on conventional forest management techniques means that it may not address all aspects of sustainable forest management, such as indigenous values, wildlife habitat, and carbon sequestration. Further research is needed to explore these aspects fully.

Despite its limitations, this long-term study is providing valuable insights into forest management practices and offering guidance to forest managers striving to balance economic and ecological goals. It also underscores the importance of continued investment in long-term research to ensure the health and sustainability of our forests for future generations.

Photo Credit

USDA Forest Service photo by Christel Kern

The Argonne Experimental Forest in northern Wisconsin was established in 1947. Most studies on the forest focus on how to bring second-growth northern hardwoods under management. 

Approach

At its inception, the forest was primarily composed of second-growth, even-aged trees, around 45 years old, with some older, low-quality trees scattered throughout. Within the study stands, different silvicultural treatments were randomly assigned to 1-hectare units. The treatments included variations of single-tree selection, diameter-limit cutting, crop tree release, and a control.

To assess the impact of these treatments, researchers established permanent sample plots in 1951 and recorded tree diameter, species, and other relevant data at regular intervals. They also evaluated factors like growth, mortality, and yield using sophisticated statistical analyses, including ANOVA and diameter-increment models.

Additionally, a financial analysis was conducted to measure the economic success of each treatment, focusing on harvested lumber volumes and values. This analysis used managed forest value (MFV) to evaluate the long-term sustainability of each silvicultural system.

The selection cuttings in this study have occurred every 10 years and have removed trees with poor form, overtopped crowns, and defects.

Cutting Methods Study Details

• The study has used three levels of tree cutting intensity: light selection (harvesting trees until about 90 square feet per acre of basal area remain), medium selection (75 square feet per acre of post-harvest basal area), and heavy selection (60 square feet per acre of post-harvest basal area).
• Diameter-limit cutting involves removing all trees 7 inches or more in diameter. The diameter limit was aimed to simply extract merchantable timber over a specified size threshold without consideration for the remaining forest or regeneration of the future forest.
• Crop tree release (also known as thinning), involves removing selected trees in younger, crowded forests to create a faster-growing, healthier forest with a greater number of desirable trees for timber. The crop tree release was a thinning tool to tend and improve the entire stand as one age class until maturity.
• Additional treatments have been applied but were not re-evaluated in the most recent analysis, including clearcutting, group selection, and strip cutting.