Optimizing Growth in Red Maple Stands Through Targeted Thinning

Recently, I conducted a growth and yield analysis to support a forest management plan in Presque Isle County, Michigan. This case study focused on a red (soft) maple–dominated stand, where I used the Forest Vegetation Simulator (FVS)—a widely adopted forest modeling tool—to evaluate how different thinning intensities and cutting cycles affect stand productivity under a selection system.

The stand had an initial basal area of 232.74 ± 53.93 ft²/acre (95% confidence interval), reflecting a dense, mature condition. My goal was to determine the optimal residual basal area—the amount of standing wood left after a harvest—and the ideal cutting cycle length, or time between harvests. In simpler terms, I wanted to find the sweet spot where we maximize growth without overharvesting or leaving too much competition behind. This analysis will help landowners and forest managers make better long-term decisions, especially when planning harvests for the Michigan Qualified Forest Program and other programs where commercial harvesting is essential.

Modeling Growth Across Thinning Intensities and Cutting Cycles

Using highly-detailed forest inventory data that included all trees down to 1-inch diameter at breast height (DBH), I created 24 FVS simulations. These scenarios tested residual basal areas from 60 to 200 ft²/acre across 10-, 15-, and 20-year cutting cycles. Including small-diameter trees in the inventory was key for assessing the stand’s regeneration capacity without needing to model additional recruitment.

The figure showcases gross annual basal area growth ft²/acre/year (vertical axis) as a function of residual basal area ft²/acre (horizontal axis) for various cutting cycle lengths. Tree growth increases with residual density, peaking around 160-180 ft²/acre for each cutting cycle (e.g., 10, 15, and 20 years). Simulated harvests followed a q-factor¹ of 1.4, which helped maintain a balanced range of tree sizes. This pattern supports using moderate thinning to maximize stand development between cutting cycles.

Identifying the Optimal Harvest Intensity

The results showed a unique parabolic trend in gross annual basal area growth relative to residual basal area. Growth peaked between 160 and 180 ft²/acre, with the highest rate—3.9 ft²/acre/year—under a 20-year cutting cycle. Shorter cycles of 10 and 15 years yielded slightly lower peaks (3.7 to 3.8 ft²/acre/year), but the optimal residual basal area range remained consistent.

Outside this range, growth declined. At lower residual basal areas (e.g., 60 ft²/acre), the stand lacked sufficient growing stock to fully utilize site resources. At higher levels (e.g., 200 ft²/acre), excessive competition reduced diameter growth and limited sapling recruitment.

This parabolic response supports the existence of an optimal harvest intensity for uneven-aged red maple stands managed using a q-factor¹ selection system—a method that maintains a balanced distribution of tree sizes and promotes structural diversity across age classes.

Implications for Sustainable Forest Management

Red maple is a common hardwood in the Lake States, offering many ecological and economic benefits to forests. Based on this case study, several practical recommendations emerge for forest managers and landowners:

• Harvesting to a residual basal area using this method maximizes annual growth, boosting productivity by 20–30% compared to under- or over-thinning.

• The selection system, when applied at this intensity, supports an uneven-aged structure, increasing resilience to disturbance and enhancing long-term forest health.

• Including small-diameter trees in pre-harvest inventories (≥1-inch DBH) improves understanding of regeneration potential, which is critical for sustaining future stand development.

This analysis aligns with silvicultural principles detailed in Ralph D. Nyland’s Silviculture: Concepts and Applications, which references earlier research by Leak et al. (1969)². As with all forest management practices, site-specific factors and landowner goals should guide implementation.

We welcome feedback and collaboration from the forestry community to refine these strategies further. If you’re interested in how these concepts could be applied to your property, please contact us.

Footnotes

1. The q-factor represents the ratio of trees within a specific diameter class to those in the next smaller diameter class. A lower q-factor indicates a greater percentage of larger diameter trees.

2. Nyland, R. D. (2016). Silviculture: Concepts and Applications (3rd ed.). Waveland Press. Based on methods adapted from Leak et al. (1969).