How to grow better pine forests for the long run: lessons from a 27-year study

In the southeastern United States, pine plantations rely on intensive site treatments to boost tree growth and shorten harvest cycles. Managers commonly raise soil beds to improve drainage and apply herbicides to reduce weeds and woody shrubs competing with young pines. Some researchers test double bedding, while others combine single bedding with herbicide applications. Although past studies show these methods enhance early growth, their long-term benefits remain uncertain.

To address this, researchers have tracked slash and loblolly pine plantations in the Lower Coastal Plain of North Florida for up to 27 years. Their long-term results, published in Forest Ecosystems, reveal which site preparation strategies deliver lasting gains in tree growth and productivity.

The University of Georgia team compared bedding timing (early vs. late), the number of bedding passes (single vs. double), and herbicide applications (pre- vs. post-plant) to identify the practices with the most sustained benefits.

They found that two-pass treatments consistently outperformed simpler methods. “Growth responses varied by location but were strongly linked to vegetation control, especially woody shrub management for long-term growth,” the authors reported. “In Florida flatwoods, early bedding followed by pre-plant herbicide applications provided the most effective vegetation control.”

More specifically, applying herbicide across the entire plot, rather than just in bands over the beds, generally resulted in equal or greater tree growth. The optimal timing for bedding depended on local conditions, but its effect was less significant than herbicide application. While double bedding improved control of woody shrubs, it often promoted herbaceous weeds, reducing its benefits unless followed by additional weed control.

These results provide valuable guidance for forest managers aiming to maximize productivity. For short-rotation timber crops, the study strongly recommends integrating herbicide use with bedding. For longer rotations, management can be more flexible, since growth differences between treatments tended to narrow over time.

Overall, the study highlights a key takeaway: effective control of both woody and herbaceous competitors is critical for improving pine growth. Investing in site preparation at the beginning sets plantations up for decades of stronger growth and higher productivity.