Economic feasibility of and vegetation responses to biomass harvest in managed loblolly pine plantations

ABSTRACT

We evaluated two biomass harvest methods, (1) Whole Tree Thinning (WTT; third-row thinning), and (2) Whole Tree Thinning with Fuelchips (WTTF; third-row thinning plus remove all accessible hardwood stems >2.5 cm diameter at breast height and understory shrubs in thinned area of stand) in a 21-year-old loblolly pine (Pinus taeda L.) plantation in northwest Florida for their harvesting yields and productivities, costs, and effects on groundcover. Both WTT and WTTF produced similar quantities of roundwood (~70 Mg ha⁻¹) and chips (8.43–13.12 Mg ha⁻¹) without significantly added operational time (15.77–28.12 Mg h⁻¹). On-board costs of chip production (US$6.93 to 10.60 Mg⁻¹) and total cost of roundwood and chip production (~22.5 US$ Mg⁻¹) of the two harvest methods also did not differ significantly. Following either WTT or WTTF, overall percent groundcover recovered within 6 months. While shrub and grass cover were similar, forb cover in WTT increased significantly following six months of harvests. Importantly, the study suggests that biomass removal is an attractive option that could be integrated with traditional silvicultural thinning methods to manage vegetation and alleviate hazardous fuel and wildfire conditions, leading to improved forest health.

KEYWORDS:

• Restoration
• harvest methods
• southern pine
• even-aged stand
• forest health
• silviculture
• bioenergy

Acknowledgments

The study was funded by the Florida Department of Agriculture and Consumer Services (Contract # 018711). The authors gratefully acknowledge Florida Forest Service for allowing access to the study site at the Blackwater River State Forest, FL, and coordinating the harvest operation as per study guidelines. Justin McKeithen and Jesse Goyer are gratefully thanked for their efforts with data collection and valuable inputs to the manuscript. Comments of two anonymous reviewers helped significantly improve the manuscript. The authors or their affiliations do not endorse any brand or model names mentioned in the study. The use of any brand or model name in this manuscript is purely for the information to the readers.