Effect of Harvest Residue Management on Tree Productivity and Carbon Pools during Early Stand Development in a Loblolly Pine Plantation
Soil incorporation of postharvest forest floor or logging residues during site preparation increased mineral soil carbon (C) and nitrogen (N) concentration and had a differential effect on early stand growth in a clonal loblolly pine (Pinus taeda L.) plantation. Incorporating 25 Mg ha1 of forest floor (FF) (C/N ratio 112:1) or 25 (1LR) or 50 (2LR) Mg ha1 masticated logging residues (C/N ratio 856:1) increased soil C concentration by 2449% in the top 60 cm of soil compared with that for a nontreated control or a raked (R) treatment where the forest floor (25 Mg ha1) was removed. Although the long-term treatment effects on soil C are unknown, increased macro-organic matter C (150 –2,000 μm) in the recalcitrant heavy fraction coupled with an estimated 20- to 35-year turnover rate for the incorporated residues suggests that soil C will be elevated in the FF, 1LR, and 2LR treatments through the current rotation. There was a treatment age interaction on stand volume growth (P 0.03) caused by a differential response to FF and LR treatments. Relative to the control, the FF treatment increased stem volume growth and stand homogeneity, resulting in 18% more stand volume at age 6. In contrast, the LR treatments initially suppressed volume growth; however, at age 6 there were no significant differences in stem volume among control and LR treatments. Six-year stand volume was 116.6, 112.6, 135.1, 116.0, and 112.3 (SE 3.6) m3 ha1 in the control, R, FF, 1LR, and 2LR treatments, respectively. Whereas the efficacy of organic matter management will be site-dependent, our results suggest that soil incorporation of forest residues during site preparation can have positive benefits for productivity and building soil C on sites with relatively high inherent soil C stocks.