Impact of management on nutrients, carbon, and energy in aboveground biomass components of mid-rotation loblolly pine (Pinus taeda L.) plantations

CONTEXT : To sustainably manage loblolly pine plantations for bioenergy and carbon sequestration, accurate information is required on the relationships between management regimes and energy, carbon, and nutrient export. AIMS : The effects of cultural intensity and planting density were investigated with respect to energy, carbon, and essential nutrients in aboveground biomass of mid-rotation loblolly pine plantations, and the effects of harvesting scenarios on export of nutrients were tested. METHODS : Destructive biomass sampling of a 12 years-old loblolly pine culture/density experiment, and analysis of variance were used to assess the effects of cultural intensity (operational vs. intensive) and six planting densities ranging from 741 to 4,448 trees ha⁻¹. Two harvesting scenarios (stem-only vs. whole-tree harvesting) were assessed in terms of energy, carbon, and nutrient export. RESULTS : The concentrations of energy, carbon, and nutrients varied significantly among stem wood, bark, branch, and foliage components. Cultural intensity and planting density did not significantly affect these concentrations. Differences in energy, carbon and nutrient contents among treatments were mainly mediated by changes in total biomass. Nutrient contents were affected by either cultural intensity or planting density, or both. Stem-only harvesting removed 71–79 % of aboveground energy and carbon, 29–45 % of N, 28–44 % of P, 44–57 % of K, 51–65 % of Ca, and 50–61 % of Mg. CONCLUSIONS : Stem-only harvesting would be preferred to whole-tree harvesting, from a site nutrient conservation perspective.