Effects of harvest intensity, site preparation, and herbicide use on soil nitrogen transformations in a young loblolly pine plantation

The interactive effects of harvest intensity (whole-tree vs. stem-only), site preparation (chop and burn vs. shear-pile-disk), and silvicultural treatment (herbicide-pesticide vs. none) on N pools and transformations were determined in a young loblolly pine plantation on the North Carolina Piedmont. Harvest intensity had little effect on N transformations in years 3–5 post establishment, but shear-pile-disk site preparation and especially herbicide treatment caused increased net N mineralization and nitrification in the treated plots. Laboratory experiments with 15N label yielded reduced rates of N immobilization in the herbicide treated plots, demonstrating long-term consequences of treatment for soil N transformations.