Response of Soil Bulk Density and Mineral Nitrogen to Harvesting and Cultural Treatments

Abstract

The interactive effects of harvest intensity, site preparation, and fertilization on soil compaction and nitrogen mineralization were examined in a loblolly pine (Pinus taeda L.) stand growing on a sandy, well-drained soil in eastern Texas. The experimental design was 2 by 2 by 2 factorial, consisting of two harvesting treatments (mechanical whole-tree and hand-fell boles only removed), two site preparation treatments (bedded and unbedded), and two fertilization treatments (fertilized and unfertilized). Soil bulk density was measured before and after harvesting and site preparation. Ion exchange resin bags located at the bottom of soil columns were used to monitor nitrogen mineralization rates in the upper 15 centimeters of soil during the first two growing seasons following harvesting. The mechanical treatment had no effect on soil bulk density at 0 to 5 and 10 to 15 centimeter depths but significantly increased it at 20 to 25 centimeters. Bedding reduced soil bulk density at 10 to 15 and 20 to 25 centimeter depths. The mechanical treatment removed 16 percent more biomass and 127 percent more nitrogen than the hand-fell treatment, but had no affect on nitrogen-mineralization rates. Bedding significantly increased both total mineral nitrogen and nitrate formation during the first growing season but had no effect during the second year. The increase in mineral nitrogen due to the bedded preparation was equal to the increase in mineral nitrogen following application of 250 kilograms per hectare of diammonium phosphate. The results suggest that logging slash and other surface biomass has little influence on nitrogen-mineralization for the first two years after harvesting unless there is considerable soil disturbance and/or incorporation of the surface organic matter.

Citation

Zhou, Minyi; Carter, Mason C.; Dean, Thomas J. 1998. Response of Soil Bulk Density and Mineral Nitrogen to Harvesting and Cultural Treatments. Proceedings of the Ninth Biennial Southern Silvilcultural Research Conference