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This article in SSSAJ

  1. Vol. 63 No. 4, p. 990-998
     
    Received: May 18, 1998


    * Corresponding author(s): kpiatek/r6pnw_olympia@fs.fed.us
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doi:10.2136/sssaj1999.634990x

Nitrogen Mineralization in a Pine Plantation Fifteen Years After Harvesting and Site Preparation

  1. Kathryn B. Piatek *a and
  2. H. Lee Allenb
  1. a USDA-FS, Pacific Northwest Research Stn., Olympia Forestry Sciences Lab., 3625 93rd Ave., Olympia, WA 98512-9193 USA
    b Dep. of Forestry, North Carolina State Univ., Box 8008, Raleigh, NC 27695 USA

Abstract

Intensive site preparation for forest tree planting may result in a mid-rotation decline in soil N availability. Such decline has not been fully documented. This study was conducted in a loblolly pine (Pinus taeda L.) plantation in the Piedmont of North Carolina to evaluate the effects of nutrient removal during harvest and site preparation on N availability at mid-rotation. Treatments, installed in 1981, consisted of a combination of harvest (stem-only vs. whole-tree) and site preparation (chop and burn vs. shear, pile, and disk), with a split-plot of vegetation control (no herbicide vs. herbicide). In 1995 net N mineralization was examined by monthly in situ soil incubations from May through November (7 mo). Net N mineralization was approximately 3 times lower at mid-rotation than shortly after treatment. A 5°C drop in soil temperature at 10-cm depth helped explain ≈50% of this decline. At mid-rotation, harvest intensity, but not site preparation intensity, affected N mineralization, with stem-only harvest plots mineralizing 11 kg N ha−1 more than whole-tree harvest plots during the seven months. Chop–burn–no herbicide plots mineralized 34(±3) kg N ha−1, chop–burn–herbicide: 30(±3) kg N ha−1, shear–pile–disk–herbicide: 28(±3) kg N ha−1, and shear–pile–disk–no herbicide: 19(±3) kg N ha−1 in the seven months. Mid-rotation mineralization was positively correlated with soil temperature and negatively correlated with soil P and soil C:N ratio. The effect of harvest on N mineralization was probably exerted through P nutrition, whereas the lack of site preparation effects suggested that large nutrient removals that occurred with shearing and piling did not have lasting and negative effects on N availability in this plantation.

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