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Soil Science Society of America Journal Abstract - DIVISION S-7—FOREST & RANGE SOILS

Non-labile Soil 15Nitrogen Retention beneath Three Tree Species in a Tropical Plantation


This article in SSSAJ

  1. Vol. 66 No. 2, p. 612-619
    Received: Mar 22, 2001

    * Corresponding author(s): jkaye@lamar.colostate.edu
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  1. Jason P. Kaye *a,
  2. Dan Binkleya,
  3. Xiaoming Zoub and
  4. John A. Parrottac
  1. a Dep. of Forest Sciences, Colorado State Univ., Fort Collins, CO 80523
    b Terrestrial Ecology Division, Univ. of Puerto Rico, P.O. Box 363682, San Juan, PR 00936
    c USDA Forest Service, Research and Development, P.O. Box 96090, Washington, DC 20090-6090


Soil organic matter is the largest sink for N additions to forests. Species composition may affect soil N retention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree plantation with replicated stands of three species (two N-fixers, one Eucalyptus, Euc). Laboratory incubations (13 mo) with repeated leaching separated total soil N into labile (inorganic N leached) and non-labile (total N minus leached N) pools, and a labile C treatment tested linkages between C availability and N retention. We hypothesized that species composition would alter the amount and proportion of recovered tracer N in non-labile organic matter. Surface soils contained 45% of the tracer, but the amount retained in labile and non-labile pools was similar among species. In contrast, the proportion of recovered tracer in non-labile pools was greater in soils beneath N-fixers (75%) than Euc (62%). Labile C additions increased the size of the non-labile tracer N pool. We conclude that tree species composition may affect long-term soil N retention by altering the proportion of N in slow-turnover, non-labile pools. Plants may also alter soil N retention by renewing labile C pools; a continuous supply of labile C increased the transfer of 15N into non-labile organic matter.

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Copyright © 2002. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.66:612–619.