The fate of nitrogen mineralized from leaf litter — Initial evidence from ¹⁵N-labeled litter

Abstract

Decomposition of leaf litter includes microbial immobilization of nitrogen (N), followed by N mineralization. The fate of N mineralized from leaf litter is unknown. I hypothesized that N mineralized from leaf litter will be re-immobilized into other forms of organic matter, including downed wood. This mechanism may retain N in some forests. To test this hypothesis, oak leaves were enriched with a naturally occurring, stable isotope of N (¹⁵N), collected as litter, and allowed to decompose with and without wood (10 cm long, in 3 diameter classes of < 2 cm, 2-4 cm, and 4-6 cm) in litter bags in the forest floor of a central hardwood forest near morgantown, wv. as oak litter immobilized exogenous n, ¹⁵N in litter decreased due to dilution, and then did not change significantly. Nitrogen mineralization in leaf litter did not start for at least 24 months. By the 11th month of decomposition, wood N reached between 140 and 274 percent of the initial N mass, depending on wood diameter. By the 24th month, 15N was detected in wood, supporting the hypothesis. Nitrogen-label was not detected in fresh litter above litter bags, or below litter bags in partly decomposed forest floor or soil. It appears that N mineralized from leaf litter may be transferred to and immobilized in small-diameter downed wood. If these results are confirmed in a larger study, we may need to change the way we view N cycling in the leaf litter layer; N mineralized from foliar litter may not be immediately plant-available as we now assume.

Parent Publication

• Proceedings, 17th Central Hardwood Forest Conference

Citation

Piatek, Kathryn B. 2011. The fate of nitrogen mineralized from leaf litter — Initial evidence from 15N-labeled litter. In: Fei, Songlin; Lhotka, John M.; Stringer, Jeffrey W.; Gottschalk, Kurt W.; Miller, Gary W., eds. Proceedings, 17th central hardwood forest conference; 2010 April 5-7; Lexington, KY; Gen. Tech. Rep. NRS-P-78. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 164-176.