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Soil nitrogen availability and in situ nitrogen uptake by Acer rubrum L. and Pinus palustris Mill. in the southeastern U. S. Coastal Plain

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Plant uptake of soil organic N in addition to inorganic N could play an important role in ecosystem N cycling as well as plant nutrition. We measured in situ plant uptake of organic and inorganic N by the dominant canopy species in two contrasting temperate forest ecosystems (bottomland floodplain forest, subxeric sandhills long-leaf pine forest). Seedlings of Acer rubrum L. and Pinus palustris Mill. in floodplain and sandhills forests, respectively, were treated with isotopically-enriched organic N (15N-[2]-13C-glycine) or inorganic N (15NH4+) to examine in situ uptake. We also measured soil organic and inorganic N concentrations to assess the availability of N for plant uptake. Neither species took up organic N as intact 15N-[2]-13C-glycine, but significant root 15N enrichment in both species indicated that N mineralized from labeled glycine was taken up. Free amino-N dominated the total 2 M KCl-extractable N in floodplain (57 6 3%) and sandhills soils (75 6 3%), followed by NH4+ then NO3- in both soils. Up to 13% of glycine label was mineralized to NH4+ at both sites, suggesting that the majority of label was immobilized or adsorbed in the soil. Recovery of NH4+ label also indicated strong soil immobilization, particularly in sandhills soils after 24 hours. Although uptake of intact organic N did not occur in either species, N mineralized from glycine was taken up by plants in these two contrasting temperate forested ecosystems.
Jin, Virginia L. , Romanck, Christopher S. , Donovan, Lisa A. , Sharitz, Rebecca R.
nitrogen , nutrient availability , nutrient uptake , Acer rubrum , Pinus palustris , forest ecosystems , trees , isotope labeling , glycine (amino acid) , immobilization in soil , mineralization , floodplains , coastal plains , coastal dune soils , nitrate nitrogen , ammonium nitrogen
p. 339-347.
Includes references
Journal of the Torrey Botanical Society 2010, v. 137, no. 4
Journal Articles, USDA Authors, Peer-Reviewed
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