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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 Plain1

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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 ±± 3%%) and sandhills soils (75 ±± 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. , Romanek Christopher S. , Donovan Lisa A. , Sharitz Rebecca R.
Journal title changed from 'The Journal of the Torrey Botanical Society'
The journal of the Torrey Botanical Society 2010 10 v.137 no.4
Torrey Botanical Society
Journal Articles, USDA Authors, Peer-Reviewed