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

• Published in: The journal of the Torrey Botanical Society Vol. 137; no. 4; pp. 339 - 347
• Main Authors: Jin, Virginia L, Romanck, Christopher S, Donovan, Lisa A, Sharitz, Rebecca R
• Format: Journal Article
• Language: English
• Published: Torrey Botanical Society 01.10.2010
• Subjects: Acer rubrum; Acid soils; Agricultural soils; ammonium nitrogen; coastal dune soils; coastal plains; Flooded soils; floodplains; forest ecosystems; Forest soils; glycine (amino acid); immobilization in soil; isotope labeling; mineralization; nitrate nitrogen; Nitrogen; nutrient availability; nutrient uptake; Organic soils; Pinus palustris; Plants; sandhills region; Savanna soils; Soil ecology; Soil water; trees
• ISSN: 1940-0616; 1095-5674; 1940-0616
• DOI: 10.3159/10-RA-022.1

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.