Ammonium uptake by field‐grown Eriophorum vaginatum roots under laboratory and simulated field conditions

• Published in: Ecography
• Main Authors: Marion, G. M., Kummerow, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1990
• Subjects: Ecology, Evolution, Behavior and Systematics; Tundra
• Online Access: http://dx.doi.org/10.1111/j.1600-0587.1990.tb00588.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0587.1990.tb00588.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0587.1990.tb00588.x

Nitrogen (N) deficiencies in tundra ecosystems could be caused, in part, by the kinetics of root N uptake. The objectives of this study were to quantify NH 4 uptake by field‐grown excised roots of Eriophorum vaginatum I. under controlled NH 4 concentrations (0‐250 μmol I ‐1 ) and temperatures (5‐20°C) and to evaluate this laboratory derived model as a means of estimating field NH 4 uptake. There was no consistent temperature effect on root NH 4 uptake which suggests a relative in‐sensitivity of E. vaginatum roots to short‐term temperature fluctuations. The Michaelis‐Menten equation parameters for NH 4 uptake were V max = 22.1 μmol h ‐1 g ‐1 and K m = 191 μmol I ‐1 . Using field NH 4 concentrations, field E. vaginatum root biomass data, and the Michaelis‐Menten equation, an estimate was made of NH 4 uptake over a 42 day period; this estimate of NH 4 uptake accounted for 28% of the net incorporation of N into leaves and roots which is a reasonable estimate for E. vaginatum which relies primarily on N retranslocation for supplying new leaves and roots. Major uncertainties in field N uptake rates, model parameterization, and site characterization preclude an accurate model validation and indicate research areas most in need of future study.