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Nitrogen fertilization enhances water‐use efficiency in a saline environment
Author(s) -
MARTIN KATHERINE C.,
BRUHN DAN,
LOVELOCK CATHERINE E.,
FELLER ILKA C.,
EVANS JOHN R.,
BALL MARILYN C.
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.02072.x
Subject(s) - transpiration , stomatal conductance , salinity , water use efficiency , nutrient , canopy , agronomy , nitrogen , botany , environmental science , biology , horticulture , photosynthesis , ecology , chemistry , organic chemistry
Effects of salinity and nutrients on carbon gain in relation to water use were studied in the grey mangrove, Avicennia marina , growing along a natural salinity gradient in south‐eastern Australia. Tall trees characterized areas of seawater salinities (fringe zone) and stunted trees dominated landward hypersaline areas (scrub zone). Trees were fertilized with nitrogen (+N) or phosphorus (+P) or unfertilized. There was no significant effect of +P on shoot growth, whereas +N enhanced canopy development, particularly in scrub trees. Scrub trees maintained greater CO 2 assimilation per unit water transpired (water‐use efficiency, WUE) and had lower nitrogen‐use efficiency (NUE; CO 2 assimilation rate per unit leaf nitrogen) than fringe trees. The CO 2 assimilation rates of +N trees were similar to those in other treatments, but were achieved at lower transpiration rates, stomatal conductance and intercellular CO 2 concentrations. Maintaining comparable assimilation rates at lower stomatal conductance requires greater ribulose 1·5‐bisphosphate carboxylase/oxygenase activity, consistent with greater N content per unit leaf area in +N trees. Hence, +N enhanced WUE at the expense of NUE. Instantaneous WUE estimates were supported by less negative foliar δ 13 C values for +N trees and scrub control trees. Thus, nutrient enrichment may alter the structure and function of mangrove forests along salinity gradients.