title: Does soil nitrogen influence growth, water transport and survival of snow gum (Eucalyptus pauciflora Sieber ex Sprengel.) under CO enrichment?
abstract: Eucalyptus pauciflora Sieber ex Sprengel. (snow gum) was grown under ambient (370 microL L(-1)) and elevated (700 microL L(-1)) atmospheric [CO2] in open-top chambers (OTCs) in the field and temperature-controlled glasshouses. Nitrogen applications to the soil ranged from 0.1 to 2.75 g N per plant. Trees in the field at high N levels grew rapidly during summer, particularly in CO2-enriched atmosphere, but suffered high mortality during summer heatwaves. Generally, wider and more numerous secondary xylem vessels at the root-shoot junction in CO2-enriched trees conferred fourfold higher below-ground hydraulic conductance. Enhanced hydraulic capacity was typical of plants at elevated [CO2] (in which root and shoot growth was accelerated), but did not result from high N supply. However, because high rates of N application consistently made trees prone to dehydration during heatwaves, glasshouse studies were required to identify the effect of N nutrition on root development and hydraulics. While the effects of elevated [CO2] were again predominantly on hydraulic conductivity, N nutrition acted specifically by constraining deep root penetration into soil. Specifically, 15-40% shallower root systems supported marginally larger shoot canopies. Independent changes to hydraulics and root penetration have implications for survival of fertilized trees under elevated atmospheric [CO2], particularly during water stress.
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia. batwell@rna.bio.mq.edu.au
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Atwell
authors.forename: Martin L
authors.initials: ML
authors.lastname: Henery
authors.forename: Marilyn C
authors.initials: MC
authors.lastname: Ball
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D005052:Eucalyptus / Q000254:growth & development* / Q000378:metabolism; D005308:Fertilizers; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D012987:Soil / Q000032:analysis*; D014197:Trees / Q000254:growth & development / Q000378:metabolism; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000254:growth & development
chemical_list: D005308:Fertilizers; D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D009584:Nitrogen