title: Shifts in leaf N:P stoichiometry during rehabilitation in highly alkaline bauxite processing residue sand.
abstract: Large quantities of sodic and alkaline bauxite residue are produced globally as a by-product from alumina refineries. Ecological stoichiometry of key elements [nitrogen (N) and phosphorus (P)] plays a critical role in establishing vegetation cover in bauxite residue sand (BRS). Here we examined how changes in soil chemical properties over time in rehabilitated sodic and alkaline BRS affected leaf N to P stoichiometry of native species used for rehabilitation. Both Ca and soil pH influenced the shifts in leaf N:P ratios of the study species as supported by consistently significant positive relationships (P < 0.001) between these soil indices and leaf N:P ratios. Shifts from N to P limitation were evident for N-fixing species, while N limitation was consistently experienced by non-N-fixing plant species. In older rehabilitated BRS embankments, soil and plant indices (Ca, Na, pH, EC, ESP and leaf N:P ratios) tended to align with those of the natural ecosystem, suggesting improved rehabilitation performance. These findings highlight that leaf N:P stoichiometry can effectively provide a meaningful assessment on understanding nutrient limitation and productivity of native species used for vegetating highly sodic and alkaline BRS, and is a crucial indicator for assessing ecological rehabilitation performance.
authors.affiliation: Environmental Futures Research Institute, Griffith School of Environment, Griffith University, Nathan, Qld 4111, Australia.
authors.forename: Johnvie B
authors.initials: JB
authors.lastname: Goloran
authors.affiliation: Environmental Futures Research Institute, Griffith School of Environment, Griffith University, Nathan, Qld 4111, Australia.
authors.forename: Chengrong
authors.initials: C
authors.lastname: Chen
authors.affiliation: Environmental Research Department, Alcoa World Alumina Australia, Huntly Mine, P.O. Box 172, WA 6208, Australia.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Phillips
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287 USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Elser