Seedling response to phosphate addition and inoculation with arbuscular mycorrhizas and the implications for old-field restoration in Western Australia

Published Date
Environmental and Experimental Botany
September 2007, Vol.61(1):58–65, doi:10.1016/j.envexpbot.2007.03.004

• Author 

• R.J. Standish ^a,,
• B.A. Stokes ^b
• M. Tibbett ^b
• R.J. Hobbs ^a

• aSchool of Environmental Science, Division of Science and Engineering, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia
• bSchool of Earth and Geographical Sciences, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, Western Australia 6009, Australia

Received 19 July 2006. Revised 7 January 2007. Accepted 31 March 2007. Available online 6 April 2007. 

Abstract

We predicted that P-fertiliser residues will limit the establishment of native plant species and their mycorrhizas to old-fields in the wheat-growing region (i.e. the wheatbelt) of Western Australia. To test this prediction, we assessed the growth and P uptake of seedlings of three native plant species to phosphate addition and inoculation with arbuscular mycorrhizas (AM) in a pot study. The native plant species were Acacia acuminata Benth. (Mimosaceae), Eucalyptus loxophleba Benth. subsp. loxophleba (Myrtaceae) and Hakea preissii Meisn. (Proteaceae); and each pot contained one seedling. P was added to field soil to mimic pre-agricultural (P0), old-field (P1) and 10 times old-field (P10) soils. AM inoculant, which was a mix of Scutellospora calospora (Nicolson and Gerdemann) Walker and Sanders, Glomus intraradices Schenck and Smith and Glomus mosseae (Nicolson and Gerdemann) Gerdemann and Trappe, was added to half of the pots. After 12 weeks, the biomass and P uptake of the mycorrhizal A. acuminata were greater than those of the non-mycorrhizal plants across all P treatments. Plant biomass decreased significantly with increasing P addition, yet this species was apparently unable to suppress its mycorrhizal colonisation at high P despite this reduction in growth. In contrast, mycorrhizal and non-mycorrhizal E. loxophleba subsp. loxophleba were of a similar biomass after 12 weeks; maximum biomass was attained at intermediate (old-field) levels of P. P uptake increased with increasing P supply, beyond that required to attain maximum biomass. AM did not form on H. preissii. P uptake increased with increasing P supply for this species also. Overall, it is the apparent inability of these species to down-regulate P uptake rather than a lack of mycorrhizal symbiosis that will constrain their establishment on wheatbelt old-fields.

Keywords

Acacia acuminata

Eucalyptus loxophleba subsp. loxophleba

Fertiliser legacy

Hakea preissii

Pot study

Wheatbelt

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