Foliar gypsum formation and litter production in the desert shrub, Acacia bivenosa, influences sulfur and calcium biogeochemical cycling in arid habitats

Aims Some sulfiir-accumulating species from arid habitats facilitate a little-understood foliar gypsum (CaSO4•2H2O) biomineralisation. This study seeks to increase our understanding of the ecophysiological and nutritional function of phytogenic gypsum, including how gypsum-formers influence soil S a...

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Bibliographic Details
Published in:	Plant and soil 2017-08, Vol.417 (1/2), p.53-68
Main Authors:	Robson, Thomas, Stevens, Jason, Dixon, Kingsley, Reid, Nathan
Format:	Article
Language:	eng
Subjects:	Acacias (Plants) Accretion Aridity Biogeochemical cycles Biomedical and Life Sciences Calcium Concentration (composition) Cycles Degradation Deposition Ecology Encapsulation Excretion Foliage Gypsum Isotopes Leaves Life Sciences Litter Mineralogy Observations Physiological aspects Phytotoxins Plant Physiology Plant Sciences Reabsorption Regolith Regular Article Salts Senescence Soil analysis Soil environment Soil profiles Soil Science & Conservation Soil surfaces Soils Spatial distribution Stable isotopes Substrates Sulfates Sulfur Topsoil
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Summary:	Aims Some sulfiir-accumulating species from arid habitats facilitate a little-understood foliar gypsum (CaSO4•2H2O) biomineralisation. This study seeks to increase our understanding of the ecophysiological and nutritional function of phytogenic gypsum, including how gypsum-formers influence soil S and Ca (S/Ca) cycling mineralogy and distribution. Methods We studied leaf composition and mineralogy (ICP-OES, SEM-EDXS) through leaf senescence and litter degradation in Acacia bivenosa DC, together with detailed soil profile analysis (composition, S chemistry & stable isotopes). Results Acacia bivenosa accumulated foliar gypsum even when growing in surface soils without high S/Ca concentrations, accreting tissue-encapsulated gypsum, which was relatively recalcitrant to degradation, within the litter beneath the crown. Though A. bivenosa regulated limiting or potentially harmful elements during leaf senescence, it did not remobilise S/Ca or preferentially accrete gypsum in senescing foliage to enhance S/Ca excretion with litter. Instead, A. bivenosa maintained high S concentrations through reabsorption from phytogenic accretion zones supplemented by alternative sources, most likely in the deeper regolith. Conclusions Acacia bivenosa influences S/Ca cycling, mineralogy and spatial distribution with the soil environment by readily accumulating S/Ca, which it concentrates within the topsoil as phytogenic gypsum. These phytogenic accretion zones can provide a sink for S/Ca salts and other potential Phytotoxins, which could assist with revegetating sulfate-saline substrates.
ISSN:	0032-079X 1573-5036