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| Titel |
Sulfur-accumulating plants convert sulfate salts from soils into environmentally resilient biominerals |
| VerfasserIn |
Thomas Robson, Nathan Reid, Jason Stevens, Kingsley Dixon |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124639
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| Publikation (Nr.) |
 EGU/EGU2016-4106.pdf |
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| Zusammenfassung |
| Sulfur-accumulator plants (thiophores), which accumulate atypically high sulfur and calcium
concentrations in their aerial biomass, may be suitable for revegetating and phytostabilising
reactive sulfur-enriched substrates such as mine tailings, acid-sulfate soils and polluted soils.
We present biogeochemical insights on thiophores from the Australian Great Sandy Desert,
which accumulate up to 40 times as much sulfur (2-5 %S) versus comparator species. X-ray
microanalyses revealed this accumulation relates to peculiar gypsum-like mineralisation
throughout their foliage, illustrating a mechanism for sulfate removal from soils and
sequestration as sparingly soluble biominerals. However, we did not know whether these
species treat the excess Ca/S as a waste to be shed with senescent litter and, if so, how
resilient these ‘biominerals’ are to photo-biodegradation once shed and so to what extent
the accumulated elements are recycled back into the reactive/bioavailable sulfate
reservoir.
To address these questions, we sampled four foliage (phyllode) fractions from ten
individuals of the thiophore, Acacia bivenosa: healthy mature phyllodes, senescent phyllodes
on the branch, recently shed and older, more degraded ground litter. We selected two
thiophores (A. bivenosa and A. robeorum) and a non-thiophore (A. ancistrocarpa) for
detailed soil/regolith studies. Samples were collected from trenches bisected by each
tree, taken from varying depth (20-500 mm) and distance from the stem (0.1-5 m).
Dried foliage was cleaned, sectioned for SEM-EDXS examination and elemental
compositions of foliage and soils were determined (microwave-assisted acid digestion +
ICP-OES/MS).
Each species generated a ‘halo’ of elevated S/Ca in the soil immediately beneath their
crowns, although that of A. ancistrocarpa was of minor magnitude. These anomalies were
confined to shallow soil (20-50 mm i.e. influenced by litter), suggesting limited S/Ca
re-mobilisation from the litter. Foliar elemental concentration ratios, which indicate relative
variations in composition through the litter cycle (healthy > senescent > fresh litter >
degraded litter), reveal potentially limiting nutrients were recovered from senescing
phyllodes: P (0.38 ± 0.13), Zn (0.59 ± 0.24), Mo (0.71 ± 0.28), Mg (0.86 ± 0.13). Some
non-limiting nutrients or potentially harmful elements were hyper-deposited in
senescent tissues: Ba (1.29 ± 0.22), Ca (1.17 ± 0.08), Co (1.33 ± 0.33), Fe (1.49 ±
0.59) and Mn (1.39 ± 0.49). Despite this evidence for nutrient recovery and waste
removal behaviour (e.g. calcium oxalate production), sulfur remained constant (1.08 ±
0.12), suggesting thiophores do not regulate sulfur as a limiting nutrient or use
biomineralisation to immobilise/detoxify sulfur. Whilst some elements (K, Mg, P) were
leached from the litter through photo-biodegradation, sulfur (0.91 ± 0.12) and
calcium (0.99 ± 0.09) levels remained relatively constant in recent/aged litter, and
extensive gypsum-like mineralisation was retained in tissues of even the most degraded
litter.
These findings suggest that thiophores, which bioconcentrate sulfur several hundred times
from soils into their foliage, return sulfur to the soil as a tissue-encapsulated, sparingly
soluble mineral that is recalcitrant to photo-biodegradation under semi-arid climates. These
traits show the potential of these plants as part of the toolkit for restoring degraded soils and
polluted substrata. |
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