Acacia auriculiformis

Overview

Acacia auriculiformis is described from coastal habitats such as tidal flats and salt lagoons and has also been studied under soil salinization and diluted-seawater irrigation. Soil EC and irrigation-water EC from different studies are not interchangeable and do not represent every population. [S1, S3, S4]

Names and classification

Acacia auriculiformis Benth. is treated as a species-level taxon. Regional sources from Southeast Asia and the Pacific record it from tidal flats and salt lagoons; other sources also report cultivation, floodplains, and forest margins. [S1]

Morphology and identification

A small to medium tree whose mature foliage consists mainly of flattened, curved phyllodes with several longitudinal veins. Yellow flowers are borne in spikes; mature pods are curved to coiled, and the seeds often have a brightly coloured aril. [S1]

Distribution, habitat and phenology

PROSEA and regional cultivation or flora accounts describe parts of the species’ range as including tidal flats and salt lagoons; other records place it in floodplains, forest and forest margins. The available sources provide no long-term survey of species-specific salt-marsh populations or measurements of natural root-zone salinity. [S1]

The available sources do not provide a consistent flowering or fruiting season for the species.

Salinity in natural habitats

Regional accounts record coastal, floodplain and forest-margin habitats; root-zone salinity has not been measured for individual coastal populations. [S1]

Salinity studies

Patel et al. amended pot soil with NaCl and measured EC in a 1:2 soil:water suspension, not a saturated-paste extract (ECe). The emergence series covered 0.3–13.9 dS/m and was recorded daily for 30 days; emergence was only 8% at 13.9 dS/m, and those seedlings were not used in the growth trial. A separate group grew for six months at 0.3–12.1 dS/m, with seedling growth declining significantly as soil salinity increased. [S3]

Annual seedlings were irrigated with diluted natural seawater at ECw values of 4, 8, and 12 dS/m through day 150; plant height, leaf area, chlorophyll, and biomass-related traits were measured on days 90 and 150. Growth declined as irrigation-water EC increased. At day 150, leaf area at 12 dS/m was 68% below the control and height was 39% lower. ECw is not soil EC or NaCl concentration, and root-zone salinity was not measured; these results do not define a sustained root-zone tolerance threshold. [S4]

Reported mechanisms and ecological adaptations

As pot-soil salinity increased, seedling tissues accumulated more proline, K, Na and N, while P, Ca, Mg and Fe declined; these changes occurred alongside altered water status and reduced growth. [S1, S3, S4]

Conclusions and evidence gaps

eHALOPH lists both woodland and coastal habitats, drawing on a remnant-forest study and a seawater-addition study; neither directly verifies a wild salt-marsh population. The two experiments report different exposures—soil EC after NaCl amendment and ECw of diluted seawater—and should not be combined into one salinity range. [S1, S2, S3, S4, S5]