Plant species associations with alkaline environments associated with artesian spring wetlands

Extraordinary concentrations of local endemism associated with arid-land springs

“…The terrestrial endemic plant species are associated with unusual alkaline soda rich (NaHCO 3 ) or neutral gypsum-rich (CaSO 4 ) saline environments. These environments are a product of the evaporites of the groundwater and the endemic halophytes have a specific adaptation to these specialised environments (Fensham et al, 2021).…”

“…These habitats are not wetlands despite being characterised by salts which are concentrated by the evaporation of groundwater. In Australia, the soils in these habitats typically have pH values greater than 9 supporting a low cover of succulent plants (Fensham et al, 2021). These habitats also support endemic species with very local distributions compared to other species specialised to non-alkaline saline environments.…”

“…We define the term 'spring endemic' as meaning any species confined to a spring-dependent ecosystem, including the aquatic species confined to groundwater-fed wetlands, as well as terrestrial species confined to the specialised (often saline) habitats on the periphery of springs (Fensham et al, 2021). Endemic terrestrial plant species associated with spring-related terrestrial environments at Cuatro Ciénegas were identified as those occurring in chaparral; desert scrub, bajadas, and flats, as well as gypsum dunes and flats (Pinkava, 1984).…”

“…The water in these wetlands is generally less than 1 cm deep, but up to 10 cm deep near the discharge vents. The pH of these springs is relatively neutral but the CaHCO 3 -type water leaves evaporites of alkaline salts accumulating around the spring margins, creating scalded habitat where pH reaches 10.3 (Fensham et al, 2021). Discharging groundwater is not geothermal, although temperatures in the pools vary between about 5 °C and 40 °C, depending on distance from the discharge point, and seasonal and diurnal conditions (Rossini, et al, 2017a).…”

“…Discharging groundwater is not geothermal, although temperatures in the pools vary between about 5 °C and 40 °C, depending on distance from the discharge point, and seasonal and diurnal conditions (Rossini, et al, 2017a). Conductivity is 300 μS cm -1 within the wetlands but can be higher than 100,000 μS cm −1 in the scalded terrestrial habitats surrounding the spring pools (Fensham et al, 2021). Total discharge from the springs has been estimated as 22 L s −1 , has been substantially lower in the recent past but was almost certainly higher prior to extraction by free-flowing bores for pastoralism (Fensham and Laffineur, 2022).…”