Growth of Atriplex amnicola on salt-affected soils in Western Australia.
On a broad scale, growth of Atriplex amnicola declined greatly in response to reduced depth to the water table during the summer. On a micro-environmental scale of 2-10 m, growth was limited by a combination of adverse soil physical properties, salinity, drought and waterlogging. Waterlogging occurred after rains in low lying areas and elevated regions where perched water tables developed above the dense clay subsoil. Salinity, measured as electrical conductivity, varied greatly over short distances and in extreme cases ranged from 300 to 6500 mS m-1 over a distance of c. 10 m. The sandy A-horizons of the soil profile varied from 10 to 110 cm in depth but were generally shallow (average depth c. 40 cm) and had limited reserves of moisture. The penetrability of the clay subsoils was low, reaching 5-8 MPa in places, preventing the entry of plant roots except where fossil root channels existed. Where plant roots were confined to shallow sandy surface soils they were exposed to drought during summer (leaf water potentials as low as -5.5 MPa).