Waterlogging tolerance of the threatened grass Arthraxon hispidus and implications for its habitat niche within endangered wetlands in north-eastern New South Wales

Abstract

Knowledge of a target species’ habitat niche and physiological tolerances is important for conservation planning. However, these factors are not well understood for the threatened annual grass Arthraxon hispidus in New South Wales (NSW). Although the species is widespread in modified environments, recent studies have suggested that several threatened wetland types may represent original native habitat for the species, but documented field examples are lacking and the species’ physiological response to soil moisture is not clear. We undertook a detailed survey of an A. hispidus population within a relatively intact native sedgeland community, and carried out a nursery experiment to test the hydrological tolerances of the species. We found that A. hispidus plants grew more vigorously in poorly drained or waterlogged conditions, suggesting that the species is well-adapted to overcome such stressors, possibly through the formation of adventitious roots, a trait shared by many wetland plants globally. Our field survey confirmed that the A. hispidus population within the study site occurred only within species assemblages that were characteristic of a freshwater wetland formation and that matched descriptions of a listed endangered ecological community. These findings provide a deeper insight into the species’ habitat and threats, and offer a valuable management focus for conservation of A. hispidus as a component of threatened wetland communities in north-eastern NSW.