The effect of disturbance and drought on Hairy Jointgrass (Arthraxon hispidus) in north coast New South Wales: Understanding threatened species populations in a dynamic landscape

Abstract

AbstractEcological disturbances such as fire, grazing or mechanical cultivation can promote or suppress plant populations within vegetation communities. Therefore, such processes can threaten vulnerable species, or play a significant role in their conservation, so an understanding of a species’ ecological response to disturbance is foundational to threatened species management. Various types of anthropogenic disturbance are listed as threats to the vulnerable‐listed Arthraxon hispidus (Hairy Jointgrass) (Poaceae) in NSW; however, there is evidence that slashing, grazing and fire can stimulate the recruitment and establishment of this annual species in some circumstances. We undertook field experiments to investigate the effects of each of these disturbance regimes on A. hispidus populations over two growing seasons within modified wetlands/moist pastures in north coast NSW. We found that the application of fire in winter had a stronger promotional effect on A. hispidus recruitment than slashing, though both treatments increased its abundance and reduced the height and cover of surrounding vegetation, particularly exotic perennial grasses. Following initial establishment, A. hispidus declined under drought conditions during the study, and continuous grazing exacerbated this effect. Drought also increased the abundance of introduced species relative to native wetland species across the study sites. Results confirm that disturbance, particularly fire, can promote A. hispidus populations in some vegetation communities; however, climatic variation also plays a role in its population dynamics. Consideration of each of these factors and their potential interactions is important when developing conservation approaches for this threatened species.