The effect of flood frequency and soil character on the distribution of a perennial shrub, Lignum (Muehlenbeckia florulenta)

Abstract

Water and soil nutrient availability are the primary factors determining the distribution and maintenance of floodplain vegetation in semi-arid ecosystems. Indeed, the distribution of plants within semi-arid floodplains varies according to flood tolerance, water resource availability and the presence of sufficient soil nutrients to support and stimulate plant growth. This paper investigates whether soil character or water availability is the most important driver of growth and productivity for the perennial shrub Lignum, an important habitat in semi-arid wetlands. Lignum size, density and health was assessed at 40 locations within the Narran Lakes, a floodplain-wetland system at the terminus of the Narran River in northern NSW, and compared to the frequency of inundation and a suite of physical and geochemical soil properties. Flood frequency was found to exert the strongest influence on lignum size and density with the largest lignum occurring in zones that flood, on average, once in 2-3 years.