The effect of dryland salinity on arbuscular mycorrhizal fungi in southern New South Wales

Dryland salinity, a result of large-scale land clearing and, to a lesser extent, the natural accumulation of salt in the soil is a significant environmental problem that affects land productivity and biodiversity in Australia. Much of the research into dryland salinity focuses on plant productivity, but less is known about its effect on beneficial soil microorganisms such as arbuscular mycorrhizal fungi (AMF), known to be important for the establishment and growth of plants. Research into AMF in naturally salinised environments has established that AMF vary in their tolerance to saline soil and are low in diversity at both local and regional scales. There is no information in the literature about the effects of human-induced salinity or dryland salinity on AMF populations. This thesis addresses this knowledge gap by examining a community of AMF at a dryland salinity-affected field site in southern New South Wales. The aims of the research were to (1) examine the persistence and infectivity of AMF isolated from a dryland salinity-affected site, (2) to determine if dryland salinity reduces the genetic diversity of AMF and (3) to investigate the effect of AMF in improving the growth and nodulation of Melilotus siculus (Messina, an important pasture species for dryland salinity-affected environments).Intact soil cores from areas of varying salinity were excavated from a dryland-salinity-affected agricultural site. Trifolium michelanium (balansa clover) was grown in the cores for approximately five months over which time AMF colonisation and several plant growth parameters were measured. Overall, colonisation was slow to establish and was low in plants growing in the least saline soil and colonisation was negligible in plants growing in the most saline soil. Only two spore morphotypes were consistently identified from the soil and spore numbers did not differ significantly between soil salinity levels.