Isolated Trees in Pasture Landscapes Contribute to and Enhance Soil Health: A Study in Central-West New South Wales, Australia

Isolated farm trees are a distinct feature of the Australian landscape, previously part of a forested landscape, until extensive clearing occurred for agricultural purposes post European settlement. A majority of studies has focused on the beneficial effects of tree clusters, such as shelterbelts and windbreaks and little pertains to characterizing the role of isolated farm trees (also referred as isolated farm trees, IFTs). IFTs are generally older than their tree cluster counterparts, with little to no chance of regenerating in a grazed landscape. Both tree clusters and IFTs contribute to the health of the soil by increasing soil nutrients, protecting pastures and stock from harsh weather, reducing erosion levels, providing habitat for vertebrate and invertebrate species and increasing agricultural productivity. With the loss of the IFTs from the landscape, the many benefits they provide have also been lost. The purpose of the study was to examine the role IFTs have on enhancing soil health in pastures using physical, chemical and biological soil-health indicators. Leaf litter and soil sampling and soil CO2 efflux readings were made from beneath the canopy and in the surrounding pasture of nine isolated farm trees (Eucalyptus melliodora, E. viminalis, and E. bridgesiana) in Central-west Tablelands of NSW in spring 2014 and autumn 2015. The results indicate IFTs enhance soil health in pasture landscapes with greater arthropod abundance and diversity, higher rates of soil respiration, greater concentrations of total nitrogen and phosphorous, and lower levels of soil compaction closer to the tree compared with surrounding pasture landscape. Collectively these findings point to a positive influence on soil health in grazed pastures by isolated farm trees.