Induction of water repellency by leaves of contrasting Australian native species: effects of composition and heating

Aims This study identifies the contribution of leaf matter from individual plant species on water repellency with a focus on the composition of organic compounds and the role of heat in releasing these compounds to soil. Methods Leaf powder from four plant species (Banksia menziesii, Eucalyptus marginata, Allocasuarina fraseriana, Xanthorrhoea preissii) was mixed with acid-washed sand (AWS) under a range of temperatures and WR measured. Plant chemical composition was characterized by extraction of leaf powder and GC/MS analysis. Results Increasing concentrations of plant powder mixed with AWS increased WR for three species; whereas for X. preissii there was no WR at any concentration. Heating increased WR for all species over the range of 30 to 120 °C. B. menziesii had the greatest WR, which was associated with the largest diversity of fatty acids and n-alcohols and highest concentration of alkanes, whereas X. preissii with the smallest WR had only C16 alcohol and C16 fatty acids at relatively low concentration. Conclusions Physically mixing leaf powder with AWS allows the contribution of different plant species on WR to be directly examined. WR appears to be related to differences in the concentrations and diversity of n-alcohols, n-fatty acids, and high n-alkanes in the leaves. The observed temperature effects on WR provide insights into the kinetics of release and dispersal of organic compounds from interstitial material.