Do dieback-affected Eucalyptus pauciflora subsp. niphophila have fewer roots colonised by ectomycorrhizae than healthy trees? Ectomycorrhizae in dieback-affected Eucalyptus pauciflora spp. niphophila

Abstract

Eucalyptus dieback is a severe phenomenon impacting the health of Eucalyptus pauciflora subsp. niphophila (snow gum) in Kosciuszko National Park. Ectomycorrhizal (ECM) colonies within the feeder roots of species such as E. pauciflora subsp. niphophila can greatly improve tree health in light of dieback stress. We investigated if there was greater ECM presence in healthy E. pauciflora subsp. niphophila than in those suffering from severe dieback. Feeder root samples were compared between healthy E. pauciflora subsp. niphophila stands in Perisher Valley and dieback-affected E. pauciflora subsp. niphophila stands 500 m from Perisher Valley. Across the sites, 42.92% of healthy feeder roots from 13 trees were colonised by ECM, compared to 32.77% of dieback-affected feeder roots in 13 trees. However, this difference was not statistically significant. Interestingly, a post hoc observation noted dieback trees had fewer available feeder roots. Although this study was unable to demonstrate if fewer available feeder roots were a cause or effect of dieback, it was unsurprising that fewer roots sustain trees in poorer health condition, such as those affected by dieback. These novel findings stress the need for further research into the causes of widespread dieback in E. pauciflora subsp. niphophila, including a microbiome study to classify ECM samples as a function of fungal diversity and a more robust analysis of root counts to better understand the dieback phenomena.