Thesis RA3: Effect on organic layer biomass

Hua W. 2021. Effect of kauri dieback on organic layer biomass and proportion of kauri components Unpublished Masters thesis, University of Auckland.

This thesis is not publicly available online. For further information please contact supervisor, Dr. Luitgard Schwendenmann at the University of Auckland (l.schwendenmann@auckland.ac.nz)

Kauri (Agathis australis) is one of the largest and longest-lived conifer species in the world. Kauri is endemic to New Zealand and is now listed as threatened because of the decline caused by the oomycete pathogen Phytophthora agathidicida. In this study, organic litter layer (litter (Litter) and partially decomposed (OF) layer) biomass was measured under kauri trees differing in health status. The material was also sorted into its major components (leaves, twigs, pollen cones, seeds, bark, roots). It was further tested if Litter and OF layer depth is related to the biomass of these layers. The study selected two locations, Cascades and Piha, in the Waitakere Ranges Regional Park in Auckland, New Zealand, and selected symptomatic plots and control plots respectively. The samples were collected between May and July 2021. The Litter and OF biomass in the Cascades plots was higher than in the Piha plots. This may be the effect of the size of the trees, or it may be the effect of the duration of the disease. The proportion of reproductive material in the control plot was higher than that in the symptomatic plot, which will lead to fewer and fewer kauri in the symptomatic plots in the future. No relationship between biomass and forest floor depth has been found. This study discussed the impact of kauri dieback on biomass and litter fractions and proposed the idea that the smell can be used to distinguish whether kauri is diseased.