RA3 THESIS: Leaf litter nutrient concentrations

Effect of kauri dieback on leaf litter nutrient concentrations

2022

Sharma I. 2022. Effect of kauri dieback on leaf litter nutrient concentrations. Unpublished Honours thesis, University of Auckland.

NOTE:

This thesis is not publicly available online. For further information please contact supervisor, Dr. Luitgard Schwendenmann at the University of Auckland

ABSTRACT

Kauri dieback, caused by Phytophthora agathidicida, is threatening the survival of the iconic kauri (Agathis australis) species. Kauri has been found to modify their environment through significant effects on soil processes. Leaf litter is the primary nutrient input to soil, with litter analysis being widely used to assess overall plant and soil health. The extent of how kauri dieback impacts these processes is largely unknown. This study seeks to identify whether leaf litter nutrient concentrations are impacted through P. agathidicida infection. Three sites in the Waitākere Ranges Regional Park have been selected for this study. Macro- and micronutrients have been selected for analysis, along with litter biomass and tree size. A comparison of kauri leaf litter to broadleaf litter is also presented, to understand whether nutrient concentrations differ between species of the same forest ecosystem. A significantly higher litter biomass in the site characterized by large trees was observed. Some effects of sample type on nutrient concentrations was also observed. Kauri leaf litter nutrient concentrations were significantly higher for carbon, calcium, and the C:N ratio, whilst broadleaf litter was significantly higher for boron and copper concentrations. Primarily, P. agathidicida infection did not have a significant effect on leaf litter nutrient concentrations when sites were grouped. However, differences were seen when sites were separated. This indicates that the effects of P. agathidicida infection on leaf litter nutrient concentrations was site specific. Most kauri leaf litter macro- and micronutrients concentrations tended to be lower underneath trees showing kauri dieback symptoms. Lower leaf litter nutrient input may result in long term changes to species compositions and biogeochemical processes in kauri dieback affected forests.