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Kumari Rajapaksha

Candidature

PhD Candidate

Thesis title

Searching for Meaningful Belowground Indicators of Heath in Threatened Ecological Communities

Research project

Kumari RajapakshaAboveground and belowground communities are intrinsically linked to each other with important implications for ecosystem functioning. Aboveground attributes are most often studied, as they are most directly affected and highly responsive to disturbances such as removal of species, excessive proliferation of native plants, lack of periodic natural fires and exotic plant invasions. However, still it remains unclear whether information on plant community attributes (e.g. diversity, richness and composition) can be used to predict belowground attributes (e.g. abundance, diversity, nutrient availability and belowground functions), that are also important for ecosystem functions. This study aims at investigating how belowground communities and aboveground communities are linked across different ecological health conditions in different woodland ecosystems varying in nutrient availability. The first study focuses on investigating the relationship between soil food web structure and aboveground communities, and nutrient availability under different ecosystem health conditions in Cumberland Plain Woodland (CPW), a threatened ecological community (TEC). Soil food web structure will be assessed via microbial biomass, microbial lipids (PLFA indicating large microbial functional groups and protozoa) and nematode abundance. Soil nutrient availability (C, N, P) and aboveground attributes will also be assessed in the same localities. For the second study, different ecosystem health conditions, in three TECs, varying in water and nutrient availability, (CPW, Castlereagh Scribbly Gum Woodland and Blue Gum High Forest), are used to investigate whether soil biodiversity relate with plant communities in different ecosystem conditions. Metagenomics for microbes and nematodes will be used to assess soil biodiversity. The third study focuses on the responses of belowground ecosystem functions to aboveground health conditions across contrasting woodland types. Litter decomposition, nutrient availability, soil respiration, enzyme activity and soil faunal feeding activity will be analysed as belowground ecosystem functions. Finally, soil biological indicators of ecosystem functioning will be identified for monitoring TECs. This study will explore the attributes of belowground communities and their functions which are mostly related to the status of the aboveground communities with the broader goal of providing information for conservation, management and rehabilitation of these TECs.

Publication

Birnbaum C, Dearnaley J, Egidi E, Frew A, Hopkins A, Powell J, Aguilar-Trigueros C, Liddicoat C, Albornoz F, Heuck M, Dadzie FA, Florence L, Singh P, Mansfield T, Rajapaksha K, Stewart J, Rallo P, Peddle SD, Chiarenza G, (2024) 'Integrating soil microbial communities into fundamental ecology, conservation, and restoration: examples from Australia', New Phytologist, vol.241, no.3, pp 974-981

Supervisors

Dr Yolima Carrillo, Professor Jeff Powell, A/Professor Uffe Nielsen, Dr Bryony Horton (DPIE, NSW)