Impacts of plant and microbial diversity interactions on key soil functions

Abstract

The current unprecedented rate of biodiversity loss warrants an urgent need for a quantitative understanding of the relationship between biodiversity and ecosystem functioning (BEF). Ecological theories and empirical evidence indicate a positive relationship between plant diversity and rates, resilience, and stability of ecosystem functions. Recent studies also provide considerable evidence that microbial diversity plays essential roles (e.g., primary production, detoxification, decomposition,) in maintaining rate and resilience of multiple ecosystem functions and climate change regulation. Further, above- and belowground diversities are intrinsically linked, and their interaction may directly impact BEF relationships. Some observational evidence to support such biotic interactions and relative importance of plant and microbial diversity in driving multiple ecosystem functions has been provided, but there is still very limited experimental evidence. An investigation of biotic interactions by manipulative experiments under global change scenarios is required to better understand various mechanisms that underpin BEF relationships. In my thesis, I have conducted two controlled environment glasshouse experiments and a field-based experiment to simultaneously assess consequences of loss of microbial and plant diversity and their interactions on ecosystem functioning and BEF relationships during disturbances such as xenobiotic contamination and drought. The first experiment investigates the role of soil nutrient management and plant presence, or both, and their interaction on biodegradation (specialized ecosystem function) of a pollutant using soils with contrasting microbial diversity (Chapter 2). In the second experiment, I simultaneously manipulated both plant and microbial diversity in a large-scale microcosm glasshouse experiment and assessed the effects of these biotic interactions on belowground functions (i.e., soil nutrient availability and mineralization) during disturbance such as drought (Chapter 3). The third chapter, a field experiment evaluates the influence of plant diversity and plant functional traits on soil functions and decomposition rate using litter mass loss approach (Teabag index). (Chapter 4). Overall, these studies provide key insights on how interactions between above- and belowground diversity and biotic interactions among above- and belowground communities and disturbance impact BEF shape and strength in the changing future environments. Such knowledge is crucial to assess the consequences for ecosystem functions caused by global change-induced diversity loss and may inform the development of effective management and policy decisions.

Date of Award	2022
Original language	English