Effects of elevated CO2 on fine root dynamics and nutrient acquisition strategies under P-limitation

Abstract

This PhD thesis focused on identifying the effect of elevated CO2 on: 1) patterns of fine root growth; and 2) the role of water and nutrient availability as regulators of such effects. Fine root responses were studied quantitatively - assessing changes in biomass, production and turnover rates (Chapters 2 and 3) - and qualitatively, examining shifts in fine root morphological and chemical traits (Chapters 3, 4 and 5). This comprehensive approach allowed me to explore the linkages between these fine root adaptations and many of the diverse ecosystem processes driving C and nutrient cycling, including the transfer of C, N and P to the soil from fine root turnover (Chapter 3), the activity of microbial communities in the rhizosphere (Chapters 4 and 5), the uptake and use of nutrients by plants (Chapter 4and 5), and rates of CO2 exchange (Chapter 4). In all the experiments conducted, either in the field or the glasshouse, I addressed these questions using P-limited soils characteristic of vast areas from South East Australia (Peñuelas et al. 2013). The scarce information about the role of P-limitation on ecosystem responses to rising [CO2] adds further novelty to my work, addressing an important knowledge gap in climate change research. In addition, glasshouse experiments were designed to provide mechanistic insight into the potential for changes in fine root structure and function to overcome soil P-limitation under future climate change scenarios. Taken together, the information generated in this project can then be integrated in Earth System Models to predict potential feedbacks of terrestrial ecosystems on C cycling under eCO2 while accounting for the widespread phenomenon of P-limitation (Norby et al. 2016).

Date of Award	2018
Original language	English