Consequences of Climate Change for Upland and Boreal Ecosystems: Assessing the Role of Soil Microbes in Carbon Cycling.

The burning of fossil fuels and land use changes have substantially altered the composition of the atmosphere. Consequently, the climate is changing into a warmer more volatile state. This thesis investigates how the soil microbial cycling of carbon changes under climate change. The second chapter investigates how trend climate change (CO₂ fertilisation), combined with nitrogen deposition and the alleviation of phosphorus limitation, alters soil microbial biodiversity and communities. In this chapter, two phosphorous limited grasslands’ response is assessed over a year. Elevated CO₂ appeared to strongly influence soil microbial communities, particularly bacterial communities, and to a greater extend in the acidic grassland compared to the limestone. The two grasslands appeared to have opposing soil organic carbon storage trends under eCO2. There was also evidence that eCO2 can extend summer communities into autumn when they would usually undergo change at that time. The third chapter is a methods chapter and aims to improve understanding about how common soil sample storage methods alter the measured soil properties commonly used in research. This chapter illustrates that soil sample storage should be avoided where possible and analysis should be conducted on fresh soil, apart from for δ13C of organic carbon as it is stable under all storage methods tested. The fourth chapter investigates how extreme event damage, investigated by removing aboveground plant material mimicking high plat mortality, can strongly influence soil respiration but that soil organic carbon appeared unaffected. In contrast, site level effects such as soil moisture (drought) and time of year appeared to strongly alter soil organic carbon.