Functional Differences in the Microbial Processing of Recent Assimilates under Two Contrasting Perennial Bioenergy Plantations

Land use change driven alteration of microbial communities can have implications on belowground C cycling and storage, although our understanding of the interactions between plant C inputs and soil microbes is limited. Using phospholipid fatty acids (PLFA's) we profiled the microbial communities under two contrasting UK perennial bioenergy crops, Short Rotation Coppice (SRC) willow and Miscanthus Giganteus (miscanthus), and used C-13 - pulse labelling to investigate how recent carbon (C) assimilates were transferred through plant tissues to soil microbes. Total PLFA's and fungal to bacterial (F:B) ratios were higher under SRC willow (Total PLFA = 47.70 +/- 1.66 SE mu g PLFA g(-1) dry weight soil, F:B = 0.27 +/- 0.01 SE) relative to miscanthus (Total PLFA = 30.89 +/- 0.73 SE mu g PLFA g(-1) dry weight soil, F:B = 0.17 +/- 0.00 SE). Functional differences in microbial communities were highlighted by contrasting processing of labelled C. SRC willow allocated 44% of total C-13 detected into fungal PLFA relative to 9% under miscanthus and 380% more C-13 was returned to the atmosphere in soil respiration from SRC willow soil compared to miscanthus. Our findings elucidate the roles that bacteria and fungi play in the turnover of recent plant derived C under these two perennial bioenergy crops, and provide important evidence on the impacts of land use change to bioenergy on microbial community composition. Crown Copyright (C) 2017 Published by Elsevier Ltd. All rights reserved.