This dataset describes monthly measurements of soil CO2 efflux, soil water content, and soil temperature in subplots with daily applications of root exudate solution (RE) or a procedural control solution (CP), applied using the Automated Root Exudate System (ARES) within experimental litter removal (0L) and control plots (1L) in an old-growth deciduous woodland in Wytham, Oxfordshire UK. Full descriptions of the study site and experimental design are given in the paper and appendices. Column headings and abbreviations are as follows: block = replicate block A-E; Plot = unique experimental plot identifier P1-P15; treatm = litter manipulation treatment, where 0L is litter removal and CT is control; ARES = subplot treatment, where RE is root exudate solution, CP is procedural control and 'plot' is the main litter manipulation plot; year = year of study; month = month of measurement; nom.date = nominal date of measurement (set at 1st of the month); time = consecutive time point during the study; swc = soil water content at 0-6 cm depth in %; temp10 = soil temperature at 0-10 cm depth; Rsoil = soil CO2 efflux in mg C m2-1 h-1; Flux = soil CO2 efflux in umol m-2 s-1; Comments = reasons for outliers and missing values; ObsDateTime = actual date and time of each measurement.