Fig. 1

ARGs grouped by season in soils and wastewater adjacent to swine feedlots. a Normalized ARG abundance relative to 16S rRNA gene; b ARG abundance relative to the CK soil (fold change). The initial letters in the abbreviations W and S represent winter and summer, respectively. The latter two capital letters, ‘CK’ represent control soil without a history of livestock farming or manure application; ‘BW’, working feedlot in Beijing; BA, abandoned feedlot in Beijing; ‘HW’, working feedlot in Hefei; ‘HA’, abandoned feedlot in Hefei. Lower case letters ‘t’ and ‘s’ indicate topsoil and subsurface soil, respectively. The number involved represents sampling sites indicated in Additional file 1: Fig. S1. Samples with a last capital ‘W’ represents wastewater (the pollution source) or sediment collected from the wastewater discharging ditches