Fig. 2

a Number of publications per year between 2011 and 2020 for 377 publications found with “rhizosphere microbiome” search terms. b Number of publications investigating woody and non-woody roots that separated the root systems based on a root trait at the time of sampling for two time periods. Total bar height represents the total number of studies; black bars represent the number of studies that separated roots (8% of the total) for herbaceous and woody root systems within two time periods. Studies that examined both plant types (n = 7) were excluded from the figure. c Stacked bar chart displays the number of papers that separated roots before removing the rhizosphere for both woody and non-woody plants. Colors in each bar represent the root trait used to separate roots. d Tree plot of rhizosphere removal methods with box area proportional to the percentage of papers using each removal method. Colors depict overarching four categories of methods: wet (blue), dry (orange), unknown (no information provided on the method; green), and other (gray). Subcategories are indicated by text within boxes for wet and dry methods. The unknown (unk.) subcategories refer to studies which provided sufficient information to establish whether a method was wet or dry, but insufficient information to determine the specific approach