Additional file 1 of Changing soil carbon: influencing factors, sequestration strategy and research direction

Additional file 1: Fig. S1. The numbers of published papers with meta-analyses related to soil carbon and all studies related to soil carbon from 2009 to 2018. Fig. S2. Keyword distributions of meta-analyses and all studies related to soil carbon. The bar plot indicates the percentage changes in keyword distributions in the 11 ecosystems, 12 indices and 29 influencing factors between the meta-analyses and all studies related to soil carbon. The network indicates the keyword distributions in the 11 ecosystems, 12 indices and 29 influencing factors and the co-occurrence frequency of two groups; the vertex indicates the relative percentage of each group; the numerical value of the vertex of each group = 50 * keyword count of each group/the maximum keyword count; and the edges indicate the co-occurrence frequency of two groups. The numerical value of the edge of each group = 50 * co-occurrence frequency of each pair of two groups/the maximum co-occurrence frequency. Table S1. Changes in C losses and C assimilation due to different influencing factors. The C losses include CO2 emissions, CH4 emissions and carbon decomposition. C assimilation includes underground biomass, aboveground biomass, plant biomass, net primary production and so on. NA means that no data were reported in the studies or that there were not enough data for the t-tests. Table S2. List of the references that the meta-analysis results were collected.