Table 2 Linear model results of the time series analysis of DDG variables (D_max and R_max) across richness components for each lake. Here, +: positive slope of linear model (Meaning for D_max: becomes shallower; Meaning for R_max: more species); −: negative slope of linear model (Meaning for D_max: becomes deeper; Meaning for R_max : less species); significance levels of p-values: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1