highly significantP < 0.01
Between the three layers, TRL was well preserved: TRL 20 was correlated to TRL 40 at r = 0.77, TRL 40 to TRL 60 at r = 0.80 and even TRL 20 was correlated to TRL 60 at r = 0.62, which was highly significant ( P < 0.01) (Supplementary Table S1 ).