Fig. 2: Global trend of normalized sedimentary δ15N abundance and total nitrogen concentration (TN) in the past 300 years.
From: Global change pattern of sedimentary nitrogen isotope during the Anthropocene epoch
a normalized trend of sedimentary δ15N in disturbed sites. b normalized trend of sedimentary δ15N in natural sites. c normalized trend of sedimentary TN in disturbed sites. d normalized trend of sedimentary TN in natural sites. The results of the Davies hypothesis test indicate that (a–d) had least one breakpoint statistically (p < 0.01). Specifically, the red curve represents the non-linear fitting of pyGAM; The blue curve represents the 95% confidence interval for nonparametric fitting; the vertical yellow line indicates the year of the breakpoint; and the vertical green lines demonstrated the ± 1 standard deviation for the breakpoint.
