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. 2018 Jun 4;7(1):21. doi: 10.1186/s13717-018-0132-x

Fig. 5.

Fig. 5

The causal effects of total nitrogen on invertebrates in different ecoregions of the Western United States. a Forested Mountains. b Great Plains. c North American Deserts. The black solid lines and black dashed lines are the mean estimations by generalized propensity score of the TN-IR dose-response function and the corresponding 95% confidence boundaries, respectively. The gray solid lines are the estimations by the general additive model in a and c and the estimations by simple linear regression in b. The gray dashed line in b is the estimation by multiple linear regressions and nearly overlaps the simple linear regression line