Fig. 4: Relations between tree cover change, disturbances, and vegetation type between the southern and northern boreal forest biome boundaries.
From: Northern expansion is not compensating for southern declines in North American boreal forests
Tree cover changes are visualised along standardised boundary distances from south (−1) to north (1) as model fits ± standard errors around the fitted lines from a generalised additive mixed-effects model (see Supplementary Fig. 17b for relative tree cover change). We included standardised boundary distance as fixed smooth explanatory variable in the model. We further included interaction effects within the smoothing term considering 30 different combinations of disturbances (panel columns and colours) and vegetation types (panel rows). We accounted for spatial correlation in the model and treated sample transects as random effects. Horizontal dashed lines represent the southern, interior, and northern boreal forest boundaries. Fitted model lines including raw data points are shown in Supplementary Fig. 17a.
