Fig. 3: Tree cover change of North American boreal forests between 2000–2019 by disturbance type.
From: Northern expansion is not compensating for southern declines in North American boreal forests
a Tree cover changes by disturbance type expressed as running means along south-north boundary distances with bins of 0.025 (original results in Supplementary Fig. 16a). Boundaries were derived from Gauthier et al. 5. b Fitted tree cover changes from generalised additive mixed-effects models. Data are presented as model fits ± standard errors around the fitted lines. Standardised boundary distance was included as fixed smoothed explanatory variable in the model and fitted using disturbance type as interaction term. Tree cover changes were calculated as described in Fig. 2. Disturbances by wildfire and timber harvest cover the periods 1985–1999 and 2000–2019 and were derived from the CANLaD data set (see Methods for details). Undisturbed forests are defined as areas unaffected by fire and harvest since 1985. Relative tree cover changes by disturbance type are shown in Supplementary Fig. 16b. Fitted model lines including raw data points are shown in Supplementary Fig. 7.
