Fig. 1.

Locations of the 96 forest plots in Canada's boreal forest. The red and black circles represent plots with respectively decreasing and increasing rates of biomass change. The size of the circle is proportional to the plot-specific slope of the ordinary least-squares regression for the rate of biomass change as a function of the calendar year. Thus, the circle size reflects the rate of annual change in biomass. The background colors of green and light green represent the boreal and hemiboreal regions, respectively. In total, 80 plots (83% of the 96 forest plots) were located in the boreal region and 16 (17%) were located in the hemiboreal region. A total of 70 plots were located in the western region (Alberta, Saskatchewan, and Manitoba) and 26 were located in the eastern region (Ontario and Quebec). In total, 89% of the plots (62/70) in the western region and 46% of the plots (12/26) in the eastern region experienced decreasing rate of biomass change. The shapefiles defining Canada's boreal and hemiboreal zones were developed by J. P. Brandt of Natural Resources Canada (SI Appendix, ref. S16) and were obtained from the agency's Web page (http://canadaforests.nrcan.gc.ca/download; accessed December 23 2011).