Figure 2.

The relationship between year and δ¹³C values for global atmospheric CO₂, North American jack pine (P. banksiana) tree ring cellulose, and Isle Royale moose (A. alces) and wolf (C. lupus) bone collagen. δ¹³C data are reported in per mil (‰) relative to Pee Dee Belemnite (PDB) limestone standard. Each panel includes individual δ¹³C values (open symbols) and a simple linear regression line for the relationship between time and δ¹³C values. Jack pine data are a 5-year running average (see §2). Note increasing trend in correlation from trees to moose to wolves.