Table 1. Sassafras albidum δ¹³C root data from trees labeled with 99% ¹³CO₂.

Year	Root age (d)	Number of days post-labeling
		3	6	19
Structural δ13C (Control = −28.13±0.24 (n = 9))
2008	>14	−2.18±3.38 (n = 14)	−5.75±1.28 (n = 13)	−6.23±3.89 (n = 8)
2009		5	14
Structural δ13C (Control = −27.85±0.38 (n = 2))
	16	−16.84±3.73 (n = 3)	−18.93±3.76 (n = 2)
	28	−19.99±1.46 (n = 13)	−21.87±1.22 (n = 13)
	71	−21.99±1.91 (n = 4)	−22.04±1.87 (n = 3)
Starch δ13C (Control = −27.64±0.09 (n = 2))
	16	−16.66±3.91 (n = 3)	−12.17±8.08 (n = 2)
	28	−14.90±2.57 (n = 13)	−15.50±2.70 (n = 13)
	71	−17.38±4.51 (n = 4)	−5.41±12.77 (n = 3)
Sugar δ13C (Control = −26.38±0.25 (n = 2))
	16	−0.68±5.81(n = 3)	−9.11±1.98 (n = 2)
	28	−0.18±1.37 (n = 13)	−10.86±1.77 (n = 13)
	71	−2.93±9.11 (n = 4)	−14.91±1.04 (n = 3)

Data showing the number of samples (n) analyzed as well as the average δ¹³C and associated standard error for each root age class, sampling date, and carbon pool from trees labeled with 99% ¹³CO₂ in 2008 (n = 3) and 2009 (n = 1), where less negative values indicate greater isotopic enrichment. ¹³CO₂ labeling significantly enriched the root structural δ¹³C in 2008 (n = 35, P<0.0001) and 2009 (n = 38, P = 0.02). Additionally, both the root starch and root sugars were significantly enriched in 2009 (n = 38, P_starch<0.0001, P_sugars = 0.001). The number of days sampling occurred post labeling did not significantly affect enrichment in root structural δ¹³C in 2008 (P = 0.19) nor root structural δ¹³C nor root starch δ¹³C in 2009 (P_structural = 0.14, P_starch = 0.26). In 2009 root sugars were significantly affected by the days post labeling (P = 0.005), with roots sampled later showing decreased enrichment. The age of the roots at the time of labeling did not significantly affect enrichment in any of the carbon pools in 2009 (P_structural = 0.15, P_starch = 0.26, P_sugars = 0.09).