Figure 1.
A. Sassafras albidum tree covered in a clear mylar balloon during the 13CO2 labeling process. B. Example of a root box showing roots that were traced on a clear acetate window facing the study tree using different color paint pens.
Figure 2.
Sassafras albidum root cross-section.
Micrograph depicting how higher-order roots (approximately 4th or 5th order) were dissected prior to δ13C analysis in 2008.
Figure 3.
Mean Sassafras albidum first-order root structural carbon δ13C values.
Data from an unlabeled control tree, and trees labeled in 2008 and in 2009. All roots were at least 2 weeks old at the time of labeling and subsequent sampling and some were older than 71 days. Black bars represent roots sampled prior to whole-tree labeling and grey bars represent roots sampled after whole-tree labeling. Note that less negative values indicate greater isotopic enrichment. Error bars denote standard error between individual sampled roots. Different lower case letters denote significant differences at P≤0.05 using a one tailed T-test between pre- and post-labeled roots.
Figure 4.
Mean Sassafras albidum root structural carbon δ13C values from higher-order dissected roots.
Trees were labeled and sampled in 2008. Control roots were sampled from unlabeled control trees and labeled roots were sampled from trees labeled with 99% 13CO2. Late wood refers to the innermost portion of the dissected roots (see Figure 2). Early wood refers to the root tissue immediately surrounding the late wood. Secondary cortex refers to the outermost portion of the root surrounding the early wood. Note that less negative values indicate greater isotopic enrichment. Error bars denote standard error. Different lower case letters denote significant differences at P≤0.05 using a one tailed T-test between dissected root tissue from unlabeled control trees and labeled trees.
Figure 5.
Mean Sassafras albidum first-order root carbon δ13C values.
Roots were at least two weeks old at the time of whole tree labeling in 2009. Black bars represent roots that were sampled immediately prior to whole-tree labeling. Light grey bars represent roots sampled after whole-tree labeling. Note that less negative values indicate greater isotopic enrichment. Error bars denote standard error. Different lower case letters denote significant differences at P≤0.05 using a one tailed T-test between pre- and post-labeled roots of each tissue type.
Table 1.
Sassafras albidum δ13C root data from trees labeled with 99% 13CO2.
Figure 6.
Mean Sassafras albidum root structural carbon δ13C values verses root age at time of sampling.
Circles represent roots sampled in 2009. The triangle represents the mean of the late wood (lw) structural root tissue from the 2008 dissection samples which were older than one year when sampled but the exact age is unknown. The grey horizontal bar shows the 95 percentiles for background δ13C structural carbon values from 2008 and 2009. Note that less negative values indicate greater isotopic enrichment. Error bars denote standard error.