MEDINA, E., L. STERNBERG, and E. CUEVAS. 1991. Vertical stratification of delta-C-13 values in closed natural and plantation forests in the luquillo mountains, puerto-rico. Oecologia 87 (3): 369-72.
Abstract:
The variability of 13C values was measured
in leaf, stem and root tissues of several tree species growing
in closed natural and plantation forests in the Luquillo
mountains of Puerto Rico. Results confirm a significant
decrease of <513C values from the tree canopy
to the forest floor. The values measured in understory
plants growing in gaps were not significantly different
from the average for plants growing under the forest
shade. Seedling leaf values tended to be more positive
than those of saplings, probably reflecting the contribution
of organic matter from the mother tree. Photosynthetic
independence on the forest floor results in a reduction
in ?13C value. Stem and root tissue values of seedlings
and saplings were less negative than those of the
leaves of the same plants. It is suggested that this difference
results from the slower change in isotopie composition
experienced by the woody tissue, as the seedlings
become photosynthetically independent in the forest
floor.