Wood anatomy
To examine whether the forest species exhibit functional anatomic
adaptations to explore niche water, we collected stem samples at 0.20,
1.30 and 3.00 m height from 12 trees of each species in mixed stands
using a wood core (cylinder 1.5” x 1”) (n= 24 samples) to determine
vessel elements. From the same trees, we also excavated four fine roots
(approximately three millimeters in diameter) close to the stem at 15-25
cm depth (n=24) to determine root anatomical/ structural
characteristics. All samples included sap wood and vascular cambium so
to examine vessel elements. Slides were prepared to gather data on
vessel elements, fiber lengths and tracheids. Once wood samples were
collected, they were immediately fixed with FAA (Formaldehyde Alcohol
Acetic Acid, 0.1:0.5:0.05 + 0.35 water)
(Berlyn & Miksche, 1976) in the field. In
the laboratory, samples were washed and stored in GAA (glycerin-95%
ethanol-water, 1:1:1). Transverse and radial sections 30 - 40 mm thick
including wood and vascular cambium were obtained with a sliding
microtome. For each sample, unbleached sections
(Ruzin, 1999) were stained with
safranin-fast green (Johansen, 1940) and
mounted on microscopic slides with synthetic resin. Macerations were
prepared using Jeffrey’s solution (Berlyn
& Miksche, 1976). Temporary slides were prepared to gather data on
vessel elements, fiber lengths and tracheids. Measurements were made
with the image analyzer BIO7 1.6 (Eclipse Public License) attached to a
video camera (Hitachi KP-D51) on a microscope (Olympus BX-50). The
terminology used for wood description follows the recommendations of the
International Association of Wood Anatomists
(IAWA Comittee, 1989).