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).