PARENT SESSION
Oral Session #11: Biodiversity and Ecosystem Function. Presiding: A. Downing.
Monday, August 6, 2001. 1:00 PM to 4:45 PM. Madison Ballroom C.
Canopy Structure in an age sequence of stands dominated by Pseudotsuga menziesii.
Van Pelt, Robert1,2, Nadkarni, Nalini1, Rentmeester, Steve1, 1 2
ABSTRACT- Eight stands spanning an age range of nearly a millennium, were established in the Southern Washington Cascades during 2000. Within each stand, randomly located transects were laid out in proportion to the dominant tree height for the stand. Each transect was 3 x 0.3 the height of the stand. This allowed for capturing enough of the stand for analysis without oversampling the small trees in the younger stands. Tree heights and diameters ranged up to 90 m and 309 cm. A total of 5,737 trees among the 32 transects were mapped and measured for height, diameter, crown height, and four crown radii. Throughout the chronosequence the stands go from being nearly completely dominated by Pseudotsuga menziesii, to being increasingly dominated by Tsuga heterophylla, and, to a lesser extent, Thuja plicata. The structure of the canopy goes from a simple, fairly even monolayer in the youngest stands to a very complex, highly diffuse canopy with extreme variability in both horizontal and vertical dimensions. In the older stands individuals of Pseudotsuga become highly complex, often with multiple, reiterated trunks, and canopy foliage spanning over 70 m. The stands with the highest component of structural complexity were aged between 500 and 700 years and retained 20.7 Pseudotsuga/ha. Complexity diminished in the oldest stand due to all but a single Pseudotsuga/ha remaining. Several parameters of structural and canopy complexity were examined and are summarized.
KEY WORDS: Canopy, Structure, Chronosequence, Pseudotsuga menziesii