PARENT SESSION
Contributed Oral Session 95: Forest Ecology: Physiological Processes
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Within-canopy variance in leaf photosynthesis and leaf density within a mature stand of American Chestnut.
Brown, Kim*,1, Joesting, Heather1, McCarthy, Brian 1, 1 Ohio University, Athens, OH, USA
ABSTRACT- American chestnut ((Castanea dentata (Marsh.) Borkh.) disappeared as a major component of eastern deciduous forests approximately 60 years ago, due to the accidental introduction of the fungal pathogen Cryphonectria parasitica (Murr.) Barr. Few forest stands remain where one might find a population of mature (canopy-emergent) chestnut trees. Due to the timing of the blight and the emergence of ecophysiology as a science, the ecophysiological capacity of this species is relatively unknown. The objective of our research was to characterize the within-canopy variance of leaf photosynthesis and leaf mass in one of the few remaining stands of American chestnut near La Crosse, Wisconsin. This stand was planted by a farmer ca. 120 years ago in a location outside the naturally occurring range of chestnut and so escaped the blight until relatively recently. In July 2004, utilizing tree-climbing techniques, we accessed 10 mature trees (with mean canopy height of 21.4 m), in addition to working with 13 saplings (2.82 m mean height) and 15 seedlings (0.8 m mean height). Mean (s.e.) rates of leaf maximum net photosynthesis (Amax) were 13.88 (1.06), 7.97 (0.95), and 9.03 (0.49) umol m-2 s-1 for trees, saplings and seedlings, respectively. Leaf mass per unit area (LMA, g m-2) was well correlated with canopy height in this dense stand (r2 = 0.90), but was weakly correlated with Amax and leaf dark respiration (r2 = .34) and poorly correlated other photosynthetic parameters (r2 < .05). Based on LAI-2000 data from 30 plots within the 20 ha stand had a mean (s.e.) unadjusted LAI of 3.14 (.021). Additional canopy structural data (TRAC-based canopy clumping factor and percent canopy openness from hemispherical photographs) will be presented. These canopy physiological and structural data will be useful in stand productivity modeling efforts, whether taking into consideration past forest productivity (pre-blight) or future productivity (post-chestnut restoration).
Key words: Castanea dentata, LMA, photosynthesis, canopy structure