PARENT SESSION
Oral Session #13: Plant Ecology: Light Relationships. Presiding: J. Rebbeck.
Monday, August 6, 2001. 1:00 PM to 4:30 PM. Hall of Ideas P&Q.
The influence of stand structure on light interception and ecophysiological leaf characteristics of Pinus ponderosa.
NAGEL, LINDA1, O'HARA, KEVIN2, 1 2
ABSTRACT- The relationships between canopy depth and area-based (Aarea) and mass-based (Amass) maximum photosynthetic rates, specific leaf area (SLA), and area-based (Narea) and mass-based (Nmass) leaf nitrogen were investigated for even-aged and multiaged stand structures of ponderosa pine (Pinus ponderosa Dougl. ex Laws.). The primary stand structural difference involves greater canopy depth in the multiaged stand structures, which possibly influences the light relations within the canopy. Both Aarea and Amass were relatively constant with canopy depth in both stand structures. Narea and Nmass decreased with increasing canopy depth in the even-aged stand structures but not in the multiaged stand structures. SLA tended to increase with increasing canopy depth, although this relationship was significant only in the multiaged stand structures. The typical linear relationship observed for many species between photosynthetic rate and leaf nitrogen was not present in either stand structure on either an area- or a mass-basis. Narea was highly correlated to SLA in both even-aged and multiaged stand structures (R2 = 0.66 and R2 = 0.52, respectively). These data suggest that leaf structure and nitrogen investment are allocated in ponderosa pine such that photosynthesis is maximized in comparable ways throughout the canopies of both types of stand structure. This finding supports the notion that multiaged stand structures of ponderosa pine have the physiological potential to produce similar amounts of wood volume as even-aged stand structures.
KEY WORDS: forest stand structure, gas exchange, Pinus ponderosa, specific leaf area