The influence of stand structure on ecophysiological leaf characteristics of Pinus ponderosa in western Montana

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The effects of vertical arrangement of foliage in even-aged and multiaged stand structures of ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) on overall stand growth, light interception, and physiological leaf properties were tested on five plot pairs in western Montana. The primary structural difference between stand structures involves greater canopy depth and stratification of foliage in the multiaged stands. Both area- and mass-based maximum photosynthetic rates (Aarea and Amass) were relatively constant with canopy depth in both stand structures. Area-and mass-based leaf nitrogen (Narea and Nmass) decreased with increasing canopy depth in the even-aged stand structures but not in the multiaged. Specific leaf area (SLA) tended to increase with increasing canopy depth, although this relationship was only significant 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; however, Narea was highly correlated to SLA in both even-aged and multiaged stand structures (R2 = 0.66 and R2 = 0.52, respectively). There were no differences in the light extinction coefficient (k), basal area growth or efficiency, or stand-level leaf area index between even-aged and multiaged plot pairs. Relative constancy in leaf physiology combined with similarities in site occupancy and growth rates help explain how different stand structures of ponderosa pine maintain similar rates of woody biomass productivity.

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Canadian Journal of Forest Research