© 2004 Heron Publishing—Victoria, Canada
Integrating within-crown variation in net photosynthesis in loblolly and slash pine families
Robert C. McGarvey (1, 2), Timothy A. Martin (1, 3) and Timothy L. White (1)
1. School of Forest Resources and Conservation, University of Florida, Gainesville, FL, USA / 2. Warnell School of Forest Resources, University of Georgia, Athens, GA, USA / 3. Corresponding author (tamartin@ufl.edu) / Received December 3, 2003; accepted March 20, 2004; published online September 1, 2004
Summary
We examined photosynthetic characteristics of two fast- and two slow-growing half-sib families of both loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii var. elliottii Engelm.) on two sites in northern Florida to: (1) quantify variation in light-saturated net photosynthesis (Amax) associated with vertical crown position and foliage age; (2) quantify the amount and distribution of leaf area by foliage
age class; and (3) determine whether photosynthetic indices, ranging from leaf-level through whole-crown Amax, were related to growth differences among species and families. In both species, leaf-level Amax was higher in more recently formed foliage both within the same year (where Amax in the third flush averaged 10 to 30% higher than Amax in the first flush) and between years (where Amax in current-year foliage averaged 20 to 40% higher than Amax in 1-year-old foliage). When expressed on a leaf area basis, Amax of current-year foliage was higher in slash pine than in loblolly pine, but Amax expressed on a mass basis did not differ between species. Loblolly pine had higher whole-tree leaf area than slash pine,
whereas whole-tree Amax did not differ between species. When the mean values for fast-growing families were compared with the mean values for slow-growing
families, there were no differences in leaf-level characteristics, whereas at the whole-tree level, fast-growing families
had higher leaf area and whole-tree Amax than slow-growing families in both species. When comparisons were made among the individual fast- and slow-growing families,
however, results were more variable. In both species, stem volume growth was strongly correlated with whole-tree Amax, with most of the strength of the correlation deriving from the relationship between volume growth and tree leaf area.
Keywords:
foliar nitrogen concentration, photosynthetic capacity, Pinus elliottii, Pinus taeda, specific leaf area.
