Document: GRE-3-30-25

The influence of photosynthetic capacity and leaf area on growth differences associated with fertilization and competition control in Pinus taeda L. stands.

MUNGER, G.T.* and R.E.WILL

University of Georgia, Athens, GA 30602 USA ¹

Abstract:
Growth of forest stands is strongly influenced by nutrient availability. As part of a comprehensive study exploring the biological potential of loblolly pine (Pinus taeda L.) stands through yearly nitrogen fertilization and elimination of competing vegetation across a range of sites and stand ages in Georgia, we assessed the relative role of leaf area and light saturated photosynthetic rate on treatment-induced increases in stand growth . Fertilization and competition control had significant positive effects on litterfall based estimates of stand leaf area. Annual litterfall surface area (all-sided) was 3.72, 5.54, 5.76, and 7.18 m² m^-2 of plot area for the Piedmont site and 5.00, 7.46, 5.46, and 8.20 m² m^-2 at the Coastal Plain site, for check, fertilization, competition control, and fertilization competition control treatments, respectively. No clear pattern in light-saturated photosynthetic rate (A_sat) was associated with the treatments. Mean values of A_sat taken over five measurement periods from April 1999 to December 1999 were 2.61, 2.51, 2.49, and 2.41 micromol m^-2 s^-1 at the Piedmont site and 3.55, 3.51, 3.32, and 3.40 at the Coastal Plain site, for check, fertilization, competition control, and fertilization competition control treatments, respectively. We conclude that differences in growth associated with fertilization and competition control were mediated by leaf area, not by the light saturated photosynthetic capacity of the foliage.

Keywords: competition, fertilization, leaf area, photosynthetic capacity, Pinus taeda L.

This abstract is being presented at: 2:45 PM in session:
Oral Session #50: Plant Gas Exchange.