Effects of Annual Fertilization and Sustained Weed Control on Dry Matter Partitioning, Leaf Area, and Growth Efficiency of Juvenile Loblolly and Slash Pine

Abstract

Productivity and stand development of juvenile loblolly (Pinus taeda L.) and slash pine (P. elliottii Engelm. var. elliottii) were investigated using a 2 x 2 x 2 factorial experiment (species, fertilization, weed control) in north-central Florida. After four growing seasons, annual fertilization and complete weed control produced similar levels of response, increasing aboveground biomass 700% for loblolly pine and 300% for slash pine. The combined treatment improved total dry matter production 1600% (from 1.9 to 32.2 Mg ha-1) for loblolly pine and 450% (from 4.3 to 23.6 Mg ha-1) for slash pine. Equally large treatment-associated increases (up to 1210%) in all-sided leaf area index were measured. Cultural treatments increased the proportional allocations of dry matter to stem wood, stem bark, and branches for both species, a consequence of accelerated stand development. Regardless of treatment, dry matter partitioning to bole (stem wood and stem bark) tissues was greater for slash than loblolly pine (58 vs. 44%), whereas the opposite was true for the crown (foliage and branches) components (42 vs. 57%). Bole production per unit leaf area (growth efficiency) improved with increasing intensity of cultural treatments and was significantly greater for slash than loblolly pine. Results indicate that the potential to increase southern pine productivity on Lower Coastal Plain flatwoods sites is large, and that soil-plant nutrient availability is an important limiting factor. For. Sci 36(4):995-1014.