• Research

• Longleaf Pine Research
• Plant Ecology and Biodiversity
• Productivity and Nutrient Cycling
• Carbon Fine Root Allocation and Transfer at Ecosystem Scales
• Elevated Atmospheric CO2 Influences on Longleaf Pine Grasslands
• Nitrogen Fixation by Legumes
• Fire and Nitrogen Cycling Studies
• Crown and Canopy Structure
• Long-term Research on Productivity and Biodiver sity
• Ecosystem Restoration
• Conservation Management
• Aquatics Research
• Wildlife Research
• Research Publications
• Graduate Projects

Crown and Canopy Structure Across a Complex Environmental Gradient: Quantification and Relation to Productivity

Research Team: Dr. Steven B. Jack (Conservation Ecologist) and Jennifer Gagnon (Research Technician III)

In forested ecosystems, differences in site resource availability (i.e. light, water and nutrients) have been shown to affect the leaf, shoot and branch structure of trees. In turn, crown characteristics have been reported to influence pine productivity (i.e., carbon sequestration) by affecting the amount of light interception through the display of foliage and the phenological development of shoots within the crown. Based on these studies, differences detected in above ground net primary productivity (ANPP) along a soil moisture gradient in longleaf pine forests (1.5 and 4.96 Mg·ha^-1·year^-1 on xeric and mesic sites, respectively) were predicted to be a result of distinct differences in the crown structure and phenology of mature longleaf pine. We initiated a study to examine shoot and needle phenology and crown and canopy structure across an environmental gradient and to determine how structural features affect production in the overstory pine.

Canopy towers located at two extremes of the soil moisture gradient on Ichauway (i.e., a xeric site and a mesic site) were used to access the crowns of mature longleaf pine. Bi-weekly measurements of shoot and needle elongation (phenology) were recorded for three growing seasons (February through October, 1999-2001). In addition, crown morphology, leaf area patterns and needle abscission were examined. These measurements were then related to environmental variables, such as gap fraction, soil moisture content and predawn needle water potential.

Our hypotheses were:

1. Shoot and needle phenology will vary with site resource availability.
2. Differences in phenological development will result in differences in leaf areas and arrangement of foliage.
3. Differences in individual crown structures will result in canopy structure variation across the soil moisture gradient.
4. These expected structural differences, at both the crown and canopy levels, will be strongly related to observed aboveground productivity differences across the gradient.

Additional Information:

Sheffield, MCP, Gagnon, JL, Jack, SB, and McConnville, DJ. In Press. Phenological patterns of mature longleaf pine (Pinus
palustris Miller) under two different soil moisture regimes. For. Eco. Manage.

Funded by: The Joseph W. Jones Ecological Research Center