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Physiological Ecology

Physiological Investigation of Shade Tolerance in Longleaf Pine

Longleaf pine has been classified as very shade intolerant based on the need for canopy gaps for successful regeneration. Of the southern pines, longleaf is considered the most intolerant of competition. Shade tolerance of longleaf pine has been defined primarily by seedling survival, height and root collar diameter growth in gaps. However, longleaf may be moderately tolerant when young but become more intolerant of shade with age and therefore exhibit plasticity in shade tolerance. To the best of our knowledge, no study has examined physiological shade tolerance defined by light response curves and leaf morphology in different size longleaf trees and in different geographic sources. Therefore, the objective of this research is

To better define physiological plasticity in shade tolerance in longleaf pine by examining physiological shade tolerance in grass stage seedlings from and in branches of young longleaf pine approximately 10 m tall.

Photosynthetic response to light, chlorophyll concentrations and needle structure in foliage subjected to 0%, 50% and 70% reductions in ambient light were examined over one growing season. This study will yield a better understanding of ecological requirements of longleaf pine and will aid in refining process models that model carbon uptake of ecosystems.