On an ecological level, there are many unanswered questions relating to the effects of rising CO₂ on competition, distribution and species biodiversity, particularly in long-lived tree species. The question of the impact of environmental change on the forest ecosystem of the southeast is unknown. The objectives of this project were to determine emission rates of the hydrocarbons as affected by temperature, tree organ and age in loblolly and slash pine, and to determine how the carbon physiology of these pines are affected by climate change factors of elevated temperature, increased CO₂, and drought.

Terpene emission rates and needle terpene concentrations of total, alpha- and beta-pinene were significantly affected by species, age and time of year. Loblolly pine showed the largest emission rate at 25⁰C in controlled environment in quarter 2 (June) with emission rate increasing with all age. Similar age effects were observed in splash pine in both quarters 1 and 2. For both species, Similar age affects were observed in splash pine in both quarters 1 and 2. For both species, emission rates dropped off during the fall and winter (quarters 3 and 4). Needle terpene concentrations in loblolly pine exhibited a significant quarter-by-age interaction, showing increased concentrations with age. The response of loblolly and slash pine to elevated temperature, high CO₂ and drought were dramatic. Biomass distribution between stems and branches and foliage was significantly reduced in the drought treatment while the CO₂ treatment resulted in increased biomass. Stem biomass increased in elevated CO₂ with little change in either branch or foliage biomass. Leaf area followed the same treatment trend as total biomass indicating the tight linkage between biomass accumulation and leaf area. Trees in elevated CO₂ exhibited a shift in partitioning front the foliage to the stem while droughted trees allocated less biomass to stem and more to branches in loblolly pine and more to foliage in splash pine.

Implications of global climate change on the forest ecosystem of the southeastern United States appear to be great, based on this project. First, with increasing atmospheric CO₂ concentrations, both pine species could show significant increases in stem biomass without any additional nutrient input, if extrapolation from a two year exposure pronounced in loblolly pine. Drought, on the other extreme, could negate any positive effects of increasing CO₂ . Shifting rainfall patterns resulting in prolonged drought could decrease forest productivity across the south. Elevated temperature was moderately detrimental to tree growth, due to increased respiratory carbon loss.