Title

A Pilot Study of Individual-tree and Ecosystem Level Carbon Sequestration in High and Low Elevation, Mixed-Mesophytic Forests of the Great Smoky Mountains

Abstract

Increased atmospheric greenhouse-gas (GHG) concentrations are projected to cause significant warming of Earth's climate. These projections have initiated projects aimed at monitoring and sequestering CO2 to mitigate the likely warming trend. Measuring carbon storage in forests as well as predicting future sequestration trends and determining the factors influencing sequestration has become one important strategy of GHG mitigation. There is significant controversy surrounding the limitations of carbon uptake and sequestration in forests, especially forests considered to be old-growth. The primary goal of this experimental research, therefore, is to quantify and compare the amount of above ground carbon storage and trends in these stores between high and low elevation stands of old-growth mixed-mesophytic forest in the Smoky Mountains. Tree-ring analysis will be used to quantify the disturbance history and climatic response at the ecosystem level to determine how they constrain carbon sequestration. A secondary goal is to contrast the climatic response at the ecosystem and species level. Similarly, carbon sequestration at the ecosystem and individual-tree level growth rates will be compared to determine how carbon sequestration at the ecosystem level compares to the individual-tree level.

Research Objectives, Questions & Rationale:

Objectives: The primary goal of this experimental research is to quantify and compare the amount of aboveground carbon storage and trends in these stores between high and low elevation stands of old-growth, mixed-mesophytic forest in the Smoky Mountains. The research will reveal tree ages, disturbance history and the influence of climate on productivity at the tree and ecosystem level to address questions related to carbon sequestration. A secondary goal is to contrast climatic response at the ecosystem and species level.

A Few Potential Research Questions:

• Do old-growth forests have the ability to sequester additional carbon or are they at equilibrium?

• What role does climate play in the ability of natural forests to sequester carbon?

• Do ecosystem- and tree-level productivity vary in equal proportions?

Answers to this question could have important management implications regarding the influence of climate across hierarchical levels.

Rationale: Examination of ecosystem productivity as proposed here is inspired by the classic ecological work of Whittaker (1956), who examined the distribution of species and ecosystems across gradients in the Smoky Mountains. This project will update Whittaker's research using a macroecological approach (Brown, 1995) through the use of tree-ring analysis. Macroecology incorporates longer time scales over a larger spatial scale than more traditional ecological studies. The research proposed here will therefore add the dimension of time to the framework of Whittaker's classic study.

Related Research: A preliminary study of the longevity and climatic sensitivity of yellow buckeye and Carolina silverbell in the Great Smoky Mountains has been initiated. Findings from the longevity and climatic sensitivity research will lay the foundation for the creation of tree-ring chronologies of less-often studied species common in the southern Appalachian Mountains.