FY 05/06

Scaling of carbon exchange from intensively measured plots to the upper Neuse River basin

The aggrading forests of the southeastern United States have some of the highest rates of carbon (C) sequestration in the world. Long growing seasons, extensive forest regrowth, and typically humid conditions provide consistently high rates of atmospheric CO₂ uptake and retention by the land surface. However, precise estimates of C sequestration at the regional scale are limited due to the patchiness of the landscape, with significant mixing of broadleaf, conifer, agricultural, and urban surfaces. Variability in surface hydrology and land cover induces significant feedbacks in energy partitioning, vapor flux, atmospheric boundary layer dynamics, and carbon cycling processes, which further preclude precise C estimates.

This project aims to develop methods to scale carbon cycling and uptake from plot levels that respond to topographic, soil, and moisture conditions, to the aggregate response of the landscape. The project will focus on the Upper Neuse River Basin (UNRB) of North Carolina because of the availability of hierarchical land cover classification data, long streamflow records, and intensively measured plot level data. An estimate of net primary production (NPP) for the UNRB for the years 2002 and 2003 (a dry and a wet year, respectively) will be developed through two approaches: 1) transpiration will be derived from streamflow data, and then used to estimate gross primary production (GPP) using a simple water/carbon coupling model; and 2) process-based ecosystem models will be used to scale plot level fluxes to landscape. NPP will be estimated under both non-limiting and limiting soil moisture conditions, and these estimates will be compared with MODIS NPP products and forest inventory data. The knowledge gained through this project will enable scientists to develop better predictive tools for estimating CO₂ uptake under various land-use classes and future climate scenarios over length scales ranging from individual plots to the regional watershed.

The working group is composed of an interdisciplinary team of experimentalists and modelers from a number of institutions:
Sari Palmroth, Environmental Sciences and Policy, Duke University
Dafeng Hui, Environmental Sciences and Policy, Duke University
Rob Jackson, Environmental Sciences and Policy, Duke University
Gabriel Katul, Environmental Sciences and Policy, Duke University
Ram Oren, Environmental Sciences and Policy, Duke University
Roni Avissar, Civil and Environmental Engineering, Duke University
Lawrence Brand, Department of Geography, University of North Carolina
Steve McNulty, Southern Research Station, USDA-Forest Service