Reducing carbon cycle uncertainties in pine forests in the southeastern U.S. coastal plain

Timothy A. Martin, University of Florida

Co-Investigators: Gregory Starr (University of Florida), Wendell P. Cropper, Jr. (University of Florida), Henry L. Gholz (National Science Foundation), Michael W. Binford (University of Florida)

Abstract

This project has four objectives: (1) To develop a portable eddy covariance (EC) system deployment protocol that will enable us to estimate annual net ecosystem exchange of CO₂ (NEE) in multiple stands per year with acceptable error; (2) To identify and better understand what ecosystem and site-related factors control stand-to-stand NEE variation in pine plantation forests of the southeastern U.S. Coastal Plain (SECP); (3) To evaluate existing remote-sensing and model-based protocols for NEE estimation in the study region; and (4) To use this information to derive robust C balances for pine-dominated SECP landscapes.

The research will take place in industrial slash pine plantations in north-central Florida, on stands predicted by a previous remote-sensing analysis to be in the lower, middle, and upper quintiles of NEE.

The approach uses a portable EC system to sample stand-to-stand variation in NEE. In the first phase, the portable system will be deployed for six month periods in two stands: one planted in the same year as our permanent "Donaldson Tract" mid-rotation slash pine site, and the other the same age as the permanent "Mize" aggrading slash pine plantation site. These medium-term campaigns will provide reference NEE periods which can be used to test sampling regimes to determine the combination of campaign length, number of campaigns, and campaign timing which produce reasonable estimates of larger temporal scale NEE (Objective 1). In the second phase, the regime developed in Objective 1 will be used to sample plantation sites across a large range of NEE, as predicted by an earlier remote sensing / modeling analysis. Ecological and site variables will be measured at each campaign site. Together, these measurements will enable us to better understand the magnitude of and factors driving stand-to-stand NEE variation (Objective 2). A series of NEE estimation protocols will be tested against measured NEE at each campaign site (Objective 3). Information from the research for Objectives 1-3 will be used to guide a remote sensing / modeling estimate of NEE for 900 km² of forested landscape in the region (Objective 4).

The proposed research will produce: rational protocols for sampling stand-to-stand NEE variation using port able eddy covariance systemes; an improved understanding of the independent site and ecosystem factors driving NEE variation in SECP pine forests; evaluation of several NEE estimation protocols of varying complexity; and improved estimates of largescale NEE in the region. Deliverables will include project reports, gap-filled EC data and ecological data posted to the CDIAC data repository within one year of collection, technology transfer talks and reports to stakeholder industrial forest land managers, and peer-reviewed publications.

Publications

Powell, T.L., H.L. Gholz, K.L. Clark, G. Starr, W.P. Cropper, Jr., and T.A. Martin. 2007. Carbon exchange of a naturally-regenerated pine forest in north Florida. Global Change Biol, in review.