Site description

US-NC2: Loblolly pine plantation site

The North Carolina Loblolly Pine site is located in a pine plantation amongst the mixed forests of the North Carolina lower coastal plain. During the late 19th and early 20th centuries the region was logged extensively. After a series of clearcuts, the land was transformed for agricultural practices. In 1967 and 1969, 4000 ha was sold to the Weyerhauser company for agriculture, preservation, and commercial logging of loblolly pines in a series of plantations. The fifth rotation stand surrounding the tower was established in 1992. The only significant natural disturbances during the measurement period was a severe drought that spanned the entire duration of the 2007 growing season. Consequently, the 2007 total amount of precipitation was 486 mm below the 30-year norm. In the same year, the plantation was thinned and fertilized. The stand was thinned in Oct 2009. The eastern half of the site was fertilized in January 2011, and the entire site was fertilized in October 2012.

The research and science objectives of the North Carolina Loblolly Pine site are as follows: 1) quantify age-related changes in carbon and water exchange, environmental regulation and stress sensitivity; 2) partition causes of variability between environmental and management factors; 3) Identify primary vulnerabilities to environmental stresses, and develop potential adaptive measures; 4) Characterize the sources of interannual variability in the fluxes, including sensitivity to natural disturbances such as severe droughts; 5) Examine the effects of ecosystem conversion from wetlands to intensively managed forests on plant hydraulic properties and water balances.

US-NC3: Clearcut site followed by planting loblolly pine seedlings

The North Carolina Clearcut site was set up to complement NC2, and continue in place of NC1. The previous rotation of loblolly pine was harvested in the spring of 2012, the site was prepared and replanted with 2-yr old seedlings in the winter of 2012/2013.

The goal is to refine understanding of post-disturbance carbon fluxes, respiration partitioning, and decomposition dynamics.

US-NC4: Lower coastal plain forested wetland

The North Carolina Alligator River site was established to provide core measurements for understanding carbon cycling in natural coastal forested wetlands. It serves as a reference for NC1, NC2 and NC3, representing an ecosystem type that dominated the area prior to European settlement.

Site layout

At all the sites, the flux tower is the central point to position all the survey plots. Ideally, the 13 plots are located in the 1-km2 area surrounding the tower to cover the footprint of the tower measurements. In the following sketch map, the width of the outer square is 1 km, and the width of the inner square is 500 m.

We conduct vegetation survey at the end of every year at all the 13 plots, basically measuring the tree diameters and use allometric equations to estimate the total biomass and then calculate the annual biomass production.

At the five central plots, we conduct flux measurements (e.g. soil respiration) and other experiments (e.g. leaf litter decomposition). Frequency of these measurements or experiment depends on the study design. For example, we usually measure soil respiration biweekly or monthly.