Carbon and Water Fluxes in a Drained Coastal Clearcut

The effects of clear-cutting and cultivating for timber on ecosystem carbon and water fluxes were evaluated by comparative measurements of two drained coastal wetland systems in the North Carolina coastal plain. Measurements were conducted from January through September, 2005 in a recent clearcut (CC) of native hardwoods and a loblolly pine (Pinus taeda) plantation (LP) that represent a chronosequence after replacing native coastal hardwood species with fast-growing commercial species. Each of the study sites is an independent ditched block representing a complete watershed and has long-term hydrological record. Results suggest that evapotranspiration (ET) rates for both stands were similar, except during the early summer (April to June) when ET was significantly (p < 0.01) higher in LP. Despite the fact that the plant photosynthetic contribution in the CC was a small fraction of the LP; there was only a 20% difference in ET rates between the stands. Moreover, we observed a significant (p<0.01) negative relationship between ET and carbon flux (Fc) in LP, but a weak relationship in the CC stand. The LP was storing carbon whereas the CC was a source of carbon on a daily basis. We reason that photosynthesis is the dominant process in the LP stand whereas decomposition is the dominate process in the CC stand, which can explain observed ET and Fc relationship between the two stands. The study will continue in 2006 and 2007 to contrast water and carbon balances at multiple temporal scales between the two stands.