PARENT SESSION
Poster Session 32: Biogeochemistry
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Shifts in the Carbon Budget During Succession in the Shenandoah Valley of Northern Virginia.

Wang, Jin^*,1, Epstein, Howard², ¹ University of Virginia, Charlottesville, VA² University of Virginia, Charlottesville, VA

ABSTRACT- Patterns of carbon cycling during secondary succession have been developed theoretically, yet few data exist to test hypotheses on carbon dynamics from cultivation abandonment to secondary forest regrowth. We compared the characteristics of carbon dioxide fluxes as well as carbon pools in both soil and vegetation at different stages of succession at the Blandy Experimental Farm, located in the Shenandoah River Valley in north-central Virginia (39°09′N, 78°06′W). The mean annual temperature is 11.8 °C and the annual precipitation is 940 mm. Four sites were used to represent three different stages of succession. Among the four sites, two are at mid-successional stages (14 and 18-years old), and the other two represent early (4-years old) and late succession (80+ years old). To determine the shifts in carbon cycling during succession, we measured soil respiration, net ecosystem production, soil carbon content, aboveground biomass, and vegetation NDVI and LAI. The aboveground vegetation composition at different distances from the forest edge was investigated in summer 2004, the soil seed bank composition was also investigated twice a year by greenhouse germination. Preliminary results showed that soil respiration significantly increased with temperature, but there was no distinct relationship between soil respiration and soil moisture. The early successional stage had greater average soil respiration than the mid-successional stage, while the late successional site (secondary forest) had similar soil respiration to the early successional site despite relatively low soil temperatures in the forest. The mid-successional sites had significantly greater biomass than the early successional site. Significantly more species were found to germinate in soils from the early successional site, and in soils closer to the surface, compared to other sites and deeper soils. The seed bank composition and diversity differed substantially from that of the extant plant community.

Key words: carbon cycling, succession, eddy-covariance, soil seed bank