The atmospheric concentration of CO2 (abbreviated [CO2]a) has increased from 280 ppm to 360 ppm during the past 200 years and will double during the next century. Increases in forest productivity (and hence C-storage in tree biomass) are anticipated with the increase in [CO2]a. The increase in forest productivity will likely be limited by the availability of soil nitrogen (N) and phosphorus (P). We will examine the relationships between forest productivity and nutrient cycling in response to CO2 fertilization by working in a closed-canopy forest growing under Free-Air CO2 Enrichment (FACE) in the Duke Forest. To test whether nutrients will limit the growth of forests under elevated [CO2]a we will measure: (1) N & P fluxes in soils (microbial dynamics, N & P availability); (2) N & P uptake by trees; and (3) the major controls over the flux of N & P from vegetation to soils.
