Temporal and spatial patterns of soil CO2 efflux, soil carbon, and root biomass associated with bedding in young loblolly pine plantations

We measured soil CO2 efflux (Fs) in four loblolly pine plantations in the coastal plain of South Carolina in an effort to understand how site preparation, drainage, and microclimate affect Fs, root biomass, and soil carbon pools during early stand development. All plantations were site prepared: sheared, raked, and bedded. Soil CO2 efflux, temperature (Ts), moisture (θ), root biomass (Rb), coarse (COF) and fine (FOF) organic fragments, and mineral soil carbon (Cs) were measured quarterly during the first two years of stand growth. Mean daily Fs were similar between sites and ranged from 0.5 to 12 mmol m-2 s-1 during the winter and summer, respectively. Soil CO2 efflux, COF, FOF, and Cs were significantly greater in the beds than inter-rows on wet sites, but not on the dry site. Soil temperature accounted for 26-55 percent of the variation in Fs across all sites. Soil θ and Cs explained a significant, but small amount (6-22 percent) of variance in Fs. Annual soil carbon efflux ranged from 12 to19 Mg C ha-1 yr-1. We conclude that bedding during site preparation can have significant effects on the spatial variation in Fs and associated drivers, with some site-specific caveats.