PARENT SESSION
Poster Session #35: Decomposition and Soil Respiration.
Thursday, August 9, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Soil CO₂ efflux, soil organic matter and root development in newly planted loblolly pine plantations.

Maier, Chris¹, Dougherty, Phillip², Anderson, Pete¹, ^{1 2}

ABSTRACT- We measured soil CO₂ efflux, soil carbon and root biomass in newly planted loblolly pine plantations in an effort to understand how site preparation, soil physical characteristics, microclimate and root development influenced soil carbon fluxes. Measurements were made in the coastal plain of South Carolina on five soil types that differed in drainage class and clay content. All sites were bedded creating three distinct micro-sites: beds, inter-beds and troughs. In each of these micro-sites, soil CO₂ efflux (S_f), soil temperature, soil moisture (), root biomass (R_b), coarse (COM) and fine (FOM) organic matter and mineral soil carbon (C_ms) and nitrogen (N_ms) were measured quarterly for two years. There were significant site differences in COM, FOM, C_ms and N_ms. Mean S_f for all sites ranged from 0.5 to 2.0 mol m^-2 s^-1 during the winter to 6 to 10 mol m^-2 s^-1 during the summer. Soil temperature accounted for 62% of the variation in S_f across all sites; however, significant site differences existed in basal S_f (corrected to 20 ^oC) and Q₁₀ (1.9 to 3.1). Basal S_f was negatively correlated to (r² = 0.30 to 0.70). Within sites, COM, FOM, R_b, C, N and S_f were greater in the beds than in inter-beds or troughs. R_b was the single best variable explaining micro-site variation in S_f (r²=0.20 to 0.40). These results suggest that site-specific factors control soil CO₂ efflux.

KEY WORDS: soil CO₂ efflux, soil respiration, soil carbon, loblolly pine