PARENT SESSION
Oral Session 96: Forest Ecology V: Soils and Nutrient Cycling.
Presiding: G Newman and S Bigelow
Thursday, August 5, 8:00 AM to 11:30 AM, Meeting Room B 114.

Soil respiration, microbial biomass and fine root production in forests of varying soil texture.

Dilustro, John^*,1, Collins, Beverly¹, Duncan, Lisa¹, Crawford, Chris¹, ¹ Savannah River Ecology Laboratory, Aiken, SC, 29802

ABSTRACT- Soil respiration represents a major flux of carbon from forest ecosystems. The combination of soil variability along the southeastern US costal plain/ piedmont fall line and loss of surface sand from eroded piedmont soils results in soil heterogeneity over small scales. We sampled mixed pine forest stands on soils of varying textures at Ft. Benning, Georgia to determine the influence of soil heterogeneity on soil CO₂ flux. These forests are managed via prescribed burning on three-year rotations and were burned in 2000 prior to the study. Soil CO₂ flux was measured quarterly using an infrared gas analyzer with permanently installed soil rings. Initial measurements in two sites in September 2001, revealed soil respiration and temperature were greater in a sandy (7% clay) stand (5.81 mol/m²/s and 25.4 ^oC) than in a clayey (26% clay) stand (4.66 mol/m²/s and 24.8 ^oC). Measurements were begun in additional sites in 2003 to further investigate soil CO₂ flux, including the contribution of surface roots and microbial biomass over a range of soil textures. Root production measured via root ingrowth in 2002 and 2003 over a 9-month sampling interval was greater in sandy stands (n=4) (279.4 g/m²) than clayey stands (n=4)(199.7g/m²), but 2003 soil microbial biomass carbon was lower on the sandy stands (n=4) (132.4 g/g) than clayey stands (n=4) (249.6 g/g). Understanding the physical and biological factors that control soil carbon efflux can contribute to improved estimates of carbon loss from southeastern mixed pine forests.

Key words: fine root production, soil texture, soil respiration, microbial biomass