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Abstract
Changes in the heterotrophic (Rh) proportion of total soil respiration (Rs) due to silvicultural treatments and seasonal variation across an annual cycle were measured in six loblolly pine (Pinus taeda) plantations in the Piedmont and Coastal Plain of Georgia and Alabama. Silvicultural treatments included fertilizer and herbicide application, and measurements were taken every three months to assess seasonality. Soil respiration was measured with (Rh) and without (Rs) root exclusion collars. Soil characteristics were used to predict the Rh proportion, and to parameterize the DAYCENT biogeochemical model. No significant differences in the Rh proportion were detected between treatments, while fall values were significantly higher than other seasons. Rs and Rh were well predicted (R2 of ~60 and 70%) using moisture, temperature, and soil attributes but Rh proportion was not. DAYCENT reproduced seasonal patterns of Rs but did not reproduce patterns of the Rh proportion.