TRACE GAS EXCHANGES IN MIDWEST CROPPING SYSTEMS
Location: Soil, Water, and Air Resources Research Unit
Title: Carbon sources and dynamics in afforested and cultivated US corn belt soils
Submitted to: World Congress of Soil Science
Publication Type: Proceedings
Publication Acceptance Date: August 6, 2010
Publication Date: August 6, 2010
Citation: Hernandez Ramirez, G., Sauer, T.J., Cambardella, C.A., Brandle, J.R., James, D.E. 2010. Carbon sources and dynamics in afforested and cultivated US corn belt soils. In: Gilkes, R.J. and Prakongkep, N., editors. Proceedings of the 19th World Congress of Soil Science, Aug. 6-10, 2010, Brisbane, Australia. DVD.
Afforestation in degraded cropland can sequester atmospheric carbon (C), but soil organic C (SOC) sources in such ecosystems are not well-characterized. This study assessed SOC dynamics and sources in two 35-yr-old, coniferous afforestation sites (i.e., a forest plantation and a shelterbelt situated at Sac, Iowa and Mead, Nebraska, respectively) and the adjacent agricultural fields. Composite soil samples were randomly collected at Sac and in a sampling grid at Mead to determine C and nitrogen (N) contents, and stable carbon isotope ratios (d13C, natural abundance). In these fine-textured soils, afforestation of croplands carried out through either shelterbelt or forest plantation caused substantial increases of SOC accrual (>57%; P’s <0.05) at surface layers relative to conventionally-tilled cropping systems. Soils exhibited a pronounced gradient of d13C signatures from near constant values in cropped fields (-17 ± 0.1‰) to much depleted in afforested soils (-22 ± 0.4‰) capturing a gradual shift in C sources. Sources-partitioning assessments revealed that tree-derived C contributed with roughly half of the SOC found directly beneath trees indicating that the additional SOC accrued in these afforested sites can be fully explained by tree-derived inputs.