Carbon Sources and Dynamics in Afforested and Cultivated Corn Belt Soils
- Guillermo Hernandez-Ramirez *a,
- Thomas J. Sauerb,
- Cynthia A. Cambardellab,
- James R. Brandlec and
- David E. Jamesb
- a New Zealand Institute for Plant and Food Research, Canterbury Agriculture and Science Centre, Private Bag 4704, Christchurch, New Zealand
b USDA-ARS, National Lab. for Agriculture and the Environment, Ames, IA 50011-3120
c School of Natural Resources, Univ. of Nebraska-Lincoln, Lincoln, NE 68583-0974
Afforestation of degraded cropland can sequester atmospheric C; however, source partitioning and turnover of soil organic C (SOC) in such ecosystems are not well documented. This study assessed SOC dynamics in two 35-yr-old, coniferous afforestation sites (i.e., a forest plantation situated in northwestern Iowa on a silty clay loam soil and a shelterbelt situated in eastern Nebraska on a silt loam soil) and the adjacent agricultural fields. Soil samples were collected at both sites to determine SOC and total N concentrations and stable C isotope ratios (δ13C, natural abundance) in both whole soil and the fine particulate organic matter (POM) fraction (53–500 μm size). In these fine-textured soils, afforestation of cropland performed through either shelterbelt or forest plantation caused substantial increases in surface SOC storage compared with conventionally tilled cropping systems (≥57%; P < 0.05); this confirms the direct benefits of tree planting on SOC sequestration. Relative to cropped soils, afforested soils exhibited a more depleted δ13C signature (−17 vs. −22‰), indicating a shift in C sources. Source-partitioning assessment revealed that tree-derived C contributed roughly half of the SOC found directly beneath the trees. The C-enriched afforested surface soils exhibited SOC turnover rates of 0.018 to 0.022 yr−1 and mean residence times of 55 to 45 yr. Fine POM in afforested surface soils accounted for a large proportion (21%) of the existing SOC, 79% being derived from tree inputs. This supports the role of POM as a significant sink for recently sequestered SOC in these ecosystems.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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