BURIED SOILS AS AN IMPORTANT CONTROL ON C STORAGE ALONG HUMAN-IMPACTED LANDSCAPES IN KENTUCKY, USA

One aim of floodplain restoration is to improve human-impacted wetlands, which affects carbon storage. However, few studies have assessed the long-term (>10 y) benefits of such restoration work. This study examines soil organic carbon (SOC) with depth in alluvial profiles that vary by restoration age as well as hillslope and upland profiles in western KY, USA. Five sites were examined. Three of the sites are floodplain soil profiles located in a (1) recently-restored (<1 year), (2) post-restored (>10 years), and (3) unrestored (0 years) setting. Two additional soil profiles along a foot slope and upland summit were examined that experienced reforestation following late nineteenth and early twentieth century deforestation and farming. The SOC was estimated from soil organic matter (SOM) measurements using loss-on-ignition (LOI) on oven-dried soil samples. Bulk density was also measured to calculate SOC stocks, reported here in kg C m^-2. The recently-restored site contains the highest SOC stock (22.39 kg C m^-2) and is situated on a clay-rich wetland adjacent to a former backchannel slough. The post-restored and unrestored sites have low SOC stock in the surface soil (3.35 and 5.58 kg C m^-2, respectively), yet higher SOC stocks at depth in buried soils (11.97 and 8.12 kg C m^-2, respectively). A similar pattern was noted at the footslope site, where the SOC stock in the surface soil (9.07 kg C m^-2) was lower than that of the buried soil (12.82 kg C m^-2). An average SOC stock was calculated for each buried and surface soil and a grand mean was then calculated for each group (buried soils, n=3; surface soils, n=5). The average SOC stock for buried soils (10.64±3.94 kg C m^-2) is similar to that of surface soils (10.97±2.35 kg C m^-2). The similarity between SOC stocks suggest that the presence of buried soils is an important control on carbon storage along human-impacted and restored floodplains and footslopes in western KY. The occurrence and extent of buried soils should be considered in restoration and carbon storage studies. Future research will include taking more samples at different locations to verify the similarity between SOC stocks of buried and surface alluvial soils and comparing different C analysis methods to account for structural water using the LOI method._­