Characteristics and functions of labile organic carbon in coastal wetland soils of the mississippi river deltaic plain
Document Type
Article
Publication Date
10-28-2015
Abstract
The Mississippi River deltaic plain (MRDP) coastal wetlands are one of the largest in the United States. Adequate characterization of labile organic C (LOC) is essential for understanding the C transformation and overall biogeochemistry in these wetland soils. Among different MRDP wetlands, freshwater and brackish marsh soils contain higher LOC than saline marsh and forest swamp soils. Labile organic C estimated by aerobic incubation and salt and cold water extractions is generally less than 0.5% of soil organic C (SOC), whereas hot water extraction and especially acid hydrolysis yield 1.2 to 3.49% and 12.8 to 43% of SOC, respectively. Carboxyl C was the primary component of LOC by cold water and salt extractions, whereas both carboxyl C and O/N-alkyl C were released by aerobic mineralization. On the other hand, LOC by hot water extraction contains mainly carbonyl C, whereas acid hydrolysis includes the contribution of alkyl C besides O/N-alkyl C. In addition, higher LOC in freshwater marsh soils than in saline and forest swamp soils facilitates higher denitrification potential of the former, which is negatively correlated with the presence of phenolic aldehydes and ketones in these wetland soils. The addition of clay sediments reduce LOC degradation as is evident by lowered CO2 emissions. Monovalent K+ holds more DOC in forest swamp soils, whereas divalent Ca2+ retains more DOC in marsh soils. Selective degradation of syringyl lignin structure over guaiacyl occurs in both dissolved organic matter (DOM) and bulk soil organic matter (SOM) in the MRDP wetlands, which could enhance overall SOC lability and potentially contribute to the northern Gulf of Mexico hypoxia if exported offshore.
Publication Source (Journal or Book title)
Labile Organic Matter: Chemical Compositions, Function, and Significance in Soil and the Environment
First Page
315
Last Page
336
Recommended Citation
Wang, J., Dodla, S., & DeLaune, R. (2015). Characteristics and functions of labile organic carbon in coastal wetland soils of the mississippi river deltaic plain. Labile Organic Matter: Chemical Compositions, Function, and Significance in Soil and the Environment, 315-336. https://doi.org/10.2136/sssaspecpub62.2014.0046