Localization of denitrification activity in macropores of a riparian wetland

• Published in: Soil biology & biochemistry Vol. 36; no. 4; pp. 563 - 569
• Main Authors: Casey, Ryan E., Taylor, M.D., Klaine, Stephen J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-04-2004; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; bulk density; Chemical, physicochemical, biochemical and biological properties; Denitrification; Freshwater; Fundamental and applied biological sciences. Psychology; Macropore; macropores; Nitrate; nitrates; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Pipe flow; Riparian; riparian areas; soil organic matter; soil sampling; Soil science; soil water content; soil water movement; Wetland; wetlands; South Carolina; Denitrification; Nitrate; Pipe flow; Riparian; Wetland; Macropore; Nitrates; Soil science; Macroporosity
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2003.11.003

Soil structure heterogeneity in the form of macropores and preferential flow channels can complicate efforts to quantify the physical and biological characteristics of wetland systems. We collected soil cores from two riparian wetlands to determine whether soil associated with macropores had elevated denitrification potentials compared to bulk soil from the same core. Cores were inspected for obvious macropores, which were distinguished as visible holes in the core, sometimes with decaying root matter, or as highly unconsolidated layers that appeared to have a substantially lower bulk density than the surrounding soil. Denitrification potentials were significantly higher in pores (
P<0.05) for six of the 16 cores that were obtained from the Cheraw State Park site. In cores obtained from a second site, denitrification potentials were significantly higher in pores for six of 20 cores and the trend of higher denitrification in pores was present in the majority of cores that had measurable activity. In cores with significant differences, denitrification was often 1–2 orders of magnitude greater in soil surrounding the macropore than in the bulk soil. Denitrification potentials of the bulk soils were similar in magnitude to the potentials measured in composited cores from previous studies. It is possible that the difference between macropore and bulk denitrification rates developed due to preferential flow of nitrate-rich water through the macropores. Previous work showed that water entering these riparian systems in groundwater and storm runoff had elevated levels of NO
3
−.