Hydrogeomorphology influences soil nitrogen and phosphorus mineralization in floodplain wetlands

By: , and 



Conceptual models of river–floodplain systems and biogeochemical theory predict that floodplain soil nitrogen (N) and phosphorus (P) mineralization should increase with hydrologic connectivity to the river and thus increase with distance downstream (longitudinal dimension) and in lower geomorphic units within the floodplain (lateral dimension). We measured rates of in situ soil net ammonification, nitrification, N, and P mineralization using monthly incubations of modified resin cores for a year in the forested floodplain wetlands of Difficult Run, a fifth order urban Piedmont river in Virginia, USA. Mineralization rates were then related to potentially controlling ecosystem attributes associated with hydrologic connectivity, soil characteristics, and vegetative inputs. Ammonification and P mineralization were greatest in the wet backswamps, nitrification was greatest in the dry levees, and net N mineralization was greatest in the intermediately wet toe-slopes. Nitrification also was greater in the headwater sites than downstream sites, whereas ammonification was greater in downstream sites. Annual net N mineralization increased with spatial gradients of greater ammonium loading to the soil surface associated with flooding, soil organic and nutrient content, and herbaceous nutrient inputs. Annual net P mineralization was associated negatively with soil pH and coarser soil texture, and positively with ammonium and phosphate loading to the soil surface associated with flooding. Within an intensively sampled low elevation flowpath at one site, sediment deposition during individual incubations stimulated mineralization of N and P. However, the amount of N and P mineralized in soil was substantially less than the amount deposited with sedimentation. In summary, greater inputs of nutrients and water and storage of soil nutrients along gradients of river–floodplain hydrologic connectivity increased floodplain soil nutrient mineralization rates.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Hydrogeomorphology influences soil nitrogen and phosphorus mineralization in floodplain wetlands
Series title Ecosystems
DOI 10.1007/s10021-012-9597-0
Volume 16
Issue 1
Year Published 2013
Language English
Publisher Springer
Publisher location Amsterdam, Netherlands
Contributing office(s) Branch of Regional Research-Eastern Region
Description 20 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecosystems
First page 75
Last page 94
Country United States
State Maryl;Virginia
Google Analytic Metrics Metrics page
Additional publication details