Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland

Journal of Geophysical Research: Biogeosciences
By: , and 

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Abstract

Understanding the controls on floodplain carbon (C) cycling is important for assessing greenhouse gas emissions and the potential for C sequestration in river-floodplain ecosystems. We hypothesized that greater hydrologic connectivity would increase C inputs to floodplains that would not only stimulate soil C gas emissions but also sequester more C in soils. In an urban Piedmont river (151 km2 watershed) with a floodplain that is dry most of the year, we quantified soil CO2, CH4, and N2O net emissions along gradients of floodplain hydrologic connectivity, identified controls on soil aerobic and anaerobic respiration, and developed a floodplain soil C budget. Sites were chosen along a longitudinal river gradient and across lateral floodplain geomorphic units (levee, backswamp, and toe slope). CO2 emissions decreased downstream in backswamps and toe slopes and were high on the levees. CH4 and N2O fluxes were near zero; however, CH4emissions were highest in the backswamp. Annual CO2 emissions correlated negatively with soil water-filled pore space and positively with variables related to drier, coarser soil. Conversely, annual CH4 emissions had the opposite pattern of CO2. Spatial variation in aerobic and anaerobic respiration was thus controlled by oxygen availability but was not related to C inputs from sedimentation or vegetation. The annual mean soil CO2 emission rate was 1091 g C m−2 yr−1, the net sedimentation rate was 111 g C m−2 yr−1, and the vegetation production rate was 240 g C m−2 yr−1, with a soil C balance (loss) of −338 g C m−2 yr−1. This floodplain is losing C likely due to long-term drying from watershed urbanization.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland
Series title Journal of Geophysical Research: Biogeosciences
DOI 10.1002/2014JG002817
Volume 120
Issue 1
Year Published 2015
Language English
Publisher Wiley
Contributing office(s) National Research Program - Eastern Branch
Description 19 p.
First page 77
Last page 95
Country United States
State Virginia
Other Geospatial Difficult Run, Potomac River
Online Only (Y/N) N
Additional Online Files (Y/N) N