Comparing carbon sequestration in temperate freshwater wetland communities

Abstract

High productivity and waterlogged conditions make many freshwater wetlands significant carbon sinks. Most wetland carbon studies focus on boreal peatlands, however, with less attention paid to other climates and to the effects of hydrogeomorphic settings and the importance of wetland vegetation communities on carbon sequestration. This study compares six temperate wetland communities in Ohio that belong to two distinct hydrogeomorphic types: an isolated depressional wetland site connected to the groundwater table, and a riverine flow-through wetland site that receives water from an agricultural watershed. Three cores were extracted in each community and analyzed for total carbon content to determine the soil carbon pool. Sequestration rates were determined by radiometric dating with 137 Cs and 210 Pb on a set of composite cores extracted in each of the six communities. Cores were also extracted in uplands adjacent to the wetlands at each site. Wetland communities had accretion rates ranging from 3.0 to 6.2 mm yr À1 . The depressional wetland sites had higher (P < 0.001) organic content (146 ± 4.2 gC kg À1 ) and lower (P < 0.001) bulk density (0.55 ± 0.01 Mg m À3 ) than the riverine ones (50.1 ± 6.9 gC kg À1 and 0.74 ± 0.06 Mg m À3 ). The soil carbon was 98-99% organic in the isolated depressional wetland communities and 85-98% organic in the riverine ones. The depressional wetland communities sequestered 317 ± 93 gC m À2 yr À1 , more (P < 0.01) than the riverine communities that sequestered 140 ± 16 gC m À2 yr À1 . The highest sequestration rate was found in the Quercus palustris forested wetland community (473 gC m À2 yr À1 ), while the wetland community dominated by water lotus (Nelumbo lutea) was the most efficient of the riverine communities, sequestering 160 gC m À2 yr À1 . These differences in sequestration suggest the importance of addressing wetland types and communities in more detail when assessing the role of wetlands as carbon sequestering systems in global carbon budgets.

Carbon Sequestration and Sedimentation in Mangrove Swamps Influenced by Hydrogeomorphic Conditions and Urbanization in Southwest Florida

“…Total carbon (TC, %) was analyzed by combustion at 900˝C. Samples for the determination of inorganic carbon (IC, %) were pre-treated with 10 mol¨L´1 H 3 PO 4 , then combusted at 200˝C, using standard procedures for wetland soils [42][43][44][45]. Total organic carbon (TOC) within each depth segment was calculated as the difference between TC and IC concentrations.…”

Sedimentation in created freshwater riverine wetlands: 15 years of succession and contrast of methods

“…Sedimentation has been measured with several methodologies, including: rare-earth stable tracer horizons like Cs-137 and Pb-210 (Craft and Richardson, 1993;Bernal and Mitsch, 2012), horizon markers (Knaus and Van Gent, 1989;Harter and Mitsch, 2003;Hupp et al, 2008), sediment traps and bottles (Mitsch et al, 1979a;Brueske and Barrett, 1994;Fennessy et al, 1994;Braskerud et al, 2000;Braskerud, 2001;Nahlik and Mitsch, 2008), dendrogeomorphic techniques (Hupp and Morris, 1990;Hupp et al, 1993), and sedimentation plates (Mitsch et al, 1979b;Braskerud et al, 2000;Braskerud, 2001). Variable methodologies have led to inconsistent and poorly comparable sedimentation rates.…”

Effects of land use on greenhouse gas fluxes and soil properties of wetland catchments in the Prairie Pothole Region of North America

“…Research also has shown that that estimating carbon sequestration rates for wetland catchments can be difficult, and published rates are highly variable and associated with a great deal of uncertainty (Euliss et al, 2006;Gleason et al, 2008;Kayranli et al, 2010;Badiou et al, 2011;Bernal and Mitsch, 2012;Mitsch et al, 2013). Gleason et al (2008) suggested that in addition to factors such as land-use history, restoration methods, soils, and time, carbon sequestration rates of restored PPR wetlands could be affected by climate.…”