Wetland Carbon and Environmental Management. Группа авторов

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Wetland Carbon and Environmental Management - Группа авторов


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3.1). At Time 1, Wetlands 1 and 2 had a positive radiative balance over a 100‐year period, indicating that the warming due to CH4 emissions was greater than the cooling due to long‐term carbon preservation in each wetland. For Wetland 1, the radiative balance was exactly the same in the two time periods because carbon sequestration and CH4 emission rates did not change. Thus, the radiative forcing of Wetland 1 was zero (Table 3.1) and its contribution to Earth’s energy budget had not changed over time. In contrast, the radiative balance in Wetland 2 was lower in Time 2 than in Time 1 due to a management action. This means that radiative forcing was negative, such that the perturbation (that is, the management action) applied to Wetland 2 had offset some of the climatic warming from fossil fuel combustion and land use changes. In this example, Times 1 and 2 correspond to any pair of years. In the context of the attribution of current climate change, the Intergovernmental Panel on Climate Change (IPCC) reports radiative forcing relative to the year 1750 (i.e., the pre‐Industrial era; Myhre et al., 2013). Determining what the radiative balance of a wetland was more than 250 years ago presents considerable challenges.

      Finally, please note that the GWP and SGWP are properties of greenhouse gases, not of an ecosystem. We sometimes see them incorrectly used as a synonym for radiative balance, as in the “global warming potential (GWP) was calculated in CO2 equivalents” or “we observed a significant difference in GWP between aerobic and anaerobic treatments.” We do not wish to single out specific authors, so we have purposely not provided citations for these quotes. Instead, our goal is to illustrate how these terms have been misused in the scientific community.

      Wetlands are global hotspots for the preservation of organic carbon in terms of the total amount of preserved carbon (Sabine et al., 2004), the annual rate of carbon preservation (Mcleod et al., 2011), and the efficiency of carbon preservation (e.g., >5% of ecosystem net primary production stored in peatlands vs. <<1% in ocean sediments; Frolking et al., 2010; Hedges & Keil, 1995). From a climate perspective, organic carbon preserved in a wetland represents CO2 that was fixed by primary producers in the wetland (or elsewhere) and therefore is no longer in the atmosphere acting as a greenhouse gas. The long‐term preservation of organic carbon in wetland soils is the major reason why wetlands can have beneficial climatic effects (Frolking & Roulet, 2007). Below, we discuss factors that contribute to carbon preservation in wetland soils.

      3.3.1. Carbon Inputs

Schematic illustration of wetland carbon inflows, outflows, and preservation.

       Autochthonous Production

       Allochthonous Inputs

      Wetlands can be sinks for a variety of allochthonous materials including sediment‐associated carbon (discussed in this section), organic detritus, and atmospheric inputs of dust, ash, and pollen. Organic detritus can take the form of plant material (e.g., leaves, wood) from terrestrial systems (Fetherston et al., 1995; Holgerson et al., 2016) as well as phytoplankton, macroalgae, and seagrass detritus from aquatic environments (Hanley et al.,


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