Biomass wetlands

Biomass can provide substitutes for fossil fuels as well as electricity and heat. Its resource base is varied. Arid land, wetlands, forest, and agricultural lands can provide a variety of plants and organic matter for biomass feedstock. 

Methane is produced by bacteria under anaerobic conditions in wet environments such as wetlands, swamps and rice fields. It is also produced in the stomachs of cattle and by termites. Typical anthropogenic sources are from fossil fuels such as coal mining and as a byproduct in the burning of biomass. The latter sources are considerably heavier in C than the former. Recently, Keppler et al. (2006) demonstrated that methane is formed in terrestrial plants under oxic conditions by an unknown mechanism. The size of this methane source is stiU unknown but it might play an important role for the methane cycle. 

Dichloromethane is a widely used industrial and academic laboratory solvent. New natural sources are recognized subsequent to the previous review, although the amounts are small compared to industrial emissions (Table 3.2). These include estimates of biomass combustion (256, 283, 286), oceanic sources (250, 253, 256, 275, 302), wetlands (275), and volcanoes (216, 217). Macroalgae (Desmarestia... 

Iodomethane has several terrestrial biogenic and abiotic sources (Table 3.6). It is emitted from volcanoes (216, 217), fungi (273), wetlands (275), peatlands (267), rice paddies (262-266, 374), and oat plants (374). Biomass combustion also accounts for some CH3I (284, 285, 288). The abiotic soil source cited earlier can also produce CH3I (175). 

Blake DR, Smith Jr. TW, Chen T-Y, Whipple WJ, Rowland FS (1994) Effects of Biomass Burning on Summertime Nonmethane Hydrocarbon Concentrations in the Canadian Wetlands. J Geophys Res 99 1699... 

Bano et al. (1998) Wetland Natural and artificial Bacterial biomass +104%—1-172%... 

Figure 6.1. Ecosystem area and soil carbon content to 3-m depth. Lower Panel Global areal extent of major ecosystems, transformed by land use in yellow, untransformed in purple. Data from Hassan et al. (2005) except for Mediterranean-climate ecosystems transformation impact is from Myers et al. (2000) and ocean surface area is from Hassan et al. (2005). Upper Panel Total C stores in plant biomass, soil, yedoma/permafrost. D, deserts G S(tr), tropical grasslands and savannas G(te), temperate grasslands ME, Mediterranean ecosystems F(tr), tropical forests F(te), temperate forests F(b), boreal forests T, tundra FW, freshwater lakes and wetlands C, croplands O, oceans. Data are from Sabine et al. (2004), except C content of yedoma permafrost and permafrost (hght blue columns, left and right, respectively Zimov et al., 2006), and ocean organic C content (dissolved plus particulate organic Denman et al., 2007). This figure considers soil C to 3-m depth (Jobbagy and Jackson, 2000). Approximate carbon content of the atmosphere is indicated by the dotted lines for last glacial maximum (LGM), pre-industrial (P-IND) and current (about 2000). Reprinted from Fischlin et al. (2007) in IPCC (2007). See color insert.

Three areas of uncertainty in this present inventory of natural sulfur emissions which need further work include natural variability in complicated wetland regions, differences in emission rates in the corrected SURE data and those reported by Lamb et al. (1) and Goldan et al. (21) for inland soil sites, and biomass emissions for which only a very limited data base easts. The current difficulty in determining the sources of variability emphasizes the need to better understand natural sulfur release mechanisms. At present, it may be useful to consider the emission rates based on the corrected SURE data as an upper bound to natural emissions and use the emission rates based on data described by Lamb et al. (1) as a more conservative estimate of natural sulfur emissions. However, this still leaves a factor of 22 difference between the suggested upper bound and our best current estimate. 

Fig. 1.1. Seasonal estimates of standing-dead litter of J. effusus (a) and litter-associated fungal biomass (b) at the Talladega Wetland Ecosystem, Alabama. Data from Wetzel and Howe (1999) and Kuehn and Suberkropp (1998a). Vertical lines indicate +1 SE (n = 6).

Value of total biomass for Pa was from Olson et al. (1983) for wetlands in the tropics, assuming mean carbon content of 0.45. 

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