Connecting methane fluxes to vegetation cover and water table fluctuations at microsite level: A modeling study

Abstract

[1] The paper presents a process-based model describing methane flux dynamics in different microsites of boreal peatlands. The simulated fluxes matched well to measurements in all microsites without any parameter adjustment. The model emphasizes the importance of microsite characteristics, water table and vegetation cover for methane fluxes. Water level determines the moisture and oxygen profile in peat matrix and therefore affects methane production and oxidation rates in peat profile. Vascular plants provide methanogenesis with substrates, form a pathway for methane to liberate from peat to the atmosphere and enhance methane oxidation by transporting oxygen to water saturated peat. The model connects methane fluxes to the seasonal photosynthetic cycle of plants at the microsite level and hence dynamically combines the microbial processes in peat to changing environmental factors in the level of peatland ecosystem. Sensitivity analysis of the model reveals the importance of substrate supply to methane fluxes. In addition, the capability of the vascular plants to transport oxygen downwards has a large effect on model outcome. Lack of oxygen and methane keep methane oxidation at a low level in the model simulations, and changes that compensate for these lacks have a remarkable decreasing effect on simulated flux. Dry periods decrease the simulated methane flux considerably, especially if the drought prevails long, threshold for a dramatic decrease lying between 4 and 6 weeks of drought. Increase in air temperature enhances methane flux, especially if the effect of increased temperature on gross primary production is taken into account.

Reviews and syntheses: Four decades of modeling methane cycling in terrestrial ecosystems

“…For example, three pathways of CH 4 transports were represented in Kettunen (2003) and Walter et al (1996), but none of those modeled results have been evaluated against observational results for those individual processes. One reason is that measurements rarely distinguish between individual processes; another reason is that the majority of CH 4 models do not explicitly represent all processes (Table 2).…”

“…The fourth model algorithm considers the primary substrates for methanogenesis, that is, acetate and single-carbon compounds (Eq. 4); examples are Kettunen's model (Kettunen, 2003), Segers' model (Segers and Kengen, 1998;Segers and Leffelaar, 2001a, b;Segers et al, 2001), van Bodegom's model (van Bodegom et al, 2000(van Bodegom et al, , 2001, and the ecosys model (Grant, 1998). Methanogenesis is a fundamental process for CH 4 cycling, and the majority of models simulate methanogenesis in either implicit or explicit ways (Tables 2 and 3 (Table 3).…”

Spatial and temporal patterns of CH<sub>4</sub> and N<sub>2</sub>O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model

“…where F P is the CH 4 transport via vascular plant (g C m −2 d −1 ); V plant, trans is the transport coefficient of CH 4 transportation through plant (m d −1 ), which is set as 0.68 (Kettunen, 2003); [CH 4 ] max is the maximum CH 4 concentration in soil solution (g C m −3 ); GPP is the gross primary productivity of current day (g C m −2 d −1 ); GPP max is the maximum daily GPP (g C m −2 d −1 ), which is set as 5 in this study; β is the Bunsen solubility coefficient (0.035 ml ml −1 ) (Yamamoto et al, 1976). Since there is no report on the plantmediated transport of CH 4 by woody plant, the DLEM assumes that the plant-mediated transport only occurs in herbaceous biomes; F P is set to zero for all woody ecosystems.…”

Methane Fluxes from Alpine Wetlands of Zoige Plateau in Relation to Water Regime and Vegetation under Two Scales

“…There are many references based on vegetation types to estimate methane flux in different ecosystems all over the world (Rinnan et al 2003;Nilsson et al 2001;Kettunen 2003;Hirota et al 2004;Crozier and DeLaune 1996;Bubier 1995;Bergstrom et al 2007). Some studies also attempted to estimate methane flux based on soil types (Sommer and Fiedler 2002).…”