Biogeochemical controls on methane, nitrous oxide, and carbon dioxide fluxes from deciduous forest soils in eastern Canada

Abstract

[1] The exchange of the important trace gases, methane (CH 4 ), nitrous oxide (N 2 O), and carbon dioxide (CO 2 ), between forested soils and the atmosphere can show great temporal and spatial variability. We measured the flux of these three gases over 2 years along catenas at two forested sites, to determine the important controls. Well-drained soils consumed atmospheric CH 4 , while poorly drained swamp soils embedded in depressions were a source. CH 4 fluxes could be predicted primarily by temperature and moisture, and tree cover exerted an influence mainly through the creation of large soil porosity, leading to increased consumption rates. In contrast, there were very poor relationships between N 2 O fluxes and environmental variables, reflecting the complex interactions of microbial, edaphic, and N cycling processes, such as nitrification in well-drained soils and denitrification in poorly drained soils, which led to N 2 O production (or consumption) in soils and hence larger variability. At the broad temporal and spatial scale, soil C:N ratio was a good predictor of N 2 O emission rates, through its influence upon N cycling processes. Soil CO 2 emission rates showed less spatial and temporal variability, and were controlled by temperature and moisture. The source strength, in global warming potential of CH 4 and N 2 O fluxes in CO 2 equivalents, was reduced markedly when trace gas fluxes from 5 to 15% poorly drained soils were included in the net global warming potential calculation of whole forested watersheds. Soils drainage class integrates many of the biogeochemical processes controlling the flux of these gases providing a framework for extrapolating results.

Carbon and greenhouse gas balances in an age sequence of temperate pine plantations

“…In our study, we did not find any agerelated differences for organic matter turnover when comparing litterfall and decomposition rates among the three older sites. Decomposition rates were within the range of those previously reported for other Canadian coniferous forests (Moore et al, 1999;Trofymow et al, 2002) and appeared to be unaffected by either stand age or site quality. In contrast, age-related differences in the litterfall rates were apparent when comparing the 35-and 70-year-old stands, with the latter one having higher rates (but similar SI values).…”

“…Using a process-based model, Inatomi et al (2010) similarly found that the GHG balance was mainly driven by the CO 2 exchange in a 50-year-old cool-temperate deciduous forest. However, the contribution of non-CO 2 GHG could be substantial in poorly drained locations within temperate forests (Ullah and Moore, 2011). The relative contribution of CH 4 and N 2 O to the forest GHG balance might further be considerably affected by more frequent freeze-thaw events (Luo et al, 2012;Teepe et al, 2001), altered N input (Liu and Greaver, 2009) as well as by contrasting forest management and tree growth responses to climatic changes in the future (Metsaranta et al, 2011;Ximenes et al, 2012).…”

“…Tree root development, litterfall, canopy shading and cessation of N-fertilizer application, for instance, may trigger changes in physical, biogeochemical and hydrological properties of the soil, which may affect the net exchange of CH 4 and N 2 O (Ball et al, 2007;Christiansen and Gundersen, 2011;Christiansen et al, 2012;Gundersen et al, 2012;Peichl et al, 2010b;Priemé et al, 1997;Smith et al, 2003;Ullah and Moore, 2011), as well as the cycling of dissolved organic carbon (DOC) (Camino-Serrano et al, 2014;Gielen et al, 2011;Rosenqvist et al, 2010). Such alterations might modify the net ecosystem production (NEP) and the GHG balance (Luyssaert et al, 2010Schulze et al, 2009Schulze et al, , 2010.…”

Landscape analysis of soil methane flux across complex terrain

“…Although many studies have quantified the magnitude and variability of CH 4 fluxes, they often covered large spatial extents (from transects that are tens of meters to hundreds of kilometers long) which captured significant environmental gradients at those scales, but sampling locations were generally sparse (Del Grosso et al, 2000;Yu et al, 2008;Teh et al, 2014;Tian et al, 2014). The smaller-scale patterns of CH 4 fluxes within these landscapes has not been investigated as thoroughly as ecosystem scale gradients, which could be problematic if those patterns are important for estimating CH 4 fluxes Ullah and Moore, 2011;Nicolini et al, 2013).…”

“…A spatially explicit understanding of heterogeneity in CH 4 fluxes is necessary for appropriate watershed scale budgets (Ullah and Moore, 2011;Bernhardt et al, 2017), particularly in mountainous regions, where the spatial distribution of resources could have a significant influence on the direction and magnitude of CH 4 fluxes due to the lateral redistribution of water and substrates caused by convergent and divergent areas of the landscape (Davidson and Swank, 1986;Meixner and Eugster, 1999;Wachinger et al, 2000;von Fischer and Hedin, 2002). Although many studies have quantified the magnitude and variability of CH 4 fluxes, they often covered large spatial extents (from transects that are tens of meters to hundreds of kilometers long) which captured significant environmental gradients at those scales, but sampling locations were generally sparse (Del Grosso et al, 2000;Yu et al, 2008;Teh et al, 2014;Tian et al, 2014).…”