Forest ecosystem changes from annual methane source to sink depending on late summer water balance

Shoemaker, Julie K.; Keenan, Trevor F.; Hollinger, David Y.; Richardson, Andrew D.

doi:10.1002/2013gl058691

Cited by 48 publications

(37 citation statements)

References 34 publications

(44 reference statements)

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“…Meanwhile, high-frequency field observational data are also needed, particularly long-term observational data in some less-studied ecosystems; for example, Arctic tundra ecosystems have been considered an important contributor to the global CH 4 budget in the changing climate (IPCC, 2013;Koven et al, 2011); however, a longterm data set of CH 4 flux is lacking. It is well known that inter-annual variation of climate may turn an ecosystem from a CH 4 sink to a CH 4 source (Nauta et al, 2015;Shoemaker et al, 2014); therefore, a long-term observational data set that covers these temporal shifts in CH 4 flux and its associated ecosystem information would improve our understanding of the processes and our representation of them in CH 4 models. Second, microbial community shifts and their role in CH 4 processes are important, although information is incomplete for model representation of this mechanism (McCalley et al, 2014;Schimel and Gulledge, 1998).…”

Section: Data Needsmentioning

confidence: 99%

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

et al. 2016

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Abstract. Over the past 4 decades, a number of numerical models have been developed to quantify the magnitude, investigate the spatial and temporal variations, and understand the underlying mechanisms and environmental controls of methane (CH 4 ) fluxes within terrestrial ecosystems. These CH 4 models are also used for integrating multi-scale CH 4 data, such as laboratory-based incubation and molecular analysis, field observational experiments, remote sensing, and aircraft-based measurements across a variety of terrestrial ecosystems. Here we summarize 40 terrestrial CH 4 models to characterize their strengths and weaknesses and to suggest a roadmap for future model improvement and application. Our key findings are that (1) the focus of CH 4 models has shifted from theoretical to site-and regional-level applications over the past 4 decades, (2) large discrepancies exist among models in terms of representing CH 4 processes and their environmental controls, and (3) significant datamodel and model-model mismatches are partially attributed to different representations of landscape characterization and inundation dynamics. Three areas for future improvements and applications of terrestrial CH 4 models are that (1) CH 4 models should more explicitly represent the mechanisms underlying land-atmosphere CH 4 exchange, with an emphasis on improving and validating individual CH 4 processes over depth and horizontal space, (2) models should be developed that are capable of simulating CH 4 emissions across highly heterogeneous spatial and temporal scales, particularly hot moments and hotspots, and (3) efforts should be invested to develop model benchmarking frameworks that can easily be used for model improvement, evaluation, and integration with data from molecular to global scales. These improvements in CH 4 models would be beneficial for the Earth system models and further simulation of climate-carbon cycle feedbacks.

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Section: Data Needsmentioning

confidence: 99%

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

et al. 2016

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“…Measuring CH 4 exchange is more challenging than measuring CO 2 exchange due to low flux rates from spatially restricted areas within a forest and therefore relatively few MM studies exist to date (Nicolini 2013). CH 4 exchange between forest stands and the atmosphere has been measured by EC (Smeets et al, 2009;Shoemaker et al, 2014), relaxed EC (Sakabe et al, 2012;Ueyama et al, 2012), and by gradient methods (Simpson et al, 1997;Bowling et al, 2009;Querino et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Methane exchange in a boreal forest estimated by gradient method

Sundqvist

Mölder

Crill

et al. 2015

Tellus B: Chemical and Physical Meteorology

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A B S T R A C T Forests are generally considered to be net sinks of atmospheric methane (CH 4 ) because of oxidation by methanotrophic bacteria in well-aerated forests soils. However, emissions from wet forest soils, and sometimes canopy fluxes, are often neglected when quantifying the CH 4 budget of a forest. We used a modified Bowen ratio method and combined eddy covariance and gradient methods to estimate net CH 4 exchange at a boreal forest site in central Sweden. Results indicate that the site is a net source of CH 4 . This is in contrast to soil, branch and leaf chamber measurements of uptake of CH 4 . Wetter soils within the footprint of the canopy are thought to be responsible for the discrepancy. We found no evidence for canopy emissions per se. However, the diel pattern of the CH 4 exchange with minimum emissions at daytime correlated well with gross primary production, which supports an uptake in the canopy. More distant source areas could also contribute to the diel pattern; their contribution might be greater at night during stable boundary layer conditions.

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“…Because diffusive gas transport through soils is reduced with increasing SWC, hydrologic variations can strongly affect soil O 2 levels, which in turn influence the relative rates of (anaerobic) methanogenesis and (aerobic) methanotrophy. Although saturated soils (e.g., wetlands) are major terrestrial sources of CH 4 emissions (6), emission may at times occur from unsaturated soils, depending on the finescale heterogeneity of soil redox status (7); in some cases, CH 4 source/sink switching behavior is observed with seasonal flooding or drydown (8)(9)(10)(11)(12).Little is known about how soil microbial community structure is influenced by both historical and contemporary environmental conditions of subalpine forested soils (13) and how microbial community structure might correlate with soil fluxes of CO 2 and CH 4 . Landscape factors that may influence the occurrence and abundance of microorganisms include geographic location (14), topographic features such as drainages (15), and soil characteristics across spatial scales (16).…”

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confidence: 99%

mentioning

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Landscape Position Influences Microbial Composition and Function via Redistribution of Soil Water across a Watershed

Riveros-Iregui

Jones

et al. 2015

Appl Environ Microbiol

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g Subalpine forest ecosystems influence global carbon cycling. However, little is known about the compositions of their soil microbial communities and how these may vary with soil environmental conditions. The goal of this study was to characterize the soil microbial communities in a subalpine forest watershed in central Montana (Stringer Creek Watershed within the Tenderfoot Creek Experimental Forest) and to investigate their relationships with environmental conditions and soil carbonaceous gases. As assessed by tagged Illumina sequencing of the 16S rRNA gene, community composition and structure differed significantly among three landscape positions: high upland zones (HUZ), low upland zones (LUZ), and riparian zones (RZ). Soil depth effects on phylogenetic diversity and ␤-diversity varied across landscape positions, being more evident in RZ than in HUZ. Mantel tests revealed significant correlations between microbial community assembly patterns and the soil environmental factors tested (water content, temperature, oxygen, and pH) and soil carbonaceous gases (carbon dioxide concentration and efflux and methane concentration). With one exception, methanogens were detected only in RZ soils. In contrast, methanotrophs were detected in all three landscape positions. Type I methanotrophs dominated RZ soils, while type II methanotrophs dominated LUZ and HUZ soils. The relative abundances of methanotroph populations correlated positively with soil water content (R ‫؍‬ 0.72, P < 0.001) and negatively with soil oxygen (R ‫؍‬ ؊0.53, P ‫؍‬ 0.008). Our results suggest the coherence of soil microbial communities within and differences in communities between landscape positions in a subalpine forested watershed that reflect historical and contemporary environmental conditions. I n the western United States, approximately 70% of carbon sink activity is located at elevations above 750 m, where 50 to 85% of land is dominated by hilly or mountainous topography (1). Fluxes of carbonaceous gases, such as carbon dioxide (CO 2 ) and methane (CH 4 ), significantly affect the size of the carbon sink, with soil respiration accounting for the largest terrestrial CO 2 flux to the atmosphere (2). CO 2 in soil pore spaces is derived primarily from autotrophic (root) and heterotrophic (microbe) respiration, which is mediated by environmental factors such as temperature, soil water content (SWC), O 2 availability, and organic matter (3-5). The direction and intensity of CH 4 flux depends on the local balance of the CH 4 consumption by methanotrophs and CH 4 production by methanogens, both of which also are subject to such environmental influences. Because diffusive gas transport through soils is reduced with increasing SWC, hydrologic variations can strongly affect soil O 2 levels, which in turn influence the relative rates of (anaerobic) methanogenesis and (aerobic) methanotrophy. Although saturated soils (e.g., wetlands) are major terrestrial sources of CH 4 emissions (6), emission may at times occur from unsaturated soils, depending on th...

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Forest ecosystem changes from annual methane source to sink depending on late summer water balance

Cited by 48 publications

References 34 publications

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

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

Methane exchange in a boreal forest estimated by gradient method

Landscape Position Influences Microbial Composition and Function via Redistribution of Soil Water across a Watershed

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