The hidden roots of wetland methane emissions

Wetlands are the largest natural source of methane (CH4) globally. Climate and land use change are expected to alter CH4 emissions but current and future wetland CH4 budgets remain uncertain. One important predictor of wetland CH4 flux, plants, play an important role in providing substrates for CH4‐producing microbes, increasing CH4 consumption by oxygenating the rhizosphere, and transporting CH4 from soils to the atmosphere. Yet, there remain various mechanistic knowledge gaps regarding the extent to which plant root systems and their traits influence wetland CH4 emissions. Here, we present a novel conceptual framework of the relationships between a range of root traits and CH4 processes in wetlands. Based on a literature review, we propose four main CH4‐relevant categories of root function: gas transport, carbon substrate provision, physicochemical influences and root system architecture. Within these categories, we discuss how individual root traits influence CH4 production, consumption, and transport (PCT). Our findings reveal knowledge gaps concerning trait functions in physicochemical influences, and the role of mycorrhizae and temporal root dynamics in PCT. We also identify priority research needs such as integrating trait measurements from different root function categories, measuring root‐CH4 linkages along environmental gradients, and following standardized root ecology protocols and vocabularies. Thus, our conceptual framework identifies relevant belowground plant traits that will help improve wetland CH4 predictions and reduce uncertainties in current and future wetland CH4 budgets.

Here, we present a new conceptual framework of wetland root trait connections to CH 4 processes and highlight key knowledge gaps.The conceptual framework is based on a literature review of observational studies and reviews that link root traits to CH 4 .First, we describe the overall conceptual framework (Section 2), followed by discussion of root functions (Sections 2.1-2.4) and their potential trait-trait connections in wetlands (Section 2.5), and conclude with recommendations for future research (Section 3).
Throughout this paper, we use the term 'root traits' for brevity but include traits from a variety of belowground plant compartments: the root system, traits related to mycorrhizal associations, and rhizomes.Our discussion is largely based on the following terms: 'root' (belowground organ of varying length and diameter with an ability to elongate via cell division), 'fine root' (ca.<2 mm in diameter; usually responsible for nutrient and water acquisition), 'coarse root' (ca.>2 mm in diameter; usually no acquisition and only responsible for transport), 'rhizome' (horizontally growing stem of a clonal plant able to grow new rooting units of the genetically same individual), and 'rhizosphere' (the surrounding soil influenced by the root system).While a distinction between absorptive and transport roots based on root orders might be more accurate in ecosystem function context, for simplicity, we use the traditional diameter-based classification.In addition, while this paper has been written from a wetland perspective, many of the discussed trait-PCT linkages could be applied to upland ecosystems as well, because many wetlands exhibit a range of oxic-anoxic gradients (e.g., Balasooriya et al., 2008;Chowdhury et al., 2014;Courtwright & Findlay, 2011;Miao et al., 2017;Waddington & Roulet, 1996).

| C ATEG ORIE S OF ROOT FUN C TI ON S RELE VANT FOR CH 4
We found that the following four broad categories of root functions relate to wetland CH 4 cycling: gas transport, C substrate provision, physicochemical influences and root system architecture (Figure 1).Each category contains a range of root traits that could be connected to PCT (Figure 2; Data S1).The 'gas transport' category refers to traits influencing the flux of oxygen (O 2 ) and CH 4 within the plant, 'C substrate provision' to traits contributing to the availability of C substrates for microbes taking part in methanogenic decomposition pathways, 'physicochemical influences' to traits related to root effects on soil physicochemical properties that affect PCT, and 'root system architecture' to traits describing the spatial distribution of roots within the soil volume.The category-specific linkages to PCT are discussed in detail in the following Sections 2.1-2.4.The categories are linked to each other, altering the resultant PCT and net CH 4 emission (Section 2.5; Data S2).

| Gas transport
Root traits involved in gas (O 2 and CH 4 ) transport between soils and the atmosphere affect CH 4 production and consumption.
Rhizosphere oxygenation can enhance CH 4 consumption and decrease CH 4 production and transport.In the rhizosphere, O 2 acts as an electron acceptor for aerobic metabolism or contributes to the formation of alternative electron acceptors, namely nitrogen (N), iron (Fe) and sulfur (S) compounds in their oxidized forms (Laanbroek, 2010;Megonigal et al., 2004).O 2 and alternative electron acceptors are used in energetically more favorable anaerobic metabolism pathways, leading to the suppression of methanogenesis (Andrews et al., 2013;Laanbroek, 1990Laanbroek, , 2010)).Thus, increased root biomass and rhizosphere oxygenation can lead to a prevalence of CH 4 oxidation over production, and ultimately decreased net CH 4 emission (Noyce et al., 2023).Increased rhizosphere oxygenation can also result in inhibition of CH 4 production due to O 2 -toxicity (Fetzer et al., 1993;Jespersen et al., 1998) and methanotrophic CH 4 consumption (Laanbroek, 2010;Megonigal & Schlesinger, 2002).
Another important trait reflecting rhizosphere oxygenation and, thus, CH 4 consumption and suppression of CH 4 production, is the Fe (oxyhydr)oxide [Fe(III)] coating on roots.Fe(III) plaque is a commonly used trait for estimating wetland soil saturation (Mendelssohn et al., 1995) and is related to root radial O 2 loss, defined as the flow of O 2 from the root to the soil (Colmer, 2003).Root radial O 2 loss is controlled by root porosity, wall permeability, and surface area, plant respiration (i.e., root tissue O 2 demand) and soil saturation (Armstrong, 1971;Lai et al., 2012;Pedersen et al., 2021;Visser et al., 2000).Root radial O 2 loss is most efficient at the root tips and fine roots (Colmer, 2003;Henneberg et al., 2012;Pi et al., 2009) due to lower suberin concentration and/or less tightly packed cells than in the coarser basal roots (Armstrong & Armstrong, 1988; De F I G U R E 1 A conceptual framework of root trait influence on wetland CH 4 emissions.P = CH 4 production, C = CH 4 consumption and T = CH 4 transport.The four circles represent categories of root functions in wetland CH 4 cycling.Colors around the circles represent the general direction of the effect of the categorized root traits on PCT.Blue = a positive relationship; red = a negative relationship and yellow = uncertain or unknown relationship between the root trait value and P, C, or T. 'M' in Physicochemical influences stands for 'metal' (see discussion of chelation in Section 2.3).Simone et al., 2003;Kotula et al., 2009;Soukup et al., 2007).Heavily suberized rhizomes (Sorrell et al., 1997) have generally low O 2 loss rates (Armstrong et al., 1992;Armstrong & Armstrong, 1988), except at their budding apices (Armstrong & Armstrong, 1988).Increased root/rhizome suberin content could also decrease CH 4 transport via reduced CH 4 permeability (Beckett et al., 2001), suggesting root/ rhizome suberin content as a potential PCT trait.
Increased Fe(III) concentrations on root surfaces (Inoue et al., 2011;Sutton-Grier & Megonigal, 2011) and Fe(III) reduction rates in the soil (Neubauer et al., 2005;Roden & Wetzel, 1996;van der Nat & Middelburg, 1998a) are negatively correlated with CH 4 production in anoxic soils (Figure 2), indicating a shift towards non-methanogenic metabolism (Sutton-Grier & Megonigal, 2011).Indeed, poorly crystalline rhizospheric Fe(III) is more labile for Fe-reducing bacteria than in the surrounding soil where Fe(III) is highly crystalline (Weiss et al., 2004), which can lead to as fast rhizospheric Fe(III)-reduction as Fe(III) deposition on root surfaces (Weiss et al., 2005), and, thus, maintained root-driven Fe cycling and suppression of methanogenesis.However, similar observations could also be linked to Fe(III) reduction-related anaerobic CH 4 oxidation (Cai et al., 2018;Chen et al., 2022;Yan et al., 2018).In addition, Fe(III) plaque formation is dependent on the available Fe pools, the size of which can vary between and within different wetlands due to variation in soil pH, organic matter content, texture and reduction-oxidation (redox) potential (Mendelssohn et al., 1995;Yu et al., 2021).While Fe cycling occurs in saline wetlands (Hyun et al., 2007), methanogenesis is suppressed primarily by sulfate (SO 2− 4 ) as the dominant electron acceptor (Howarth & Giblin, 1983;King & Wiebe, 1980;Klepac-Ceraj et al., 2004;Laanbroek, 2010), limiting the use of Fe(III) plaque as a trait in saline wetlands.Furthermore, Vroom et al. (2022) suggest that Fe(III) plaque could theoretically act as a barrier for CH 4 transport but this remains to be investigated.Fe(III) plaque is a useful proxy for separating the effects of root-mediated C (i.e., electron donor) provision and rhizosphere oxygenation (i.e., electron acceptor provision) on CH 4 production, a separation which is often neglected (Sutton-Grier & Megonigal, 2011).
Root exudation rate is one of the core traits contributing to C substrate provision.Root exudation rate is highest at the root tips (Canarini et al., 2019;Jones, 1998) while in rhizomes, exudation seems to be strongest at apices (Coupland & Peabody, 1981).Root exudates enhance CH 4 production by providing bioavailable organic acids for heterotrophic microorganisms which convert them into H 2 , acetate, and other low-molecular-weight compounds, which in turn can be used by methanogens (Joabsson et al., 1999;Le Mer & Roger, 2001) (Figure 2).Root exudation can also stimulate the decomposition of bulk soil organic matter, leading to production of soil-derived CH 4 (as opposed to exudate-derived CH 4 ) and increased CH 4 emissions (Waldo et al., 2019).Moreover, root exudates can suppress methanotrophy due to increased competition between methanotrophs and other heterotrophic microbes for available O 2 (Turner et al., 2020;Waldo et al., 2019).In addition, methanotrophy can be inhibited due to the toxicity of the exuded substrates at low pH (Wieczorek et al., 2011).However, contrasting results were obtained in a rice paddy where root exudates increased methanotroph abundance and CH 4 consumption (Chen et al., 2019).Moreover, root exudates can bind with root Fe(III) plaque (Wei et al., 2022), which could mitigate the stimulating effect of root exudation on CH 4 production (Karvinen, 2016).Exudation rate is primarily controlled by photosynthesis (Kuzyakov & Cheng, 2001;Kuzyakov & Gavrichkova, 2010), but also by salinity, soil moisture and mycorrhizal colonization (Vranova et al., 2013;Wen et al., 2022), as well as specific root length (Guyonnet et al., 2018;Williams et al., 2022; but see Wen et al., 2022).Specific root length is root length per unit mass and is an important trait expressing plant C allocation for soil exploration (Freschet, Pagès, et al., 2021).Root exudate composition and abundance can vary according to vegetation composition with significant alterations to CH 4 production potential (Koelbener et al., 2010;Ström et al., 2003;Ström & Christensen, 2007).To date, most studies have used proxies for root exudation and substrate provision, such as aboveground biomass and gross photosynthetic rate, and additional hypothesis testing is needed to isolate the effects of root exudation on PCT (e.g., Chanton et al., 1995Chanton et al., , 2008;;Dorodnikov et al., 2011;Greenup et al., 2000;Joabsson & Christensen, 2001;Whiting & Chanton, 1992).
Since mycorrhizal hyphae are thinner than fine roots (e.g., Defrenne et al., 2021) and seem to have shorter lifespan than roots (Godbold et al., 2006;Olsson & Johnson, 2005;Staddon et al., 2003), hyphal turnover and soil C input could be significant in soil with high hyphal biomass (De Vries et al., 2009;Staddon et al., 2003).In addition, hyphal exudates, labile C substrates released by mycorrhizal hyphae (Toljander et al., 2007), could potentially play a similar role as root exudates in regulating PCT.Increased mycorrhizal colonization could thus enhance C substrate provision for CH 4 production but, as with other mycorrhiza-CH 4 linkages, no evidence for these relationships exists yet.In addition, studies of hyphal decomposition, turnover and exudation in the context of soil C cycling are very scarce (Hawkins et al., 2023;Wen et al., 2022).

| Physicochemical influences
Roots and rhizomes affect PCT by influencing the physicochemical properties of the surrounding soil.Roots alter soil pH, an important control of methanogenesis and methanotrophy, by releasing protons (H + ) or hydroxides (OH − ) into the rhizosphere, which decreases or increases the soil pH, respectively, possibly creating methanogenic microsites (Hinsinger et al., 2003).As H + and OH − are released mostly along fine and coarse roots and behind root tips (Blossfeld & Gansert, 2007;Hinsinger et al., 2003;Marschner et al., 1982;Weisenseel et al., 1979), possible traits to use as proxies for H + and OH − release and the subsequent alterations in PCT could include root tip density and specific root length.Simultaneously with H + release, root radial O 2 loss induces Fe(II) oxidation where H + are produced and pH decreases (Begg et al., 1994;Yang et al., 2012).Conversely, Fe(III) can be reduced into Fe(II), resulting in H + consumption and increased pH (Hinsinger et al., 2003), and possibly CH 4 production (Tang et al., 2016;Wagner et al., 2017).Thus, Fe(III) plaque could be used as an additional trait reflecting changes in rhizosphere acidity and alterations in PCT.Furthermore, root and microbial respiration can lower pH, via CO 2 release, or increase it via root CO 2 uptake (Begg et al., 1994).Acids in root exudates can also lower rhizospheric pH (Casarin et al., 2004;Dutton & Evans, 1996), but their overall significance in rhizosphere acidification can be low in comparison with H + release (Hinsinger et al., 2003(Hinsinger et al., , 2009;;Petersen & Böttger, 1991).
Mycorrhizae can release chelators as well (Dutton & Evans, 1996;Taylor et al., 2009;van Hees et al., 2006) but also reduce root chelator exudation (Nazeri et al., 2014;Ryan et al., 2012).Altogether, it is unclear, whether chelated metals stimulate or suppress CH 4 production in wetlands.Thus, traits such as root and hyphal exudation rate and composition, could aid in understanding their significance for PCT.
Taken together, traits related to phenolic influence on PCT could include root exudation and root/rhizome decomposition rate and turnover, and tissue phenolic concentration (Williams & Yavitt, 2010;Zwetsloot et al., 2018).However, studies investigating these connections with the inclusion of root/rhizome traits are rare (but see Williams & Yavitt, 2010; Figure 2; Data S1).
In contrast to oxygenating the rhizosphere, the root system can also create anoxic microsites optimal for CH 4 production.Traits contributing to anoxic microsite formation include root and hyphal respiration and exudation.Root respiration rate describes the amount of CO 2 released or O 2 absorbed by roots, per unit root mass, length, volume or surface area (Freschet, Pagès, et al., 2021) and, along with hyphal respiration (Storer, 2013;Verchot et al., 2000), may dictate the formation of anoxic microsites for CH 4 production in oxic soils (Brewer et al., 2018;McLain et al., 2002;Verchot et al., 2000;Yang & Silver, 2016).In addition, root exudation and mucilage (Baumert et al., 2018;Six et al., 2004;Traoré et al., 2000) and hyphal entanglement and exudation (Leifheit et al., 2014;Rillig et al., 2015;Rillig & Mummey, 2006;Six et al., 2004) can increase anoxic soil aggregate formation (Andersen et al., 1998), which could lead to CH 4 production (Kimura et al., 2012).Still, the effect of anoxic microsites on net soil CH 4 emission in general remains largely unclear (Angle et al., 2017;Yang & Silver, 2016), and their significance in wetlands may be low due to the prevailing anoxic conditions in the whole ecosystem scale, despite the presence of oxic (i.e., CH 4 -consuming) soil patches.Therefore, the formation of oxic microsites may be more important in wetlands whereas anoxic microsites may contribute more to the net CH 4 emission in upland ecosystems.

| Trait-trait relationships in wetlands
Root traits interact within and between our four proposed categories, and alterations in these interactions can lead to variation in CH 4 emissions (Data S2).For example, increases in root system architectural traits (e.g., maximum rooting depth and rhizome length) could extend gas transport (Granse et al., 2022), rhizosphere acidification/ alkalinization (Blossfeld et al., 2011;Blossfeld & Gansert, 2007), and distribution of phenolics, chelators and C substrates provided by roots (Holz et al., 2018).Root exudates may also induce changes in root branching and root system distribution via root-root signaling (Caffaro et al., 2011;Depuydt, 2014).As another example, increased plant decomposition in wetlands can lead to accumulation of organic acids (Drew & Lynch, 1980), some of which could increase root cell wall suberization, leading to a decrease in root radial O 2 loss (Colmer et al., 2019).
Environmental variables may alter or override trait-trait and trait-PCT relationships in determining the net CH 4 emission.Trait shifts could be triggered by environmental variables, for example soil moisture and temperature, salinity, and nutrient availability.
For example, decreases in soil water saturation may result in increased lateral rooting extent, mean and maximum rooting depth (e.g., Comas et al., 2013;Fan et al., 2017), enhanced decomposition of root/rhizome phenolic compounds (Wilmoth et al., 2021), and wider spatial distribution of root exudates within the soil volume, all of which could lead to simultaneous net increase in both CH 4 consumption and production.However, the network of various abiotic and biotic controls of wetland CH 4 emission is complex and the relative importance of each variable differs between wetland types and climatic regions (Turetsky et al., 2014), PFTs (Bhullar et al., 2013) and plant species (Bhullar et al., 2014;Koelbener et al., 2010) and along spatial (Malhotra & Roulet, 2015) and temporal scales (Moore et al., 2011;Sturtevant et al., 2015).In particular, soil temperature and water table level are often the dominant controls of wetland CH 4 emission (e.g., Evans et al., 2021;Henneberg et al., 2016;MacDonald et al., 1998;Moore et al., 2011;Moore & Roulet, 1993;Waddington et al., 1996), sometimes overriding vegetation effects in the longer term (Moore et al., 2011;Sturtevant et al., 2015;Turetsky et al., 2014;Waddington et al., 1996).For example, water table level below maximum rooting depth can prevent effective root-mediated transport of CH 4 (Kutzbach et al., 2004;Waddington et al., 1996).
Therefore, the traits in our framework should be investigated together with environmental variables (van der Plas et al., 2020), in order to determine the relative importance of each biotic and abiotic variable on PCT.
Disturbances, such as permafrost thaw (e.g., Christensen et al., 2004;Knoblauch et al., 2018;Malhotra & Roulet, 2015) and coastal wetland extension due to sea level rise (e.g., Kirwan et al., 2023;Mueller et al., 2020), may further complicate the linkages between the traits and environmental controls of wetland CH 4 emissions.This underlines the importance of investigating the influence of multiple root traits on wetland CH 4 emissions.

| RECOMMENDATI ON S FOR FUTURE RE S E ARCH
Incorporating root trait information into wetland CH 4 research could greatly improve our understanding and predictions of wetland CH 4 processes.Based on our hypothesized connections between different root traits and PCT processes, we recommend the following priorities for future wetland root trait and CH 4 research: -Include traits from multiple root function categories: In order to form a comprehensive view of root-mediated wetland CH 4 cycling, several root traits with different effects on PCT processes should be measured.For example, combining traits from root system architecture with traits from other categories may prove highly valuable, given that root system traits could help scale up processes from other categories.-Use established methods and controlled vocabularies: As the number of studies including root traits in CH 4 studies is growing and the field of root ecology is still relatively young, it is essential to use established terminology and methods in order to ensure meaningful comparisons between studies (Freschet, Pagès, et al., 2021;Garnier et al., 2017).Researchers can leverage the Root Trait Inventory of the Fine Root Ecology Database (Iversen et al., 2017(Iversen et al., , 2021; https:// roots.ornl.gov/ ), and Freschet, Pagès, et al. (2021) for terminology, and methodology.
-Separate plant belowground material into compartments: In order to accurately investigate and, eventually, describe the role of roots and rhizomes in wetland CH 4 cycling, dividing plant belowground material into fine and coarse, as well as absorptive and transport classes (McCormack et al., 2015) and rhizomes, is needed.
-Consider environmental, species and climatic gradients: In order to fully understand variation in PCT and CH 4 emissions within and across wetlands, different root traits from a variety of species and PFTs along different environmental and climatic gradients should be investigated (Andrews et al., 2013;Bouchard et al., 2007;Kao-Kniffin et al., 2010;Mueller et al., 2020;Noyce et al., 2023).This is particularly important in wetlands with high spatiotemporal soil moisture variation (e.g., peatlands with hummock-hollow microtopographies) and coastal wetlands subject to sea level rise.It could also be valuable to estimate intraspecific variation in root traits in order to estimate trait shifts during environmental change, due to heritable belowground traits changing at a similar pace with the environment, significantly altering C cycling (Vahsen et al., 2023).
-Couple root traits with microbial communities: In order to reveal plant-microbe trait linkages, it is necessary to include assessments of methanogen and methanotroph abundance and community composition in studies investigating root-mediated CH 4 fluxes.In particular, it may be useful to observe the interactions between CH 4 -cycling microbes in the entire soil column (e.g., Franchini et al., 2014;Turner et al., 2020), on root surfaces (e.g., Heilman & Carlton, 2001;King, 1994), and within roots (e.g., King, 1994;Watanabe et al., 1997) for a better estimate of the spatial variability of root-microbe relationships.
-Implement new technologies for measuring root traits: Measuring root traits from wetland soil samples is labor intensive and time consuming, and often daunting or inaccessible for researchers unfamiliar with root ecological methods.To make the inclusion of root traits in wetland CH 4 research more accessible to a larger group of researchers, it is necessary to develop and make use of new technologies for the trait measurements.For estimating the general and species-specific living and dead root biomass from wetland soil samples, near-infrared (Laiho et al., 2014;Lei & Bauhus, 2010;Picon-Cochard et al., 2009;Roumet et al., 2006), Fourier transform infrared spectroscopy (Straková et al., 2020), C andN isotopes (Corre-Hellou &Crozat, 2005;Eleki et al., 2005;Polley et al., 1992;Rewald et al., 2012) and biomarker (Dawson et al., 2000;Ofiti et al., 2023;Roumet et al., 2006) techniques could be used in addition to or instead of manual root separation and inspection.Furthermore, planar optode technology has been promising in visually estimating the spatial distribution of rhizosphere oxygenation and pH (e.g., Blossfeld et al., 2011;Blossfeld & Gansert, 2007;Lenzewski et al., 2018;Waldo et al., 2019).X-ray computed tomography could be a useful tool for examining root system architecture and its potential influence on C substrate provision, gas transport and microbial distribution (Handakumbura et al., 2021;Hou et al., 2022;Yang et al., 2017).Minirhizotrons, together with improved artificial intelligence methods for imagebased root-detection, have been successfully applied in wetlands (Arnaud et al., 2021;Defrenne et al., 2021;D'Imperio et al., 2018;Iversen et al., 2012;Peters et al., 2023;Rodgers et al., 2004;Sciumbata et al., 2023).

| CON CLUS IONS
Wetland CH 4 studies have long focused on plant aboveground traits, leaving a large belowground knowledge gap.We constructed a conceptual framework connecting root traits to CH 4 PCT processes and found that (1) root traits can be divided into four main categories of

CO N FLI C T O F I NTE R E S T S TATE M E NT
The authors declare no conflicts of interest.

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Include mycorrhizae: Mycorrhizae are one of the least studied predictors of CH 4 cycling.Thus, we suggest the following research questions for different wetland and plant types: (1) How does presence/absence of mycorrhizae affect CH 4 emission rates?(2) How do dominant mycorrhizal association type and colonization intensity affect wetland CH 4 emission rates?And (3) what is the role of hyphal exudation concurrent with root exudation and can we differentiate their individual effects on CH 4 emission rates?
CH 4 -relevant root function, namely gas transport, C substrate provision, physicochemical influences and root system architecture, (2) root trait effects on PCT vary both within and between categories, and (3) large knowledge gaps remain especially around how physicochemical and mycorrhizal traits influence PCT, temporal dynamics of C substrate provision, and the impact of root system architecture on scaling the other trait categories.Our conceptual framework underscores the urgent need to fill the highlighted gaps by bringing together expertise from the traditionally disparate fields of root ecology and CH 4 biogeochemistry.Furthermore, root traits and CH 4 emissions are both expected to respond to climate and land use change.Thus, improving root-CH 4 linkages in process-based models will help reduce uncertainties in not just current but also future wetland CH 4 budgets.AUTH O R CO NTR I B UTI O N S Tiia Määttä: Conceptualization; investigation; visualization; writing -original draft; writing -review and editing.Avni Malhotra: Conceptualization; funding acquisition; supervision; writing -original draft; writing -review and editing.ACK N O WLE D G E M ENTS We acknowledge funding from the University of Zurich Stiftung für Wissenschaftliche Forschung (STWF-22-028) and the Swiss National Science Foundation (project 200021_215214) awarded to AM. AM was also supported by COMPASS-FME, a multi-institutional project supported by the U.S. Department of Energy, Office of Science, Biological and Environmental Research as part of the Environmental System Science Program.The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RL01830.