@article{martinez_ardon_carmichael_2022, title={Identifying Sources and Oxidation of Methane in Standing Dead Trees in Freshwater Forested Wetlands}, volume={9}, ISSN={["2296-665X"]}, DOI={10.3389/fenvs.2021.737379}, abstractNote={Wetlands are large sources of methane (CH4), therefore it is vital to understand the pathways, mechanisms, and sources to anticipate future positive feedbacks to climate change. Plant mediated transport of CH4 from sediment-borne gases is thought to be a major contributor in wetland ecosystems, though few studies have measured standing dead trees (snags). Snags are expected to become more common across the southeastern coast as marshes migrate into freshwater forested wetlands. In this study, our goal was to distinguish the main sources of CH4 being emitted from snags, that is, from soil or in situ origin. The δ2H and δ13C stable isotopic composition from various sources was sampled for source determination. We measured CH4 in various components: emissions from snag stem sides and the soil-atmosphere interface; and concentrations from snag trunk airspace at various heights from ground level (30, 60, and 120 cm), and soil porewater. Potential CH4 production and oxidation in tree cores from two heights (60 and 120 cm) was also measured to examine the potential for CH4 generation or oxidation in stems. We found that CH4 concentrations inside snags (∼10–200 ppm) were 2–50 times higher than atmospheric levels, and generally decreased with increasing stem height. The stable isotopes δ13C and δ2H showed an enrichment from porewater to soils and snag stems. δ13C enrichment of CH4 in snag stems suggests that CH4 is being oxidized as it moves through snags. The tree core vial incubations showed that very few cores produced small amounts of CH4 under anaerobic conditions (n = 5 out of 50), and very few cores oxidized CH4 under more aerobic conditions (n = 5 out of 50). It is possible that a small amount of CH4 is produced in-situ within the heartwood, but it is likely this depends on the density, porosity, and aeration of snags (degree of decay). Our results highlight that high concentrations of CH4 can persist within the heartwood of snags long after initial decay, and that CH4 emitted from snags is largely derived from deep wetland soils and oxidized during transport (via diffusion) throughout the stem of snags.}, journal={FRONTIERS IN ENVIRONMENTAL SCIENCE}, author={Martinez, Melinda and Ardon, Marcelo and Carmichael, Mary Jane}, year={2022}, month={Feb} }
 @article{martinez_ardon_2021, title={Drivers of greenhouse gas emissions from standing dead trees in ghost forests}, volume={154}, ISSN={["1573-515X"]}, url={https://doi.org/10.1007/s10533-021-00797-5}, DOI={10.1007/s10533-021-00797-5}, abstractNote={Coastal freshwater forested wetlands are rapidly transitioning from forest to marsh, leaving behind many standing dead trees (snags) in areas often called ‘ghost forests’. Snags can act as conduits for soil produced greenhouse gases (GHG) and can also be sources as they decompose. Thus, snags have the potential to contribute GHGs to the atmosphere, but emissions are not well understood. We assessed GHG emissions (carbon dioxide—CO2, methane—CH4, and nitrous oxide—N2O) from snags and soils in five ghost forests along a salinity gradient on the coast of North Carolina, USA. Mean (± SE) soil GHG fluxes (416 ± 44 mg CO2 m−2 h−1, 5.9 ± 1.9 mg CH4 m−2 h−1, and 0.1 ± 0.06 mg N2O m−2 h−1) were ~ 4 times greater than mean snag GHGs (116 ± 15 mg CO2 m−2 h−1, 0.3 ± 0.09 mg CH4 m−2 h−1, and 0.04 ± 0.009 mg N2O m−2 h−1). Hydrological conditions and salinity influenced soil GHG fluxes between the two field campaigns, but snags were less predictable and more variable. Snag and soil CO2/N2O fluxes were influenced by similar environmental parameters. The drivers for soil and snag CH4 however, were often not the same and at times oppositely correlated. Our results illustrate the need to further research into the drivers and importance of GHG emissions from snags, and the need to include tree stems into ecosystem GHG research.}, number={3}, journal={BIOGEOCHEMISTRY}, publisher={Springer Science and Business Media LLC}, author={Martinez, Melinda and Ardon, Marcelo}, year={2021}, month={Jul}, pages={471–488} }
 @article{gundersen_corbett_long_martinez_ardon_2021, title={Long-Term Sediment, Carbon, and Nitrogen Accumulation Rates in Coastal Wetlands Impacted by Sea Level Rise}, volume={44}, ISSN={["1559-2731"]}, url={https://doi.org/10.1007/s12237-021-00928-z}, DOI={10.1007/s12237-021-00928-z}, number={8}, journal={ESTUARIES AND COASTS}, publisher={Springer Science and Business Media LLC}, author={Gundersen, Gillian and Corbett, D. Reide and Long, Austyn and Martinez, Melinda and Ardon, Marcelo}, year={2021}, month={Dec}, pages={2142–2158} }
 @article{behtash_kamata_martinez_schafer_skokov_2021, title={Transasymptotics and hydrodynamization of the Fokker-Planck equation for gluons}, volume={103}, ISSN={["2470-0029"]}, url={http://inspirehep.net/record/1830583}, DOI={10.1103/PhysRevD.103.056010}, abstractNote={We investigate the non-linear transport processes and hydrodynamization of a system of gluons undergoing longitudinal boost-invariant expansion. The dynamics is described within the framework of the Boltzmann equation in the small-angle approximation. The kinetic equations for a suitable set of moments of the one-particle distribution function are derived. By investigating the stability and asymptotic resurgent properties of this dynamical system, we demonstrate, that its solutions exhibit a rather different behavior for large (UV) and small (IR) effective Knudsen numbers. Close to the forward attractor in the IR regime the constitutive relations of each moment can be written as a multiparameter transseries. This resummation scheme allows us to extend the definition of a transport coefficient to the non-equilibrium regime naturally. Each transport coefficient is renormalized by the non-perturbative contributions of the non-hydrodynamic modes. The Knudsen number dependence of the transport coefficient is governed by the corresponding renormalization group flow equation. An interesting feature of the Yang-Mills plasma in this regime is that it exhibits transient non-Newtonian behavior while hydrodynamizing. In the UV regime the solution for the moments can be written as a power-law asymptotic series with a finite radius of convergence. We show that radius of convergence of the UV perturbative expansion grows linearly as a function of the shear viscosity to entropy density ratio. Finally, we compare the universal properties in the pullback and forward attracting regions to other kinetic models including the relaxation time approximation and the effective kinetic Arnold-Moore-Yaffe (AMY) theory.}, number={5}, journal={PHYSICAL REVIEW D}, publisher={American Physical Society (APS)}, author={Behtash, A. and Kamata, S. and Martinez, M. and Schafer, T. and Skokov, V}, year={2021}, month={Mar} }
 @article{behtash_cruz-camacho_kamata_martinez_2019, title={Non-perturbative rheological behavior of a far-from-equilibrium expanding plasma}, volume={797}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2019.134914}, abstractNote={For the Bjorken flow we investigate the hydrodynamization of different modes of the one-particle distribution function by analyzing its relativistic kinetic equations. We calculate the constitutive relations of each mode written as a multi-parameter trans-series encoding the non-perturbative dissipative contributions quantified by the Knudsen $Kn$ and inverse Reynolds $Re^{-1}$ numbers. At any given order in the asymptotic expansion of each mode, the transport coefficients get effectively renormalized by summing over all non-perturbative sectors appearing in the trans-series. This gives an effective description of the transport coefficients that provides a new renormalization scheme with an associated renormalization group equation, going beyond the realms of linear response theory. As a result, the renormalized transport coefficients feature a transition to their equilibrium fixed point, which is a neat diagnostics of transient non-Newtonian behavior. As a proof of principle, we verify the predictions of the effective theory with the numerical solutions of their corresponding evolution equations. Our studies strongly suggest that the phenomenological success of fluid dynamics far from local thermal equilibrium is due to the transient rheological behavior of the fluid.}, journal={PHYSICS LETTERS B}, author={Behtash, Alireza and Cruz-Camacho, C. N. and Kamata, Syo and Martinez, M.}, year={2019}, month={Oct} }