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Wetland methane (CH4) fluxes are highly variable over spatial and temporal scales due to variations in CH4 production, oxidation, and transport. While some aspects of temporal variability in CH4 fluxes are well documented, diel variability is poorly constrained, and studies report conflicting findings, making it difficult to generalize. Topographic, geochemical, hydroclimatic, and vegetative variability can result in characteristically different "patches" that likely influence differences in diel patterns. We investigated diel patterns of CH4 fluxes from a large seasonal‐mineral soil wetland in Maryland (USA) across three functionally unique patches: two with vegetation (emergent and submerged aquatic vegetation) and one without (open water) during the summer of 2021. To explore the relationships between vegetation, environmental conditions, and flux patterns, we also measured physiochemical variables (air and water temperature, pH, relative humidity, PAR, dissolved oxygen, and water depth). To our knowledge, this is the first study comparing diel variability using chambers across such distinct vegetation patch types. We found that diel patterns were strongly linked to patch types: CH4 fluxes from the emergent vegetation did not display a consistent diel pattern, while fluxes from the submerged vegetation and no vegetation patches frequently peaked at 13:00 and 05:00, respectively. These differences could be a direct result of vegetation impact on production, oxidation, and/or transport of CH4 or on conditions covarying with patch type. This study contributes to the growing understanding of how CH4 fluxes vary spatially over diel cycles and emphasizes the importance of considering spatially varying diel patterns when estimating fluxes. Plain Language Summary: Methane (CH4) emissions from wetlands are known to vary over space and time, to be largely controlled by vegetation, and exhibit strong seasonal patterns. Yet daily patterns are not well characterized due to the limited number of studies and to difficulties in obtaining nighttime measurements. To address this, we investigated CH4 flux patterns over day and night cycles in patches characterized by emergent, submerged, or no vegetation in a temperate freshwater herbaceous wetland. We show that daily patterns of CH4 emissions are strongly linked to the type of vegetation present but the mechanistic influence of plants on production and consumption is unclear. This work contributes to the growing understanding of how CH4 varies within wetland landscapes over time. Key Points: Vegetation presence and type can control day and nighttime methane (CH4) fluxesPatterns in CH4 flux over diel cycles and across vegetation patch types vary such that a single daily measurement may not adequately capture variability of diel fluxesVegetation function that facilitates both production and oxidation of CH4 can lead to unpredictable diel patterns in CH4 flux [ABSTRACT FROM AUTHOR]

Methane (CH4) dynamics in wetlands are spatially variable and difficult to estimate at ecosystem scales. Patches with different plant functional types (PFT) represent discrete units within wetlands that may help characterize patterns in CH4 variability. We investigate dissolved porewater CH4 concentrations, a representation of net CH4 production and potential source of atmospheric flux, in five wetland patches characterized by a dominant PFT or lack of plants. Using soil, porewater, and plant variables we hypothesized to influence CH4, we used three modeling approaches—Classification and regression tree, AIC model selection, and Structural Equation Modeling—to identify direct and indirect influences on porewater CH4 dynamics. Across all three models, dissolved porewater CO2 concentration was the dominant driver of CH4 concentrations, partly through the influence of PFT patches. Plants in each patch type likely had variable influence on CH4 via root exudates (a substrate for methanogens), capacity to transport gas (both O2 from and CH4 to the atmosphere), and plant litter quality which impacted soil respiration and production of CO2 in the porewater. We attribute the importance of CO2 to the dominant methanogenic pathway we identified, which uses CO2 as a terminal electron acceptor. We propose a mechanistic relationship between PFT patches and porewater CH4 dynamics which, when combined with sources of CH4 loss including methanotrophy, oxidation, or plant‐mediated transport, can provide patch‐scale estimates of CH4 flux. Combining these estimates with the distribution of PFTs can improve ecosystem CH4 flux estimates in heterogenous wetlands and improve global CH4 budgets. Plain Language Summary: Methane is a potent greenhouse gas and understanding what controls methane production from microbes to plant communities can improve our estimates of wetland fluxes and global methane budgets. We propose characterizing methane dynamics in herbaceous wetlands at the scale of plant patches as patches integrate multiple local properties, are generally discrete, and relatively easy to map and measure. To characterize common wetland patch types, we investigate patterns of dissolved methane, soil biogeochemistry, and plant properties in 4 vegetated (submerged vegetation, forb, grass, and sedge) and 1 unvegetated wetland patch types in a temperate, freshwater, herbaceous wetland. We found that methane production differs significantly across patches and is largely correlated with each plant's capacity to transport gas to and from the soil, the quality of plant litter, and the properties of dissolved organic carbon in each patch. This work improves our understanding of how patches uniquely influence methane and by mapping the distribution of these patches we can improve our estimates of wetland methane fluxes. Key Points: Herbaceous plant patches present a unit of measure that can integrate multiples scales controlling wetland methane dynamicsMethane dynamics in the soil are linked to plant‐mediated rhizosphere oxygenation, litter quality, and DOC compositionGrass and sedge functional types seem to modulate methane via different mechanisms, highlighting the importance of using functional type [ABSTRACT FROM AUTHOR]

Disturbances are increasing in size and frequency with climate change, facilitating species that opportunistically exploit areas where habitat‐forming foundation species have been removed. Although it is well‐recognized that consumers, disease and weedy space‐holders can affect foundation species' resistance to and recovery from disturbance, how predators influence their resilience is less clear.In salt marshareas de‐vegetated by drought and intensive snail Littoraria irrorata grazing (hereafter, 'die‐offs'), we monitored bird use and experimentally manipulated bird and nekton access to the vegetated borders of die‐off mudflats across periods of both vegetation die‐off and regrowth to explore how these predators mediate the resilience of cordgrass Spartina alterniflora, the foundation species that structures US Atlantic coast salt marshes.Surveys revealed that birds, especially probers that agitate soils, forage year‐round for invertebrates in die‐off mudflats in our study area but not in adjacent vegetated areas.During periods of die‐off, cordgrass borders accessible to bird and nekton predators retreated >3‐times slower and snail densities were halved, relative to predator exclusion cages. In predator‐accessible plots, slower border retreat corresponded to greater snail infection by a bird host‐dependent trematode parasite. During recovery, cordgrass borders revegetated more quickly, and snail densities declined faster over time in unmanipulated controls relative to predator exclusions.Synthesis. These findings suggest that birds, through their transmission of parasites to snails, appear to act synergistically with snail‐consuming nekton to slow cordgrass loss after drought‐snail disturbances. Predator access also corresponds to faster cordgrass recovery as environmental conditions improve, although the mechanisms behind this need further investigation. Thus, predators that opportunistically forage within disturbances have the potential to suppress consumer impacts through multiple mechanisms, including consumption and disease transmission, thereby bolstering foundation species' resilience and modulating whole ecosystem responses to climate change. [ABSTRACT FROM AUTHOR]