Hyperspectral Reflectance for Measuring Canopy‐Level Nutrients and Photosynthesis in a Salt Marsh

Abstract

Canopy photosynthesis (F A ) in salt marshes is a major carbon flux that is at least 12% higher than F A from terrestrial ecosystems and other freshwater wetlands (Lu et al., 2017;Xiao, 2004;Zhang et al., 2007). Despite the global relevance of F A from these ecosystems, salt marshes have been underrepresented in process-based models due to their unique spatial and temporal variability (Ward et al., 2020) and the limited information about the biophysical controls of their carbon cycle (Delwiche et al., 2021;Knox et al., 2019;. In particular, the role of macro-and micronutrients on F A is largely missing at the ecosystem and canopy scales, despite the importance of nutrients on the optimal growth of vegetation (Marschner & Marschner, 2012). Because of the relevant role of salt marshes on the local-to-global carbon budget, there is a need to identify the influence of leaf-and canopy-level nutrients on F A to better explain the underlying mechanisms of spatial variability of

Empirical Dynamic Modeling Reveals Complexity of Methane Fluxes in a Temperate Salt Marsh

“…Despite good performance, this model still considerably underpredicted during senescence and overpredicted during green‐up. Consequently, these transitions represent a challenge as rapid metabolic and structural changes happen in the plant canopy while microbial community activity could also be altered (Capooci et al., 2024; Vazquez‐Lule et al., 2022). Although we included the full suite of associated variables identified by CCM, this could indicate that additional variables omitted or not measured (e.g., sediment redox potential, biomass, sediment substrate availability) are essential to explain these unusually high fluxes during senescence.…”

“…patens and P . australis along the upland terminus (Vázquez‐Lule & Vargas, 2021; Vázquez‐Lule et al., 2022). The prevailing paradigm assumes that low methanogenesis is expected in these salt marshes, but recent studies have challenged it by demonstrating high rates of methanogenesis (particularly methylotrophic) at the study site (Capooci & Vargas, 2022; Capooci et al., 2019, 2024; Seyferth et al., 2020).…”

“…A range filter was not applied to CH 4 data as spikes due to ebullition could occur, and the goal was to incorporate all CH 4 dynamics within the 30‐min block averaging period. In addition, we used an optimal friction velocity ( u* ) threshold of 0.069 m s −1 to remove low turbulence conditions and applied a fetch/footprint filter to exclude fluxes originating from forested regions beyond the marsh terminus (Vázquez‐Lule & Vargas, 2021; Vazquez‐Lule et al., 2022).…”

“…Vegetation is dominated by a monoculture of short-form S. alterniflora (∼66%). The remaining cover (∼33%) is associated with tall S. alterniflora, S. cynosuroides, and P. australis, which flank tidal creeks, and S. patens and P. australis along the upland terminus Vázquez-Lule et al, 2022). The prevailing paradigm assumes that low methanogenesis is expected in these salt marshes, but recent studies have challenged it by demonstrating high rates of methanogenesis (particularly methylotrophic) at the study site (Capooci & Vargas, 2022;Capooci et al, 2019Capooci et al, , 2024Seyferth et al, 2020).…”

Canopy Heterogeneity and Environmental Variability Drive Annual Budgets of Net Ecosystem Carbon Exchange in a Tidal Marsh

“…NEE becomes suppressed during active tidal flooding due to the reduction of gas exchange from inundated plants (Forbrich & Giblin, 2015;Guo et al, 2009;Hawman et al, 2021Hawman et al, , 2023Kathilankal et al, 2008;Nahrawi et al, 2020), however tidal flooding provides flushing and nutrient input increasing NEE (Knox et al, 2018). Lastly, canopy nutrient content varies across tidal marshes, and its influence on canopy fluxes (photosynthesis) can be dependent on the species and underlying biogeochemical conditions affecting nutrient availability (Vázquez-Lule et al, 2022).…”