425 / 2024-09-16 20:20:48

Canopy Heterogeneity and Drought Drive Interannual Variability in Carbon Source-Sink Periods in Tidal Wetlands

wetlands,carbon,drought

Session 18 - The River-Estuary-Bay Continuum: Unveiling the Carbon and Nitrogen Cycles Under Global Change

Tidal salt marsh species distribution and within species’ canopy characteristics such as canopy height and biomass vary across short distances. Additionally, tidal salt marshes are found throughout the North American mid-Atlantic and Gulf of Mexico coasts where they experience varying seasonal climate patterns. In this work, we present first a case study on how within-marsh spatial variation influences interannual atmospheric carbon (C) budgets and second, how the timing and duration of C sequestration varied along a latitudinal gradient. First, we found that marsh zones (marsh edge vs interior) sampled by our Eddy Covariance (EC) flux tower hard a large effect on C budgets where marsh edges had 3-fold greater carbon absorption than interiors. Therefore, flux tower placement, along with seasonal wind direction influencing C flux footprints and the variability of within flux source areas (e.g., leaf area and biomass) could lead to uncertainties in annual C budgets when scaled to larger regional areas. Second, we present work comparing the latitudinal variation in the timing and duration of source-sink periods in marshes found along a latitudinal gradient. Across all sites, the timing of start-of-sink periods varied up to 5-fold, while end-of-sink periods were not different. The length of the carbon sink period decreased with increasing latitude. We also found that lower latitude sites experienced higher variance in the timing of source-sink transitions and could be explained by drought conditions. These findings, at two spatial scales, indicate large variation in C dynamics related to both within-site and between site differences.