DOI: 10.5061/dryad.vmcvdncs7
title: Effects of salt marsh vegetation zonation on carbon and nitrogen cycling in Connecticut

description: Coastal marshes fringing the Long Island Sound (Connecticut, USA) are
 dynamic ecosystems positioned at the interface between land and sea, and
 provide an array of essential ecosystem services to society associated
 with improved water quality, carbon sequestration, and disturbance
 regulation. However, these wetlands are increasingly altered by rising
 seas and invasive species, and have been affected by historical
 management such as tidal manipulation. We conducted a
 survey of 20 Connecticut salt marshes (10 tidally restored, 10
 unrestricted references) in 2017 to quantify carbon mineralization,
 denitrification potential, microbial community composition, above and
 belowground biomass and a suite of sediment characteristics. Carbon
 density was our only paramenter that differed between
 unrestricted and tidally restored marshes, but we observed strong
 differences across vegetation zones, with vegetation being a top predictor
 of microbial respiration and potential denitrification rates. Based on
 sea-level rise model projections, the replacement of S. patens by
 short-form S. alterniflora is expected to be widespread across the
 Connecticut coastline, decreasing statewide potential denitrification from
 the low-to-high marsh transitional zone. Our results suggest that changes
 in vegetation zones can serve as landscape-scale predictors of the rapid
 changes occurring in salt marshes.
description: We sampled 20 polyhaline salt marshes (10 reference marshes with
 no history of restriction or restoration (i.e., "reference
 sites"), 10 tidally restored) along the north shore of the Long
 Island Sound in Connecticut (CT), USA. Sites were selected based on their
 restoration history and presence of target vegetation:
 <i>Spartina alterniflora </i>(short-form, &lt; 30 cm
 tall), <i>S. patens</i>,<i> </i>and
 <em>Phagmites</em> <i>australis</i>. Within each
 vegetation zone at each site, we sampled three 1-m<sup>2</sup>
 plots in mid-August 2017. We visually estimated percent cover of all
 plants in each plot. From each plot we collected aboveground biomass (from
 a randomly selected 25 x 25 cm subplot) and three surface soil cores (5-cm
 diameter to 10-cm depth; 196-cm<sup>3</sup> volume);
 samples were composited by zone and used to estimate above and belowground
 biomass (C and N content), bulk density, microbial process rates
 (denitrification potential, carbon mineralization, substrate induced
 respiration) and a suite of soil chemistry parameters using standarized
 methods (soil pH and specific electrical conductivity, soil
 moisture, total C and N, soil organic matter, carbon density, and soil
 SO4<sup>2-</sup>, Cl<sup>-</sup>,
 NH<sub>4</sub><sup>+</sup><sub>
 </sub> concentrations).  Please see
 associated manuscripts (Barry et al. 2021, Ooi et al in revision) for
 details on data collection and analysis: Barry, A.,
 Ooi, S.K., Helton, A.M. <i>et al.</i> Vegetation Zonation
 Predicts Soil Carbon Mineralization and Microbial Communities in Southern
 New England Salt Marshes. <i>Estuaries and Coasts</i> (2021).
 https://doi.org/10.1007/s12237-021-00943-0
description: Plant, microbial process rates, and sediment chemistry are in
 associated CSV file titled "LISS_2017survey"  Responses with
 "NA" indicate that no data are available, either due to sample
 processing error or concentrations below the instuments detection limit. A
 brief description of the response metric headers and their associated
 units can be found in the CSV file titled
 "LISS_2017survey_metadata." Geographic locations of sample
 points are in associated CSV file titled
 "LISS_2017survey_locations".  Soil bacterial sequences generated
 in this study are available in the NCBI sequence read archive under the
 accession number PRJNA555079. Please
 see associated manuscripts (Barry et al. 2021, Ooi et al in revision) for
 details on data collection and analysis: Barry, A.,
 Ooi, S.K., Helton, A.M. <i>et al.</i> Vegetation Zonation
 Predicts Soil Carbon Mineralization and Microbial Communities in Southern
 New England Salt Marshes. <i>Estuaries and Coasts</i> (2021).
 https://doi.org/10.1007/s12237-021-00943-0