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Abstract Salt marshes are vital but vulnerable ecosystems. However, our understanding of disturbance‐induced dieback and recovery processes in multi‐specific marshes remains limited. This study utilized remote sensing data (2001–2021) to analyze a dieback event and subsequent recovery in the multi‐specific San Felice marsh within the Venice lagoon, Italy. A significant dieback ofSpartina maritima(Spartina) was identified in 2003, likely triggered by a drought event and heat stress. This resulted in a conversion of 4.6 ha of marsh predominantly colonized bySpartina(fractional cover ofSpartina> 50%) in 2001 to bare soil in 2003. These bare areas were then gradually encroached by vegetation, indicating the occurrence of the recovery. Despite gradually gaining ground,Spartinaonly dominated 6.4 ha marshes in 2021, significantly lower than its pre‐dieback area (21.3 ha). However, other species also encroached on the dieback area, such that the aboveground biomass returned to pre‐dieback levels, indicating that the shift in marsh species composition that occurred as a consequence of the event compensated for this ecosystem service. Vegetation recovery, spanning from 1 yr to more than 18 yr, was found to be slowest in areas of lowest elevation. This study provides evidence that dieback and recovery can modify the species composition of multi‐specific marshes over decades. These insights contribute to a better understanding of marsh resilience to drought and elevated temperature, both of which are likely to increase in the future.
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Salt Marsh Light Use Efficiency is Driven by Environmental Gradients and Species‐Specific Physiology and Morphology
Abstract Light use efficiency (LUE) of salt marshes has not been well studied but is central to production efficiency models (PEMs) used for estimating gross primary production (GPP). Salt marshes are typically dominated by a species monoculture, resulting in large areas with distinct morphology and physiology. We measured eddy covariance atmospheric CO2fluxes for two marshes dominated by a different species:Juncus roemerianusin Mississippi andSpartina alterniflorain Georgia. LUE for theJuncusmarsh (mean = 0.160 ± 0.004 g C mol−1photon), reported here for the first time, was on average similar to theSpartinamarsh (mean = 0.164 ± 0.003 g C mol−1photon). However,JuncusLUE had a greater range (0.073–0.49 g C mol−1photon) and higher variability (15.2%) than theSpartinamarsh (range: 0.035–0.36 g C mol−1photon; variability: 12.7%). We compared the responses of LUE across six environmental gradients.JuncusLUE was predominantly driven by cloudiness, photosynthetically active radiation (PAR), soil temperature, water table, and vapor pressure deficit.SpartinaLUE was driven by water table, air temperature, and cloudiness. We also tested how the definition of LUE (incident PAR vs. absorbed PAR) affected the magnitude of LUE and its response. We found LUE estimations using incident PAR underestimated LUE and masked day‐to‐day variability. Our findings suggest that salt marsh LUE parametrization should be species‐specific due to plant morphology and physiology and their geographic context. These findings can be used to improve PEMs for modeling blue carbon productivity.
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- Award ID(s):
- 1832178
- PAR ID:
- 10374716
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 126
- Issue:
- 5
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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