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- Title
Salt Marsh Light Use Efficiency is Driven by Environmental Gradients and Species‐Specific Physiology and Morphology.
- Authors
Hawman, Peter A.; Mishra, Deepak R.; O'Connell, Jessica L.; Cotten, David L.; Narron, Caroline R.; Mao, Lishen
- 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 CO2 fluxes for two marshes dominated by a different species: Juncus roemerianus in Mississippi and Spartina alterniflora in Georgia. LUE for the Juncus marsh (mean = 0.160 ± 0.004 g C mol−1 photon), reported here for the first time, was on average similar to the Spartina marsh (mean = 0.164 ± 0.003 g C mol−1 photon). However, Juncus LUE had a greater range (0.073–0.49 g C mol−1 photon) and higher variability (15.2%) than the Spartina marsh (range: 0.035–0.36 g C mol−1 photon; variability: 12.7%). We compared the responses of LUE across six environmental gradients. Juncus LUE was predominantly driven by cloudiness, photosynthetically active radiation (PAR), soil temperature, water table, and vapor pressure deficit. Spartina LUE 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. Plain Language Summary: To analyze salt marsh carbon budgets, we need to understand their photosynthetic efficiency under different environmental conditions. We studied a fundamental property of vegetation, called light use efficiency (LUE), which is the efficiency of marsh plants to utilize carbon dioxide and light to carry out photosynthesis. This is an important component of ecosystem productivity models that rely on satellite data to map landscape‐scale productivity. We focused on LUE in salt marsh vegetation, wherein existing salt marsh models, LUE has been parameterized with only a few environmental variables and not distinguished by species. Salt marshes often consist of different species and can represent wide‐ranging environmental conditions depending on their location. We compared two marshes dominated by different species to examine their LUE. We found that relationships between LUE and environmental conditions vary with species and geographic characteristics. We have summarized the relationship between a variety of environmental parameters and salt marsh LUE. Ours is the first study to report the LUE of a Juncus marsh, a dominant brackish marsh species in the southeast US. Our findings will help in improving salt marsh productivity modeling, particularly when using satellite data. Key Points: Salt marsh light use efficiency (LUE) variation was explained by species‐specific canopy structure and tolerances to radiation, temperature, and water tableThe magnitude of LUE varied with the definition used, and those differences were dependent on canopy density and greennessJuncus roemerianus LUE, measured for the first time, had a broader range and fluctuation than Spartina alterniflora
- Subjects
SALT marshes; PRIMARY productivity (Biology); REMOTE sensing; PLANT morphology; PLANT physiology; JUNCUS; SPARTINA
- Publication
Journal of Geophysical Research. Biogeosciences, 2021, Vol 126, Issue 5, p1
- ISSN
2169-8953
- Publication type
Article
- DOI
10.1029/2020JG006213