Physiological responses of Spartina alterniflora to varying environmental conditions in Virginia marshes

Abstract

Physiological measurements were used to investigate the dependence of photosynthesis on light, temperature, and intercellular carbon dioxide (CO 2 ) levels in the C 4 marsh grass Spartina alterniflora. Functional relationships between these environmental variables and S. alterniflora physiological responses were then used to improve C 4 -leaf photosynthesis models. Field studies were conducted in monocultures of S. alterniflora in Virginia, USA. On average, S. alterniflora exhibited lower light saturation values (*1000 lmol m -2 s -1 ) than observed in other C 4 plants. Maximum carbon assimilation rates and stomatal conductance to water vapor diffusion were 36 lmol (CO 2 ) m -2 s -1 and 200 mmol (H 2 O) m -2 s -1 , respectively. Analysis of assimilation-intercellular CO 2 and light response relationships were used to determine Arrhenius-type temperature functions for maximum rate of carboxylation (V cmax ), phosphoenolpyruvate carboxylase activity (V pmax ), and maximum electron transport rate (J max ). Maximum V cmax values of 105 lmol m -2 s -1 were observed at the leaf temperature of 311 K. Optimum V pmax values (80.6 lmol m -2 s -1 ) were observed at the foliage temperature of 308 K. The observed V pmax values were lower than those in other C 4 plants, whereas V cmax values were higher, and more representative of C 3 plants. Optimum J max values reached 138 lmol (electrons) m -2 s -1 at the foliage temperature of 305 K. In addition, the estimated CO 2 compensation points were in the range of C 3 or C 3 -C 4 intermediate plants, not those typical of C 4 plants. The present results indicate the possibility of a C 3 -C 4 intermediate or C 4 -like photosynthetic mechanism rather than the expected C 4 -biochemical pathway in S. alterniflora under field conditions. In a scenario of atmospheric warming and increased atmospheric CO 2 concentrations, S. alterniflora will likely respond positively to both changes. Such responses will result in increased S. alterniflora productivity, which is uncharacteristic of C 4 plants.Electronic supplementary material The online version of this article (

Carbon dioxide fluxes of an urban tidal marsh in the Hudson‐Raritan estuary

“…However, although in our study salinity exhibited a weak correlation, it provides a stressor to the grasses and may determine competitiveness [ Teal and Weishar , ; Wijte and Gallagher , ]. The salinity level changes may also explain some of the divergence found in earlier studies on S. alterniflora [ Howes et al , ; Jiang et al , ; Kathilankal et al , ; Kirwan et al , ]. In addition, salinity affects growth over longer periods of time and thus may determine the competitive advantage of one species over another [ Teal and Weishar , ; Wang et al , ; Wijte and Gallagher , ].…”

The role of elevation, relative sea-level history and vegetation transition in determining carbon distribution in Spartina alterniflora dominated salt marshes

“…In general, lower elevations with optimum growth conditions are characterized by relatively taller and highly productive vegetation communities. However, the distribution of vegetation characteristics and thus above-and below-ground carbon storage over a given area can vary largely depending on different factors including salinity levels and inundation (Kathilankal et al, 2011) that are directly affected by elevation. Thus, an improved understanding on the spatial heterogeneity of salt marsh vegetation distribution, and above-and below-ground carbon stocks, more specifically with respect to the elevation, will enable better understanding and thus improved predictions of the consequences of relative sea-level rise on their future roles as important carbon sinks.…”

Ecological parameter reductions, environmental regimes, and characteristic process diagram of carbon dioxide fluxes in coastal salt marshes

“…In contrast, in the low LUE zone (LUE < 0.002), the range of temperature and salinity were relatively low (~ ≤ 18 °C) and high (29-38 ppt), respectively. Although adequate sunlight was available for photosynthesis in the low LUE regime (average PAR = 1,130 µmol/m 2 /s) 45,46 , the CO 2 uptake (0.05-3 µmol/m 2 /s; Table 2) and corresponding LUE (< 0.002) were considerably low. Similar to the low LUE regime, salinity was very high (30-40 ppt) in the transitional regime where the range of temperature was comparable to the high LUE regime.…”