In this study, in-situ simulated control experiments were conducted to investigate the effects of straw burial on vegetation recovery and carbon sequestration function of eutrophic salt marshes, by monitoring plant growth traits, photosynthetic characteristics, and greenhouse gas fluxes, as well as the soil organic carbon density measured at the end of the experiment. The results revealed that under a high exogenous nitrogen input, straw burial was beneficial for the growth of Phragmites australis and carbon sequestration of wetland, specifically by promoting CO2 uptake, inhibiting CH4 emissions, and increasing soil organic carbon density. The findings of this study aim to address the current lack of understanding regarding the carbon sequestration potential of salt marsh ecosystems. Through investigating the utilization of salt marsh straw, this study can provide technical support for vegetation restoration and carbon sequestration in the coastal wetlands, and may help promote the utilization of salt marsh straw.
The SLAMM (Sea Level Affecting Marshes Model) is employed to simulate a wetland’s evolution by considering scenarios of sea level rise and whether the wetland is protected by seawalls. This study investigates the effects of tidal range, slope, and land subsidence on wetland stability. The findings are as follows: ① Chongming Dongtan wetland will be reduced in size in future under the influence of sea level rise. From 2020 to 2050, its wetland area retention rate will be 0.732 ~ 0.763. In addition, the Chongming Dongtan wetland is expected to begin shrinking as early as 2039. ② The seawall in the restored area of Chongming Dongtan wetland can prevent reverse succession and transitional salt marsh during the response to sea level rise; ③ The changes in tidal range, slope, and land subsidence can affect the stability of the Chongming Dongtan wetland. If the goal is to stabilize Chongming Dongtan wetland by 2050, the tidal range must reach at least 3.0 meters or the slope of the profile must be above 2.06‰.
Estuarine wetlands are important components of coastal ecosystems that contribute tremendously to global blue carbon sinks. The amount and quality of dissolved organic matter (DOM) vary significantly with tidal exchange and seasonal cycles. Focusing on the Chongming Dongtan salt marshes in Shanghai under the influence of the Yangtze River, we conducted high-frequency sampling across a complete tidal cycle in each season and characterized the dynamics of the quantity (expressed by the C content in DOM, i.e., the concentration of dissolved organic carbon (DOC)) and spectral characteristics (expressed by the light absorption characteristics of chromophoric DOM (CDOM)) of DOM across tidal and seasonal scales. The results indicated that on the tidal scale, waters leaving the marshes during the ebbing tide were rich in DOC, strong in optical absorbance (${a_{{\rm{CDOM}}}} $(350) and ${a_{{\rm{CDOM}}}^*} $(350)), with high aromaticity (specific ultraviolet absorbance, SUVA254) and low spectral slope (S275-295), compared to water entering the marshes during the flooding tide. On a seasonal scale, waters in the ebbing tide during summer and fall had elevated DOC concentrations, high absorption and aromaticity, and correspondingly lower spectral slopes relative to waters collected in winter and spring. The results of on-site incubation experiments demonstrated that photochemical degradation was the major process that removed the colored fraction from the DOM pool, whereas microbial processing played an important role in affecting the bulk DOM. This study helps improve our understanding of the dynamics of marsh DOM and the mechanisms of its degradation processes associated with lateral transport from estuarine marshes to adjacent estuaries.
Scirpus mariqueter is a pioneer and keystone species of the salt marsh ecosystem in the Yangtze River Estuary. Seeds produced via sexual reproduction are the primary means of long-distance population dispersal. This study investigated the seed production, characteristics of dormancy, and germination of S. mariqueter populations along gradients of elevation in tidal flats using field surveys, seed storage experiments, and germination tests. The results of seed production studies showed that the elevation of tidal flats significantly influenced plant density and seed production of S. mariqueter (p < 0.05). Sampling areas at an elevation of 2.8 m and above were found to have the highest plant density and seed production at (682 ± 27) ind/m2 and (1724 ± 101) seeds/m2, respectively. Areas between 2.5 ~ 2.8 m of elevation had a plant density of (256 ± 41) ind/m2 and a seed production of (613 ± 101) seeds/m2. The lowest values were observed in sampling areas between 2.0 ~ 2.5 m elevation, with a plant density of (138 ± 27) ind/m2 and absence of seed production. The seed production of mature communities in suitable habitats could reach up to (1724 ± 101) seeds/m2. The results of seed storage, dormancy, and germination experiments showed that the seeds of S. mariqueter matured in autumn with an inherent dormancy state. After being buried in soil seed banks, the seeds enter enforced dormancy during winter. These seeds can germinate rapidly in spring when temperature and moisture conditions in favorable habitats become suitable. However, if the seeds experience environmental stresses during this period, such as deep sedimentation or flooding, they cannot germinate and instead will re-enter induced dormancy during the high temperatures of summer. Seeds in induced dormancy require another process of vernalization to break dormancy and germinate under suitable conditions. The seeds of S. mariqueter can survive for many years after entering induced dormancy and can be placed in a persistent seed bank. The findings of this study can contribute to a deeper understanding of the characteristics of seed biology for S. mariqueter and provide an important scientific basis for the ecological restoration and reconstruction of S. mariqueter populations.
中国综合性科技类核心期刊(北大核心)
