Saltmarsh is one of the blue carbon ecosystems for the highest carbon burial efficiency.However,the buried carbon in saltmarsh may still be exported to coastal water through porewater exchange,a process that has often...Saltmarsh is one of the blue carbon ecosystems for the highest carbon burial efficiency.However,the buried carbon in saltmarsh may still be exported to coastal water through porewater exchange,a process that has often been overlooked in previous studies.A typical tidal creek of the Dongtan saltmarsh wetland in Chongming Island,Shanghai,China,was studied.The224Ra and223Ra activities were measured and the hydrological parameters such as water flow were determined,from which the porewater exchange rate in the tidal creek was estimated to be 1.78±1.73 cm/d.Meanwhile,the carbon concentrations in porewater were determined,based on which the fluxes of dissolved inorganic carbon(DIC),dissolved organic carbon(DOC),CH_(4),and CO_(2)exported from porewater exchange were derived to be 60±17,6.6±4.0,0.082±0.079,and 16±11 mmol/(m^(2)·d),respectively.In addition,analysis on different species of carbon in the creek water showed that,the fluxes of DIC,DOC,CH_(4),and CO_(2)exported laterally from tidal creek to coastal sea were 58±14,7.6±2.3,0.0011±0.00063,and 1.5±0.68 mmol/(m^(2)·d),respectively,indicating that the porewater exchange-derived carbon fluxes accounted for a large portion of the lateral carbon outwelling,and even much higher than those in CH_(4)and CO_(2)fluxes.Furthermore,the carbon exported from porewater exchange accounted for 50%of the carbon burial in the tidal creek system,of which DIC accounted for 73%of the total carbon flux transported by porewater exchange.Therefore,this study indicated that the porewater exchange-derived carbon fluxes to the tidal creek water may cause an overestimation in the carbon sequestration capacity of saltmarsh wetlands,and revealed the importance of porewater exchange for the carbon cycle of tidal creek system of saltmarsh wetlands.展开更多
A saltmarsh has developed rapidly on the mudflat of Andong Shoal,in southern Hangzhou Bay,over the last decade since embankment.The saltmarsh vegetation changes are driven by both sediment dynamic conditions and the c...A saltmarsh has developed rapidly on the mudflat of Andong Shoal,in southern Hangzhou Bay,over the last decade since embankment.The saltmarsh vegetation changes are driven by both sediment dynamic conditions and the competition between the exotic species Spartina alterniflora(S.alterniflora) and the native species Scirpus mariqueter(S.mariqueter).This study attempted to investigate large-scale spatial variations in the exotic and native species,by analyzing and interpreting a time series(2016-2018) of high-resolution(less than 1 m) remote sensing images.The total area of the saltmarsh increased at a rate of 1.07 km^2/year,due to the accretion of the whole tidal flat.The spatial patterns revealed a new bimodal pattern for S.alterniflora invasion.S.alterniflora expanded over the upper to middle saltmarsh at a rate of1.68 km2/year.However,the S.alterniflora patches at the seaward edge expanded at a negative rate of-0.005 km^2/year,indicating a different pattern in competition:S.alterniflora had more advantages in the upper saltmarsh,while S.mariqueter had more advantages in the pioneer zone with low elevation.Consequently,S.alterniflora mainly established new habitats by invading S.mariqueter in the middle saltmarsh,but S.mariqueter occupied the bare mudflat for tradeoff.Our results aindicated that the interspecific competition result between S.alterniflora and S.mariqueter depended on elevation,and low elevation might create a favorable environment for S.mariqueter to win the competition with exotic species.This finding could be applied to future invasive species control and saltmarsh management.展开更多
Background:Animals need to adjust their vigilance strategies when foraging between physically contrasting veg-etated and non-vegetated habitats.Vegetated habitats may pose a greater risk for some if vegetation charact...Background:Animals need to adjust their vigilance strategies when foraging between physically contrasting veg-etated and non-vegetated habitats.Vegetated habitats may pose a greater risk for some if vegetation characteristics function as a visual obstruction but benefit others if they serve as protective shelter.Variation in group size,presence of similar species,along with variation in environmental conditions and anthropogenic disturbance can also influence vigilance investment.Methods:In this study,we quantified the vigilance behaviour of two large-bodied,sympatric migratory curlew species-Far Eastern Curlew(Numenius madagascariensis)and Eurasian Curlew(N.arquata)-in vegetated Suaeda salsa saltmarsh and non-vegetated mudflat habitat in Liaohekou National Nature Reserve,China.We used linear mixed models to examine the effects of habitat type,season,tide time,flock size(conspecific and heterospecific),and human disturbance on curlew vigilance investment.Results:Both species spent a higher percentage of time under visual obstruction in S.salsa habitat compared to mudflat habitat but in response,only Far Eastern Curlew increased their percentage of vigilance time,indicating that visual obstruction in this habitat is only a concern for this species.There was no evidence that S.salsa vegetation served as a form of cryptic background colouration since neither species decreased their vigilance effect in S.salsa habitat in spring compared to the autumn migration season.The effect of curlew social environment(i.e.flock size)was habitat dependent since percentage of vigilance time by curlews in saltmarsh increased with both the number of individual curlews and number of other birds present,but not in mudflat habitat.Conclusions:We conclude that both migratory curlew species exhibit a flexible vigilance adjustment strategy to cope with the different environmental and social conditions of adjacent and sharply contrasting coastal habitats,and that the trade-off between the risks of foraging and the abundance of prey may be a relatively common phenom-enon in these and other shorebird populations.展开更多
The retreat of cliffs(lateral expansion)within tidal creeks results in a net loss of saltmarshes,but this retreat process can be retarded by root systems.To understand the interaction between root presence and bank se...The retreat of cliffs(lateral expansion)within tidal creeks results in a net loss of saltmarshes,but this retreat process can be retarded by root systems.To understand the interaction between root presence and bank sediment,quantitative measurements of two saltmarsh species root systems(Atriplex portulacoides and Juncus maritima)were carried out in a saltmarsh in Southern England,and their relationships with bank stability were examined.Computed Tomography(CT)Scanning techniques were used to investigate three-dimensional root architecture.The data obtained(e.g.,root volume,diameter,and distribution patterns of roots)were examined alongside more traditional root density measurements.The volumetric percentage,ratio between horizontal(lateral)and vertical roots(H/V ratio),and root diameter distribution are discussed in relation to their influence on bank sediment erosion threshold and shear strength.The results suggest that Atriplex portulacoides is more effective than Juncus maritimus in stabilising banks.This is because root systems that provide a high resistance to flow-induced erosion are better than those that provide a high resistance to gravity-induced erosion in stabilising cliff banks.This conclusion is relevant to future saltmarsh protection and re-establishment.展开更多
基金Supported by the National Key R&D Program of China(No.2022YFE0209300)the National Natural Science Foundation of China(Nos.42106043,42141016)。
文摘Saltmarsh is one of the blue carbon ecosystems for the highest carbon burial efficiency.However,the buried carbon in saltmarsh may still be exported to coastal water through porewater exchange,a process that has often been overlooked in previous studies.A typical tidal creek of the Dongtan saltmarsh wetland in Chongming Island,Shanghai,China,was studied.The224Ra and223Ra activities were measured and the hydrological parameters such as water flow were determined,from which the porewater exchange rate in the tidal creek was estimated to be 1.78±1.73 cm/d.Meanwhile,the carbon concentrations in porewater were determined,based on which the fluxes of dissolved inorganic carbon(DIC),dissolved organic carbon(DOC),CH_(4),and CO_(2)exported from porewater exchange were derived to be 60±17,6.6±4.0,0.082±0.079,and 16±11 mmol/(m^(2)·d),respectively.In addition,analysis on different species of carbon in the creek water showed that,the fluxes of DIC,DOC,CH_(4),and CO_(2)exported laterally from tidal creek to coastal sea were 58±14,7.6±2.3,0.0011±0.00063,and 1.5±0.68 mmol/(m^(2)·d),respectively,indicating that the porewater exchange-derived carbon fluxes accounted for a large portion of the lateral carbon outwelling,and even much higher than those in CH_(4)and CO_(2)fluxes.Furthermore,the carbon exported from porewater exchange accounted for 50%of the carbon burial in the tidal creek system,of which DIC accounted for 73%of the total carbon flux transported by porewater exchange.Therefore,this study indicated that the porewater exchange-derived carbon fluxes to the tidal creek water may cause an overestimation in the carbon sequestration capacity of saltmarsh wetlands,and revealed the importance of porewater exchange for the carbon cycle of tidal creek system of saltmarsh wetlands.
基金supported by the National Natural Science Foundation of China(Grant No.41776096).
文摘A saltmarsh has developed rapidly on the mudflat of Andong Shoal,in southern Hangzhou Bay,over the last decade since embankment.The saltmarsh vegetation changes are driven by both sediment dynamic conditions and the competition between the exotic species Spartina alterniflora(S.alterniflora) and the native species Scirpus mariqueter(S.mariqueter).This study attempted to investigate large-scale spatial variations in the exotic and native species,by analyzing and interpreting a time series(2016-2018) of high-resolution(less than 1 m) remote sensing images.The total area of the saltmarsh increased at a rate of 1.07 km^2/year,due to the accretion of the whole tidal flat.The spatial patterns revealed a new bimodal pattern for S.alterniflora invasion.S.alterniflora expanded over the upper to middle saltmarsh at a rate of1.68 km2/year.However,the S.alterniflora patches at the seaward edge expanded at a negative rate of-0.005 km^2/year,indicating a different pattern in competition:S.alterniflora had more advantages in the upper saltmarsh,while S.mariqueter had more advantages in the pioneer zone with low elevation.Consequently,S.alterniflora mainly established new habitats by invading S.mariqueter in the middle saltmarsh,but S.mariqueter occupied the bare mudflat for tradeoff.Our results aindicated that the interspecific competition result between S.alterniflora and S.mariqueter depended on elevation,and low elevation might create a favorable environment for S.mariqueter to win the competition with exotic species.This finding could be applied to future invasive species control and saltmarsh management.
基金supported by National Key Research and Develop-ment Program of China(No.2017YFC1403500 to JL)National Natural Science Foundation of China(No.31911540468 and 31672316 to DL)+1 种基金non-profit Foundation of Marine Environment and Ecological Conservation of CNOOC(CF-MEEC/TR/2020-20 to ZZ)Natural Science Foundation of Liaoning Province of China(2019-MS-154 to DL).
文摘Background:Animals need to adjust their vigilance strategies when foraging between physically contrasting veg-etated and non-vegetated habitats.Vegetated habitats may pose a greater risk for some if vegetation characteristics function as a visual obstruction but benefit others if they serve as protective shelter.Variation in group size,presence of similar species,along with variation in environmental conditions and anthropogenic disturbance can also influence vigilance investment.Methods:In this study,we quantified the vigilance behaviour of two large-bodied,sympatric migratory curlew species-Far Eastern Curlew(Numenius madagascariensis)and Eurasian Curlew(N.arquata)-in vegetated Suaeda salsa saltmarsh and non-vegetated mudflat habitat in Liaohekou National Nature Reserve,China.We used linear mixed models to examine the effects of habitat type,season,tide time,flock size(conspecific and heterospecific),and human disturbance on curlew vigilance investment.Results:Both species spent a higher percentage of time under visual obstruction in S.salsa habitat compared to mudflat habitat but in response,only Far Eastern Curlew increased their percentage of vigilance time,indicating that visual obstruction in this habitat is only a concern for this species.There was no evidence that S.salsa vegetation served as a form of cryptic background colouration since neither species decreased their vigilance effect in S.salsa habitat in spring compared to the autumn migration season.The effect of curlew social environment(i.e.flock size)was habitat dependent since percentage of vigilance time by curlews in saltmarsh increased with both the number of individual curlews and number of other birds present,but not in mudflat habitat.Conclusions:We conclude that both migratory curlew species exhibit a flexible vigilance adjustment strategy to cope with the different environmental and social conditions of adjacent and sharply contrasting coastal habitats,and that the trade-off between the risks of foraging and the abundance of prey may be a relatively common phenom-enon in these and other shorebird populations.
基金supported by a Dorothy Hodgkin Postgraduate Award(Grant No.EP/P500753/1)the preparation of the manuscript was funded by a NSFC Project(Grant No.41776096).
文摘The retreat of cliffs(lateral expansion)within tidal creeks results in a net loss of saltmarshes,but this retreat process can be retarded by root systems.To understand the interaction between root presence and bank sediment,quantitative measurements of two saltmarsh species root systems(Atriplex portulacoides and Juncus maritima)were carried out in a saltmarsh in Southern England,and their relationships with bank stability were examined.Computed Tomography(CT)Scanning techniques were used to investigate three-dimensional root architecture.The data obtained(e.g.,root volume,diameter,and distribution patterns of roots)were examined alongside more traditional root density measurements.The volumetric percentage,ratio between horizontal(lateral)and vertical roots(H/V ratio),and root diameter distribution are discussed in relation to their influence on bank sediment erosion threshold and shear strength.The results suggest that Atriplex portulacoides is more effective than Juncus maritimus in stabilising banks.This is because root systems that provide a high resistance to flow-induced erosion are better than those that provide a high resistance to gravity-induced erosion in stabilising cliff banks.This conclusion is relevant to future saltmarsh protection and re-establishment.
