[Characteristics of Soil Carbon, Nitrogen, Phosphorus, and Ecological Stoichiometry in Vegetable Fields and Orchard in the Coastal Area of Fuzhou].

The soil ecological stoichiometric characteristics of different agricultural land use types have a certain indicator function for characterizing the level of soil nutrient supply and are of great significance to the management of nutrient resources in farmland ecosystems. In order to reveal the soil carbon (C), nitrogen (N), and phosphorus (P) contents and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land use types, this study took vegetable fields (taro field and jicama field) and orchards (citrus tree orchard, watermelon field, and pear tree orchard) as the research objects in the coastal area of Fuzhou City. The contents of soil C, N, and P and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land uses were measured and analyzed. The soil C and N contents were in the order of orchard>vegetable field (P<0.05). The C content in the citrus tree orchard was the highest (4.44 g·kg-1), and the N content in the watermelon field was the highest (1.46 g·kg-1). The soil P content was vegetable field>orchard (P<0.05), and the jicama field had the highest P content (0.19 g·kg-1). The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) were orchard>vegetable field (P<0.05). Among them, the citrus tree orchard had the highest C/N (7.40) and C/P (61.43), and the watermelon field had the highest N/P (10.27). Soil N content was significantly and negatively correlated with bulk density and conductivity (r=-0.49, r=-0.28, P<0.05), and there was a significant and positive correlation with soil water content (r=0.61, P<0.05). C/P and C/N were significantly and positively correlated with SOM (r=0.71, r=0.64, P<0.01). In the process of crop planting and management in the coastal area of Fuzhou City, it is necessary to reasonably add nitrogen fertilizer to compensate for the N limitation, and slow-release nitrogen fertilizer is better for promoting the sustainable supply of nitrogen nutrients in the growth and development of crops.

[Soil Organic Carbon Storage, Active Component Contents, and Stability Along a Flooding Gradient in the Tidal Wetland of the Jiulong River Estuary].

Flooding is one of the key environmental factors affecting the carbon sequestration potential of estuarine tidal flat wetlands. In order to reveal the effect of flooding on soil carbon (C) sinks in estuarine tidal wetlands, we investigated and analyzed the soil organic carbon (SOC) storage, the contents of active SOC components, and SOC stability indicators across a tidal flat in the Jiulong River estuary in southeast China. The results showed that the SOC storage gradually decreased by 54% with the increase in flooding frequency. The change pattern of microbial biomass carbon (MBC), dissolved organic carbon (DOC), and liable organic carbon (LOC) followed the change pattern of the SOC storage. With the increase in flooding frequency, DOC/SOC and LOC/SOC increased by 80% and 26%, respectively, whereas MBC/SOC decreased by 29%. As flooding frequency increased, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) contents decreased by 81% and 35%, respectively. The decreases in POC contents were correlated with the increases in soil pH, whereas the decreases in MAOC contents were associated with the decline in clay contents. Soil carbon stability index (CSI) increased by 246% with increasing flooding frequency. These combined results indicated that SOC storage decreased, but SOC stability increased, with the increased flooding frequency. Mineral-bound organic carbon was the main protection mechanism for the SOC stability, which was of great significance to the soil C sink of the estuarine tidal wetlands.

[Latitudinal variations of seed functional traits of Phragmites australis in Chinese coastal marsh]. / 中国滨海沼泽湿地芦苇种子功能性状的纬度梯度变异.

Functional traits of seeds reflect plant reproductive strategies adapting to environmental changes, which is an evolutionary behavior in natural selection and genetics. Study on seed functional traits is of great significance to deeply understand the long-term adaptive evolution of plants and seeds. We measured seed functional traits of a main indigenous species Phragmites australis, including seed size, seed weight, seed set, and seed production, in nine coastal marshes of the six provinces/cities along the coastal zone of China (21°29'-40°57' N), and analyzed latitudinal variations of functional traits. The results showed that seed functional traits of P. australis in Chinese coastal marshes varied significantly with latitude and that there were significant correlations among different traits. Seed size (including seed length, seed width, seed shape index, aspect ratio, and seed surface area), and 100-seed weight showed significant quadratic function relation with latitude, which firstly decreased and then increased with the increases of latitude, while seed setting rate firstly increased and then reduced. There was a trade-off between the number and size of P. australis seeds. Seed production per unit area significantly increased with latitude. Results of stepwise regression analysis showed that climatic factors were the main driver resulting in the difference of seed functional traits of P. australis between latitudes, followed by pH and salinity of soil porewater.

[Effect of Increasing Tidewater Inundation on Porewater Geochemistries and CO2 and CH4 Effluxes in the Tidal Freshwater Marshes of the Minjiang River Estuary, Southeast China].

While the effect of increasing tidewater inundation caused by sea-level rise on carbon cycling had been well studied in saltmarshes, little is known about the effect of increasing tidewater inundation on CO2 and CH4 effluxes in the tidal freshwater marsh soils. Herein, the effects of tide inundation on porewater geochemistries (NH4+, NO3-, DOC, dissolved CH4, and DIC) and CH4 and CO2 effluxes were examined in the soils of tidal freshwater marshes in the Minjiang River Estuary, East China Sea. By applying "mesocosm" and a simulated tide pool, the tide inundation height increased by 15 cm and 30 cm over the control (CK). The CO2 effluxes decreased by 28.53% and 36.56%, and the dissolved CH4 concentrations increased by 47.83% and 73.91%, in treatments (CK+15 cm) and (CK+30 cm), respectively. The CH4 effluxes did not change significantly in the treatment (CK+15 cm), but increased by 29.27% in treatment (CK+30 cm). The increasing tidewater inundation had no significant impact on DOC concentrations, but increased NH4+ concentrations and decreased DIC and NO3- concentrations. Increasing tide inundation also reduced the temperature sensitivity of CH4 and CO2 effluxes. The study highlighted that the sea level rise-induced increase in tidewater inundation would decrease the annual global warming potential of tidal freshwater wetlands by 28% and 35% in the next 50 and 100 years, respectively.

[Nutrient Distribution of Overlying Water in Tidal Marshes in Five Estuaries and Bays of the Fuzhou Region in Autumn].

Overlying water from the tidal marshes in five estuaries and bays, namely, Xinghua Bay (Fuzhou Part), Fuqing Bay, Luoyuan Bay, Minjiang River Estuary, and Aojiang River Estuary of the Fuzhou region were collected in autumn of 2015, and the nitrogen and phosphorus nutrient concentration and other physical and chemical indicators of the overlying water were measured to discuss the reasons for the differences in the nutrient concentration of the overlying water in tidal marsh wetlands in different bays and estuaries. There were significant differences in the nitrogen and phosphorus nutrient concentrations of the overlying waters of the tidal marshes in the different bays and estuaries (P<0.05). The concentrations of nitrogen and phosphorus in Fuqing Bay were relatively high, while Xinghua Bay had the lowest nitrogen nutrient concentration and Aojiang River Estuary had the lowest phosphorus nutrient concentration. The nutrient concentration of the overlying water in Fuqing Bay is mainly affected by regional aquaculture, land-source pollution, and topography, while that in Xinghua Bay is mainly affected by tides. The vegetation type had an effect on the nutrient concentration of the overlying water in the wetlands. The concentration of nitrogenous nutrients in the overlying water of the marsh wetland in the Suaeda australis community was relatively high, while the nitrogen and phosphorus nutrient concentrations in the overlying water of the Spartina alterniflora community wetland was relatively low; the concentrations of nutrients in the overlying water of different plant communities in the same bay or estuary marsh wetland were different, and the relationships were complex. Tides, surface runoff, plant communities, topography, and human activities all had an important impact on the nutrient concentrations in the overlying waters of the bay and estuary wetlands.

[Parallel Factor Analysis of Fluorescence Excitation Emission Matrix Spectroscopy of CDOM from the Mid-culture Period of Shrimp Ponds in a Subtropical Estuary].

Components of chromophoric dissolved organic matter (CDOM) from eight coastal land-based shrimp ponds in the Minjiang, Mulan, and Jiulong rivers of subtropical southeastern China were determined by fluorescence excitation emission matrix spectroscopy combined with parallel factor analysis (EEMs-PARAFAC). Four separate fluorescence components, including two protein-like components (C1, C4) and two humic-like components (C2, C3), were identified as the dominant components of the CDOM in these shrimp ponds. The fluorescence indices (FI, BIX, and HIX) suggest that the CDOM of shrimp ponds shows low humification and is mainly derived from spontaneous sources. The protein-like and humic-like components have similar sources and exhibit a similar geochemical behavior. The salinity is negatively correlated with all CDOM fractions, whereas the DOC concentrations show only a positive correlation with the humic fractions of the CDOM. This study provides a scientific basis for the photochemical properties of CDOM in shrimp ponds.

[Diurnal Variations of CH4 and N2O Fluxes from the Drained Aquaculture Pond in the Minjiang River Estuary During Early Winter].

Annual drainage is a typical management activity practiced by operators as a way to export aquaculture effluent, accelerate aerobic decomposition of bottom soils, and avoid eutrophication during the non-culture period after harvest. Drainage activities can cause large changes in hydrology, nutrient cycling, sediment physicochemical properties, and even broad ecosystem functions. In order to understand the effects of drainage on the diurnal variation characteristics and magnitude of greenhouse gas (CH4 and N2O) fluxes from the aquaculture ponds of the estuaries, a 24-hour continuous monitoring was conducted from one undrained pond (UDP) and one drained pond (DP) during early winter in the Minjiang River estuary on the southeast coast of China. Over the entire study period, the fluxes of CH4 from the UDP and DP ranged from 0.04 to 0.10 mg·(m2·h)-1 and 14.04 to 33.72 mg·(m2·h)-1, respectively, with means of (0.07±0.01) mg·(m2·h)-1 and (24.74±2.33) mg·(m2·h)-1. The CH4 flux was lower during the day and higher at night with a net flux as the sources of the CH4. The fluxes of N2O from the UDP ranged from -0.027 to 0.011 mg·(m2·h)-1, and the average fluxes of (0.002±0.004) mg·(m2·h)-1 showed "weak absorption by day and emission at night." The N2O fluxes from the DP were emitted all day (ranging from 0.59 to 1.76 mg·(m2·h)-1) with the average fluxes of N2O (1.07±0.15) mg·(m2·h)-1 indicating higher fluxes at night and lower fluxes during the day. Our research demonstrated that drainage would significantly enhance CH4 and N2O release from the aquaculture ponds. The study also preliminarily confirms that the undrained pond converted to a drained pond considerably alter the diurnal variation characteristics of the CH4 and N2O emissions during early winter. Clearly, future measurements in situ at high frequency over a long time and at different spatial scales would be worth researching from drained aquaculture ponds.

[Diurnal Variations of Concentration of Porewater Dissolved CH4 and CO2 in a Brackish Marsh Dominated by Cyperus malaccensis and Phragmites australis During Neap and Spring Tidal Days in the Minjiang River Estuary].

Understanding of diurnal variation of soil porewater dissolved CO2 and CH4 concentration plays an important role in revealing carbon cycling in estuarine wetlands.During neap and spring tidal days in April and September 2010,the diurnal variations of soil porewater dissolved CO2 and CH4 concentrations and main impacting factors in a brackish marsh ecosystem dominated by two species of Cyperus malaccensis(brevifolius) and Phragmites australis(common reed) were determined in the ShanYutan in the Min River estuary,southeast China.The results showed that:① the soil porewater dissolved CH4 concentration during the spring and neap tidal days in April and September ranged from 88.20 to 190.74,53.42 to 141.24,16.27 to 81.89 and 44.90 to 88.53 µmol·L-1,respectively.The mean of dissolved CH4 concentration was higher at nighttime than at daytime during the spring and neap tidal days in April,but the mean of dissolved CH4 concentration was higher at daytime than at nighttime during the spring and neap tidal tidal days in September.② the soil porewater dissolved CO2 concentration during the spring and neap tidal days in September ranged from 19.33 to 40.1 µmol·L-1 and 9.69 to 29.96 µmol·L-1,respectively,and the dissolved CO2 concentration during daytime was lower than that at night;③ the mean of dissolved CO2 concentration was lower during the inundation period than in the exposed soil surface period,but the mean of dissolved CH4 concentration was higher during the inundation period than in the exposed soil surface period.

[Short-term Effects of Nitrogen Deposition on CO2 and CH4 Fluxes from Wetlands in the Minjiang River Estuary].

In order to evaluate the effects of nitrogen deposition on CO2 and CH4 fluxes from a Cyperus malaccensis marsh in the Min River estuary at Daoqingzhou, Fujian, static chamber-gas chromatography (GC) techniques were used. CO2 and CH4 fluxes at a control (CK)[0 g·(m2·a)-1], N1[24 g·(m2·a)-1], N2[48 g·(m2·a)-1], and N3[96 g·(m2·a)-1] were measured and analyzed and the related environmental factors were recorded. The results show that,① compared to the control treatment, the effects of nitrogen deposition on the CO2 fluxes for N1 and N3 increased by 20.30% and 4.06%, respectively, whereas the CO2 fluxes for N2 reduced by 10.05%, furthermore, the CO2 fluxes under different treatments were not significantly different (P>0.05), except for the N2 and N3 treatments in December (P<0.05). ② Compared to the control treatment, the effects of nitrogen deposition on CH4 fluxes at N1, N2, and N3 were increased by 64.51%, 30.23%, and 80.57%, respectively, whereas the CH4 fluxes under different treatments were not significantly different (P>0.05). ③ There was significant positive correlation between CO2 and CH4 fluxes and soil temperature (P<0.05), however, the CO2 and CH4 fluxes were not significant with regards to soil pH and soil EC (P>0.05).

[Short-term Effects of Nitrogen and Sulfate Addition on CH4 and CO2 Emissions in the Tidal Marsh of Minjiang River Estuary].

In April 2015, using enclosed static opaque chamber-GC techniques, the short-term effects of nitrogen and sulfate addition on the CH4 and CO2 emissions were measured in the Cyperus malaccensis marsh in the high tidal flat of the Minjiang River estuary, and the key factors controlling the variation of CH4 and CO2 were examined. The influences of nitrogen and sulfate addition on the CH4 and CO2 emissions were different in different time scales. CH4 emission increased significantly under the NH4Cl (NH) and NH4NO3+K2SO4 (NS) additions (P<0.01), CO2emission increased significantly with NS addition (P<0.05), but CH4 and CO2 emissions demonstrated an obvious fluctuation pattern with KNO3 (NO) and K2SO4(S) additions. Compared with the control (CK), average CH4 emissions increased by 286.36% and 122.73%, respectively, in the NH and NS addition treatments, average CO2 emissions increased by 39.92% and 34.24%, respectively, with the NH and NS additions treatments. The nitrogen and sulfate addition changed the temporal variation of CH4 and CO2emissions from the C. malaccensis wetlands in growing season. Significant correlations were found among CO2, CH4 emissions, and soil temperature, electrical conductivity (EC), DOC (dissolved organic carbon) and NH4+-N (P<0.05 or P<0.01) in the treatments with NH and NS additions; and soil temperature, EC, DOC and NO3--N (P<0.05 or P<0.01) in the treatments with NO and NS additions. Temperature, EC and nitrogen availability were the dominant factors controlling the temporal variations of CH4 and CO2emissions in estuarine tidal marsh ecosystem.

[Porewater Dissolved Methane in Cyperus malaccensis Marshes Along Salinity Gradient in the Minjiang River Estuary].

Physicochemical properties of soil and dissolved methane concentrations of porewater in the sediments of the Cyperus malaccensis marshes along a salinity gradient in the Minjiang River estuary were evaluated, and the spatial-temporal characteristics and main impact factors were discussed. The average concentrations of dissolved methane in porewater were 331.18, 299.94 and 638.58 µmol x L(-1), respectively in the Shanyutan, Bianfuzhou and Xiayangzhou wetlands in summer. In the winter, they were 9.04, 266.67 and 322.68 µmol x L(-1), respectively. The dissolved methane concentration in porewater was higher in summer than those in winter (P < 0.05). Overall, the concentrations of dissolved methane in porewatdr showed an increasing trend from brackish to freshwater marshes. Multivariate statistics analysis showed that the concentrations of dissolved methane in porewater was positively correlated with soils temperature and DOC (P < 0.05), but negatively correlated with soils pH, salinity, and the concentrations of porewater SO4(2-) and Cl-. Spatial-temporal distribution of porewater dissolved methane in estuarine marshes represents a final result of multiple factors, including soil physicochemical properties and hydrodynamic condition.

[Diurnal variations of greenhouse gas fluxes at the water-air interface of aquaculture ponds in the Min River estuary].

Wetland reclamation and aquaculture is one of the main disturbance types in coastal wetlands. Diurnal variations of CO2, CH4 and N2O fluxes at the water-air interface were determined using a floating chambers + gas chromatography method in a shrimp pond, and a mixed culture pond of fish and shrimp in October in the Shanyutan Wetland of the Min River estuary, southeast China. Meanwhile, the meteorological indicators in ground surface and physical, chemical and biological indicators of surface water were also measured. CO2, CH4 and N2O fluxes at the water-air interface all demonstrated distinct diurnal variations. Both shrimp pond and mixed culture pond of fish and shrimp functioned as a sink of CO2 [the diurnal averaged CO2 fluxes were -48.79 and -105.25 mg x (m2 x h)(-1), respectively], and a source of CH4 [the diurnal averaged CH4 fluxes were 1.00 and 5.74 mg x (m2 x h)(-1), respectively]; the diurnal averaged CO2 and CH4 fluxes at the water-air interface of the mixed culture of fish and shrimp pond were higher than that of the shrimp pond. Greenhouse gas fluxes at the water-air interface from the aquaculture ponds were influenced by many factors. Multiple stepwise regression analysis showed that the concentration of Chlorophyll was the major factor affecting the CO2 fluxes, and the concentrations of SO4(2-) and PO4(3-) were the major factors affecting the CH4 fluxes at the water-air interface of the shrimp pond; whereas water temperature and Chlorophyll were the major factors affecting the CO2 fluxes, and dissolved oxygen, PO4(3-) and pH were the major factors affecting the CH4 fluxes at the water-air interface of the mixed culture pond of fish and shrimp.

[Construction of Sjcb2 DNA vaccine and its expression in HeLa cells].

A recombinant plasmid containing cathepsin B endopeptidase of Schistosoma japonicum (Sjcb2) was constructed, indentified by PCR, restrictive enzyme, digestion and DNA sequencing, and expressed into mammalian cells. Immunochemistry examination showed that the Sjcb2 gene can be expressed in the eukaryotic system, providing a basis for the development of schistosome DNA vaccine.