Suaeda Salsa Research Articles

Variation in Bacterial Community Structure in Rhizosphere and Bulk Soils of Different Halophytes in the Yellow River Delta

Soil microorganisms play the important role in driving biogeochemical cycles. However, it is still unclear on soil microbial community characteristics and microbial driving mechanism in rhizosphere and bulk soils of different halophyte species. In this study, we analyzed bacterial communities in the rhizosphere and bulk soils of three typical halophytes in the Yellow River Delta, i.e., Phragmites communis, Suaeda salsa, and Aeluropus sinensis, by high-throughput sequencing. The contents of total carbon, total nitrogen, and available phosphorus in rhizosphere soils of the three halophytes were significantly higher than those in bulk soils, which suggested a nutrient enrichment effect of the rhizosphere. Rhizosphere soil bacterial α-diversity of P. communis was higher than that in bulk soil, whereas bacterial α-diversity in rhizosphere soil of S. salsa and A. sinensis was lower than those in bulk soil. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Chloroflexi, and Bacteroidetes, which accounted for 31, 20.5, 16.3, and 10.3%, respectively. LDA effect size (LEfSe) analysis showed that the bacterial species with significant differences in expression abundance was obviously different in the rhizosphere and bulk soil of three halophytes. The principal component analysis (PCoA) showed that bacterial community composition was greatly different between rhizosphere and bulk soils of P. communis and S. salsa, while no difference in A. sinensis. Changed bacterial community composition was mainly ascribed to salinity in rhizosphere and bulk soils. Additionally, salinity was positively correlated with Bacteroidetes and negatively correlated with Actinobacteria and Acidobacteria. Our study clarified the variation in bacterial community structure between rhizosphere and bulk soils with soil physicochemical properties, which proved a biological reference to indicate the characteristics of saline and alkaline land.

Effect of daily salinity fluctuation on the intraspecific interactions of a euhalophyte (Suaeda salsa) along a salinity gradient

AbstractHeterogeneity of soil salinity is a prominent environmental characteristic in the intertidal zone of estuaries, affecting the plant growth and the shift of biotic interactions in the salt marsh. This study aims to examine the interactive effects of a salinity gradient and salinity fluctuations on intraspecific interactions of a euhalophyte. We assessed the impact of daily fluctuating salinity on the outcome of intraspecific interactions by cultivating seeds of Suaeda salsa (Chenopodiaceae) in river sand. The experiment was conducted in a greenhouse with three treatments: daily salinity fluctuations (static and fluctuating salinity), a salinity gradient (200 and 400 mmol L−1) and three planting densities (1, 2 and 4 plants/pot). First, height and biomass of plants were measured at both the start and end of the experiment. Then, the growth indexes and log response ratio of S. salsa were analyzed. The outcome of intraspecific interactions of S. salsa shifted from competition in low salinity to facilitation in high salinity, and high conspecific density strengthened the competition and facilitation intensities. Daily salinity fluctuation did not significantly affect the plant growth and the outcome of intraspecific interactions, but did have a significant influence on belowground biomass. Our results suggest that the stress-gradient hypothesis may apply to predicting the variation of the intraspecific relationship of a salt-tolerant species along a salinity gradient, and the magnitude of this variation is density dependent. These findings help us understand how individuals and populations of a euhalophyte species respond to the natural variation or human modification of salinity conditions.

Assessing the Ecosystem Health of Coastal Wetland Vegetation (Suaeda salsa) Using the Pressure State Response Model, a Case of the Liao River Estuary in China.

Suaeda salsa (S. salsa) is an important ecological barrier and tourism resource in coastal wetland resources, and assessing changes in its health is beneficial for protecting the ecological health of wetlands and increasing finances. The aim was to explore improvements in the degradation of S. salsa communities in the Liao River Estuary National Nature Reserve since a wetland restoration project was carried out in Panjin, Liaoning Province, China, in 2015. In this study, landscape changes in the reserve were assessed based on Sentinel-2 images classification results from 2016 to 2019. A pressure-state-response framework was constructed to assess the annual degradation of S. salsa communities within the wetlands. The assessment results show that the area of S. salsa communities and water bodies decreased annually from 2016 to 2019, and the increased degradation indicators indicate a state of continued degradation. The area of types such as aquaculture ponds and Phragmites australis communities did not change much, while the estuarine mudflats increased year by year. The causes of S. salsa community degradation include anthropogenic impacts from abandoned aquaculture ponds and sluice control systems but also natural impacts from changes in the tidal amplitude and soil properties of the mudflats. The results also indicate that the living conditions of S. salsa in the Liao River estuary wetlands are poor and that anthropogenic disturbance is necessary to restore the original vegetation abundance.

辽河口盐地碱蓬湿地景观破碎化及驱动机制

湿地景观破碎化的加剧严重影响了湿地生物多样性保护和湿地生态系统服务功能的维持, 本研究以辽河口盐地碱蓬(Suaeda salsa)湿地为研究对象, 基于GIS平台构建1985-2019年间湿地景观数据库, 定量分析湿地景观破碎化特征及其驱动因素。结果表明: 1985-2019年间, 辽河口盐地碱蓬湿地呈退化趋势, 具体表现为湿地面积萎缩, 湿地景观破碎化加剧。盐地碱蓬湿地面积在1988年达到最大值4158.81 hm², 景观聚集度较高, 此后, 湿地景观破碎度出现先增大后减小再增大的波动变化, 2003年和2019年盐地碱蓬湿地景观破碎化最为严重, 破碎度分别达到5.90和7.89;影响辽河口盐地碱蓬湿地景观破碎化主要驱动因素为人为开发活动和水文过程; 景观破碎化的整体上升趋势与道路修建、农田开发、水产养殖、径流量和输沙量有较好的空间对应关系, 道路修建、农田开发和水产养殖面积的增加以及年径流量的减少是导致盐地碱蓬湿地景观破碎化的主导因素。;The intensification of wetland landscape fragmentation has seriously affected the protection of wetland biodiversity and the maintenance of wetland ecosystem service functions. This study took the Suaeda salsa wetland in the Liaohe River Estuary as the research object, and constructed the wetland landscape database from 1985 to 2019 based on the GIS platform, quantitative analysis of wetland landscape fragmentation characteristics and its driving factors. The results showed that from 1985 to 2019, the Suaeda salsa wetland in the Liaohe River Estuary showed a degrading trend, which was manifested in the shrinkage of wetland area and increased fragmentation of wetland landscape. The area of Suaeda salsa wetland reached its maximum of 4, 158.81 hectares in 1988, and the degree of landscape aggregation was relatively high. After that, the wetland landscape fragmentation first increased, then decreased and finally increased. Suaeda salsa wetland landscape fragmentation in 2003 and 2019 was the most serious, with fragmentation degrees reaching 5.90 and 7.89, respectively; the main driving factors affecting the landscape fragmentation of Suaeda salsa wetland in the Liaohe River Estuary were man-made development activities and hydrological processes; the overall upward trend of landscape fragmentation was related to road construction and farmland development. There was a good spatial correspondence between aquaculture, runoff and sediment transport. Road construction, farmland development, increase of aquaculture area, and reduction of runoff and sediment transport were the main factors leading to the fragmentation of the Suaeda salsa wetland landscape.

Tiny-Scene Embedding Network for Coastal Wetland Mapping Using Zhuhai-1 Hyperspectral Images

The fine mapping of coastal wetlands is a major challenge due to the spectral aliasing of vegetation. In this letter, we selected Zhuhai-1 hyperspectral images (HSIs) for coastal wetland mapping and proposed a tiny-scene embedding network (TSE-Net) based on scene representation and attention mechanism. In TSE-Net, the tiny-scene representation associated with each hyperspectral pixel was extracted and used to enhance the spectral discrimination of ground objects. DenseNet was chosen as the backbone network, and the attention mechanism was introduced into the dense blocks to extract remarkable features. Experiments on the Yellow River estuary coastal wetland showed that the results of TSE-Net had a significant improvement in accuracy compared to other models, especially for the coastal wetland vegetation with confusing spectra, such as Spartina alterniflora, Suaeda salsa, Phragmites australis, and Tamarix.

Seasonal Response of Suaeda Salsa to Hydrological Connectivity in Intertidal Salt Marshes Through Changing Trait Networks

Seasonal Response of Suaeda Salsa to Hydrological Connectivity in Intertidal Salt Marshes Through Changing Trait Networks

Citric Acid Can Enhance the Uptake and Accumulation of Organophosphate Esters (Opes) in Suaeda Salsa Rhizosphere: Potential for Phytoremediation

Citric Acid Can Enhance the Uptake and Accumulation of Organophosphate Esters (Opes) in Suaeda Salsa Rhizosphere: Potential for Phytoremediation

Characteristics of growth rates as a result of salt impact on seedlings of Suaeda

This article presents the experiment data on pre-sowing treatment of Suaeda salsa Pall. seeds by different concentrations of salts (Na2SO4 and NaCl) and soil extract solutions (0 %, 0.6 %, 1.2 %, 1.8 %, 2.8 %, and 3.6 %). The reaction of seedlings and young roots of S. salsa was observed, grown after treatment to salt solutions and soil extracts. In addition, based on the results of the growth of young roots and shoots which are exposed to salt, a comparative description of the growth rates of seedlings and young roots before and after salt stress was made. The results of the experiment showed that S. salsa seeds have a high germination capacity after the elimination of the high level of salt stress and soil extract solution. The significant changes in development rate of S. salsa juvenile root and shoot during and after the salt stress, as well as increasing the germination rate after influence of salt stress were noticed. It was discovered that the growth rates of young roots and shoots of S. salsa are different, salt solutions considerably inhibited the growth of roots of plants seedlings compared to soil extract solution. The salt concentration has a greater effect on roots development. It was found that after the removal of salt stress, the germination rate and regenerative capacity of S. salsa seedlings increased.

Evolutions of 30-Year Spatio-Temporal Distribution and Influencing Factors of Suaeda salsa in Bohai Bay, China

Suaeda salsa (L.) Pall. (S. salsa) acts as a pioneer species in coastal wetlands due to its high salt tolerance. It has significant biodiversity maintenance, socioeconomic values (e.g., tourism) due to its vibrant color, and carbon sequestration (blue carbon). Bohai Bay region, the mainly distributed area of S. salsa, is an economic intensive region with the largest economic aggregate and population in northern China. The coastal wetland is one of the most vulnerable ecosystems with the urbanization and economic developments. S. salsa in Bohai Bay has been changed significantly due to several threats to its habitat in past decades. In this paper, we analyzed all available archived Landsat TM/ETM+/OLI images of the Bohai Bay region by using a decision tree algorithm method based on the Google Earth Engine (GEE) platform to generate annual maps of S. salsa from 1990 to 2020 at a 30-m spatial resolution. The temporal-spatial dynamic changes in S. salsa were studied by landscape metric analysis. The influencing factors of S. salsa changes were analyzed based on principal component analysis (PCA) and a logistic regression model (LRM). The results showed that S. salsa was mainly distributed in three regions: the Liao River Delta (Liaoning Province), Yellow River Delta (Shandong Province), and Hai River Estuary (Hebei Province, Tianjin). During the past 31 years, the total area of S. salsa has dramatically decreased from 692.93 km2 to 51.04 km2, which means that 92.63% of the area of S. salsa in the Bohai Bay region was lost. In the 641.89 km2 area of S. salsa that was lost, 348.80 km2 of this area was converted to other anthropic land use categories, while 293.09 km2 was degraded to bare land. The landscape fragmentation of S. salsa has gradually intensified since 1990. National Nature Reserves have played an important role in the restoration of suitable S. salsa habitats. The analysis results for the natural influencing factors indicated that precipitation, temperature, elevation, and distance to the coastline were considered to be the major influencing factors for S. salsa changes. The results are valuable for monitoring the dynamic changes of S. salsa and can be used as effective factors for the restoration of S. salsa in coastal wetlands.

Effect of two organic fertilizers on some anatomical features of Pinus pinea L. seedlings grown in field and lathe house

Effect of two organic fertilizers on some anatomical features of Pinus pinea L. seedlings grown in field and lathe house

Improving soil fertility by driving microbial community changes in saline soils of Yellow River Delta under petroleum pollution

It is promising to use indigenous microorganisms for fertility improvement in petroleum-contaminated coastal soil. As a result, the microbial community and physicochemical property are the base for the restoration. For the detailed information, the Phragmites Communis (P), Chinese Tamarisk (C), Suaeda salsa (S), and new Bare Land (B) soil of Yellow River Delta was 90 g in 100 mL sterile bottles simulated at 25 °C with soil: petroleum = 10:1 in the incubator for four months. The samples were detected at 60 and 120 days along with untreated soil and aged Oil Sludge (O) as control. The results showed that all the samples were alkaline (pH 7.99–8.83), which the salinity and NO3− content of incubate soil followed the in situ samples as P (1.09–1.72‰, 8.02–8.17 mg kg−1), C (10.61–13.79‰, 5.99–6.07 mg kg−1), S (10.19–12.43‰, 3.64–4.22 mg kg−1), B (31.85–32.45‰, 3.56–3.72 mg kg−1) and O (31.61–34.30‰, 0.89–0.90 mg kg−1). NO3− and organic carbon decreased after incubation, which the polluted samples (86.63–92.63 g kg−1) still had higher organic carbon than untreated ones with more NH4+ consumption. The high-throughput sequence results showed that the Gammaproteobacteria and Alphaproteobacteria were dominant in all samples, while sulfate reducting bacteria Alphaproteobacteria decreased at 120 days. Meanwhile, the electroactive Gammaproteobacteria might symbiosis with Methanosaetaceae and Methanosarcinaceae, degrading petroleum after electron receptors depletion. Nitrososphaeraceae and Nitrosopumilaceae oxidise NH4+ to NO2− for intra-aerobic anaerobes and denitrifying bacteria producing oxygen for biodegradation in polluted Phragmites Communis soil. The halotolerant Halomicrobiaceae and Haloferacaceae predominated in saline Chinese Tamarisk, Suaeda Salsa and Bare Land, which were potential electroactive degradater. As the ageing sludge formed, the hydrogen trophic methanogens Methanothermobacteraceae (73.90–92.72%) was prevalent with the petroleum pollution. In conclusion, petroleum initiated two-phase in the sludge forming progress: electron acceptor consumption and electron transfer between degradater and methanogens. Based on the results, the domestic sewage N, P removal coupling and electron transport will be the basement for polluted soils fertility improvement.

Gracilibacillus suaedae sp. nov., an indole acetic acid-producing endophyte isolated from a root of Suaeda salsa.

A Gram-stain-positive, facultatively anaerobic, spore-forming, motile with unipolar biflagella, rod-shaped, indole acetic acid-producing bacterium, named LD4P30T, was isolated from a root of Suaeda salsa collected in Inner Mongolia, northern China. Strain LD4P30T grew at pH 6.0-11.0 (optimum, pH 7.0), 10-40 °C (35 °C) and in the presence of 1-15% (w/v) NaCl (5%). The strain was positive for oxidase and negative for catalase. The major cellular fatty acids of strain LD4P30T were iso-C15:0, C15:1 ω5c and anteiso-C15:0; the major polar lipids were diphosphatidylglycerol and phosphatidylglycerol; and menaquinone-7 was the only respiratory quinone. The genomic DNA G+C content was 36.7 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain LD4P30T clustered with Gracilibacillus thailandensis TP2-8T, Gracilibacillus saliphilus YIM 91119T and Gracilibacillus lacisalsi BH312T, and showed 99.0, 98.9, 98.0 and <97.7% 16S rRNA gene similarity to G. thailandensis TP2-8T, G. saliphilus YIM 91119T, G. lacisalsi BH312T and all other current type strains, respectively. The digital DNA-DNA hybridization and average nucleotide identity based on blast values between strain LD4P30T and G. saliphilus YIM 91119T, G. thailandensis TP2-8T and G. lacisalsi BH312T were 44.9, 44.7 and 44.4%, and 91.1, 91.0 and 90.8%, respectively. Based on its phenotypic, physiological and phylogenetic characteristics, strain LD4P30T represents a novel species, for which the name Gracilibacillus suaedae is proposed. The type strain is LD4P30T (=CGMCC 1.17697T=KCTC 82375T).

Impacts of Spartina alterniflora invasion on the benthic food web in the Yellow River Delta during autumn

Spartina alterniflora was introduced into the Yellow River Delta (YRD) in 1990 with the purpose of shore protection and siltation accretion. However, it spread rapidly and became a severe threat to the local coastal wetland ecosystem. To assess the impacts of S. alterniflora invasion on the benthic food web, we sampled the potential food sources of macrobenthos in November 2020, analyzed the trophic level and the benthic food web structure based on stable isotope technique. Results showed that the average δ13C values of macrobenthic food sources followed an order: sediment organic matter (SOM) > S. alterniflora > benthic microalgae > particulate organic matter (POM) > Suaeda salsa. The average δ15N values significantly differed among food sources, ranging from 1.24‰ to 9.03‰. The trophic levels of different macrobenthos ranged from 1.73 to 4.19, of which the bivalve species was the lowest one. S. alterniflora and the decayed debris were the most important food sources for macrobenthos, but without any impact on the trophic level structure of macro-benthos. In conclusion, Spartina alterniflora invasion distinctly changed the composition of food sources of macrobenthos through a "bottom-up" effect, which would probably impact the local food web structure in the YRD wetland.

Effect of different salts on the seed germination of halophyte Aksora (Suaeda Salsa Pall.)

The stress effects of a solution of salts and soil extract on the seeds of euhalophyte Aksora (Suaeda salsa Pall.) were studied. Treatment of euhalophyteSuaeda salsa Pall. seeds of salts (Na2SO4 and NaCl) and soil extract solutions in different concentrations (0; 0.6; 1.2; 1.8; 2.8; 3.6 g / 100 ml).Monitoring of the relationship between salts (Na2SO4 and NaCl) and soil extract solutions of grown Aksora seedlings after treatment. Additionally, provide the description of the germination of seedlings grown at different concentrations of solutions of different salts and soil extracts. Determination of endurance of seeds to different concentrations of Na2SO4 and NaCl salts and soil extract solution, based on the germination of Axora seeds. Study of the endurance of Axora seeds to salt stress. The experimental results showed that the growth rate of Aksora seedlings in different salts (Na2SO 4 and NaCl) and soil extracts is expected to be different. Based on the germination rate of seeds and Aksora seeds respond differently to stresses of different concentrations of Na2SO4 and NaCl salts and soil solution, the stress effect of Aksora seeds can be expressed by the following relationship NaCl&gt; soil extract&gt; Na2SO4. Due to the endurance of Aksora to salt stress, it was found that it is very prone to saline and saline soils. Key words:Saline soils, halophytes, Aksora (Suaeda).

Ionomic and Metabolomic Analyses Reveal Different Response Mechanisms to Saline-Alkali Stress Between Suaeda salsa Community and Puccinellia tenuiflora Community.

Soil salinization imposes severe stress to plants, inhibits plant growth, and severely limits agricultural productivity and land utilization. The response of a single plant to saline-alkali stress has been well investigated. However, the plant community that usually works as a group to defend against saline–alkali stress was neglected. To determine the functions of plant community, in our current work, Suaeda salsa (S. salsa) community and Puccinellia tenuiflora (P. tenuiflora) community, two communities that are widely distributed in Hulun Buir Grassland in Northeastern China, were selected as research objects. Ionomic and metabolomic were applied to compare the differences between S. salsa community and P. tenuiflora community from the aspects of ion transport and phenolic compound accumulation, respectively. Ionomic studies demonstrated that many macroelements, including potassium (K) and calcium (Ca), were highly accumulated in S. salsa community whereas microelement manganese (Mn) was highly accumulated in P. tenuiflora community. In S. salsa community, transportation of K to aboveground parts of plants helps to maintain high K+ and low Na+ concentrations whereas the accumulation of Ca triggers the salt overly sensitive (SOS)-Na+ system to efflux Na+. In P. tenuiflora community, enrichment of Mn in roots elevates the level of Mn-superoxide dismutase (SOD) and increases the resistance to saline–alkali stress. Metabolomic studies revealed the high levels of C6C1-compounds and C6C3C6-compounds in S. salsa community and also the high levels of C6C3-compounds in P. tenuiflora community. C6C1-compounds function as signaling molecules to defend against stress and may stimulate the accumulation of C6C3C6-compounds. C6C3-compounds contribute to the elimination of free radicals and the maintenance of cell morphology. Collectively, our findings determine the abundance of phenolic compounds and various elements in S. salsa community and P. tenuiflora community in Hulun Buir Grassland and we explored different responses of S. salsa community and P. tenuiflora community to cope with saline–alkali stress. Understanding of plant response strategies from the perspective of community teamwork may provide a feasible and novel way to transform salinization land.

Abiotic stress-by-competition interactions drive hormone and nutrient changes to regulate Suaeda salsa growth

During the growth cycle, complex and variable environmental conditions, such as salinity, moisture, nutrients, and plant-plant interactions, may prompt plants to modulate ecological strategies. As a typical halophyte, the response mechanism and adaptation strategy of Suaeda salsa to various abiotic stress-by-competition interactions are still unclear. In this study, we aimed to explore the responses of S. salsa to combined abiotic stress and competition conditions to gain further insights into the ecological adaptation of halophytes to stress conditions. In this study, we aimed to explore the responses of S. salsa to combined abiotic stress and competition conditions to gain further insights into the ecological adaptation of halophytes to stress conditions. In a pot experiment, we set five density gradients of 1, 3, 6, 9, and 12 plants and conducted salt and drought stress experiments to explore the ecological adaptation strategies under abiotic stress-by-competition and the direct and/or indirect effects of key endogenous hormones and nutrients on plant growth. The results demonstrated that drought and planting density were the main environmental factors that restricted growth. Drought decreased biomass accumulation and competition intensity and delayed reproductive phenology and senescence. Competition promoted early anthesis and fructescence and reduced the vegetative organ to reproductive organ ratio to improve fitness. Changes in hormone and nutrient levels driven by the environment directly and/or indirectly affected growth independently and/or jointly. Total leaf phosphorus content and the endogenous hormone strigolactones directly affected biomass in different interaction modes and had positive and negative effects, respectively. This study improves our understanding of the importance of hormones and nutrients in plant ecological adaptation strategies and provides an effective reference for explaining the physiological mechanisms of plant ecological adaptation.

Nitrogen cycling in plant and soil subsystems is driven by changes in soil salinity following coastal embankment in typical coastal saltmarsh ecosystems of Eastern China

Recently, coastal land reclamation through the use of embankments has increased worldwide, and its impacts on ecosystem processes and functionality have been widely reported. However, the ecosystem nitrogen (N) cycling turnover processes following the establishment of coastal embankments remain unknown. For this study, we investigated stocks of various types of N in soils, N storage in plant subsystems, the microbial immobilization and mineralization of N, as well as soil physiochemical properties in embanked and adjacent unembanked Spartina alterniflora, Suaeda salsa, and Phragmites australis saltmarshes in the coastal wetlands of China. Coastal embankments in a S. alterniflora saltmarsh significantly decreased the total plant N storage by 50.24%, concentrations of total soil organic N (SON) by 55.16%, ammonia nitrogen (NH4-N) by 32.33%, nitrite nitrogen (NO2-N) by 41.23%, nitrate nitrogen (NO3-N) by 13.38%, and the value of soil net ammonification (RA) by 83.49%. However, in P. australis saltmarshes they significantly increased the total plant N storage by 160.24%, concentrations of SON by 57.28%, NH4-N by 7.89%, NO2-N by 101.76%, NO3-N by 32.05%, and the value of RA by 392.95%. Nevertheless, there were no significant differences in N cycling following the establishment of coastal embankments in S. salsa saltmarshes. Significant changes in the organic and inorganic soil N pools of S. alterniflora and P. australis saltmarshes were driven by plant residue inputs, which were significantly affected by decreasing soil salinity in these coastal wetlands. Furthermore, our results indicated that coastal embankments altered the immobilization of soil N and mineralization of microorganisms by influencing the growth and activities of soil microbes, which were primarily associated with changes in soil organic and inorganic N pools following the development of coastal embankments. In summary, alterations in the organic N inputs of plants were initiated by the dramatically decreased soil salinity, which was the main determinant that drove N cycling in the soil subsystems of coastal wetlands subsequent to the establishment of coastal embankments.

Changes of mercury and methylmercury content and mercury methylation in Suaeda salsa soil under different salinity.

In this paper, we studied the changes of Hg and MeHg contents in Liaohe estuarine Suaeda salsa soils under anaerobic conditions by simulated indoor incubation at constant temperature and whether the changes of salinity (CK, 0.5%, 1.0%, 1.5%, 2.0%) affected SRB and dominated the formation of MeHg. The lowest Hg content is found in the subsurface Suaeda salsa soils at 2.0% salinity. The MeHg content in the soil also showed a general trend of increasing and then decreasing with increasing flooding salinity, and the MeHg content was higher at 0.5-1.0% flooding salinity. SRB was present in the soil under all salinity conditions and reached the maximum value at 15days of incubation. The SRB content was higher under CK, S1 and S2 conditions, and the soil MeHg content showed a significant positive correlation with the number of SRB bacteria, indicating that the formation of MeHg was related to SRB which is of great significance to the study of estuarine wetlands.

Canopy spectral characteristics of typical invasive and native plants in the coastal wetland of Yancheng City, China

Spartina alterniflora (S. alterniflora) is a dominant invasive alien species that occurs in Yancheng Wetland National Nature Reserve, the largest coastal wetland in China. It expands rapidly and exerts great threats to local ecosystem. The main native species there are Phragmites australis (P. australis) and Suaeda salsa (S. salsa), respectively. In order to monitor their dynamics, it is of great significance to analyze their spectral discrimination. Canopy spectra of these typical species were measured in July and October in order to compare species differences, as well as the seasonal variation. The Normalized Difference Vegetation Index (NDVI) was calculated based on canopy spectra. The significances of differences in spectral characteristic among species were tested using the one-way analysis of variance (ANOVA) (P < 0.05). The results showed that the visible (VI) bands were the optimum wavelengths for species discrimination in both seasons. S. alterniflora always had the greatest green peak height and red absorption depth. S. salsa had no obvious green peak, but an obvious red reflection peak. P. australis generally had intermediate values. Spectra in the near-infrared (NIR) bands were not appropriate for delineating S. alterniflora and P. australis in summer, as they showed similar values in these wavelengths. But NIR bands could be used to distinguish S. salsa in summer, as it had significantly lower reflectance in NIR bands than the others. Meanwhile, the reflectance in short-wavelength infrared (SWIR) bands became another suitable approach for distinguishing species in autumn. S. salsa had significantly higher values than the others in SWIR regions. Significant NDVI differences between different species proved that it could improve the species discrimination. S. alterniflora always had the highest NDVI values, while S. salsa had the lowest values. The seasonal trend of canopy spectra was also revealed. With plant maturity, the reflectance values in green bands and NIR bands decreased significantly, but increased significantly around the yellow-red wavelengths. The green peak heights, red absorption depths, and NDVI values of the species decreased remarkably. Furthermore, S. alterniflora and P. australis illustrated obvious ‘blue shift’ of the red edge with senescence. These results pointed out the the potential bands and appropriate spectral parameters appropriate for species discrimination, and highlighted the influence of seasonality on spectral information. They provided an important basis for salt marshes identification and dynamic monitoring on a large scale.

Growth characteristics of Suaeda salsa under different soil salinity gradients in controlled experiments

Xinjiang is the province with the largest saline-alkali land in China. The growth of halophytes will be stressed when their salt content reaches the threshold. In this study, the pot experiments were conducted and Suaeda salsa, a typical halophyte, was selected as the object to explore the relationship between growth characteristics and salt content under different soil salinity gradients. Salinity gradients were set according to the maximum soil salinity in the current years of Ebinur Lake Wetland National Nature Reserve (ELWNNR). They were classified using the following threshold values: ≤2 g/kg (Control Group), 10 g/kg, 20 g/kg, 30 g/kg, and 40 g/kg. The original spectrum, trilateral position and growth characteristics were used as indexes for analysis. With the increase of soil salt content, the red edge shift occurs first, followed by the blue edge shift. The position of yellow edge, green peak and blue edge were not sensitive with the change of soil salinity. This indicates that the red edge is the best indicator for evaluating plant growth. Compared with the Control Group, when the salt content is less than 10 g/kg, the growth status of plant seems not significantly affected. However, plant growth begins to be stressed when the salt content increases to 20 g/kg, which is a turning point for plant health. The increase of soil salt content can inhibit chlorophyll synthesis and plant growth. Plants begin to die when the salt content reaches the 40 g/kg. Therefore, 40 g/kg could be regarded as the critical point of salt content which inhibits plant growth. The study also shows that the relationship between plant-height change rate and soil salt content is the most significant, indicating that the plant-height change rate is significantly impacted by soil salt content. Keywords: Suaeda salsa, soil salt content, gradient, spectral, growth characteristics DOI: 10.25165/j.ijabe.20211405.5871 Citation: Zhang F, Chen Y, Yuan J, Ma L G, Liu C J. Growth characteristics of Suaeda salsa under different soil salinity gradients in controlled experiments. Int J Agric & Biol Eng, 2021; 14(5): 142–148.