Yancheng National Nature Reserve Research Articles

Microplastics footprint in nature reserves-a case study on the microplastics in the guano from Yancheng Wetland Rare Birds National Nature Reserve, China

Bio-ingestion of microplastics poses a global threat to ecosystems, yet studies within nature reserves, crucial habitats for birds, remain scarce despite the well-documented ingestion of microplastics by avian species. Located in Jiangsu Province, China, the Yancheng Wetland Rare Birds Nature Reserve is home to diverse bird species, including many rare ones. This study aimed to assess the abundance and characteristics of microplastics in common bird species within the reserve, investigate microplastic enrichment across different species, and establish links between birds' habitat types and microplastic ingestion. Microplastics were extracted from the feces of 110 birds, with 84 particles identified from 37.27% of samples. Among 8 species studied, the average microplastic abundance ranged from 0.97 ± 0.47 to 43.43 ± 61.98 items per gram of feces, or 1.5 ± 0.87 to 3.4 ± 1.50 items per individual. The Swan goose (Anser cygnoides) exhibited the highest microplastic abundance per gram of feces, while the black-billed gull (Larus saundersi) had the highest abundance per individual. The predominant form of ingested microplastics among birds in the reserve was fibers, with polyethylene being the most common polymer type. Significant variations in plastic exposure were observed among species and between aquatic and terrestrial birds. This study represents the first quantitative assessment of microplastic concentrations in birds within the reserve, filling a crucial gap in research and providing insights for assessing microplastic pollution and guiding bird conservation efforts in aquatic and terrestrial environments.

Breeding records and the detection of nesting predators of wild-release red-crowned cranes into non-breeding areas of the Yancheng National Nature Reserve, China.

The western population of the red-crowned crane Grus japonensis in mainland China has been decreasing in the past few decades and wild population enhancement programmes have been launched in this country. First, 14 captive-bred red-crowned cranes were released into the core area of Yancheng National Nature Reserve for Rare Birds (YNNR), one of the most important wintering areas of this species, in 2013 (seven individuals) and 2015 (seven individuals) and then 8 more captive-bred cranes were released into YNNR from February 2022 to February 2023. We used satellite positioning and drone monitoring to study the status of released cranes. The results showed that two individuals (No. BJZ001 and BJZ008) from the first group of released cranes were found breeding in 6 of 7 years in the YNNR from 2017 to 2023. Three individuals (No. WNNR022, WNNR025 and WNNR026) from the second group of released cranes were recorded breeding in YNNR in 2023. All released cranes lived in the YNNR year round and did not migrate with wild cranes. Raccoon dogs, Nyctereutes procyonoides, were first recorded as red-crowned crane nest predators in the YNNR. Although these released cranes breed successfully in the YNNR, nestlings might face the threat of predators in non-traditional breeding areas. Further research is needed to determine whether offsprings of released individuals migrate with wild cranes and if breeding in their original wintering grounds is truly beneficial for population growth.

Habitat utilization of the Eurasian spoonbill (Platalea leucorodia) wintering in the Yancheng National Nature Reserve: relative importance of artificial habitats

Coastal wetlands are among the most modified habitats because of the loss and degradation of tidal flats, resulting in a rapid decline in waterbirds migrating along flyways. Understanding the relative importance of multiple types of wetlands as habitats for waterbirds and the factors influencing their utilization could improve management effectiveness. During the wintering seasons of 2021-2022 and 2022-2023, we documented the distribution of Eurasian spoonbills (Platalea leucorodia), a wetland specialist, in the Yancheng National Nature Reserve (YNNR) and quantified the surrounding environments as influencing factors to assess the relationship between their habitat use patterns and environmental characteristics. Our results showed that spoonbills inhabit common seepweed (Suaeda glauca) marshes, reed (Phragmites australis) ponds, aquaculture ponds, and agricultural channels. Although natural wetlands supported a greater number of spoonbills in the YNNR, spoonbills were able to forage in artificial wetlands. The environmental features where the spoonbills were distributed were found to influence their habitat use, and the most important factor was water depth, followed by species richness and vegetation cover. These results demonstrated that spoonbills rely on both natural and artificial wetlands in the core and buffer zones of the YNNR. Our research thus underlined that conservation interventions of natural and artificial wetlands, such as controlling the water depth and diminishing human activities, might maximize the effects of total conservation outcomes for the Eurasian spoonbills, as well as for various coastal waterbirds with similar ecological requirements.

Research on Grus japonensis habitat requirements for developing restoration plans

As an endemic species in Asia, Grus japonensis reproduction and survival rely on natural wetland resources. In the Yancheng coastal wetlands, the wintering habitat of Grus japonensis had been destroyed due to rapid social and economic development. At the same time, its population also declined leading to land use changes. Therefore, it was urgent to conduct scientific restoration and management of the winter habitat. Based on the structural habitat demand for Grus japonensis, traffic light warning analysis and landscape structure index system were used to guide habitat restoration. The main conclusions were as follows: the population of Grus japonensis in Yancheng coastal wetlands reached its highest recorded number of 952 in 2000. The population showed a tendency to concentrate in the core area (CA) of the Yancheng National Nature Reserve (YNNR). The locations of restoration areas under yellow, green and peak historical state were determined by the traffic light warning analysis. Landscape indicator thresholds were set based on the landscape conditions of the habitat in 2000. After restoration, the habitat should contain at least two landscape types: Phragmites australis (P. australis), Suaeda salsa (S. salsa) and ponds, with a minimum patch area of 5.22–19.11 km2 and 5–17 patches. Habitat should be located at least 500 m from roads and farmland and 1000 m from residential areas. From the perspective of improving landscape diversity, “P. australis-pond habitat”, “P. australis-S. salsa habitat”, “Continuous P. australis habitat” and “Continuous S. salsa habitat” were constructed by landscape patterns. Finally, according to the land use situation around the habitat, the “Friendly” land use layout of “Salt marsh wetland--Low intensity ecological aquaculture pond--Farmland--Construction land” from sea to land was developed. This mode provides a reference for the habitat restoration of coastal wetlands.

Evaluation of soil fauna biodiversity in restored farmland for protection of wetland ecology by planting different crops

Wetlands play a crucial role in oxygen production, air purification, and quality maintenance. Thus, conservation of wetland is essential in response to natural and anthropogenic damaging activities. Restored farmland, utilized to repair the southern buffer zone of Jiangsu Yancheng Wetland National Nature Reserve for Rare Birds, was used to investigate and analyze the diversity of migratory birds and soil fauna. In this study, five different crops, colza oil, mustard, Chinese cabbage, wheat, and barley, were planted in the restored plots, which were foraged by overwintering migratory birds, resulting in low crop yield. The soil fauna biodiversity and biomass in the wheat, Chinese cabbage, and colza oil plots during winter were relatively rich, which attracted many migratory birds to roost and feed. The variability and population of migratory birds significantly improved (18 species and 164231 migratory birds), which was owed to soil fauna and planted crops. Therefore, based on the results of our study, farmland restoration could significantly enrich the biodiversity of soil fauna and migratory birds, improve the ecological environment of wetlands, and attract more migratory birds as inhabitants.

Responses of photosynthetic characteristics of Phragmites australis to simulated warming in salt marshes of the Yellow Sea and Bohai Sea, China.

Coastal wetlands are highly efficient in blue carbon sequestration. The impacts of climate warming on photosynthetic rates and light response characteristics of wetland plants would change the magnitude of carbon sequestration in coastal wetlands. We constructed warming observation stations in Phragmites australis (Phragmites) wetlands located in the Yellow River Delta in Dongying with dry climate, and in Yancheng by the Yellow Sea with wet climate. By using a Li-6800 photosynthesis system, we investigated the responses of simulated warming on photosynthetic characteristics of Phragmites in both wetlands, and compared the difference between months (June and August) in Dongying wetland. The results showed the photosynthetic rates of Phragmites were higher in June than in August. Warming increased net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs) and intercellular carbon dioxide concentration (Ci) in the two months, but the variability of Pn to warming was lower in August. The Pn and water use efficiency (WUE) of Phragmites in the Yancheng wetland were higher than Dongying wetland, and the maximum net photosynthetic rate (Pn max), light saturation point (LSP), apparent quantum efficiency (AQY), and dark respiration rate (Rd) of the former responded more positively to warming. The values of AQY, LSP and Pn max of Phragmites in the Yancheng wetlands were increased by 16.7%, 53.6% and 30.3%, respectively, in the warming plots. Our results suggested that warming could improve the utilization efficiency of weak light, the adaptability to strong light and photosynthetic potential of Phragmites under rainy and humid conditions. This study is of importance for accurately quantifying carbon sequestration of coastal wetlands at the regional and seasonal scales in the context of climate warming.

Multi-scale habitat selection modeling using combinatorial optimization of environmental covariates: A case study on nature reserve of red-crowned cranes

Multi-scale habitat selection modeling (HSM) has garnered attention due to its ability to incorporate scale dependence of species. The key of multi-scale HSM is to select the appropriate combination of scales for different resources or environmental conditions, and then construct a set of multi-scale environmental covariates as the features of HSM. However, the existing scale selection methods do not determine the combination of scales under a unified model. In this study, a combinatorial optimization approach is proposed. We regard the combination of different scales as a search space, and use a heuristic optimization algorithm to search for the best-fitting model to determine the optimal scales for each resource or environmental condition. In a case study conducted in Yancheng National Nature Reserve, the proposed approach is applied to model the habitat selection of the endangered red-crowned crane. We compare the proposed method with single-scale, random-scale and other multi-scale approaches. The results show that the combination of scales selected based on the proposed method obtained the best accuracy in the spatial prediction of habitat suitability with a test AUC of 0.865 for the daytime scenario and 0.932 for the nighttime scenario. Moreover, the selected scales are utilized to generate response curves, providing suggestions for habitat restoration and management of the red-crowned crane population in the nature reserve.

Pixel-based unique phenological feature composite method: tackle the challenges of Spartina alterniflora identification and salt marsh classification in mixed vegetations area

Coastal salt marshes are valuable wetland ecosystems, and obtaining accurate information on their spatial and temporal distribution is crucial. However, due to the strong spectral similarity among various types of salt marshes, distinguishing them is difficult, especially in areas with mixed salt marsh growth. In this study, we developed a pixel-based unique phenological feature composite method (PUpf-CM). First, we identified a unique phenological period for each type of salt marsh by analyzing the normalized difference vegetation index time-series of Spartina alterniflora (S. alterniflora) and native salt marshes [Suaeda salsa (S. salsa), Phragmites australis (P. australis), and Imperata cylindrica (I. cylindrica)] in Yancheng National Nature Reserve, Jiangsu Province, China. Then, we generated a composite image for each unique phenological period, maximizing the spectral separability between the corresponding salt marsh and background species. Second, we used the composite images obtained at the unique phenological period of S. alterniflora as input to the random forest classifier, achieving high precision identification of S. alterniflora. Compared with the previously developed pixel-based PUpf-CM, the overall accuracy (OA) of PUpf-CM was 98.26% to 99.42%, and the Kappa was 0.940 to 0.975, indicating an improvement of 0.87% to 4.94% and 0.031 to 0.179, respectively. Finally, we tested the possibility of applying PUpf-CM to salt marsh classification by stacking four composite images obtained at different unique phenological periods. We found that the maximum spectral separability was achieved for the combination of four unique phenological periods, and the OA and Kappa of the PUpf-CM-based salt marsh classification reached 97.54% and 0.969, respectively.

Distribution, sources and risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Yellow Sea coast, China

To study the distribution, sources, ecological/health risks, and the impact of regional economic variations on polycyclic aromatic hydrocarbons (PAHs) contaminations along the coast of the Yellow Sea in China, sediments from a broad coastal coverage were collected and analyzed. The total contents of 16 priority PAHs varied between 1.4 and 1675.9 ng/g except in the site of H18 (3191.4 ng/g) adjacent to Qingdao City, with an average value of 295.7 ng/g. PAH pollution along the coast presented a distinctive geographical feature, which was closely linked to local human activities, such as Rongcheng with industrial zones and aquacultural areas, and Yancheng Wetland with developed aquaculture. The source analysis results indicated that PAHs were mainly from pyrolytic sources, with smaller contributions from petroleum spills and combustion. Risk assessment suggested that PAH pollution along the Yellow Sea coast showed negligible biological risks and health risks in most areas.

Evolution and mammalian adaptation of H3 and H10 subtype avian influenza viruses in wild birds in Yancheng Wetland of China

Wild birds play a critical role in avian influenza virus (AIV) ecology and some outbreaks of avian influenza in human originate from wild birds, suggesting that epidemiological surveillance and interspecies-transmission analysis of AIVs in wild birds are critical. Since 2019, we have performed sampling in Yancheng Wetland along the East Asian-Australasian Flyway. Totally, 2054 fecal swabs were collected and one H3N8, two H3N1, one H10N8, and three H10N1 were isolated. Three H3 gene of AIVs we isolated belonged to Eurasian lineage, but the four H10 gene clustered into North American lineage. What’s more, the H3 and the foreign H10 gene had generated novel reassortants in Yancheng wetland. Receptor binding assay indicated that nearly all strains, except D369/H10N1, presented a dual receptor-binding profile and bound to avian-type receptor preferentially. In animal experiment, all isolates could infect mice without prior adaptation and induce histopathological changes in mice lungs, moreover, all H3 subtype AIVs obviously triggered weight loss of mice. In addition to lung and turbinate, D322/H3N1, D338/H3N8, D211/H10N8 and D266/H10N1 could spread to brain and kidney or liver or spleen, showing a wider range of tissue tropism. Multiple mutants associated with mammalian adaptation were also detected in all isolates according to molecular analysis. These findings revealed that H3 and H10 AIVs circulating in wild birds in Yancheng Wetland underwent complex reassortment and increased mammalian adaptation, which highlighted the necessity to monitor the diverse reassortment of AIVs in wild birds and evaluate the risks of H3 and H10 viruses to human health.

Effects of tidal flat reclamation on the stability of coastal wetland ecosystem services: A case study in Jiangsu Coast, China

Tidal flats have great potential to expand human living space and provide abundant resources. However, large-scale reclamation and development activities have had profound impacts on regional ecosystems, and it is important to grasp the comprehensive characteristics of the effects from a macro perspective. We selected the coastal area Jiangsu, China, as a typical area, and investigated the impact of reclamation on the coastal wetland system from the perspective of ecosystem services stability. The optimal equilibrium state was used as a benchmark and a stability deviation index (SDI) of ecosystem services was constructed by clarifying the connotation of stability. The stable state and evolution characteristics of ecosystems in different areas (coastal administrative areas, tidal flat areas, and Yancheng National Nature Reserve (YNNR)) were screened and evaluated. Based on the SDI, an overall ecological impact assessment system was developed, and the impact of tidal flat reclamation on ecological stability and its cumulative effects were quantified. The results showed that in the past 40 years, the overall ecological stability of Jiangsu coastal area was “Basically Stable (II)”, while that of the YNNR was “Weakly Stable (III)”. The impact of reclamation on the ecosystem stability of the coastal tidal flat area was significant, with a contribution rate of 73.5 %, and the threshold of stability transition in this area was reached when the reclamation amount was 1251.33 km2. The extent to which reclamation explained the stability variation in the core zone, buffer zone, and experimental zone of YNNR gradually decreased, indicating that the impact of reclamation was greater when strong protection measures were in place. The southern region will reach the maximum threshold of the cumulative effect of instability in 2072. This study provides ideas for the analysis of the comprehensive impact of reclamation on coastal wetland ecosystems, and can provide guidance for the efficient utilization and protection of tidal flats.

Cover Picture and Issue Information

Journal of EcologyVolume 110, Issue 10 p. 2265-2267 COVER PICTURE AND ISSUE INFORMATIONFree Access Cover Picture and Issue Information First published: 09 October 2022 https://doi.org/10.1111/1365-2745.13705AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover image: A drone photo of the iconic “Red Beach” coastal ecosystem located in Yancheng National Nature Reserve, Jiangsu Province, China. The dominant plant species are Suaeda salsa (red) and Spartina alterniflora (green). The ring-like pattern of Spartina alterniflora may be an indication of strong intra-specific competition that induces mortality of inner-circle individuals. Photograph by Guoyuan Chen. For full details see pages 2268–2287. Volume110, Issue10October 2022Pages 2265-2267 RelatedInformation

Satellite-Based Monitoring of Coastal Wetlands in Yancheng, Jiangsu Province, China

The dynamic process of the wetland can reflect its impact on the environment, and finding a balance point supporting harmonious coexistence between man and nature has become an issue of increasing concern. On the basis of previous studies that have focused on local coastal wetlands, the temporal and spatial changes and driving forces of wetlands in the Yancheng coastal area from 1991 to 2021 were analyzed over a larger area. According to the study findings: (1) The results of the study of the Yancheng coastal wetland with a larger scope differed significantly from findings resulting from a study of coastal wetland only. This difference was mainly reflected in the relatively stable situation of wetland ecology as a whole, while the changes in local surface features were more significant. (2) Natural wetlands were transformed into artificial wetlands and non-wetland types, and artificial wetlands were transformed into non-wetland types; additionally, reverse transformations and internal transformations of surface features also took place. For instance, the saltpan was transformed into mudflats (86.26 km2), and some mudflats into herbaceous vegetation (193.47 km2). (3) When analyzing the impact intensity of human activities on the Yancheng wetland, it was found that this factor has experienced a process of first rising and then falling. The index was 0.650, 0.653, 0.664, 0.661, and 0.641 in 1991, 2000, 2008, 2016, and 2021, respectively. (4) Lastly, an analysis of factors driving wetland change revealed that human factors were the most critical reasons for wetland landscape change. Our work can play a reference and inspiration role in the monitoring and protection of similar coastal wetlands.

Integrating two aspects analysis of hydrological connectivity based on structure and process to support muddy coastal restoration

With social and economic development and population growth, a series of human activities have intensified the destruction and degradation of muddy coastal wetlands, thus it is necessary to strengthen their protection and restoration. Hydrological connectivity is a basic condition for the existence and restoration of wetland ecosystems. This study selected the northern buffer zone of Yancheng National Nature Reserve (YNNR) as the research area. Combining field survey data with GF-2 remote sensing data, hydrological structure and process connectivity were integrated to evaluate the hydrological connectivity through internal and land-sea aspects. On this basis, the restoration priority area and the easy restoration area were determined by hot spot analysis and minimum unit of restoration. Our results showed that: 1) the hydrological connectivity within the region was great, with most of the total area. Land use types had a greater impact on the hydrological connectivity, and the hydrological connectivity of the farming pond area were generally higher than for farmland; 2) the sea-land hydrological connectivity decreased from the sea to the land, which was vertical with the coastal seawall, but the rate of change varied.; 3) the hydrological connectivity hotspot analysis showed that the site of the level 1 priority restoration was almost the same as the salt water dominant restoration area; the priority level 2 was in the freshwater dominant restoration area, accounting for 8.87% of the area; 4) the easy-to-restore areas were mainly distributed in the priority restoration areas of level 1–3, with an area of 11.7 km2, accounting for 6% of the study area. These research results can provide a better scientific basis for regional muddy wetland restoration planning activities.

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.

Novel Quantitative Method for Assessing Driving Forces of Landscape Succession: Case Study From Yancheng Coast, China

Variations in landscape patterns can provide key information on the effects human activity has on landscapes, and consequently, have received increased attention in recent years. This paper mainly deals with the spatio-temporal variation and driving force of the landscape pattern on the Yancheng coast using remote sensing and GIS. The results indicate the following: (1) The landscape was mostly farmland from 1984 to 2008, not wetlands. The landscape matrix changed from a situation in which the natural landscape was equal to the artificial landscape in 1984, while the latter was dominant between 1990 and 2008. The area of natural landscape decreased considerably—the proportion of natural landscapes was 51.07% in 1984, while it decreased to 28.82% in 2008. Artificial landscapes increased significantly—the majority of the increased artificial landscapes were farmland and aquaculture ponds. (2) The changes in these landscapes showed a trend, changing from natural landscapes to artificial landscapes. Salinity is the decisive factor of this fixed route o the landscape successions of the coast. (3) Although Yancheng wetland nature reserve was established in 1984 and was designated as a National Nature Reserve in 1992, anthropogenic activities on the Yancheng coast continue apace, and the trend of natural landscape loss has not changed. (4) According to the analysis of the landscape transition rate of the Yancheng coast during each phase, we concluded that the main driving force of coastal landscape succession was anthropogenic activities. Our method provides a novel quantitative method to assess the driving forces behind landscape successions.

Combination of GF-2 high spatial resolution imagery and land surface factors for predicting soil salinity of muddy coasts

The distribution of soil salinity in coastal wetlands determines gradient distribution and succession of vegetation communities. Due to the inaccessibility of mudflats in coastal areas, soil salinity prediction and mapping is necessary for biodiversity protection and ecological integrity. Yancheng National Nature Reserve (YNNR) is experiencing a salinity-induced invasion of Spartina alterniflora and degradation of native vegetation (Suaeda salsa) since the 1980s, with Suaeda salsa facing the dilemma of disappearing from YNNR. This study was aimed to establish comprehensive land surface factors, such as salinity indices, vegetation characteristics, location, terrain attributes and tidal creeks, for soil salinity mapping from 2015 to 2019. Multiple linear regression (MLR) and random forest (RF) linked land surface factors and soil salinity, and RMSE of the soil salinity predictions were 0.83 ds/m for MLR and 0.72 ds/m for RF. The RF model for soil salinity mapping was more suitable. The value of soil salinity varied from 0.9 ds/m to 5.2 ds/m and decreased year by year, with average values of 3.09 ds/m, 2.87 ds/m and 2.67 ds/m for RF in 2015, 2017 and 2019. The distance from sea and vegetation type were the two most important indicators to predict the distribution of soil salinity in these mudflats, thus better predictions on how to predict the response of vegetation communities to shifting soil salinity.

An eco-parametric method to derive sedimentation rates for coastal saltmarshes

The saltmarsh plant Spartina alterniflora was introduced to the Jiangsu coasts, China and serves as an ecological engineer to reduce near-bed shear stress, trap fine-grained sediments and protect the coast from wave-induced erosion. The saltmarshes thus could record the Spartina colonization-driven changes within the sedimentary layers. Based on these ecological and sedimentological changes in sediments, we present a new eco-parametric method to estimate the sedimentation rate for the newly-formed wetlands in the Yancheng Wetland Nature Reserve for Rare Birds, Jiangsu. Sediment cores and satellite imagery were used to identify the thickness of accumulated sediment layers and the time since the Spartina colonization. We defined the original ground on which Spartina alterniflora initially colonized using pigment concentrations, grain size and stable carbon isotopic compositions of organic matter (δ13C) in sediments. We also determined the time mark of the Spartina colonization by examining the Landsat images over 1982–2018 to discriminate the Spartina alterniflora from other native plants and geomorphological features. These two datasets yielded a sedimentation rate of 3.3 cm/yr for Core A and of 9.6 cm/yr for Core B, the latter evidenced by an increase of ~ 0.51 m in the bed level from 2008 to 2014. Combining the 210Pb dating method, we further estimated the sedimentation rate for the layers beneath the original ground, which was comparable to that of the bare flats in the Jiangsu coast. Even though this new method is only applicable to newly-formed saltmarshes, it helps identify the recent sedimentation events as well as reveal the environmental changes and the evolution of saltmarsh-bare flat systems due to the interplay between vegetation, hydrodynamics and sediment dynamics. It thus could be an efficient and cost-effective tool for an improved understanding of the response of coastal wetlands to a changing climate/environment.

Mapping an Invasive Plant Spartina alterniflora by Combining an Ensemble One-Class Classification Algorithm with a Phenological NDVI Time-Series Analysis Approach in Middle Coast of Jiangsu, China

Spartina alterniflora (S. alterniflora) is one of the worst plant invaders in the coastal wetlands of China. Accurate and repeatable mapping of S. alterniflora invasion is essential to develop cost-effective management strategies for conserving native biodiversity. Traditional remote-sensing-based mapping methods require a lot of fieldwork for sample collection. Moreover, our ability to detect this invasive species is still limited because of poor spectral separability between S. alterniflora and its co-dominant native plants. Therefore, we proposed a novel scheme that uses an ensemble one-class classifier (EOCC) in combination with phenological Normalized Difference Vegetation Index (NDVI) time-series analysis (TSA) to detect S. alterniflora. We evaluated the performance of the EOCC algorithm in two scenarios, i.e., single-scene analysis (SSA) and NDVI-TSA in the core zones of Yancheng National Natural Reserve (YNNR). Meanwhile, a fully supervised classifier support vector machine (SVM) was tested in the two scenarios for comparison. With these scenarios, the crucial phenological stages and the advantage of phenological NDVI-TSA in S. alterniflora recognition were also investigated. Results indicated the EOCC using only positive training data performed similarly well with the SVM trained on complete training data in the YNNR. Moreover, the EOCC algorithm presented a more robust transferability with notably higher classification accuracy than the SVM when being transferred to a second site, without a second training. Furthermore, when combined with the phenological NDVI-TSA, the EOCC algorithm presented more balanced sensitivity–specificity result, showing slightly better transferability than it performed in the best phenological stage (i.e., senescence stage of November). The achieved results (overall accuracy (OA), Kappa, and true skill statistic (TSS) were 92.92%, 0.843, and 0.834 for the YNNR, and OA, Kappa, and TSS were 90.94%, 0.815, and 0.825 for transferability to the non-training site) suggest that our detection scheme has a high potential for the mapping of S. alterniflora across different areas, and the EOCC algorithm can be a viable alternative to traditional supervised classification method for invasive plant detection.

The changes in antibiotic resistance genes during 86 years of the soil ripening process without anthropogenic activities

This study aimed to reveal the baseline of natural variations in antibiotic resistance genes (ARGs) in soil without anthropogenic activities over the decades. Nine soil samples with different time of soil formation were taken from the Yancheng Wetland National Nature Reserve, China. ARGs and mobile genetic elements (MGEs) were characterized using metagenomic analysis. A total of 196 and 192 subtypes of ARGs were detected in bulk soil and rhizosphere, respectively. The diversity and abundance of ARGs were stable during 69 years probably due to the alkaline pH soil environment but not due to antibiotics. Increases in ARGs after 86 years were probably attributed to more migrant birds inhabited compared with other sampling sites. Multidrug was the most abundant type, and largely shared by soil samples. It was further shown that soil samples could not be clearly distinguished, suggesting a slow process of succession of ARGs in the mudflat. The variation partitioning analysis revealed that the ARG profile was driven by the comprehensive effects exhibited by the bacterial community, MGEs, and environmental factors. Besides, pathogenic bacteria containing ARGs mediated by migrant birds in the area with 86 years of soil formation history nearing human settlements needed special attention. This study revealed the slow variations in ARGs in the soil ripening process without anthropogenic activities over decades, and it provided information for assessing the effect of human activities on the occurrence and dissemination of ARGs.