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In recent years, the Chinese government has implemented a series of initiatives with the objective of eradicating the invasive Spartina alterniflora along the entire coastline. This has given rise to concerns about the potential for subsequent coastal erosion and salt marsh shrinkage. This study introduces a novel contribution in the form of a model‐based analysis, grounded in fieldwork from the Yellow River Delta, which assesses the potential of native Suaeda salsa as an alternative for coastal protection. Our approach is distinctive in that it not only compares the flow velocity reduction effects of S. alterniflora and S. salsa, but also evaluates the efficacy of three distinct planting patterns in managing tidal dynamics. In this study, we present a significant finding: while both species can mitigate tidal flow velocity, S. alterniflora shows superior performance, which represents a novel point of discussion in the field of coastal wetland management. Furthermore, our research indicates that dense aggregated planting patterns are particularly effective during storm surges, offering a strategic insight for future ecological engineering. However, we recognize the potential limitations of our approach, including the need for continuous management to control the spread of S. alterniflora and the necessity for further research to optimize the restoration potential of S. salsa under varying tidal conditions. Our findings highlight the importance of a balanced approach, suggesting the retention of a portion of S. alterniflora while also emphasizing the strategic planting of S. salsa in high‐density configurations to enhance coastal resilience. [ABSTRACT FROM AUTHOR]

Salt‐tolerant Tamarix chinensis roots are crucial in preserving wetland soil and carbon sequestration, which is essential for wetland ecology. Soil‐water‐salt conditions influence the growth of these roots in coastal saline areas, but the specific factors and their effects remain unclear. Using principal component and partial least square–structural equation modelling (SEM) methods, we studied T. chinensis root features in six Yellow River delta communities. Results showed varied root features across locations, with larger roots further inland. Root growth negatively correlated with soil texture and salinity and positively with groundwater levels. Soil texture and salinity decreased with distance from the coast, while groundwater increased with distance from the Yellow River. This suggests that geographical location influences soil‐water‐salt conditions, impacting root characteristics. The principal component analysis–derived root feature index captured 56.7% of root feature variation. SEM revealed geographical locations indirectly influence root features, with the Yellow River's proximity primarily affecting them through groundwater and coastal distance influencing via soil sand content and salinity. The study underscores the importance of these findings for wetland conservation and ecology. [ABSTRACT FROM AUTHOR]

The Yellow River estuary and its delta areas are facing severe ecological challenges due to the issues such as seawater intrusion, backflow, and invasion of exotic species. These problems have led to the shrinkage of wetlands and a decline in biodiversity within the terrestrial ecosystem. This article gave a brief introduction to the primary measures of ecological protection in the Yellow River delta. Main methods, technologies, and engineering measures adopted for wetland restoration in this region were elaborated, especially for the species of Spartina alterniflora, including its status quo and issues for prevention and control. In order to overcome the main problems presented in the protection and restoration of the ecosystem of the Yellow River delta, the promising approaches suggested could include improving regulatory systems, strengthening coordination across sectors, applying tailored instruments, and leveraging the ecological function of sediment of the Yellow River discharged into the sea [ABSTRACT FROM AUTHOR]

The encroachment of woody shrubs in grass-dominated coastal salt marsh ecosystems has potentially influenced soil physical and chemical processes at various scales. Understanding the effects of shrub encroachment on those ecosystems requires assessments of the spatial heterogeneity in soil variables across multiple scales. Combined with GIS spatial tools and sampling data, we evaluated the vertical (0–80 cm) and spatial characteristics of soil pH and soil salinity (or electrical conductivity, EC) in a coastal wetland that experienced 40 years of shrub (specifically, the Tamarix chinensis species) encroachment. In order to obtain the information of the spatial patterns and scale domains of soil pH and EC, we employed the lacunarity analysis method. Furthermore, we utilized both Mantel test and Pearson correlation to identify their relationship. The results revealed that shrub encroachment had notable impacts on the magnitude and spatial patterns of soil pH and EC. These effects were driven by specific encroaching processes. Specifically, large shrub patches (SP) resulted in a significant rise in soil pH and a noteworthy reduction in soil EC. In addition, small shrub clusters (SC) caused a notable reduction in soil EC, but did not have significant impacts on soil pH. The impacts of shrubs on soil pH were primarily observed in 0–20 cm, whereas their effects on soil EC extended to deeper soil layers (e.g., up to 60 cm). Shrub encroachment also increased the landscape heterogeneity of both soil pH and EC, with the effects being more pronounced on soil EC. The lacunarity analysis revealed that the spatial heterogeneity of soil EC differed significantly among four depths, 0–20, 20–30, 30–60, and 60–80 cm, while the heterogeneity of soil pH varied significantly between two depths of 0–60 and 60–80 cm. Furthermore, soil pH and soil EC showed a strong spatial association, with a negative relationship observed between the two variables within each soil layer. Our study at the landscape scale highlights the opposite responses of soil pH and EC in saline-alkali wetlands to shrub encroachment. By understanding the impacts of shrubs on soil properties, we can enhance our ability to effectively restore and manage these degraded ecosystems. [ABSTRACT FROM AUTHOR]

Shrub encroachment in coastal wetlands leads to heterogeneous distribution of soil resources, which may affect soil particle size distribution (PSD). Fractal theory was widely used to quantify the characteristics of soil PSD. However, exploration on the spatial changes in PSD of deep soil layers due to shrub-encroached vegetation succession is limited. Multifractal theory and GIS spatial analysis tools were used to spatially quantify the changes in soil PSD at different soil layers (0–80 cm) in a coastal wetland landscape (100 × 120 m) encroached by a native shrub Tamarix chinensis in the Yellow River Delta (YRD), China. We also discussed the potential mechanisms of soil PSD changes contributed by shrub encroachment. The results showed that higher content of fine sand, medium sand and coarse sand, while lower content of silt and very fine sand in 0–10 cm were observed in T.chinensis patches than in single T. chinensis and bare land (p < 0.05). In 30–40 cm, however, T.chinensis patches have higher soil clay content (p < 0.05). The generalized dimensional spectrum and multifractal parameters indicated that soil PSD in shrub patch area exhibited greater width and higher heterogeneity. Multifractal method could explain the changes of soil PSD better than single fractal dimension (D), and the Capacity Dimension (D0) was the most effective one to quantify the soil PSD characteristics. The values of D0 showed a clear order of shrub patch > single shrub > bare land in each layer. In addition, the D0 suggested that influences of T.chinensis on soil PSD can remain 70 cm below the surface in our case. Considering the complex sedimentary process in the YRD, the processes of water and wind erosion mediated by shrub encroachment, the positive feedback based on plant preferences and the mixed effects of shrub and grass species might promote the redistribution of soil particle size. Encroachment in coastal wetland of the YRD caused changes in soil PSD, especially at the surface soil layer. Multifractal parameters could quantify subtle characteristics of soil PSD in shrub-encroached area. Our work indicates that shrub encroachment in coastal wetland plays a significant role in altering regional and even global soil environments.Highlights: The soil in Tamarix chinensis patches showed higher content of clay, fine sand, and medium sand than bare land as a result of shrub encroachment. Multifractal parameters, especially the capacity dimension (D0), were good indicators to reveal the characteristics of soil particle size distribution (PSD). The generalized dimensional spectrum indicated that soil PSD of T.chinensis patches have high heterogeneity. The impacts of shrub on soil PSD can extend up to 70 cm depth in this T.chinensis encroached area of the Yellow River Delta. [ABSTRACT FROM AUTHOR]

In recent years, nocturnal ozone enhancement (NOE) events have emerged as a prominent research focus in the field of the atmospheric environment. By using statistical analysis methods, we conducted a comparative investigation of nocturnal ozone concentrations and NOE events in Dongying, the central city of the Yellow River Delta, China, in 2022 and 2023, and further explored the effects of NOE events on O3 and PM2.5 on the same night and the subsequent day. The results showed that from 2022 to 2023, in Dongying, the annual average nocturnal ozone concentrations increased from 51 μg/m3 to 59 μg/m3, and the frequency of NOE events was higher in the spring, summer, and autumn, and lower in the winter. The NOE events not only exhibited promoting effects on nocturnal O3 and Ox, and on the daily maximum 8 h average concentration of O3 (MDA8-O3) on the same day (comparatively noticeable in summer and autumn), but also demonstrated a clear impact on nocturnal PM2.5 and PM2.5-bounded NO3− and SO42− (especially in winter). Additionally, the NOE events also led to higher concentrations of O3 and Ox, as well as higher MDA8-O3 levels during the subsequent day, with more observable impacts in the summer. The results could strengthen our understanding about NOE events and provide a scientific basis for the collaborative control of PM2.5 and O3 in urban areas in the Yellow River Delta in China. [ABSTRACT FROM AUTHOR]

The Yellow River Delta (YRD), a critical economic zone along China's eastern coast, also functions as a vital ecological reserve in the lower Yellow River. Amidst rapid industrialization and urbanization, the region has witnessed significant land use/cover changes (LUCC), impacting ecosystem services (ES) and ecological security patterns (ESP). Investigating LUCC's effects on ES and ESP in the YRD is crucial for ecological security and sustainable development. This study utilized the PLUS model to simulate 2030 land use scenarios, including natural development (NDS), economic development (EDS), and ecological protection scenarios (EPS). Subsequently, the InVEST model and circuit theory were applied to assess ES and ESP under varying LUCC scenarios from 2010 to 2030. Findings indicate: (1) Notable LUCC from 2010 to 2030, marked by decreasing cropland and increasing construction land and water bodies. (2) From 2010 to 2020, improvements were observed in carbon storage, water yield, soil retention, and habitat quality, whereas 2020-2030 saw increases in water yield and soil retention but declines in habitat quality and carbon storage. Among the scenarios, EPS showed superior performance in all four ES. (3) Between 2010 and 2030, ecological sources, corridors, and pinchpoints expanded, displaying significant spatial heterogeneity. The EPS scenario yielded the most substantial increases in ecological sources, corridors, and pinchpoints, totaling 582.89 km2, 645.03 km2, and 64.43 km2, respectively. This study highlights the importance of EPS, offering insightful scientific guidance for the YRD's sustainable development. [ABSTRACT FROM AUTHOR]

Soil salinization and nutrient deficiency limit agricultural production in the Yellow River Delta region. This study investigates the green manure-forage grass rotation on soil quality and productivity. A two-year field experiment was conducted to investigate the effects of different varieties of Sesbania cannabina and ᵡTriticosecale Wittm rotations on soil properties, biological characteristics, and adaptability in coastal saline-alkali land. Four cropping rotation systems were set: Gaoyuan 2 - Lujing 2 (G2L2), Gaoyuan 2 - Lujing 5 (G2L5), Gaoyuan 1640 - Lujing 2 (G1640L2), and Gaoyuan 1640 - Lujing 5 (G1640L5). The G2L5 rotation demonstrated superior enhancement of soil quality. The soil organic matter increased by 35.8%, and the soil electric conductivity (CEC) increased by 20.2%. Compared with T. Wittm, S. cannabina had a significant positive effect on soil physical and chemical properties. S. cannabina L5 showed improved performance in mass density, fresh weight of stem, leaf and aboveground part, etc. After S. cannabina returned to the field, T. Wittm G2 had greater plant height, thousand-grain weight, and stem weight, and the yield reached 322 kg per 667 m2. In conclusion, G2L5 is the recommended planting model in saline-alkali soil. This research offers valuable insight for the efficient planting and sustainable development of coastal saline-alkali land.

The Yellow River Delta wetland boasts a diverse range of vegetation species and harbors an ecosystem that is both sensitive and fragile, so it is of great practical significance to accurately extract the vegetation information and analyze the spatial and temporal changes of this region. Based on the hyperspectral image data of Zhuhai-1, this study selected the characteristic bands through the continuum removal method. It combined these spectral attributes with index-based characteristics, utilizing the random forest algorithm to classify prevalent vegetation types while subjecting the outcomes to thorough analysis. It was shown that (1) when integrating spectral features, red edge indices, water indices, and vegetation indices to classify five distinct vegetation types in the Yellow River Delta during 2020 and 2022, the random forest classification algorithm showed higher classification accuracy, and the study achieved commendable overall classification accuracy rates and Kappa coefficients of 85.92% and 0.84, and 86.25% and 0.84, respectively. (2) In 2020 and 2022, the distribution of vegetation in the Yellow River Delta exhibited the following order: Suaeda glauca > Phragmites > Spartina alterniflora > Tamarisk > Typha orientalis Presl. With the exception of Spartina alterniflora, all categories of vegetation witnessed an increase in their distribution areas. Phragmites experienced the most significant growth, with an area expansion of 9.42%. (3) The ecological restoration and management measures taken in the Yellow River Delta have proven notably effective. The proportion of Spartina alterniflora within the vegetation decreased by 3.45%, the native vegetation showed a resurgence, the distribution pattern of vegetation communities moved toward stability, and the total area of vegetation in the study area exhibited an upward trajectory. [ABSTRACT FROM AUTHOR]

In recent years, nocturnal ozone enhancement (NOE) events have emerged as a prominent research focus in the field of the atmospheric environment. By using statistical analysis methods, we conducted a comparative investigation of nocturnal ozone concentrations and NOE events in Dongying, the central city of the Yellow River Delta, China, in 2022 and 2023, and further explored the effects of NOE events on O3 and PM2.5 on the same night and the subsequent day. The results showed that from 2022 to 2023, in Dongying, the annual average nocturnal ozone concentrations increased from 51 μg/m3 to 59 μg/m3, and the frequency of NOE events was higher in the spring, summer, and autumn, and lower in the winter. The NOE events not only exhibited promoting effects on nocturnal O3 and Ox, and on the daily maximum 8 h average concentration of O3 (MDA8-O3) on the same day (comparatively noticeable in summer and autumn), but also demonstrated a clear impact on nocturnal PM2.5 and PM2.5-bounded NO3− and SO42− (especially in winter). Additionally, the NOE events also led to higher concentrations of O3 and Ox, as well as higher MDA8-O3 levels during the subsequent day, with more observable impacts in the summer. The results could strengthen our understanding about NOE events and provide a scientific basis for the collaborative control of PM2.5 and O3 in urban areas in the Yellow River Delta in China.

Oil exploration fragments coastal wetland habitats, which often leads to biodiversity loss and ecosystem degradation. Assessing the negative effects of oil infrastructures at the landscape scale is critical for practical coastal wetland management and the planning of protected areas (PAs). However, information gaps involving wetland connectivity and oil exploration exist in current conservation, which limit the efficiency of PAs.Here, we used a GIS-based circuit theory model (Circuitscape) and high-resolution remote sensing data to simulate the movement patterns of random species and to elucidate the effects of oil wells on their connective elements in four types of wetlands (mudflat, saline marsh, shrub wetland and forest wetland) in the Yellow River Delta (YRD), China. The effectiveness of the Yellow River Delta Nature Reserve (YRDNR) in protecting wetland connectivity was evaluated. A planning framework to optimize wetland conservation and restoration by Linkage Mapper was then provided to improve the landscape connectivity of oil well-disturbed wetlands in this region.The results showed that oil wells significantly decreased wetland connectivity and altered their connective elements in the four wetlands of the YRD. Both the resistance of wetland species movement and the heterogeneity of species dispersal have increased. The length of potential corridors and areas possessing barriers to movement have increased by 126 km (20%) and 51 km2 (120%), respectively. Areas with pinch points that promote species movements, however, decreased by 1178 km2 (60%). The YRDNR protected less than 50% of the key corridors and ecological nodes, considering the impacts of oil wells. Mudflat is seriously affected by oil wells in the YRDNR. Consequently, new alternative corridors produced by oil wells and pinch areas at high risk of impacts by oil wells have the highest protection priorities, whereas those permeable barrier areas, such as croplands and paddy fields, have the highest restoration priorities. The results also illustrated the importance of rivers and water bodies as potential shelters for wetland species.Our research suggests that circuit theory model is an effective planning tool to quantify the negative impacts of oil activities and to identify the protection or restoration priorities of ecological hot spots which are unable to be detected by traditional PAs method. This work provides guides for improving landscape connectivity and specifying target habitats for coastal conservation management.

Soil seed bank is the growth and reproduction source of vegetation community, playing an important role in vegetation establishment, succession and renewal, biodiversity maintenance. This study has selected the nascent wetland in the Yellow River Delta (YRD) formed in 1996 as study area and investigated the diversity and key influencing factors of soil seed bank diversity. The study results show that: (1) The soil seed bank in the study area has a simple structure, containing relatively few species. A total of five plant species, which belong to four families and five genera, were found in this bank, with Phragmites australis and Suaeda salsa being the dominant plants. (2) All species are herbs without woody species. One herb is annual herb and the others are perennial herbs. (3) From the sea to the river, the changes rules of the overall density and diversity of the seed bank are not obvious. (4) The dispersal distance from salt and freshwater has a significant influence on the density of the soil seed bank but has no significant influence on the diversity. Meanwhile, the soil salt content has a significant negative influence on the diversity of seed banks. (5) Aboveground vegetation did not closely relationship with diversity of soil seed bank. All above results can provide basic data and scientific evidence for the conservation of vegetation communities in the nascent wetlands and vegetation restoration in the degraded wetlands in the YRD. [ABSTRACT FROM AUTHOR]

The Yellow River Delta (YRD) is the most complete wetland ecosystem in the warm temperate zone of China and is rich in oil resources. However, with petroleum extraction and the development of the economy, pollution of the YRD has been paid increasing attention, in particular, pollution via polycyclic aromatic hydrocarbons (PAHs), as they have caused great harm to human health and the ecosystem balance. Based on the investigations of a research group in 2009, this study re-collected samples according to the same sampling points and analyzed the concentration, composition, source, ecological risk and health risk of PAHs in 2021. The concentration of ΣPAH16 in the surface soil of YRD in 2009 ranged from 2.6 to 8275.46 ng/g, with an average of 1744.41 ng/g. The concentration of ΣPAH16 in 2021 ranged from 56.25 to 582.56 ng/g, with an average of 149.63 ng/g. Therefore, the pollution situation in the YRD in 2021 was significantly improved compared with 2009. The composition of PAHs in soil in 2009 and 2021 was similar, which was dominated by low-ring PAHs. The evaluation results of the toxicity equivalent factor method showed that there was no potential ecological risk in the soil in 2009 and 2021. The evaluation results of the lifetime cancer risk increment model showed that the incremental lifetime cancer risk models (ILCRs) of soil PAHs in 2009 and 2021 were lower than the safety threshold of 10−6; therefore, there was no carcinogenic risk. The existing management measures for oil wells need to be further promoted to protect the regional ecological environment in the YRD. [ABSTRACT FROM AUTHOR]

The Yellow River Delta, located in China, experiences prevalent soil salinization and serves as a crucial ecological management zone within the Yellow River Basin. The shallow groundwater depth and high mineralization contribute to salt accumulation in the soil, which has a negative impact on crop growth. The sustainable use of saline land in the Yellow River Delta hinges on managing the soil salinity within the crop root zone. This study investigated the spatial distribution of soil salinity in coastal saline soil in the Yellow River Delta under various ridging configurations: triangular, arch, and trapezoidal, using flat land as a control. It also examined the impact of evaporation on soil salinity migration. The findings revealed that the ridge–furrow system successfully caused salt to accumulate in the superficial layer of the ridge. Among the three ridge shapes, the triangular ridge was the most effective at concentrating salt on the ridge surface, with 54.04% of the salt mass accumulation in the ridge's top layer (0–1 cm) and with the furrow bottom achieving a maximum desalination rate of 93.07%. The results implied that the triangular ridge fostered a favorable soil environment for crop growth by minimizing the salt content in the furrow. This research provides a theoretical foundation for the sustainable advancement of saline–alkali agriculture in the Yellow River Delta, which can lead to higher crop yields and better land management practices. [ABSTRACT FROM AUTHOR]

Land motions are significantly widespread in the Yellow River delta (YRD). There is, however, a lack of understanding of the delta-wide comprehensive deformation mode and its dynamic mechanism, especially triggered by groundwater extraction. This paper adopts an integrated analysis of multidisciplinary data of image geodesy, geophysics, geology and hydrogeology to provide insights into Earth surface displacement patterns and dynamics in the YRD. Delta-scale land motions were measured for the first time using L-band ALOS images processed using multi-temporal InSAR, illustrating multiple obvious surface sinking regions and a maximum annual subsidence velocity of up to 130 mm. Then, the InSAR-constrained distributed point source model with optimal kernel parameters, a smoothness factor of 10 and a model grid size of 300 m was established and confirmed to be rational, reliable and accurate for modeling analysis over the YRD. Remarkable horizontal surface displacements, moving towards and converging on a sinking center, were recovered by means of modeling and measured using InSAR, with a maximum rate of up to 60 mm per year, which can trigger significant disasters, such as ground fissures and building damage. In addition, the annual total water storage variation at the delta scale, the most meaningful outcome, can be calculated and reaches a total of approximately 12,010 × 103 m3 in Guangrao city, efficiently filling the gap of GRACE and in situ investigations for delta-wide aquifer monitoring. Finally, a comparative analysis of time series InSAR measurements, modeling outcomes, and fault and groundwater data was conducted, and the strong agreement demonstrates that faults control aquifer distribution and hence the spatial distribution of groundwater-withdrawal-related regional land subsidence. Moreover, the obvious asymmetric displacements, demonstrating a northeasterly displacement trend, further reveal that faults control aquifer distribution and Earth surface deformation. These findings are useful for understanding the land motion patterns and dynamics, helping to sustainably manage groundwater and control disasters in the YRD and elsewhere worldwide. [ABSTRACT FROM AUTHOR]

The Yellow River Delta (YRD) has China's largest artificial Robinia pseudoacacia forest, which was planted in the late 1970s and suffered extensive dieback in the 1990s. The health grade of the R.pseudoacacia forest (named canopy vigor grade, CVG) could be achieved by using high-resolution images and canopy vigor indicators (CVIs). However, a previous study showed that there was no significant correlation between CVG and the field-estimated aboveground biomass (AGB) of R.pseudoacacia forest. Therefore, this study aims to construct forest health indicators (FHIs) based on canopy spatial structure parameters extracted from LiDAR. The FHIs included Weibull_α (the scale parameter of the Weibull density function that reflects the shape of the tree canopy), VCI (vertical complexity index), sdCC (the standard deviation of canopy cover), H99 (the 99th percentile height) and cvLAD (the coefficient of variation of leaf area density), and could significantly distinguish three forest health grades (FHG) (p

The geomorphological stability and ecological environment of megadeltas worldwide are of vital importance for their sustainable development. Deltaic hydro-morphodynamics is extremely sensitive to high riverine flow due to reduced sediment supply. However, the morphological evolution and response of deltas under high riverine flow have remained inadequately quantified. As one of the typical megadeltas, the Yellow River Delta (YRD), is becoming increasingly sensitive to environmental changes and intensified human interventions. In this study, a numerical model and field data were used to investigate the hydrodynamic changes and morphodynamic evolution induced by extreme river discharge in the YRD. The numerical experiments with different runoff scenarios reveal that high-energy riverine floods can cause significant hydrodynamic changes in bed shear stresses, water levels, and flow velocities, particularly in the abandoned river mouth. Moreover, it enhances the ebb-dominated tidal asymmetry, which considerably intensifies fluvial sediment resuspension and transport processes. The results also show high-energy riverine floods in the flood seasons trigger severe erosion in the Yellow River submerged delta, with a net erosion volume reaching −0.07 × 108 m3/year. The hydrodynamic increment in the abandoned river mouth is more significant, and therefore, severe erosion occurs, with the maximum erosion thickness reaching 7 m. These findings highlight the role of high riverine floods on the hydro-sediment dynamics of large river deltas under a sediment starvation condition. [ABSTRACT FROM AUTHOR]

Soil salinization significantly restricts crop yield, animal foraging, and biomass production for biofuels. Identifying an efficient farming system to mitigate these concerns has become a major research focus. The present study addresses the potential of rotating triticale and sweet sorghum at various planting densities to alleviate soil salt stress, enhance production, improve agronomic characteristics, and boost soil microbial communities in a saline agricultural environment in East China. Several indicators in 2017 and 2018. Results show that triticale and sweet sorghum planting significantly decreased soil salt contents compared to bare land plots. Multiple agronomic traits were measured for each planting density. For triticale, a density of 180 × 104 plants ha−1 showed the best plant height, tiller number per plant, yield, and lodging rate; for sweet sorghum, a density of 7 × 104 plants/ha showed the best plant height, yield, and lodging rate. High-density planting of triticale (180, 260, 320 × 104 plants/ha) and sweet sorghum (7, 8, 9 × 104 plants/ha) was associated with high counts of bacteria, Actinomycetes, and salt-tolerant Actinomycetes. However, planting density had no significant effect on the counts of fungi or salt-tolerant bacteria. Redundancy Discriminant Analysis (RDA) showed that plant height, yield, lodging rate, bacteria, salt-tolerant bacteria, Actinomycetes, and salt-tolerant Actinomycetes were negatively correlated with soil salinity, while tiller number per plant and stem thickness were positively correlated with soil salinity. In conclusion, a rotation system of triticale and sweet sorghum with planting densities of 180 × 104 and 7 × 104 plants/ha, respectively was established to improve and make full use of saline soil. [ABSTRACT FROM AUTHOR]

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is highly popular due to its attractive taste and flavor of fruits. However, its cultivation is facing a serious obstacle for the substantial decrease in fruit soluble solids contents. In this study, four commonly-used fertilization types, including organic manure application (OM), combined application of manure and NPK fertilizer (OC), NPK fertilizer application at high rate (HC) and NPK fertilizer application at low rate (LC) were selected to investigate their effects on soil and fruit properties. Results showed that fertilization influenced soil organic matter (SOM) and NPK contents. Fruit yield decreased as HC (3.37tha−1) > OC (2.81tha−1) > OM (2.14tha−1) > LC (1.92tha−1).Total soluble solids (TSS), protein contents, and the ratio of TSS to titratable acid (TA) were highest in OM, followed by OC, LC and HC. TSS and TSS/TA ratio in OM were 23.0% and 27.0% higher than those in HC. Fruit yield was significantly positively correlated with soil available N, vegetative shoot leaf N, and total topsoil P contents. TSS and TSS/TA ratio both significantly positively correlated with SOM of topsoil and leaf P contents. Combined application of organic and inorganic fertilizers should be the optimal mode for winter jujube production. [ABSTRACT FROM AUTHOR]

To provide scientific basis for utilizing wetland resources, the drought conditions of different wetland types were evaluated in the Yellow River Delta. Based on the wetlands classification map, the difference in water and heat flux was studied, as well as the drought conditions in different wetlands. The relationship between the retrieved land surface temperature (LST) and evapotranspiration (ET) was analyzed through two section profiles in different directions using Geographic Information System (GIS) tools. The LST is relatively lower and the ET is relatively higher in areas mostly covered by wetlands of bush swamp, water body, saltern, and waterlogged lowland. On the whole, the ET values increase from inland to coastal areas, and the corresponding drought index decreases. There is a close negative correlation between ET and the regional water index (RWSI). The coefficients of the regression equations presented by different land use types such as swamp, built area, bush swamp, dry farmland, cultural pond, and other wetland types have slight differences. Generally, the non-wetland areas still show a large RWSI value, though the ET is relatively small. On the contrary, the artificial wetland is subjected to lower drought risk as indicated by its lower RWSI in spite of the high ET level. The RWSI of some natural wetland areas is larger than that of artificial ones, which indicates that proper utilization can reduce the drought risk to a certain extent in natural wetlands. Results showed that reasonable development of wetland resources may alleviate regional drought conditions. [ABSTRACT FROM AUTHOR]

Abstract Starting from the overall pattern of wetland evolution in the Yellow River Delta, the combination of CA–Markov model and MLP model is studied. Based on the low-medium resolution Landsat data and the field survey data, the evolution trend of wetland landscape pattern in the Yellow River Delta is simulated and predicted by using the proposed models. Taking high resolution (2 m) data in 2016 as the precision verification, the model simulation results are validated. The results show that the area of natural wetlands in the Delta was decreased from 2593.63 km2 in 1976 to 1639.60 km2 in 2016, a total area of 954.03 km2wasreduced. According to the model simulation, the natural wetland area in 2026 is predicted to be 1252.7 km2, the constructed wetland area will be 1265.0 km2, and the non-wetland area will be 924.5 km2. The constructed wetland in the Yellow River Delta is increasing and spreading into the sea, but the area of natural wetland has been decreasing. If this trend be developed, the national natural wetland conservation target would not be realized. The results are of great significance to the wetland development planning, management and protection in the Yellow River Delta.

Long Short-Term Memory (LSTM) is widely used in time series prediction, however, few people have noticed its predictions always lag behind corresponding measurements, which greatly reduces the predictive and warning capabilities of LSTM. The present paper proposes a new hybrid model that couples empirical/variational mode decomposition (E/VMD) and LSTM to solve the time lag problem in LSTM forecasting. Field significant wave height and wind speed data from three typical stations around the Shandong Peninsula: Cheng Dao (CD), Zhi-Fu Dao (ZFD) and Xiao-Mai Dao (XMD), were used to test the new model. All sites proved that the proposed model mitigated the time lag problem (for 12-h ahead prediction of CD, the lag is reduced from 3 to 1; for 12-h ahead prediction of XMD, the lag is reduced from 14 to 1) of LSTM while also increasing the accuracy (for 12-h ahead prediction of CD, the R 2 is improved from 0.544 to 0.906; for 12-h ahead prediction of XMD, the R 2 is improved from 0.291 to 0.781). The improvement is because VMD separates the high-frequency noise from the slowly varying low-frequency components, enhancing the stationarity of the original sequence. This method can be extended to other time series predictions. • A VMD-LSTM model is proposed for local wave height forecasting. • Lag issue is significantly mitigated even in 12-h ahead prediction at three sites. • 12-h ahead prediction R2 is kept over 0.9 at Cheng Dao. [ABSTRACT FROM AUTHOR]

Empirical models and process-based theoretical or numerical models are valuable tools for analyzing sediment dynamics by reproducing the suspended sediment concentration (SSC) observations, but they are either limited by simplified assumptions or computationally complex. Some data-driven models have been developed to predict SSC but are still weak in explaining the causes of its changes. A field observation of silty sediment dynamics was performed in the Yellow River Delta, China. Then, a vector autoregressive (VAR) model is employed to analyze and predict the SSC variations. Using the impulse response function, the VAR model quantifies the transient and cumulative responses of the SSC to storm and current shocks (i.e., the impulse input), which reveals the key mechanisms of SSC changes from a new perspective. Results show that the storm effect on SSC in the study area lasts for ca. 85 h, and the SSC peaks at around the 36th hour with a cumulative increase of about 1.3 g/L due to the storm's cumulative effect. Quantitative analysis reveals that waves contribute 73.78% to the SSC, while tidal currents contribute 26.22%. Fine SSC is significantly impacted by horizontal advection. A single reciprocal motion of the tidal current affects the SSC for approximately 6.25 h, while the overall duration exceeds 100 h. The proposed model physically reveals that the storm-induced high concentration gradient has been pushed back and forth by the tidal currents, affecting the SSC at the observation site, and the horizontal advection effect lasts for more than 100 h. Moreover, the VAR model achieves high-accuracy interval predictions of SSC for the next 5 h using only historical hydrodynamic data, with a 100% coverage probability of the 95% prediction interval. This paper provides a simple and efficient method for sediment dynamics analysis, which is of great significance for marine environment protection and disaster warning. • A vector autoregressive model is proposed to analyze fine-grained sediment dynamics. • The transient and cumulative responses of SSC to storm and currents are quantified. • The contributions of waves and currents to SSC variation are quantified. • High-accuracy SSC interval forecasting is achieved using historical field data. [ABSTRACT FROM AUTHOR]

The Yellow River Delta wetland boasts a diverse range of vegetation species and harbors an ecosystem that is both sensitive and fragile, so it is of great practical significance to accurately extract the vegetation information and analyze the spatial and temporal changes of this region. Based on the hyperspectral image data of Zhuhai-1, this study selected the characteristic bands through the continuum removal method. It combined these spectral attributes with index-based characteristics, utilizing the random forest algorithm to classify prevalent vegetation types while subjecting the outcomes to thorough analysis. It was shown that (1) when integrating spectral features, red edge indices, water indices, and vegetation indices to classify five distinct vegetation types in the Yellow River Delta during 2020 and 2022, the random forest classification algorithm showed higher classification accuracy, and the study achieved commendable overall classification accuracy rates and Kappa coefficients of 85.92% and 0.84, and 86.25% and 0.84, respectively. (2) In 2020 and 2022, the distribution of vegetation in the Yellow River Delta exhibited the following order: Suaeda glauca > Phragmites > Spartina alterniflora > Tamarisk > Typha orientalis Presl. With the exception of Spartina alterniflora, all categories of vegetation witnessed an increase in their distribution areas. Phragmites experienced the most significant growth, with an area expansion of 9.42%. (3) The ecological restoration and management measures taken in the Yellow River Delta have proven notably effective. The proportion of Spartina alterniflora within the vegetation decreased by 3.45%, the native vegetation showed a resurgence, the distribution pattern of vegetation communities moved toward stability, and the total area of vegetation in the study area exhibited an upward trajectory.

In recent years, with the decrease of water and sediment in the basin and the continuous diversion and change of the estuary tail, the Yellow River delta has shown different degrees of erosion in other areas except the current estuary entrance. Gudong coast is the area with the strongest erosion in the Yellow River delta. The evolution process and dynamic mechanism of seabed erosion have been widely concerned, but its scouring equilibrium depth and scouring limit have not been determined. Based on the cusp catastrophe theory, according to the characteristics of nearshore sediment movement, the sediment incipient model under the joint action of wave current and sediment was established, and the prediction formula of seabed scouring equilibrium depth was derived. Through the prediction formula calculation, the equilibrium depth of seabed scouring in Gudong offshore was between 6.5-7.5 m, which was consistent with the scouring limit depth of 6.8-7.2 m obtained from the analysis of coastal profile evolution process, which proved the applicability of sediment catastrophe model in predicting seabed scouring. The prediction results show that the seabed in front of the breakwater of Gudong coast will continue to scour for about 2 m, so it is very necessary to strengthen the daily maintenance of the breakwater protection project. [ABSTRACT FROM AUTHOR]

Salt stress and nutrient deficiency strongly limited the productivity of coastal saline-alkali land in the Yellow River Delta. Biochar has been widely used to improve soil health and promote crop yield, and the positive effects of nitrification inhibitors on fertilizer use efficiency, especially nitrogen, were also verified. However, there were few types of research on the combined application of biochar and nitrification inhibitor dicyandiamide (DCD) on saline-alkali soil of the Yellow River Delta, China. In this study, five treatments, including no nitrogen (CK), normal NPK (N), NPK + 1%biochar (B), NPK + 2%DCD (D), and NPK + 1%biochar + 2%DCD (BD) were set to investigate the single and combined effect of biochar and DCD on nitrogen transform, soil properties, bacterial community structure, and soybean production. Results showed that BD application inhibited nitrification and increased the soil's nitrate supply at the flowering stage, which reduced nitrogen waste and met the nitrogen demand for soybean growth. Biochar addition increased the soil's pH and decreased the soil's electrical conductivities and accelerated the soil's macroaggregates formation, with the soil's average mass diameter and geometric average diameter increasing by 78.69% and 30% in B, and 71.29% and 29.34% in BD relative to CK. Positive effects of inhibitors on soybean production were found in increasing soybean yield, hundred-grain weight, aboveground biomass, etc. Proteobacteria was the dominant phylum in the bacterial communities detected, and bacterial community diversity was significantly explained by nitrate content and soil aggregates (p < 0.05). Soil pH and DCD addition mainly influenced the abundance of the bacterial community, especially Actinobacteria. Biochar with DCD could be a feasible fertilization scheme for the coastal saline-alkali land in the Yellow River Delta, China. [ABSTRACT FROM AUTHOR]

Highlights: What are the main findings? Nitrogen fertilizer (urea) application ameliorated salt damage and promoted the growth of wheat; 270 kg/ha nitrogen was the optimal dosage for wheat cultivation in soils of typical agricultural areas of the Yellow River delta. What is the implication of the main finding? The finding is useful for rational utilization of nitrogen fertilizer and coastal saline agriculture development. Salt-affected soils is an important soil resource. Understanding fertilizer and salinity interaction are of great economic importance for improving crop yield and fertilizer use efficiency. A pot experiment was carried out to study the application of nitrogen (N) for ameliorating salt stress in wheat grown in the coastal saline soil of the Yellow River delta. Several controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg, and 135, 270, and 405 kg/ha) were designed in a pot experiment in a stable water content state to investigate the N and salt interaction on soil properties and winter wheat growth characteristics. The results showed that the dry weight of winter wheat was promoted by salinity in the early growth stage (20 days), then it was gradually inhibited by nitrogen fertilizer. When winter wheat was grown by 54 days, the N and salinity had significant effects on the biomass of winter wheat. The nitrogen content of wheat shoot and root was mainly affected by N addition usage, and the largest value was obtained in 270 kg/ha N dosage treatments. The higher the salt content existed in the soil, the lower the growth rate shown in wheat cultivation. Under saline conditions, the N fertilizer application amount should be controlled to no more than 270 kg/ha, so that it could greatly promote wheat growth. Reasonable fertilizer usage could significantly contribute to crop yield and food quality of the saline agriculture in the Yellow River delta. [ABSTRACT FROM AUTHOR]

Estuarine wetlands provide an especially ecological home for various flora and fauna, with fragile ecological structures and functions easily affected by the external disturbances of both anthropogenic and natural activities. Recently, wetlands (such as water and marsh) of the Bohai Rim region have been, and continue to be, lost or altered under the influence of both local urbanization and economic development. There is an increasing need for crucial essential wetland change detection as one of the most critical works for relevant research. The paper’s objective focuses on detecting the annual and interannual changes at a large spatial scale for understanding the mainly changed cover type of estuarine wetlands and measuring its impact on coastline ecological factors. Two typical study areas, including the Shuangtai Estuary wetland and Yellow River Delta, are selected for the assessment of changes to wetlands in Bohai Rim region, China. Additionally, Landsat TM/OLI images between 2005 and 2015, as the standard years for change detection, are used as the experimental data resources. To realize the rapid and automatic detection of change to wetland at a larger scale, a method is constructed to extract the change information from satellite images integrating the dynamic ratio and the max-difference algorithm. Based on the remote sensing base ecological index (RSEI), three ecological indexes include water body index, vegetation index, and soil index, calculated the annual maximum difference and the inter-annual dynamic rate of change to wetland. Furthermore, wetland changes are graded and evaluated five significant levels from the annual yearly and interannual scales. Results show several significant findings: (1) from 2005 to 2015, the ecological change with an overall improvement trend was in two monitoring areas of Bohai Rim region. The annual change of ecological factors in the positively changed area (improve) was more and more significant, with the mainly converted type of the expansion of paddy field. In the negatively changing area (degrade), annual ecological change was more and more insignificant, with the main expansion of bare land. (2) The significantly increased accumulation of normalized difference vegetation index (NDVI) was the main ecological change feature of the Shuangtai Estuary wetland. The significant regional changes in the Yellow River Delta were the interaction of ecological factors, included modified normalized difference water index (MNDWI), NDVI, and normalized difference soil index (NDSI). The study on the change detection of wetland and its influence on ecological factors in Bohai Rim region between two different periods enriches remote sensing monitoring technology of change to wetlands, betters quantitative evaluation of ecological factors, and provides updated data support for the wetland natural resource inventory at the various scales.

China's Yellow River Delta represents a typical area with moist semi-humid soil salinization, and its salinization has seriously affected the sustainable use of local resources. The use of remote sensing technology to understand changes in the spatial and temporal patterns of salinization is key to combating regional land degradation. In this study, a feature space model was constructed for remote sensing and monitoring land salinization using Landsat 8 OIL multi-spectral images. The feature parameters were paired to construct a feature space model; a total of eight feature space models were obtained. An accuracy analysis was conducted by combining salt-loving vegetation data with measured data, and the model demonstrating the highest accuracy was selected to develop salinization inversion maps for 2015 and 2020. The results showed that: (1) The total salinization area of the Yellow River Delta displayed a slight upward trend, increasing from 4244 km2 in 2015 to 4629 km2 in 2020. However, the area's salting degree reduced substantially, and the areas of saline soil and severe salinization were reduced in size; (2) The areas with reduced salinization severity were mainly concentrated in areas surrounding cities, and primarily comprised wetlands and some regions around the Bohai Sea; (3) Numerous factors such as the implementation of the "Bohai Granary" cultivation engagement plan, increase in human activities to greening local residential living environments, and seawater intrusion caused by the reduction of sediment contents have impacted the distribution of salinization areas in the Yellow River Delta; (4) The characteristic space method of salinization monitoring has better applicability and can be promoted in humid-sub humid regions. [ABSTRACT FROM AUTHOR]

Forest degradation is a worldwide problem, although its causes vary due to geographical and climatic differences and man-made causes. In recent years, the Robinia pseudoacacia forest in the Yellow River Delta has suffered severe degradation. The causative mechanisms were investigated in the field over two years, and the results show that increased forest degradation was reflected by increased tree mortality, high leaf and soil sodium salt levels and groundwater depth. Average tree diameters decreased, and leaf chlorophyll and soil microbial contents decreased. Redundancy discriminate analysis (RDA) showed that degradation of the forest was correlated positively with soil salt content, but negatively with groundwater depth. Correlation analysis showed that 0.79%–0.95% soil salt content and above 1.20 m groundwater depth caused the death of R. pseudoacacia trees due to localized anthropogenic economic activities, such as rice farming, that disrupted the original water–salt balance. Measures are recommended to prevent further degradation and restore degraded forests. [ABSTRACT FROM AUTHOR]

Starting from the overall pattern of wetland evolution in the Yellow River Delta, the combination of CA–Markov model and MLP model is studied. Based on the low-medium resolution Landsat data and the field survey data, the evolution trend of wetland landscape pattern in the Yellow River Delta is simulated and predicted by using the proposed models. Taking high resolution (2 m) data in 2016 as the precision verification, the model simulation results are validated. The results show that the area of natural wetlands in the Delta was decreased from 2593.63 km2 in 1976 to 1639.60 km2 in 2016, a total area of 954.03 km2wasreduced. According to the model simulation, the natural wetland area in 2026 is predicted to be 1252.7 km2, the constructed wetland area will be 1265.0 km2, and the non-wetland area will be 924.5 km2. The constructed wetland in the Yellow River Delta is increasing and spreading into the sea, but the area of natural wetland has been decreasing. If this trend be developed, the national natural wetland conservation target would not be realized. The results are of great significance to the wetland development planning, management and protection in the Yellow River Delta. [ABSTRACT FROM AUTHOR]

Blocking of hydrological connectivity could greatly impact the sediment deposition process and change water and salinity conditions, which in turn affect plant germination, growth, and development in delta wetlands. A 2-year experiment, which included the effects of soil burial, water, and salinity on germination, growth, and production, was conducted to examine the function of hydrological connectivity blocking on the development of Suaeda salsa, a halophyte species. The results demonstrated that soil burial, water, and salinity all had significant effects on seed germination, plant growth, and production (p < 0.05). Seed germination decreased as soil buried depth increased (< 4 cm), and seeds did not germinate successfully when the buried depth was > 4 cm. Seed germination was the highest at 0 cm burial. However, moderate burial was beneficial for seedling emergence; therefore, the survival rate was the lowest when seeds were distributed at the surface (0 cm). Water and salinity both significantly affected the germination, growth, and productivity of S. salsa. Moderate salinity (10–20 g/kg) and fluctuating water (0–10 cm water depth) were suitable for seed germination and plant growth. Low salinity (< 10 g/kg), High salinity (>20 g/kg), drought, and high water levels (long-term flooding with water depth > 10 cm) were not conducive to the growth of S. salsa, and biomass and seed yield were also reduced. As a halophyte, salinity that is too low or too high is unsuitable for S. salsa population. Water and salinity also significantly affected S. salsa population (p < 0.05). In particular, water can offset the hazards of high salt concentrations. Blocking of hydrological connectivity can influence seed germination, yield, and vitality. In this case, S. salsa may have died out from the coastal wetland due to the lack of hydrological connectivity restoration.

The soils from four typical natural wetlands, namely, Phragmites australis, Tamarix chinensis, Suaeda salsa, and tidal flat, as well as reclaimed wetland, were selected to evaluate the soil quality in the Yellow River Delta. Fourteen soil physicochemical property indexes were employed to build a minimum data set (MDS). Combined with vegetation type and soil depth, the soil quality index (SQI) was conducted. A fuzzy logic model was applied for data normalization. The contrast test was conducted to verify the accuracy of the MDS. The results showed that the MDS consists of TOC, NO3--N, soil salinity, TS, TP, Mg, C/N and pH. The soil quality decreased from the inland to the coastline and from reclaimed wetland to tidal flat with the change of vegetation type. The soil quality of 0–10 cm soil depth was better than that of 20–30 cm soil depth. The soil qualities of reclaimed land were significantly better than those of natural wetlands at the same soil depth. Correlation analysis results showed that agricultural reclamation has become an important factor of soil quality change in the study area. Comparative results of two methods of MDS and the total data set (TDS) testified that the method of MDS was credible and accurate for soil quality assessment of the study area. Our results indicated that wetland protection and agricultural reclamation in coastal areas should keep a rational balance.

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nested Delft 3D and Hydrus 1D models were applied to simulate variations in the hydrological process of tidal creeks, soil water, and salt transport in the soil profile of the reconstruction area in the Yellow River Delta under six gate dam scenarios. The results showed that the gate dam set up near the sea area was more conducive to reducing the variation range of water depth in the reconstruction area. The water depth changes in scenarios with 6 m gate valves were higher than those with 3 m sluice valves in the same gate dam location. The variations in surface water salinity, cumulative flooding time, flooding frequency, and cumulative infiltration in each scenario were similar to those for water depth. Rapid changes in soil water and salt content occurred in each scenario in periods without flooding. The fluctuation of soil salt content in different soil layers was contrary to the changes in soil water content. The overall difference in the soil salt contents and soil water content of the soil profile in scenarios with a gate dam near the sea was relatively larger than that of those with a gate dam near the shore. Obvious differences in both the soil water content and soil salt content between scenarios with 3 m and 6 m gate valves were not observed. Our results contribute to the understanding of the function of gate dams in controlling soil water and salt content in coastal wetlands. [ABSTRACT FROM AUTHOR]

Exotic species invasions have profound effects on native ecosystems, with the ecological effects of non‐native plants being especially pervasive. We investigated the impacts of a plant invasion on benthic invertebrate assemblages in intertidal wetlands of the Yellow River Delta, comparing benthic communities associated with exotic Spartina alterniflora against those associated with native plants (Tamarix chinensis, Suaeda salsa, and mudflat). Our study surprisingly found that the density, diversity, and richness of benthic invertebrates associated with S. alterniflora were higher than with native habitats. Multivariate analysis also revealed that the structure of benthic invertebrates in S. alterniflora habitats was different than in T. chinensis and mudflat habitats. The structure of invertebrates associated with the invasive S. alterniflora and native S. salsa was more similar, although the dominant species differed. Indicator species analyses indicated that each habitat was characterized by unique taxa. S. alterniflora invasion increased the beta diversity of the community, with the species turnover component being of most importance. Mollusks were most likely to be influenced by Spartina invasions. Given the extent of the S. alterniflora invasion in the Yellow River Delta, altered benthic invertebrate communities will likely have important implications for the ecology of the intertidal wetland ecosystems and deserve increased attention. [ABSTRACT FROM AUTHOR]

The Yellow River Delta (YRD) has China's largest artificial Robinia pseudoacacia forest, which was planted in the late 1970s and suffered extensive dieback in the 1990s. The health grade of the R.pseudoacacia forest (named canopy vigor grade, CVG) could be achieved by using high-resolution images and canopy vigor indicators (CVIs). However, a previous study showed that there was no significant correlation between CVG and the field-estimated aboveground biomass (AGB) of R.pseudoacacia forest. Therefore, this study aims to construct forest health indicators (FHIs) based on canopy spatial structure parameters extracted from LiDAR. The FHIs included Weibull_α (the scale parameter of the Weibull density function that reflects the shape of the tree canopy), VCI (vertical complexity index), sdCC (the standard deviation of canopy cover), H99 (the 99th percentile height) and cvLAD (the coefficient of variation of leaf area density), and could significantly distinguish three forest health grades (FHG) (p < 0.05). The FHG was positively correlated with forest AGB (rs = 0.51, p = 0.004), and the similarity value with CVG was 63.33%. The results of this study confirmed that the FHIs can reflect both canopy vigor and tree productivity, and distinguish forest health status without prior classification information. [ABSTRACT FROM AUTHOR]

Smooth cordgrass Spartina alterniflora, as a species for ecological engineering, was introduced to the Yellow River Delta (the YRD) in 1990. However, it expanded rapidly due to its strong compatibility and competitiveness in recent years. It would inevitably present severe threats to native plants and local macroinvertebrates. This study aimed to test the abiotic and biotic responses to the S. alterniflora invasion by analyzing the samples of pore-waters, sediments, and macrobenthos collected in different sites following the invasion chronology in August 2018. Results showed that with the invasion time, the contents of dissolved inorganic nitrogen (NOx− and NH4+) and phosphate (PO43−) increased, while the content of silicate (SiO32−) decreased in pore-water; the content of total organic matter (TOM) decreased firstly, and then increased in the sediment; the species composition of macrobenthos also changed significantly prolong invasion time, Crustacea disappeared, and Chironomidae occurred gradually; the values of the abundance, biomass, and biodiversity of macrobenthos decreased firstly and increased subsequently with invasion history. Our findings reflect the chronological effects of S. alterniflora invasion on the benthic environment and macrobenthic community, which contribute to establishing the linkage between the exotic plant invasion and benthic ecosystem, providing a scientific basis for wetland biodiversity conservation and resource management in the YRD. [ABSTRACT FROM AUTHOR]

Abstract Background Sand burial plays an irreplaceable and unique role in the growth and distribution of vegetation on the Shell Dike Island in the Yellow River Delta. There are still some unknown on the effects of sand burial on the morphology, biomass, and especially the stoichiometry of Periploca sepium, as well as the relationship between these factors. Results Shell sand burial depth had a significant influence on seedling emergence, growth, and biomass of P. sepium. Shallow sand burial shortened the emergence time and improved the emergence rate, morphological and biomass of P. sepium compared to deep burial and the control. Burial depth significantly affected the nitrogen (N) and phosphorus (P) contents of the leaves. With deep burial, the carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratios decreased firstly and then increased with depth, while the nitrogen/phosphorus ratio (N/P) presented the contrary trend. Correlation analysis showed that the stoichiometry of N/P was positively correlated to morphology and biomass of P. sepium at different burial depths. Structural equation model analysis revealed that N was the largest contributor to P. sepium biomass. Conclusions Optimal burial depth is beneficial to the seedling emergence, growth and nutritional accumulation of P. sepium. Stoichiometry has an important influence on the morphological formation and biomass accumulation.

Abstract Exotic species invasions have profound effects on native ecosystems, with the ecological effects of non‐native plants being especially pervasive. We investigated the impacts of a plant invasion on benthic invertebrate assemblages in intertidal wetlands of the Yellow River Delta, comparing benthic communities associated with exotic Spartina alterniflora against those associated with native plants (Tamarix chinensis, Suaeda salsa, and mudflat). Our study surprisingly found that the density, diversity, and richness of benthic invertebrates associated with S. alterniflora were higher than with native habitats. Multivariate analysis also revealed that the structure of benthic invertebrates in S. alterniflora habitats was different than in T. chinensis and mudflat habitats. The structure of invertebrates associated with the invasive S. alterniflora and native S. salsa was more similar, although the dominant species differed. Indicator species analyses indicated that each habitat was characterized by unique taxa. S. alterniflora invasion increased the beta diversity of the community, with the species turnover component being of most importance. Mollusks were most likely to be influenced by Spartina invasions. Given the extent of the S. alterniflora invasion in the Yellow River Delta, altered benthic invertebrate communities will likely have important implications for the ecology of the intertidal wetland ecosystems and deserve increased attention.

Benthic diatoms are the main primary producers and are sensitive to environmental changes in the estuarine ecosystem. Therefore, it is critical to evaluate the impact of environmental stress on the benthic diatom community in the estuarine ecosystem. In this study, the sediment samples from the five sampling sites were collected from the Yellow River Delta in the four seasons, and the abundance of benthic diatoms were determined using the high-throughput sequencing of 18S rRNA genes. The results showed that the motile guild taxa, such as Navicula, Nitzschia, and Amphora, was dominated in the benthic diatom the community throughout the sampling period. The structure of the benthic diatom community was significantly different among seasons (ANOSIM P < 0.01), especially between summer and winter. Redundancy analysis showed that water temperature and the concentrations of silicate, nitrate, ammonium, and pH value are the main driving factors shaping the seasonal assembly of the benthic diatom community. The results will improve knowledge about the benthic diatom community in the estuarine ecosystem and provide a theoretical foundation for estuary environmental management.

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is highly popular due to its attractive taste and flavor of fruits. However, its cultivation is facing a serious obstacle for the substantial decrease in fruit soluble solids contents. In this study, four commonly-used fertilization types, including organic manure application (OM), combined application of manure and NPK fertilizer (OC), NPK fertilizer application at high rate (HC) and NPK fertilizer application at low rate (LC) were selected to investigate their effects on soil and fruit properties. Results showed that fertilization influenced soil organic matter (SOM) and NPK contents. Fruit yield decreased as HC (3.37tha−1) > OC (2.81tha−1) > OM (2.14tha−1) > LC (1.92tha−1).Total soluble solids (TSS), protein contents, and the ratio of TSS to titratable acid (TA) were highest in OM, followed by OC, LC and HC. TSS and TSS/TA ratio in OM were 23.0% and 27.0% higher than those in HC. Fruit yield was significantly positively correlated with soil available N, vegetative shoot leaf N, and total topsoil P contents. TSS and TSS/TA ratio both significantly positively correlated with SOM of topsoil and leaf P contents. Combined application of organic and inorganic fertilizers should be the optimal mode for winter jujube production.

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Salt stress and nutrient deficiency strongly limited the productivity of coastal saline-alkali land in the Yellow River Delta. Biochar has been widely used to improve soil health and promote crop yield, and the positive effects of nitrification inhibitors on fertilizer use efficiency, especially nitrogen, were also verified. However, there were few types of research on the combined application of biochar and nitrification inhibitor dicyandiamide (DCD) on saline-alkali soil of the Yellow River Delta, China. In this study, five treatments, including no nitrogen (CK), normal NPK (N), NPK + 1%biochar (B), NPK + 2%DCD (D), and NPK + 1%biochar + 2%DCD (BD) were set to investigate the single and combined effect of biochar and DCD on nitrogen transform, soil properties, bacterial community structure, and soybean production. Results showed that BD application inhibited nitrification and increased the soil’s nitrate supply at the flowering stage, which reduced nitrogen waste and met the nitrogen demand for soybean growth. Biochar addition increased the soil’s pH and decreased the soil’s electrical conductivities and accelerated the soil’s macroaggregates formation, with the soil’s average mass diameter and geometric average diameter increasing by 78.69% and 30% in B, and 71.29% and 29.34% in BD relative to CK. Positive effects of inhibitors on soybean production were found in increasing soybean yield, hundred-grain weight, aboveground biomass, etc. Proteobacteria was the dominant phylum in the bacterial communities detected, and bacterial community diversity was significantly explained by nitrate content and soil aggregates (p < 0.05). Soil pH and DCD addition mainly influenced the abundance of the bacterial community, especially Actinobacteria. Biochar with DCD could be a feasible fertilization scheme for the coastal saline-alkali land in the Yellow River Delta, China.

In the Yellow River Delta in China, mulch residue from croplands may pollute surrounding soil and near-shore waters. However, there is a lack of knowledge regarding the status and environmental pollution effects of mulch residue in this region. This study examined mulched croplands within 5 km of the main entering-sea rivers of this region and obtained 170 samples and 34 questionnaires. Using multiple analytical methods, we identified the key drivers of mulch residue characteristics, the effects of different types of mulch residues on soil, and potential offshore pollution zones. Mulch residue pollution in the study area was found to be heavily present (mean value of 51 kg/ha), posing a high risk of offshore pollution along the southeast and northwest coastlines. Large mulched fields with low residue levels and small debris showed a scale effect in mitigating mulch residue pollution. PBAT mulch usage was prone to the transport of small-sized residues with PE and other hard-to-degrade substances, indicating an increased offshore pollution risk. Large agglomerates in the soil, formed after using PE mulch, had poor water stability and low soil organic carbon content. Mulch residues significantly reduced the abundance of the soil fungi Ascomycota and Basidiomycota. In order to alleviate the negative effects of residual mulch, it is necessary to carry out large-scale mulching and use degradable mulches and easily recyclable thick PE mulches in the future. [Display omitted] • Southeast and northwest of Yellow River Delta has mulch residue pollution risk. • Larger areas of mulch application have fewer residues than smaller ones. • Residue of polybutylene adipate terephthalate migrate stronger than polyethylene. • Polyethylene residue reduces soil organic carbon and water-stable agglomerates. • Mulch residues influence soil fungal diversity and community succession. [ABSTRACT FROM AUTHOR]

Hydrological connectivity has significant effects on the functions of estuarine wetland ecosystem. This study aimed to examine the dynamics of hydrological connectivity and its impact on soil carbon pool in the Yellow River Delta, China. We calculated the hydrological connectivity based on the hydraulic resistance and graph theory, and measured soil total carbon and organic carbon under four different hydrological connectivity gradients (I 0–0.03, II 0.03–0.06, III 0.06–0.12, IV 0.12–0.39). The results showed that hydrological connectivity increased in the north shore of the Yellow River and the south tidal flat from 2007 to 2018, which concentrated in the mainstream of the Yellow River and the tidal creek. High hydrological connectivity was maintained in the wetland restoration area. The soil total carbon storage and organic carbon storage significantly increased with increasing hydrological connectivity from I to I gradient and decreased in IV gradient. The highest soil total carbon storage of 0–30 cm depth was 5172.34 g/m2, and organic carbon storage 2764.31 g/m2 in III gradient. The hydrological connectivity changed with temporal and spatial change during 2007–2018 and had a noticeable impact on soil carbon storage in the Yellow River Delta. The results indicated that appropriate hydrological connectivity, i.e. 0.08, could effectively promote soil carbon storage. [ABSTRACT FROM AUTHOR]

Nested Delft 3D and Hydrus 1D models were applied to simulate variations in the hydrological process of tidal creeks, soil water, and salt transport in the soil profile of the reconstruction area in the Yellow River Delta under six gate dam scenarios. The results showed that the gate dam set up near the sea area was more conducive to reducing the variation range of water depth in the reconstruction area. The water depth changes in scenarios with 6 m gate valves were higher than those with 3 m sluice valves in the same gate dam location. The variations in surface water salinity, cumulative flooding time, flooding frequency, and cumulative infiltration in each scenario were similar to those for water depth. Rapid changes in soil water and salt content occurred in each scenario in periods without flooding. The fluctuation of soil salt content in different soil layers was contrary to the changes in soil water content. The overall difference in the soil salt contents and soil water content of the soil profile in scenarios with a gate dam near the sea was relatively larger than that of those with a gate dam near the shore. Obvious differences in both the soil water content and soil salt content between scenarios with 3 m and 6 m gate valves were not observed. Our results contribute to the understanding of the function of gate dams in controlling soil water and salt content in coastal wetlands.

The Yellow River Delta is the largest and youngest estuarine and coastal wetland in China and is experiencing the most active interactions of seawater and freshwater in the world. Bacteria played multifaceted influence on soil biogeochemical processes, and it was necessary to investigate the intermodulation between the soil factors and bacterial communities. Soil samples were collected at sites with different salinity degree, vegetations, and interference. The sequences of bacilli were tested using 16S rRNA sequencing method and operational taxonomic units were classified with 97% similarity. The soil was highly salinized and oligotrophic, and the wetland was nitrogen-restricted. Redundancy analysis suggested that factors related with seawater erosion were principal to drive the changes of soil bacterial communities and then the nutrient level and human disturbance. A broader implication was that, in the early succession stages of the coastal ecosystem, seawater erosion was the key driver of the variations of marine oligotrophic bacterial communities, while the increasing nutrient availability may enhance in the abundance of the riverine copiotrophs in the late stages. This study provided new insights on the characteristics of soil bacterial communities in estuarine and coastal wetlands. [ABSTRACT FROM AUTHOR]

Territorial space is an essential carrier to support the sustainable development of ecological civilization in the human community. It is necessary to accurately identify the types of territorial space, and thereby to determine the temporal and spatial evolution characteristics and driving factors. Taking the High-Efficiency Eco-economic Zone of the Yellow River Delta as the research area, this study aims to optimize the pattern of land and space under the guideline of “process-pattern-drive”. Firstly, a territorial space classification system was constructed using the remote sensing data from 2000 to 2020. Secondly, a chord diagram model in visualization data and Geo-information Tupu were selected to describe the evolution of territorial space. A gravity-center shift model and spatial autocorrelation were used to clarify the spatial and temporal pattern in territorial space evolution. Finally, a geographic detector was used to analyze the driving mechanism of territorial space evolution. The results show that: 1) The change rates of territorial space in the Yellow River Delta were 0.39% and 2.1% in 2000-2010 and 2010-2020, respectively. There was an increasingly significant change in the territorial space structure. The territorial space evolution included the internal exchange of agricultural space, the exchange of ecological space and agricultural space, as well as the transfer of urban space to ecological space. 2) The gravity-center of ecological space shifted 23.903 km to the southeast in the Yellow River Delta, indicating the longest migration path from 2000 to 2020. Nevertheless, the gravity center of agricultural space shifted 3.241km to the northwest with the shortest migration path. In addition, the spatial agglomeration of territorial space change was mainly concentrated in the coastal areas. The agricultural and urban space occupied the ecological space from 2000 to 2010, whereas, the urban space fed back ecological and agricultural space from 2010 to 2020. 3) There were different driving factors for the spatial differentiation in the spatial change rate in various periods. Specifically, the policy and institutional environment dominated the study area after the construction of the high efficiency eco-economic zone, whereas, the traffic location and the level of economic development dominated before that. A reasonable and orderly pattern of land protection was also established to evaluate regional resources, environment carrying capacity, and territorial space suitability (“double assessment”), thereby clarifying the carrying scale and suitability level of regional development for the decision-making on the territorial space strategies. [ABSTRACT FROM AUTHOR]