Effects of Vegetation Restoration Age on Soil C:N:P Stoichiometry in Yellow River Delta Coastal Wetland of China

Vegetation restoration can alter carbon(C),nitrogen(N),and phosphorus(P)cycles in coastal wetlands affecting C:N:P stoichiometry.However,the effects of restoration age on soil C:N:P stoichiometry are unclear.In this study,we examined the re-sponses of soil C,N,and P contents and their stoichiometric ratios to vegetation restoration age,focusing on below-ground processes and their relationships to aboveground vegetation community characteristics.We conducted an analysis of temporal gradients based on the'space for time'method to synthesize the effects of restoration age on soil C:N:P stoichiometry in the Yellow River Delta wetland of China.The findings suggest that the combined effects of restoration age and soil depth create complex patterns of shifting soil C:N:P stoichiometry.Specifically,restoration age significantly increased all topsoil C:N:P stoichiometries,except for soil total phosphorus(TP)and the C:N ratio,and slightly affected subsoil C:N:P stoichiometry.The effects of restoration age on the soil C:N ratio was well constrained owing to the coupled relationship between soil organic carbon(SOC)and total nitrogen(TN)contents,while soil TP con-tent was closely related to changes in plant species diversity.Importantly,we found that the topsoil C:N:P stoichiometry was signific-antly affected by plant species diversity,whereas the subsoil C:N:P stoichiometry was more easily regulated by pH and electric con-ductivity(EC).Overall,this study shows that vegetation restoration age elevated SOC and N contents and alleviated N limitation,which is useful for further assessing soil C:N:P stoichiometry in coastal restoration wetlands.

Activity Pattern and Habitat Use of Shorebirds in an Artificial Wetland Complex:A Case Study of Breeding Pied Avocet in the Yellow River Delta,China

With the loss of substantial natural wetlands in coastal zones,artificial wetlands provide alternative habitats for many shorebirds.Scientific management of artificial wetlands used by shorebirds plays an important role in maintaining the stability of shorebird population.Satellite tracking technique can obtain high-precision location information of individuals day and night,providing a good technical support for the study of quantitative relationship between waterfowls and their habitats.In this study,satellite tracking method,Remote Sensing(RS)and Geographic Information System(GIS)technology were used to analyze the activity pattern and habitat utilization characteristics of Pied Avocet during breeding period in an artificial wetland complex in the Yellow River Delta(YRD),China.The results showed that the breeding Pied Avocets had a small range of activity,with a total core and main home range of 33.10 km^(2) and 216.30 km^(2),respectively.This species tended to forage in the pond and salt pan during the day and night,respectively,with an unfixed staying time in the breeding ground.The distance between breeding ground and feeding ground was less than 6 km.It is emphasized that in addition to improving the conditions of the remaining natural habitats,effective managing artificial habitats is a priority for shorebird conservation.This research could provide reference for the management of artificial wetlands in coastal zones and supply technique support for the protection of shorebirds and their habitats,and alleviate human-bird conflicts and sustainable development of coastal zones.

Remote Monitoring of Expansion of Aquaculture Ponds Along Coastal Region of the Yellow River Delta from 1983 to 2015

Aquaculture ponds are one of the fastest-growing land use types in valuable and fertile coastal areas and have caused serious environmental problems. Quantitative assessment of the extent, spatial distribution, and dynamics of aquaculture ponds is of utmost importance for sustainable economic development and scientific management of land and water resources in the coastal area. An object-oriented classification approach was applied to Landsat images acquired over three decades to investigate the long-term change of aquaculture ponds in the coastal region of the Yellow River Delta. The results indicated that the aquaculture ponds in the study area undergone a sharp expansion from 40.38 km^2 in 1983 to 1406.89 km^2 in 2015, and the fast expansion occurred during the period of 2010–2015 and 1990–2000. Natural wetlands, especially mudflat, and cropland were main land use types contributing to the increase of aquaculture ponds. The patches of aquaculture ponds were consequently prevalence in the north of the Yellow River Estuary and landscape metrics indicated an increase of the aquaculture ponds of the study area in the quantity and complexity. The expansion of aquaculture ponds inevitably had negative effects on the coastal environment, including loss of natural wetlands, water pollution and land subsidence, etc. The results from this study provide baseline data and valuable information for efficiently planning and managing aquaculture practices and for effectively implementing adequate regulations and protection measures.

Changes of Coastal Wetland Ecosystems in the Yellow River Delta and Protection Countermeasures to Them

Coastal wetlands in the Yellow River Delta are typical new wetland ecosystems in warm temperate zone. In recent years, influenced by natural and human factors, these coastal wetlands in the Yellow River Delta have undergone changes of landscape fragmentation, vegetation degradation, pollution, species reduction, and harmful exotic species invasion. These changes have influenced sustainable and healthy development of marine economy of the Yellow River Delta. To protect natural ecological environment of the Yellow River Delta, the authors recommended that it should establish and improve policies, laws and regulations of wetland protection; carry out wetland resource investigation and assessment and monitoring; strengthen comprehensive protection and control of wetland; reduce wetland degradation and promote sustainable use of wetland.

Possible effect of climate changes on the coastal zone of the Yangtze River Delta

A coastal historical evolution of the Yangtze River Delta was discussed in this paper on the basis of the historical data of the coastal zone and an estimation was made for the future change of the coast The emphasis was put on the future climate change that will have influence on the sea wall, coastal navigation and freshwater resources in the Delta It was also pointed out that the global warming and precipitation increase in the Yangtze River Valley may exert more impact on the zone In addition, some measures describing how to adapt to the climate change and reduce its impact were put forward

Geographic Object-Based Image Analysis of Changes in Land Cover in the Coastal Zones of the Red River Delta (Vietnam)

The majority of the population and economic activity of the northern half of Vietnam is clustered in the Red River Delta and about half of the country’s rice production takes place here. There are significant problems associated with its geographical position and the intensive exploitation of resources by an overabundant population (population density of 962 inhabitants/km2). Some thirty years after the economic liberalization and the opening of the country to international markets, agricultural land use patterns in the Red River Delta, particularly in the coastal area, have undergone many changes. Remote sensing is a particularly powerful tool in processing and providing spatial information for monitoring land use changes. The main methodological objective is to find a solution to process the many heterogeneous coastal land use parameters, so as to describe it in all its complexity, specifically by making use of the latest European satellite data (Sentinel-2). This complexity is due to local variations in ecological conditions, but also to anthropogenic factors that directly and indirectly influence land use dynamics. The methodological objective was to develop a new Geographic Object-based Image Analysis (GEOBIA) approach for mapping coastal areas using Sentinel-2 data and Landsat 8. By developing a new segmentation, accuracy measure, in this study was determined that segmentation accuracies decrease with increasing segmentation scales and that the negative impact of under-segmentation errors significantly increases at a large scale. An Estimation of Scale Parameter (ESP) tool was then used to determine the optimal segmentation parameter values. A popular machine learning algorithms (Random Forests-RFs) is used. For all classifications algorithm, an increase in overall accuracy was observed with the full synergistic combination of available data sets.

Coastal Erosion Feature and Mechanism at Feiyantan in the Yellow River Delta

Feiyantan was the discharge area of Diaokou River distributary of the Yellow River during the period of 1964 to 1976. The coastal erosion feature and morphological evolution at the Feiyantan coast are studied in the light of the topography and section depth, and the corresponding dynamics of wave and current. Results indicate that the protruding topography left after the Diaokou River distributary was abandoned is the main cause of strong coastal erosion. Further research suggests that waves start up the sediment and the tidal current transports it, and the waves and tidal current are combined to be the dominant dynamic mechanism of coastal erosion, in which the tidal residual current takes and transports the sediment outward, thus causing the sediment to wane in the coast.

Effect of Hydrological Connectivity on Soil Carbon Storage in the Yellow River Delta Wetlands of China

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(Ⅰ0‒0.03,Ⅱ0.03‒0.06,Ⅲ0.06‒0.12,Ⅳ0.12‒0.39).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 fromⅠtoⅢgradient and decreased inⅣgradient.The highest soil total carbon storage of 0‒30 cm depth was 5172.34 g/m^(2),and organic carbon storage 2764.31 g/m^(2)inⅢgradient.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.

Spatial-temporal analysis of wetland landscape pattern under the influence of artificial dykes in the Yellow River delta

The influence of anthropogenic activities,especially artificial dykes,on the coastal wetland landscape is now considered as a serious problem to the coastal ecosystem.It is important and necessary to analyze changes of coastal landscape pattern under the influence of artificial dykes for the protection and management of coastal wetland.Our study aimed to reveal the quantitative characteristics of the coastal wetland landscape and its spatial-temporal dynamics under the influence of artificial dykes in the Yellow River delta(YRD).It was analyzed by the methods of the statistical analysis of landscape structure,five selected landscape indices and the changes of spatial centroids of three typical wetland types,including reed marshes,tidal fiats and aquaculture-salt fields.The results showed that:(1)Reduction of wetland area,especially the degradation of natural wetlands,had been the principal problem since the dykes were constructed in the YRD.The dykes created conditions for the development of artificial wetlands.However,the new born artificial wetlands were still less than the vanished natural wetlands.(2)Compared with the open area,the building of artificial dykes significantly speeded up the changes of landscape patterns and the aggravation of the landscape fragmentation in the closed area.(3)The changes of area-weighted centroids of three typical wetland landscapes were greatly affected by dykes,and the movement of the centroid of the aquaculture-salt field was very sensitive to the dykes constructed in the corresponding period.

Introduction and Selection of Salt-tolerant Wheat in Yellow River Delta

[Objective] This study was to screen a salt-tolerant wheat variety in Dongying, a city in the center of the Yellow River Delta with a large area of coastal saline soil. [Method] Total 9 salt-tolerant, stress-resistant and high-yielding wheat varieties （lines） were introduced, and they were cultivated in the saline soil with total salt content of 3-4 g/kg with Dekang 961 as the control. [Result] The yields of Jinan 18, Yanjian 14 and Shanrong 3 were all significantly higher than that of Dekang 961 （P〈0.05）. These three varieties （lines） all ripen before June 13 with moderate growth period that does not affect the seeding of next-season crop. [Conclusion] Jinan 18, Yanjian 14 and Shanrong 3 are suitable for planting in light and median saline soil in the Yellow River Delta.

Study on Land Use Changes in the Yellow River Delta from 1980 to 2010

Taking the Yellow River Delta for example, this paper applied remote sensing and GIS to explore land use changes in the local area from 1980 to 2010. The results showed that arable land, and urban and rural construction land were major land use types in the Yellow River Delta, unused land also took a large ratio; land use changes occurred mainly in coastal regions, in terms of change matrix, 25.46% of the grassland was reclaimed as arable land, unused land also witnessed great changes, specifi cally, 11.14% turned to arable land, 23.25% to construction land. This study provided references for the land use planning and development of the local area.

Compound extreme inundation risk of coastal wetlands caused by climate change and anthropogenic activities in the Yellow River Delta,China

The coastal wetlands of the Yellow River Delta(YRD)in China are crucial for their valuable resources,environmental significance,and economic contributions.However,these wetlands are also vulnerable to the dual threats of climate change and human disturbances.Despite substantial attention to the historical shifts in YRD's coastal wetlands,uncertainties remain regarding their future trajectory in the face of compound risks from climate change and anthropogenic activities.Based on a range of remote sensing data sources,this study undertakes a comprehensive investigation into the evolution of YRD's coastal wetlands between 2000 and 2020.Subsequently,the potential fate of coastal wetlands is thoroughly analyzed through the Land Use/Cover Change(LUCC)simulation using System Dynamic-Future Land Use Simulation(SD-FLUS)model and the extreme water levels projection integrated future sea-level rise,storm surge,and astronomical high tide in 2030,2050,and 2100 under scenarios of SSP1-2.6,SSP2-4.5,and SSP5-8.5.Results revealed that YRD's coastal wetlands underwent a marked reduction,shrinking by 1688.72 km²from 2000 to 2020.This decline was mostly attributed to the substantial expansion in the areas of artificial wetlands(increasing by 823.78 km2),construction land(increasing by 767.71 km²),and shallow water(increasing by 274.58 km²).Looking ahead to 2030-2100,the fate of coastal wetlands appears to diverge based on different scenarios.Under the SSP1-2.6 scenario,the area of coastal wetland is projected to experience considerable growth.In contrast,the SSP5-8.5 scenario anticipates a notable decrease in coastal wetlands.Relative to the inundated area suffered from the current extreme water levels,the study projects a decrease of 6.8%-10.6%in submerged coastal wetlands by 2030 and 9.4%-18.2%by 2050 across all scenarios.In 2100,these percentages are projected to decrease by 0.4%(SSP2-4.5)and 27.1%(SSP5-8.5),but increase by 35.7%(SSP1-2.6).Results suggest that coastal wetlands in the YRD will face a serious compound risk from climate change and intensified human activities in the future,with climate change being the dominant factor.More effcient and forward-looking measures must be implemented to prioritize the conservation and management of coastal wetland ecosystems to address the challenges,especially those posed by climate change.

Land-Use Changes and Human Driving in and Near the Yangtze River Delta from 1995–2015

We analyzed the characteristics and trends of land-use change in and near the coastal zone of the Yangtze River Delta(YRD) during five periods(1995, 2000 2005, 2010, and 2015) using remotely sensed Landsat imagery. Using automatic supervised classification combined with visual interpretation, we obtained land-use information for five study areas(Nantong, Shanghai, Jiaxing, Ningbo, and Zhoushan). Significant land-use changes have occurred in this area between 1995 and 2015, characterized in particular by large reductions in cultivated land and rapid increases in urbanized land. In addition, land reclamation was very active in this period as an effective supplement to the increased demand for land development: since 1995, 1622 km^2 of land was reclaimed from near-coastal regions in the study area. This increase in urbanization was jointly driven by population, economic, transportation, and policy factors. Urban areas expanded from the center outward in concentric rings, with infrastructure guiding the radial expansion of development along transportation corridors, thus forming a network of connections. Due to the influence of national land regulation policies, the expansion rate of development in the YRD gradually diminished after 2010. This indicates that the area's resource and environmental carrying capacity has reached a saturation stage in which urbanization has transitioned from broad and incremental expansion to the intensive use of land resources.

Spatial Distribution Characteristics of Heavy Metals Cu and Zn in Coastal Wetland Sediments

The content of Cu,Zn in the sediments from coastal wetlands of the Yellow River Delta was determined.The results showed that:(i)The content of Cu,Zn range was 16.70-50.40 mg/kg,18.15-48.80 mg/kg,respectively.The mean content of Cu,Zn was 31.12mg/kg,36.74 mg/kg,respectively.Compared with the soil environmental background values of Shandong Province,the content of Cu was excessive,while the content of Zn was below the background.(ii)The concentrations of Cu,Zn in sediment in the coast of the Yellow River Delta were higher than in the other two areas.(iii)Vertical distribution characteristics of the concentrations of Cu,Zn were increasing with depth.The maximum content of Cu,Zn was 80-100 cm,in general,the content of Cu,Zn in the bottom sediments was higher than that in the surface sediments.The growth and decline trends of Zn in Tamarix and Suaeda areas were much the same and all higher than in the Phragmites communis area.(iv)The distribution characteristics of Cu concentration in different vegetation cover in sediment is Suaeda>Phragmites communis>Tamarix,which reflected different effects on retention of Cu in the sediments because of the different vegetation types.The highest content of Zn in the 0-20 cm sediments in Tamarix area was 44.07 mg/kg.

黄河三角洲滨海湿地碳储时空演变及其生态补偿研究

近年来随着油气开采、港口建设、填海造陆等活动的开展,黄河三角洲滨海湿地面临生态服务功能降低、碳汇功能受损等问题。为改善黄河三角洲滨海湿地的生态功能及有效利用其碳储功能,研究突破了碳储生态补偿价值静态核算的局限性,充分考虑黄河三角洲滨海湿地的时空异质性影响,运用ArcGIS及InVEST模型计算并分析不同土地利用类型下的碳储量变化,探究如何对碳储量损失区域进行生态补偿,并提升黄河三角洲滨海湿地生态系统的碳储功能。研究表明:(1)2013—2020年黄河三角洲滨海湿地碳储量呈现下降趋势,8年间累计总损失6.36×10^(6)吨碳。(2)碳储总值的分布与土地利用类型密切相关。(3)黄河三角洲滨海湿地2013—2020年8年间碳储经济损失价值为164.92×10^(6)美元。

围垦开发下滨海湿地格局演变的自然-人为复合驱动过程

滨海湿地具有重要的生物多样性保护价值及生态功能,围垦开发下经济快速增长的同时滨海湿地生态受损且大面积丧失。探究自然-人为复合影响下格局演变的关键驱动机制,可以为区域的生态保护和高质量发展提供指示。以围垦开发影响剧烈的黄河三角洲为研究区,克服了当前研究中驱动力的时空动态表征以及湿地格局演变的综合驱动时空交互机制研究的不足,研究构建了一套基于土地利用变化轨迹分离自然和人为驱动并表征湿地格局演变的动态驱动过程的方法,为区域尺度有效评估外界干扰对滨海湿地的影响提供了更加全面的支持。结果表明:尽管黄河三角洲滨海湿地格局演变的驱动过程轨迹类型多样,但主要受少数类型影响,以单一围垦开发为主。各驱动过程间存在着不同程度的时空交互,伴随围垦、修复、逆向演替过程的发生和转换,新生湿地的淤积及生态系统演替的自然增长过程被阻断,甚至可能对已修复湿地产生负面影响,区域湿地持续减少;人为驱动过程的影响远大于自然驱动过程,人为、自然及自然-人为复合驱动的湿地格局演变面积占比分别为55.5%、26.1%和18.4%。研究结果指示应严格管控部分生境敏感区的滩涂围垦,未来难以避免的滨海开发活动应由陆向海逐步推进,采用与新生湿地淤长方向一致的“滚动开发”模式,在兼顾经济效益的同时,维护滨海湿地生态系统的完整性和演替的连续性。

大气校正对滨海湿地Sentinel-2影像NDVI的影响

为消除卫星影像成像过程中受到的大气干扰,还原真实的地物反射率,大气校正已成为定量遥感分析研究中的关键环节。本文基于2018—2022年间5期黄河三角洲的Sentinel-2影像,通过对比分析大气校正前后的NDVI值,探究大气校正对NDVI计算的必要性。结果发现:(1)大气校正能够对滨海湿地Sentinel-2影像的整体NDVI和不同地类NDVI均产生显著影响,但对不同年份黄河NDVI的影响存在不确定性;(2)大气校正前后NDVI在不同地类间波谱特征变化无较大差异,但大气校正有效增强NDVI极差范围,提高了不同地类NDVI区分度。该研究为大气校正对NDVI存在影响的相关研究提供了参考依据。

黄河三角洲地下水关键水盐因子及其植被效应

为了解黄河三角洲地下水生态环境功能,采用数理统计、地统计和同位素方法及3S技术,对"地下水-陆生植被"系统中关键水盐因子及其植被效应进行了深入研究。结果显示,区域典型植被主要以埋深普遍较浅(1.0～3.0 m)的地下水为水源,说明地下水是生态环境的敏感要素。潜水c(Cl-)与c(TDS)均呈显著的方向性空间变异(沿地下水流向二者浓度递增),且二者具有空间分布一致性(R=0.999),表明Cl-是潜水水质的主控离子。归一化植被指数(INDVI)与潜水c(Cl-)间呈较显著的Logistic关系,揭示潜水c(Cl-)是地下水这一生态环境敏感要素中的关键因子,其对上覆植被强烈的胁迫和驱动作用引发了区域典型的生态环境效应。在黄河三角洲高效生态经济区的开发建设过程中,应特别重视植被与潜水c(Cl-)间极为密切的作用与反作用关系,积极采取有效的人为调控措施。

黄河三角洲滨海湿地健康条件评价

以黄河三角洲滨海湿地系统为研究对象,基于描述滨海湿地健康条件的4项功能,充分考虑滨海湿地生态地质环境系统的特征及其健康响应因素,建立了黄河三角洲滨海湿地健康条件评价的概念模型和指标体系。以统计监测和遥感数据为基础,采用RS和GIS技术,通过栅格化实现分区评价及其结果的优化整合,探讨了黄河三角洲滨海湿地健康的时空分布规律。结果显示:黄河三角洲滨海湿地现状健康条件处于健康的占14.2%,亚健康的占61.9%,一般病态的占23.9%;近期(2010—2015年),河口三角洲湿地生境质量会逐步改善,向健康方向发展,而北部和南部部分滩涂区及神仙沟流路等局部地区在自然和人为因素的共同作用下,环境质量会有一定的降低;影响黄河三角洲滨海湿地健康条件的主要因素是全球气候变化背景下的区域水循环关键过程及其时空变化、湿地开发等人类负面干扰和黄河下游生态调度。应继续加大黄河下游生态调度的力度、积极实施生态修复工程,以促进黄河三角洲滨海湿地持续健康发展。

黄河三角洲滨海湿地的景观格局空间演变分析

利用GIS技术、RS影像和Fragstats3.3等景观统计软件,从景观面积变化、景观斑块特征和景观整体水平格局等方面,对比研究了黄河三角洲2000年和2009年湿地不同时空尺度的景观格局变化。结果表明:10 a间黄河三角洲滨海湿地海岸线和陆地面积整体呈增长趋势,天然湿地面积急剧减少,平均分维数大部分降低,湿地景观破碎度降低,多样性和均匀性指数增加,蔓延度指数增加。湿地景观格局指数的变化反映了旱田及水田的大面积种植,盐田养殖业的大力发展以及石油开采等人为活动对景观格局的深刻影响,人类活动已经成为黄河三角洲滨海湿地景观格局变化的主要驱动因子。