Uphill or downhill?Cropland use change and its drivers from the perspective of slope spectrum

The continuous decrease of low-slope cropland resources caused by construction land crowding poses huge threat to regional sustainable development and food security.Slope spectrum analysis of topographic and geomorphic features is considered as a digital terrain analysis method which reflects the macro-topographic features by using micro-topographic factors.However,pieces of studies have extended the concept of slope spectrum in the field of geoscience to construction land to explore its expansion law,while research on the slope trend of cropland from that perspective remains rare.To address the gap,in virtue of spatial analysis and geographically weighted regression(GWR)model,the cropland use change in the Yangtze River Basin(YRB)from 2000 to 2020 was analyzed and the driving factors were explored from the perspective of slope spectrum.Results showed that the slope spectrum curves of cropland area-frequency in the YRB showed a first upward then a downward trend.The change curve of the slope spectrum of cropland in each province(municipality)exhibited various distribution patterns.Quantitative analysis of morphological parameters of cropland slope spectrum revealed that the further down the YRB,the stronger the flattening characteristics,the more obvious the concentration.The province experienced the greatest downhill cropland climbing(CLC)was Shannxi,while province experienced the highest uphill CLC was Zhejiang.The most common cropland use change type in the YRB was horizontal expansion type.The factors affecting average cropland climbing index(ACCI)were quite stable in different periods,while population density(POP)changed from negative to positive during the study period.This research is of practical significance for the rational utilization of cropland at the watershed scale.

Infestation Study of Sclerophrys camerunensis and Sclerophrys regularis (Anura: Bufonidae) by Ascaris sp in Mfilou and Ngamboulou Rivers in Brazzaville (Congo)

A study of toad infestation was carried out from July to December 2022, in the vicinity of the Mfilou and Ngamboulou Rivers, with the aim of determining the prevalence rate of parasitic carriage in these toads. After collecting 289 specimens, all belonging to the Anuran order and Bufonidae family, three species were identified: Sclerophrys camerunensis (Parker, 1936), Sclerophrys regularis (Reuss, 1834) and Sclerophrys sp. The most abundant species were Sclerophrys camerunensis, followed by Sclerophrys regularis. With regard to parasitological aspects, of the 289 specimens collected, 195 were parasitized, i.e. a percentage of 67.47%. The only parasitic species identified was Ascaris sp., which is preferentially located in the intestine.

Microplastic and Heavy Metals Distributions in Urban Rivers Sediments,China

This study investigated the distribution of microplastics and heavy metals,along with the interaction between the two in the sediments of urban rivers in China.Results showed that the abundance of microplastics ranged from 2412±187.5 to 7638±1312items kg^(-1)dry sediment across different survey stations,with an average abundance at(4388±713)items kg^(-1)dry sediment.Upon further categorization,it was found that transparent fragments were the primary color and type of microplastics present.The potential ecological risk index(RI)of heavy metals in sediments suggested a low level of ecological risk within a majority of the urban rivers studied.Cd was identified as the main potential ecological risk factor in the sediments of the studied areas.There was a relatively good significant linear relationship between the RI of heavy metals and the abundance of microplastics,bolstering the linkage between these two environmental pollutants.However,the concentrations of heavy metals in microplastics were not dependent on their corresponding contents in sediments.In fact,the concentration of Cu,Cd,and As in microplastics were higher than those in the sediments.This finding confirmed that microplastics could serve as carriers of heavy metals and introduce potential risks to aquatic wildlife and human through the food chain.

Geomorphological evidence inconvenient for the antecedent rivers of the Arun and Tista across the Himalayan range

The Arun and Tista Rivers,which flow across the Himalayas,are commonly known as antecedent valleys that overcame the rapid uplift of the Higher Himalayan ranges.To clarify whether the idea of antecedent rivers is acceptable,we investigated the geomorphology of the Himalayas between eastern Nepal and Bhutan Himalayas.The southern part of Tibetan Plateau,extending across the Himalayas as tectonically un-deformed glaciated terrain named as'Tibetan Corridor,'does not suggest the regional uplift of the Higher Himalayas.The 8,000-m class mountains of Everest,Makalu,and Kanchenjunga are isolated residual peaks on the glaciated terrain composed of mountain peaks of 4,000–6,000 m high.The Tibetan glaciers commonly beheaded by Himalayan glaciers along the great watershed of the Himalayas suggest the expansion of Himalayan river drainage by glaciation.For the narrow upstream regions of the Arun and Tista Rivers with less precipitation behind the range,it is hard to collect enough water for the power of down-cutting their channels against the uplifting Himalayas.The fission track ages of the Higher Himalayan Crystalline Nappe suggest that the Himalayas attained their present altitude by 11–10 Ma,and the Arun and Tista Rivers formed deep gorges across the Himalayas by headward erosion.

Responses of Nutrients to the Precipitation Variation and Land Use in Subtropical Monsoonal Small Mountainous Rivers:A Case Study of Baixi Watershed

Small mountainous rivers are characterized by large instantaneous fluxes and susceptible to extreme weather events,which can rapidly transport materials into the sea and have a significant impact on the ecological environment of estuaries and bays.In order to investigate the seasonal characteristics of nutrients in small mountainous rivers in the subtropical monsoon region and the output pattern to the sea during heavy precipitation,surveys on the mountainous rivers were carried out in Baixi watershed in August 2020(wet season),March 2021(dry season)and June 2021(Meiyu period).The results showed that the dissolved inorganic nitrogen(DIN)of the rivers has an average concentration of 752μg L^(−1)in the wet season and 1472μg L^(−1)in the dry season.The concentrations of dissolved inorganic phosphorus(DIP)in wet season and dry season were 63μg L^(−1)and 51μg L^(−1),respectively.Influenced by the changes of land use in sub-watersheds,DIN concentrations in the mainstream increased from 701μg L^(−1)in the upper reaches to 1284μg L^(−1)in the middle reaches.Two rainstorms during the Meiyu period in the watershed caused the pulse runoff in the river.The maximum daily runoff reached 70 times that before rains.The maximum daily fluxes of DIN and DIP were 109 and 247 times that before rains,respectively.In view that the watershed experienced several rainstorms in the wet season,the river,with pulse runoff,carries a large amount of nutrients into the sea in a short time,which will have a significant impact on the environment of Sanmen bay and its adjacent sea.

Assessment of CH_(4) flux and its influencing drivers in the rice-wheat agroecosystem of the Huai River Basin,China

To understand the CH_(4) flux variations and their climatic drivers in the rice-wheat agroecosystem in the Huai River Basin of China,the CH_(4) flux was observed by using open-path eddy covariance at a typical rice-wheat rotation system in Anhui Province,China from November 2019 to October 2021.The variations and their drivers were then analyzed with the Akaike information criterion method.CH_(4) flux showed distinct diurnal variations with single peaks during 9:00-13:00 local time.The highest peak was 2.15μg m^(-2)s^(-1)which occurred at 11:00 in the vegetative growth stage in the rice growing season(RGS).CH_(4) flux also showed significant seasonal variations.The average CH_(4)flux in the vegetative growth stage in the RGS(193.8±74.2 mg m^(-2)d^(-1))was the highest among all growth stages.The annual total CH_(4) flux in the non-rice growing season(3.2 g m^(-2))was relatively small compared to that in the RGS(23.9 g m^(-2)).CH_(4) flux increased significantly with increase in air temperature,soil temperature,and soil water content in both the RGS and the non-RGS,while it decreased significantly with increase in vapor pressure deficit in the RGS.This study provided a comprehensive understanding of the CH_(4) flux and its drivers in the rice-wheat rotation agroecosystem in the Huai River Basin of China.In addition,our findings will be helpful for the validation and adjustment of the CH_(4) models in this region.

Embracing a path of harmonious coexistence between humans and rivers River Ethics:The Flow of Harmony

Since time immemorial,humans have made their homes alongside waterways,and mighty rivers have been the cradles of human civilization.However,as society has evolved at an ever-accelerating pace,our relationship with these life-giving streams has shifted dramatically,from one of reverence to exploitation.Now,the profound water crisis has compelled humanity to reexamine its connection with rivers.

Function Evolution and Landscape Planning Strategy of Inland Rivers in Beilun Port City of Ningbo

In the history, the main roles of inland rivers in Beilun Port City of Ningbo were desalination,blocking tides, shipping, and flood control. Nowadays, with the continuous spread and deepening ofurbanization, the ecological environment of river courses has been destroyed. In the past, remediationmeasures based on engineering and technology played a certain role, but can not “cure the root cause”. Itshould respect the historical evolution process of river courses, and highlight the ecological service functionand leisure tourism value of river courses from the coordination perspective of urban and rural ecologicalenvironment, economic industries, society and culture in the planning ideas of ecology, production, andlife integration. Four aspects of the measures are as below: protecting and repairing the ecological matrixof river courses;building green space system and maintaining flood control functions through the waternetwork;protecting cultural heritage along the rivers;developing waterfront leisure tourism scenic area.

Analysis and Innovative Strategies of Tax Preferential Policies to Promote the Sustainable Development of Small-Scale Individual Businesses

This study conducted an in-depth analysis of the current tax preferential policies for small-scale individual businesses and compared them with similar policies both domestically and internationally,aiming to reveal the advantages and disadvantages of the current system.After examining the impact of these tax preferential policies on the economic status of individual business owners and the broader social economy,this article proposes a set of innovative tax preferential strategies based on theoretical foundations.By developing these innovative strategies and clarifying their implementation paths,the aim is to promote the sustainable and healthy development of small-scale individual businesses,thereby fostering comprehensive socio-economic progress.The conclusion of this study not only summarizes policy recommendations with practical significance but also provides theoretical support for the optimization and innovation of future related systems.

Future Development Direction of the Restoration of Mountains,Rivers,Forests,Farmlands,Lakes,and Grasslands and the Faced Problems

In this paper,the definition,connotation,and internal relationship of mountains,rivers,forests,farmlands,lakes,and grasslands in China are elaborated,and the current situation of ecological restoration projects for mountains,rivers,forests,farmlands,lakes,and grasslands was introduced.Moreover,the problems that have arisen in the specific implementation process of pilot projects were analyzed,such as unclear target positioning,inaccurate analysis of ecological problems,insufficient engineering design systematicness,weak operability of evaluation standards,and weak coordination in engineering management.The development direction and major needs for the protection and restoration of mountains,rivers,forests,farmlands,lakes,and grasslands in the future have been proposed from four aspects:theoretical research,engineering design,effect evaluation,and monitoring and supervision.

Study on the Countermeasures to Improve the Public Outdoor Leisure and Fitness Function on the Two Rivers and Four Banks in the Main Urban Area of Chongqing

The main urban area of Chongqing is surrounded by two rivers and set against each other.With its unique waterfront landscape,it has the resource conditions to become a leisure tourism destination.Intending to enhance people’s happiness,improve city quality,and promote Chongqing’s main urban area to become a tourist destination,this paper finds out the existing problems in the construction of public outdoor leisure and fitness facilities on the two rivers and four banks of Chongqing’s main urban area through investigation and analysis based on relevant experiences at home and abroad,takes the value chain theory as the guidance,and to find solutions to the problem.On this basis,combined with the law of economic operation,this paper puts forward the guiding ideology,principles,development goals,functional orientation,and development path for the improvement of public outdoor leisure and fitness on two rivers and four banks in the main city of Chongqing,and accordingly puts forward the policy system and guarantee measures for its improvement.

Chemical weathering in Manas River Basin:Driven by sulfuric acid or carbonic acid?

Carbonic acid produced by the dissolution of atmospheric and soil CO_(2)in water is usually the most dominant catalyst for chemical weathering,but a sulfuric aciddriven phenomenon,different from usual,was found in the orogenic belt watersheds dominated by silicate bedrock.This study,rooted in comprehensive field investigations in the Manas River Basin(MRB)north of the Tianshan Mountains,delves into the mechanisms and impacts of sulfuric and carbonic acid as catalysts driving diff erent types of chemical weathering in the Central Asian Orogenic Belt.Quantitative analyses elucidate that carbonate weathering constitutes 52.4%of the total chemical weathering,while silicate and evaporite account for 18.6%and 25.3%,respectively,with anthropogenic activities and atmospheric precipitation having little eff ect.The estimated total chemical weathering rate in MRB is approximately 0.075×10^(6)mol/km^(2)/year.Quantitative findings further suggest that,preceding carbonate precipitation(<10^(4)year),chemical weathering can absorb CO_(2).Subsequently,and following carbonate precipitation(10^(4)-10^(7)year),it will release CO_(2).The release significantly surpasses the global average CO_(2)consumption,contributing to a noteworthy climate impact.This study underscores the distinctive weathering mechanisms,wherein sulfuric acid emerges as the predominant catalyst.The quantity of sulfuric acid as a catalyst is approximately three times that of carbonic acid.Sulfuric acid-driven carbonate rock weathering(SCW)is identified as the sole chemical weathering type with a net CO_(2)release eff ect.SCW CO_(2)release flux(5176 mol/km^(2)/year)is roughly 2.5 times the CO_(2)absorption by Ca-Mg silicate weathering,highlighting the pivotal role of chemical weathering in sourcing atmospheric CO_(2)over the timescales of carbonate precipitation and sulfate reduction.Lastly,this study posits that catalyst and transport limitations are the most plausible critical factors in MRB.The interplay between sulfuric acid and dissolved CO_(2)competitively shapes the types and rates of chemical weathering reactions.

Water Quality,Influential Factors,and Management Strategies from 2016 to 2020 in the Yangtze River Economic Belt,China

The Yangtze River economic belt(YREB),China is important to the Chinese economy and for supporting sustainable development.Clarifying the relationship between water quality indices and socioeconomic indicators could help improve aquatic environment management in the YREB and our understanding of the causes and effects of water quality variations in other large river basins.In this study,river water quality,factors affecting water quality,and management strategies,and correlations between water quality indices and socioeconomic indicators in the YREB during the 13th Five-Year Plan period(2016-2020)were assessed.The single-factor evaluation method,constant price for GDP,and correlation analyses were adopted.The results showed that:1)water quality in the YREB improved during the 13th Five-Year Plan period.The number of aquatic environment sections meeting GradeⅠ-Ⅲwater quality standards increased by 13.1%and the number below Grade V decreased by 2.9%.2)The values of 12 indicators in the YREB exceeded relevant standards.The indicators with highest concentreation were the total phosphorus,chemical oxygen demand,ammonia nitrogen,and permanganate index,which were relatively high in downstream regions in Anhui Province,Jiangsu Province,and Shanghai Municipality.3)Ammonia nitrogen,chemical oxygen demand,and total phosphorus emissions per unit area and water extraction per unit area are relatively high in the three downstream regions mentioned above.4)Increased domestic sewage discharges have increased total wastewater discharges in the YREB.5)River water quality in the YREB strongly correlated with population,economic,and water resource indices and less strongly correlated with government investment,agriculture,meteorology,energy,and forestry indices.This confirmed the need to decrease wastewater discharges and non-point-source pollutant emissions.The aquatic environment could be improved by taking reasonable measures to control population growth,adjusting the industrial structure to accelerate industrial transformation and increase the proportion of tertiary industries,and investing in technological innovations to protect the environment.

Geographical Indications and Regional Public Brands of the Whole Rice Industry Chain in the Yangtze River Economic Belt

The Yangtze River Economic Belt is the main rice producing area in China.The rice industry chain is the agricultural pillar industry chain of this economic belt and it is the key to ensuring national food security and promoting comprehensive rural revitalization.This study discusses the entire rice industry chain in the Yangtze River Economic Belt from the national rice production functional zones,agricultural product quality and safety,national famous and excellent new agricultural products,national specialty agricultural products,"China s good grain and oil"products,and national advantageous characteristic industrial clusters.Then,it discusses the geographical indications of rice and its products in this economic belt from geographical indication products,geographical indication trademarks,agricultural geographical indications,geographical indication standards,geographical indication special indications,national geographical indication product protection demonstration zones,and Chinese geographical indication products protected by the European Union.In addition,it analyzes the five main problems between geographical indications and public brands,such as the limited use of geographical indication specific signs and the imperfect intellectual property protection system for geographical indications.Finally,it proposes eight strategies,including promoting the high-quality development of the entire rice industry chain,creating a geographical indication regional public brand for rice and its products,and implementing geographical indication protection projects.

Changes in River Cross-section Morphology and Response to Streamflow and Sediment Processes in Middle Reaches of Yellow River,China

Changes in river cross-section morphology have decisive influences on the flood discharge and sand transport capacity of rivers;thus,these changes strongly reflect the vitality of a river.In this paper,based on the river cross-section and water and sediment data of two different periods(1974−1987 and 2007−2021),the trend analysis,change-point analysis and sediment rating curve method were used to analyze the change process of river cross-section morphology and its response to streamflow and sediment changes in the main river stream of the Yellow River at the Longmen hydrological station.From 1974 to 1987(except in 1977),the riverbed experi-enced siltation,and the riverbed elevation rose.Conversely,from 2007 to 2021,the riverbed experienced scouring,and the riverbed el-evation gradually decreased.The cross-section shape changed from rectangular to U-shaped(deeper on the right side)at the Longmen cross-section.The changes in streamflow and sediment processes significantly impacted the evolution of river cross-section.Stream-flow(P<0.05),sediment discharge(P<0.01),and the sediment load coefficients(P<0.01)decreased significantly.The relationship between the water depth and sediment load coefficients followed a power function.The decreasing trend in sediment discharge was sig-nificantly stronger than that in streamflow.Suspended sediment particles tended to become finer.The sediment rating curve indicates that the sediment supply from upstream decreased while the erosive power in the river channel increased,leading to a gradual decline in riverbed elevation at the Longmen cross-section from 2007 to 2021.These findings help us better understand the impacts of ecological restoration on changes in river streamflow and sediment during river evolution.

Dynamic Variation of Vegetation NPP and Its Driving Forces in the Yellow River Basin, China

The productivity of vegetation is influenced by both climate change and human activities.Understanding the specific contributions of these influencing factors is crucial for ecological conservation and regional sustainability.This study utilized a combination of multi-source data to examine the spatiotemporal patterns of Net Primary Productivity(NPP)in the Yellow River Basin(YRB),China from 1982 to 2020.Additionally,a scenario-based approach was employed to compare Potential NPP(PNPP)with Actual NPP(ANPP)to determine the relative roles of climatic and human factors in NPP changes.The PNPP was estimated using the Lund-Potsdam-Jena General Ecosystem Simulator(LPJ-GUESS)model,while ANPP was evaluated by the Carnegie-Ames-Stanford Approach(CASA)model using different NDVI data sources.Both model simulations revealed that significant greening occurring in the YRB,with a gradual decrease observed from southeast to northwest.According to the LPJ_GUESS model simulations,areas experiencing an increasing trend in NPP accounted for 86.82% of the YRB.When using GIMMS and MODIS NDVI data with CASA model simulations,areas showing an increasing trend in NPP accounted for 71.42% and 97.02%,respectively.Furthermore,both climatic conditions and human factors had positive effects on vegetation restoration;approximated 41.15% of restored vegetation areas were influenced by both climate variation and human activities,while around 31.93% were solely affected by climate variation.However,it was found that human activities served as the principal driving force of vegetation degradation within the YRB,impacting 26.35% of degraded areas solely due to human activities.Therefore,effective management strategies encompassing both human activities and climate change adaptation are imperative for facilitating vegetation restoration within this region.These findings will valuable for enhancing our understanding in NPP changes and its underlying factors,thereby contributing to improved ecological management and the pursuit of regional carbon neutrality in China.

Spatial Patterns and Controlling Factors of Soil Organic Carbon and Total Nitrogen in the Three River Headwaters Region,China

The alpine ecosystem has great potential for carbon sequestration.Soil organic carbon(SOC)and total nitrogen(TN)are highly sensitive to climate change,and their dynamics are crucial to revealing the effect of climate change on the structure,function,and services of the ecosystem.However,the spatial distribution and controlling factors of SOC and TN across various soil layers and vegetation types within this unique ecosystem remain inadequately understood.In this study,256 soil samples in 89 sites were collected from the Three River Headwaters Region(TRHR)in China to investigate SOC and TN and to explore the primary factors affecting their distribution,including soil,vegetation,climate,and geography factors.The results show that SOC and TN contents in 0-20,20-40,40-60,and 60-80 cm soil layers are 24.40,18.03,14.04,12.40 g/kg and 2.46,1.90,1.51,1.17 g/kg,respectively;with higher concentrations observed in the southeastern region compared to the northwest of the TRHR.One-way analysis of variance reveals that SOC and TN levels are elevated in the alpine meadow and the alpine shrub relative to the alpine steppe in the 0-60 cm soil layers.The structural equation model explores that soil water content is the main controlling factor affecting the variation of SOC and TN.Moreover,the geography,climate,and vegetation factors notably indirectly affect SOC and TN through soil factors.Therefore,it can effectively improve soil water and nutrient conditions through vegetation restoration,soil improvement,and grazing management,and the change of SOC and TN can be fully understood by establishing monitoring networks to better protect soil carbon and nitrogen.

Runoff simulation and hydropower resource prediction of the Kaidu River Basin in the Tianshan Mountains,China

The Tianshan Mountains of Central Asia,highly sensitive to climate change,has been comprehensively assessed for its ecosystem vulnerability across multiple aspects.However,studies on the region's main river systems and hydropower resources remain limited.Thus,examining the impact of climate change on the runoff and gross hydropower potential(GHP)of this region is essential for promoting sustainable development and effective management of water and hydropower resources.This study focused on the Kaidu River Basin that is situated above the Dashankou Hydropower Station on the southern slope of the Tianshan Mountains,China.By utilizing an ensemble of bias-corrected global climate models(GCMs)from Coupled Model Intercomparison Project Phase 6(CMIP6)and the Variable Infiltration Capacity(VIC)model coupled with a glacier module(VIC-Glacier),we examined the variations in future runoff and GHP during 2017-2070 under four shared socio-economic pathway(SSP)scenarios(SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5)compared to the baseline period(1985-2016).The findings indicated that precipitation and temperature in the Kaidu River Basin exhibit a general upward trend under the four SSP scenarios,with the fastest rate of increase in precipitation under the SSP2-4.5 scenario and the most significant changes in mean,maximum,and minimum temperatures under the SSP5-8.5 scenario,compared to the baseline period(1980-2016).Future runoff in the basin is projected to decrease,with rates of decline under the SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5 scenarios being 3.09,3.42,7.04,and 7.20 m^(3)/s per decade,respectively.The trends in GHP are consistent with runoff,with rates of decline in GHP under the SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5 scenarios at 507.74,563.33,1158.44,and 1184.52 MW/10a,respectively.Compared to the baseline period(1985-2016),the rates of change in GHP under the SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5 scenarios are-20.66%,-20.93%,-18.91%,and-17.49%,respectively.The Kaidu River Basin will face significant challenges in water and hydropower resources in the future,underscoring the need to adjust water resource management and hydropower planning within the basin.

Comprehensive ecological risk assessment for heavy metal pollutions in three phases in rivers

Literature lacked in providing a comprehensive research on heavy metal detection in aquatic, biological and sedimentary states of rivers. The present study was imparted with all these three components of the river. Heavy metal toxicity or pollution index was used as a tool for ecological risk assessment by considering the single state studies conducted by many researchers. An intensive ecological risk assessment model was constructed and heavy metals were indicated as a serious threat to the environment. The model was applied to determining five toxic heavy metals in three states of the Songhua River. According to the ecological risk index, heavy metal pollution in three phases was categorized as aquatic〉biological〉sedimentary, while the overall descending order of heavy metal ecological risk index was as Cd〉Hg〉As〉Pb〉Cr. Cd and Hg were selected as the priority pollutants of Songhua River.

Vertical Distribution Characteristic of Nitrogen in the Core Sediments of Three Rivers Estuary in Poyang Lake

The vertical profile distribution characteristics of nitrogen in core sediments of Three Rivers Estuary in Poyang Lake were studied.The results showed that TN content in core sediments ranged from 480.0 to 1 900.0 μg/g with the change of depth,which was divided into three distribution types as follows:TN content decreases gradually with the increase of depth,TN content increases gradually with the increase of depth or higher content in the middle but lower content in two ends.NH4+-N content ranged from 8.7 ...