Significant impacts of artificial regulation on nutrient concentrations and transport in Huanghe River

Human perturbations such as dam regulation have led to significant changes in nutrient flux,structure,and spatiotemporal distribution through rivers and have greatly influenced coastal and estuarine ecological environments.Based on the data from 2001-2019,the impacts of the water-sediment regulation scheme(WSRS)in the Huanghe(Yellow)River on nutrient concentrations,forms,fluxes,and potential ecological effects on the Huanghe River estuary and Bohai Sea were analyzed.Nutrient concentrations and forms were significantly influenced by the different regulatory modes and were associated with hydrological and biogeochemical processes.The concentrations and forms of nutrients were strongly influenced by the riparian floodplains and scouring process of the downstream riverbed at the water draining stage,while they were influenced mainly by the mixing process in the Xiaolangdi Reservoir at the sediment desilting stage.Compared with those in non-WSRS years,the seasonal distributions of water discharge and nutrient fluxes in WSRS years significantly changed,with peaks occurring at least one month earlier than those in non-WSRS years.Nitrate(NO_(3)-N),phosphate(PO_4-P),and silicate(SiO_(3)-Si)fluxes during the WSRS,which were strongly controlled by water discharge at Lijin(the nearest hydrological station to the river mouth),accounted for more than 20%of the annual fluxes;these fluxes were more than 5-9 times greater than those during the same period in non-WSRS years.WSRS exacerbated nutrient imbalances and increased Pyrrophyta/Bacillariophyta ratios by 231%in the Huanghe River estuary,resulting in chlorophyll-a peaks in the Bohai Sea shifting from spring to autumn in the 20~(th)century to spring-summer in the 21^(st)century.

Research Progress on Distribution,Sources and Ecological Effects of Phthalate in Soil

Phthalate esters(PAEs)are widely used as main plasticizers in plastic products,agricultural regulators,toys,and other fields.This paper reviewed the research progress on the distribution,sources,and ecological effects of PAEs.The effects of PAEs on soil microorganisms,animals,plants and soil properties were explored in sequence,providing effective theoretical basis for future research on PAEs.

Evaluation on Wheat Adaptability in Hetao Area,Inner Mongolia

Wheat samples were collected from Hetao Area, Inner Mongolia, and their poisonous, harmful and beneficial elements contents were analyzed. According to the standards for heavy metals in wheat green food, the Hg, Cd, As and Pb contents in the wheat samples collected from Qiantao Area were all below the national standards, indicating that they were green; and the heavy metals contents in the wheat samples collected from Houtao Area were basically in line with the pollutionfree food hygiene standards, indicating that they were not harmful to human body. Harmful elements Cd and Hg were more enriched in the wheat samples from Qiantao Area, but their contents were all lower than the national food standards, indicating that the wheat from Qiantao Area was not harmful to human health. The wheat from Houtao Area was rich in essential trace elements Cu, Zn, Se and K, and long-term consumption was beneficial to human health.

Compound contamination and secondary ecological effects of Cd and As in soil－alfalfa ecosystems

d and As both have harmful effects on the growth,development and seed germination of alfalfa, especially in such a condition as the coexistence of Cd and As in soil environment The research using the pot-culture imitative method first found that if soil was simultaneously polluted by Cd and As,function of alfalfa absorbing Cd from soil may be promoted because of the existence of As,in conversely,Cd may inhibit alfalfa plant from absorbing As It was also found that secon- dary ecological effects were most likely to be brought out due to the coexistence of Cd and As. For example,alfalfa is passive to excessively absorb Cu and Pb .The harmful effects undoubtedly intensi- fy the contamination of alfalfa, The results showed that the mechanism of the interaction among Cd,As,Pb and Cu in soil-alfalfa ecosystems is very complicated.

Ecological Effects of Land Use Patterns in Red Soil HillyRegion

Plant biomass and biodiversity, element accumulation and return, water loss and soil erosion, and changesin soil properties were studied for up to 10 years after conversion of sparse tree-shrubby grass land into thefollowing four land use patterns: masson pine (Pznvs massonzana Lamb.) land, beautiful sweetgum (Ltq-uidambar fomosana Hance) land, vegetation reservation land, and artificial mowing land. The annualbiomass production of the masson pine land was 5060 kg ha￣-1 being 4.9, 2.1, and 6.0 times that of the beau-tiful sweetgum land, the vegetation reservation land, and the artificial mowing land, respectively. Comparedwith the background values, the number of plant species for the vegetation reservation land increased by 10species after 10 years of land utilization, while for the masson pine and the beautiful sweetgum decreased by4, and for the artificial mowing land by 9. For masson pine land, total amount of N, P, K, Ca, and Mg neededfor producing 1000 kg dry matter was only 3.5 kg, annual element return through litter was 22 kg ha￣-1, bothof which were much lower than those of the other patterns. Vegetation reservation was an effective measureto conserve soil and water and improve soil fertility in the red soil hilly region. Artificial mowing arousedserious degradation of vegetation and soil. Some measures and suggestions for management and exploitationof the red soil hilly region such as masson pine planting, closing hills for afforestation, and stereo-agricultureon one hill are proposed.

Effects of modified clay flocculation on major nutrients and diatom aggregation during Skeletonema costatum blooms in the laboratory

Harmful algal blooms(HABs) can elicit several negative effects on aquatic environment(such as depleting the oxygen, blocking the sunlight, destroying the habitats of organisms) and life health(including poisoning/killing marine mammals, birds and human). Among the various control strategies for HABs(physical manipulation needs lots of manpower and expensive equipment, chemicals treatment has some toxic byproduct and high residual, microbial agents only has limited in laboratory research), the coagulation-flocculation of HAB species by modified clay(MC) has been proven to be an effective, lowcost and environmentally friendly method that has been widely applied in the field, particularly in eastern Asia. In order to examine the long-term effects of MC treatment, this study investigated the alternations in seawater of Skeletonema costatum, a high biomass dominant HAB species along the Chinese coast, by comparing the degradation of S. costatum detritus(A1) with the application of MC treatment(A2) and MC treatment in sediment condition(A3). The low dosage of 0.25 g/L MC could efficiently remove 4×108 cells/L of S. costatum cells within 3.5 h(approximately 97% removal). In addition, the results showed that both inorganic and organic nutrients were effectively reduced from seawater by MC particles. Compared to the total nitrogen(TN) and total phosphorus(TP) concentrations in A1 seawater, 44% of TN and 93% of TP in A2 seawater, as well as 72% of TN and 93% of TP in A3 seawater were removed during the onemonth incubation period. Simultaneously, 64% of DISi in A2 and 44% of DISi in A3 significantly decreased( P <0.001). This study demonstrated that MC treatment was able to significantly increase the downward flux of nutrients and delay the release velocity of inorganic nutrient from MC-algae matrix into the overlying seawater, particularly within sediment environment.

Ecological effects of crude oil residues on the functional diversity of soil microorganisms in three weed rhizospheres

Ecological effects of crude oil residues on weed rhizospheres are still vague. The quantitative and diversity changes and metabolic responses of soil-bacterial communities in common dandelion （Taraxacum officinale）, jerusalem artichoke （Silphiurn perfoliatum L.） and evening primrose （A colypha australis L.） rhizospheric soils were thus examined using the method of carbon source utilization. The results indicated that there were various toxic effects of crude oil residues on the growth and reproduction of soil bacteria, but the weed rhizospheres could mitigate the toxic effects. Total heterotrophic counting colony-forming units （CFUs） in the rhizospheric soils were significantly higher than those in the non-rhizospheric soils. The culturable soil-bacterial CFUs in the jerusalem artichoke （S. perfoliatum） rhizosphere polluted with 0.50 kg/pot of crude oil residues were almost twice as much as those with 0.25 kg/pot and without the addition of crude oil residues. The addition of crude oil residues increased the difference in substrate evenness, substrate richness, and substrate diversity between non-rhizospheric and rhizospheric soils of T. officinale and A. australis, but there was no significant （p〉0.05） difference in the Shannon＇s diversity index between non-rhizospheric and rhizospheric soils of S. perfoliatum. The rhizospheric response of weed species to crude oil residues suggested that S. perfoliatum may be a potential weed species for the effective plant-microorganism bioremediation of contaminated soils by crude oil residues.

A review of ecological mechanisms for management practices of protective forests

A protective forest,including shelterbelt,windbreak,and shelter forest as its synonyms,is characterized by the protective functions of various forest types distributed or planted on ecologically fragile areas or nearby the objects that need to be protected using the ecological effects of forests.Ecological mechanisms for management practices of protective forests is one of the disciplinary orientations in forest ecology and management.Most protective forest studies are dependent on forestry eco-engineering,such as the Great Plains Shelterbelt Project in the United States,the Great Plan for the Transformation of Nature in the Soviet Union,and the Three-North Afforestation Program in China.The development of sustainable management of protective forests has been given increasing attention by governments,scientists,and media due to their impacts on environment conservation and global change.We introduce forestry ecoengineering and provide a review of their main ecological mechanisms for management practices of protective forests.Ecological mechanisms for management systems currently applied are emphasized,i.e.,the theory of protection maturity and phase-directional management;the relationship between structure and protective functions and structural optimization measures;and,the decline mechanism and ecological restoration strategies.In addition,several unresolved problems in management practices of protective forests are discussed as well as the prospects for ecological mechanisms for management practices of protective forests in the future,which include:(1)theories and technologies for management practices of protective forests at the landscape or regional scale;(2)the decline mechanisms and corresponding ecological restoration approaches across multiple scales;and,(3)the comprehensive assessment of forestry eco-engineering at large-scales based on ecosystem principles.

Land use change and its ecological effect in Qian’an County of Jilin Province

Based on GIS and statistical methods, with the help of searching historical literatures and calculating the landscape indices, the land use changes of Qian'an County in both spatial and temporal aspects from 1945 to 1996 has been analyzed in this paper. And the driving forces of land use changes and their ecological effects are discussed too. The main findings of this study are as follows: (1) Land use changed greatly in Qian'an during 1945-1996, characterized by a decrease in grassland, wetland and water bodies, and an increase in cultivated land, saline-alkali land, and the land for housing and other construction purposes. Grassland decreased by 175,828.66 ha, and cultivated land increased by 102,137.23 ha over the half century. Accordingly, the main landscape type changed from a steppe landscape to a managed agricultural ecosystem. (2) Results of correlation analysis show that the land use change in the study area was mainly driven by the socioeconomic factors. (3) The ecological effects of land use change in the area are characterized by serious salinization, degression of soil fertility and the weakening of landscape suitability.

Ecological effects of the microbial weathering of silicate minerals

1 Introduction Global climate change is one of the greatest challenges facing humankind in the 21st century.Studying,and utilising,the carbon sink caused by the weathering of silicate minerals has been a key research focus for

Variations of nutrient elements and its effect on ecological environment off the Changjiang estuarine waters

On the basis of the date obtained in two cruises during October 1997 and May 1998, the concentration distribution and the variation of present species of nutrient elements in the water masses are described. The transform mechanism of present species of nutrients and the of differrnt water masses, frontal area and thermohaline transition layer on convergence or divergence and the biogeochemical cycle of nutrient elements off the Changjiang Estuary are studied. Meanwhile, the environmental capaci- ty of nutrients is primarily estimated: they are 1.803 x 104t DIN and 6.18 x 102t PO43- -P in autumn, and 4.20x 102t PO43- -P in spring.

Seasonal co-occurrence patterns of bacteria and eukaryotic phytoplankton and the ecological response in urban aquatic ecosystem

Microorganisms play a key role in aquatic ecosystems.Recent studies show that keystone taxa in microbial community could change the community structure and function.However,most previous studies focus on abundant taxa but neglected low abundant ones.To clarify the seasonal variation of bacterial and microalgal communities and understand their synergistic adaptation to diff erent environmental factors,we studied the bacterial and eukaryotic phytoplankton communities in Fenhe River that runs through Taiyuan City,central China,and their seasonal co-occurrence patterns using 16S and 18S rDNA sequencing.Results indicate that positive interaction of eukaryotic phytoplankton network was more active than negative one except winter,indicating that the cooperation(symbiotic phenomenon in which phytoplankton are interdependent and mutually benefi cial)among them could improve the adaption of microbial community to the local environmental changes and maintain the stability of microbial network.The main genera that identifi ed as keystone taxa in bacterial network were Salinivibrio and Sphingopyxis of Proteobacteria and they could respond to the variation of nitrite and make use of it,while those that identifi ed as keystone taxa in eukaryotic phytoplankton network were Pseudoschroederia and Nannochloris,and they were more susceptible to nitrate and phosphate.Mychonastes and Cryptomonas were closely related to water temperature.However,the loss of the co-occurrence by environmental factor changes aff ected the stability of network structure.This study provided a reference for analyzing relationship between bacteria and eukaryotic phytoplankton and revealing potential importance of keystone taxa in similar ecological domains in carbon,nitrogen,and phosphorus dynamics.

Landscape changes and their ecological eff ects of Miaodao Archipelago with human disturbances and under natural conditions in the past 30 years

The modern landscape patterns of islands usually show obvious spatial heterogeneity and complex ecological effects due to the vulnerability of ecosystems with natural characteristics under increasing human activities.In this work,we studied the variation in landscape pattern of the Miaodao Archipelago in Bohai Sea,North China,from 1990 to 2019,and an evaluation index system was established to explore the impacts of natural conditions and human disturbances on the ecological effects in the pressure-state-response(PSR)framework.Empirical analysis was conducted on the natural conditions,human disturbances,and ecological effects.The results show that forest was the main component of the landscape pattern in the archipelago.Both of the areas offorest and construction land were increasing,and the areas of cropland and grassland were declining.Other landscape types changed slightly,and the landscape fragmentation was increasing.The natural condition exhibited positive effects while human disturbance showed negative effects on the local ecology.Human disturbances come mainly from shoreline use while the natural conditions were mainly from the elevation change.The ecological effects were resulted mainly from the net primary productivity and water yield.

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth's surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...

Analysis of ecological effects of comprehensive treatment in the Tarim River Basin using remote sensing data

Based on multi-type,multi-temporal remote sensing data,we have monitored recent changes in cultivated land use and vegetation,in sandy areas and salinized desertification in the Green Corridor zone of the main channel of the Tarim River Basin.The results of our investigation show that the ecological environment in the Green Corridor of the main channel of the Tarim River Basin has conspicuously improved from 2002 to 2004.These improvements show up largely in such aspects as an increase in the rate of vegetation cover,a reduction in desertification land areas and a weakening in the intensity of sandy and the salinized land.On the other hand,the cultivated area in the Tarim River Basin significantly increased from 2002 to 2004.The rate of growth in cultivated areas during this period was significantly higher than that from 1999 to 2002.The increase in the use of irrigation resulting from the substantial increase in cultivated areas has a long-term potential restraining effect on the restoration of ecological functions of the Tarim River.

Investigation and Assessment of Ecological Effect of Garden Plants in Linzhi, Tibet

In this study, we investigated main garden plants and assessed the eco- logical effect of garden plants in Bayi town, Linzhi district, Tibet. There are 33 land- scape plants, including 13 trees and 20 shrubs. There are 26 newly-introduced landscape plants, including 10 trees and 16 shrubs. The main landscape plants in Bayi Town could absorb 245.6 t of CO2 and release 178.66 t of 02 per year, illus- trating significant ecological effect. According to the theory that 25 m2 of lawn or 10 m2 of tree could completely absorb the CO2 breathed out by one person daily, the current green space in Bayi town could satisfy the requirement of 43 400 people. We also found that the maximum amount of retained dust by the garden plants is 12.8 t per year, which is considerable and consistent with the results from other studies.

The Research on Land-Use Change and Ecological Environment Effect of Urban Landscape in China

The rapid expansion of urban construction land has become the major characteristic of urban land-use change in China today. Meanwhile, the rapid urbanization process has led to the great changes of urban landscape in China, and it also has had certain impacts on environmental factors such as climate, soil, hydrology, biodiversity, etc., then it has made the overall ecological environment deteriorated. This study is based on the summary and analysis of research on land-use change and ecological environment effect of urban landscape in recent 20 years in China, and it aims at providing scientific bases and theoretical supports for the planning and construction of urban landscape, the sustainable land-use of city and the protection of ecological environment in China.

Annual Variations of Biogenic Element Contents of Manila Clam(Ruditapes philippinarum) Bottom-Cultivated in Jiaozhou Bay, China

Manila clam （Ruditapes philippinarum） was monthly sampled from its benthic aquaculture area in Jiaozhou Bay from May 2009 to June 2010.The annual variations of major elemental composition,organic content,fatness and element ratio of Manila clam were examined.The element removal effect of clam farming in Jiaozhou Bay was analyzed based on natural mortality and clam harvest.The results indicated that the variation trend of carbon content in shell （Cshell） was similar to that in clam （Cclam）.Such a variation was higher in summer and autumn than in other seasons,which ranged from 9.10±0.13 to 10.38 ± 0.09 mmol g^-1 and from 11.28 ±0.29 to 12.36±0.06 mmol g 1,respectively.Carbon content of flesh （Cflnesh） showed an opposite variation trend to that of shell in most months,varying from 29.42 ± 0.05 to 33.64 ± 0.62 mmol g^-1.Nitrogen content of shell （Nshell） and flesh （Nflesh） changed seasonally,which was relatively low in spring and summer.Nshell and Nflesh varied from 0.07 ±0.009 to 0.14±0.009 mmol g^-1 and from 5.46 ± 0.12 to 7.39 ± 0.43 mmol g^-1,respectively.Total nitrogen content of clam ranged from 0.50 ± 0.003 to 0.76 ± 0.10 mmol g^-1 with a falling tend except for a high value in March 2010.Phosphorus content of clam （Nclam） fluctuated largely,while phosphorus content of shell （Pshell） was less varied than that of flesh （Pflesh）.Pshell varied from 0.006±0.001 to 0.016±0.001 mmol g^-1; while Pflesh fluctuated between 0.058±0.017 and 0.293±0.029mmolg^-1.Pclam ranged from 0.015±0.002 to 0.041 ±0.006mmolg^-1.Carbon and nitrogen content were slightly affected by shell length,width or height.Elemental contents were closely related to the reproduction cycle.The removal amounts of carbon,nitrogen and phosphorus from clam harvest and natural death in Jiaozhou Bay were 2.92× 10^4t,1420t and 145 t,respectively.The nutrient removal may aid to reduce the concentrations of nitrogen and phosphorus,the main causes of eutrophication,and to maintain the ecosystem health of Jiaozhou Bay.

Changes of landuse form and their ecological effect on desert-steppe area in Ningxia

The central part of Ningxia is a desert-steppe area with a sparse population and fragile ecosystem where over-grazing has caused serious degeneration of steppe ecosystem; however, the southern part is a populous loessic hilly area subject to serious soil erosion. The central desert steppe has become an oasis with immigrants from southern loessic hilly area thanks to the implementation of new irrigated projects by pumping water from the Yellow River. Using government investment and loan of World Bank, the new irrigated area has been developed which covers an area of 32,527 ha with 145 thousand immigrants moving there from the southern loessic hilly area in 1984-1994. A new ecosystem of oasis economy has been established, socio-economic, and environmental benefits achieved, and changes in land use were prominent. In the central desert steppe of Ningxia, except the original pasture and dryland farming, irrigational farming, horticulture and livestock breeding have been developed. As a result, artificial ecosystems of various types have been formed in the irrigated areas mentioned above. This paper will particularly discusses the changes of landuse patterns in resultant ecological effects, and the environemntal problems for sustainable development in the irrigated area. For the changes of landuse patterns, four aspects are relevant: the dryland was changed into irrigated land, the grassland became irrigated farmland, the agricultural landuse pattern changed and the cropping patterns also altered. The ecological benefits of the irrigated area are as follows: 1) the desert-steppe has been partially replaced by man-made oasis; 2) drinking water for human and livestock was guaranteed; 3) the shifting sand dunes in some areas were brought under control; 4) soil erosion was mitigated; 5) soil mellow process was accelerated and soil fertility increased; and 6) the eco-economic system was diversified. Finally, the authors identifies solutions to the environmental problems, including water pollution. Soil secondary salinization, soil strucrure, improvement shelterbelt construction, all related to sustainable development in irrgational area.

ECOLOGICAL LANDSCAPE EFFECTS OF WINDBREAK SYSTEMS IN DESERT ZONE OF WESTERN CHINA

This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characteristics and ecological crises of China's desert, and especially of desert zone in western China. Furthermore, direct economic benefits are summarized.