刘家峡水库浮游植物群落结构与环境因子的关系

研究分析刘家峡水库浮游植物群落结构的变化,探讨西北地区河道型水库环境因素对浮游植物群落结构的影响,为刘家峡水库增殖渔业提供科学依据。2020年3—10月,在刘家峡水库设置11个采样点,每月对浮游植物进行定性和定量采集,同时采集水样监测总氮、总磷和高锰酸盐指数等水环境指标,分析水质变化规律,及浮游植物的优势种、多样性和群落结构的季节变化特征。结果表明:刘家峡水库共检测到浮游植物7门35属63种,其中硅藻门种类最多,共17属40种;其次为绿藻门8属12种;蓝藻门4属4种,裸藻门1属2种,黄藻门2属2种,甲藻门2属2种,金藻门1属1种。浮游植物密度在(3.17—59.09)×10⁴个/L,平均密度为13.54×10⁴个/L。浮游植物生物量在0.0370—0.5004 mg/L,平均生物量为0.2137 mg/L。浮游植物密度和生物量均有在4、5月份上升和6月份骤然下降的趋势,最高值均出现在5月份。多样性指数H′值在1.16—2.43,平均值为1.84;丰富度指数D值在1.22—1.57,平均值为1.42;均匀度指数J值在0.23—0.51,平均值为...     

植物水分传输过程中的调控机制研究进展

农田土壤水分的转化利用与调控是以土壤-植物-大气连续体(SPAC)为基础,以植物为核心,其中水分在植物体内的传输与调控研究一直是国际学术研究的前沿性热点课题。本文概述了植物水分传输的驱动力和传输途径,重点从植物的气孔调节、水容调节、渗透调节、水孔蛋白调节、贮水调节、气穴和栓塞调节等方面综述了植物水分传输过程中的调控机制研究进展。通过对植物存在优化调控水分平衡的潜在能力的研究,不仅可充实SPAC系统水分传输理论,而且有助于明确植物对环境的适应机制和高效用水的潜力及其节水调控的效应,对指导干旱半干旱地区农业生产提供理论依据。     

Impacts of large dams on riparian vegetation: applying global experience to the case of China’s Three Gorges Dam

Dams are widely recognised as having significant negative consequences for the surrounding natural ecosystems and environment. China’s Three Gorges Dam, being one of the largest in the world, stands to inflict more damage than most for numerous reasons. This paper reviews the current knowledge on the impacts of dams and impoundments with regard to reservoir riparian vegetation in order to apply this knowledge to the Three Gorges Project. It also summarises research performed to date on the effects of the Three Gorges Dam on the local riparian zone and vegetation. The known and potential outcomes for local plant communities are examined in terms of their responses to the increased water levels, altered hydrological characteristics and other adverse effects associated with the construction of the dam. Vegetation responses will be diverse and change over time, but will ultimately result in a markedly different landscape and riparian zone within the Three Gorges Reservoir. These changes will take place through a loss of previous vegetation, potential invasion by exotics and result from the significant alteration in hydrological regimes and also erosion and sedimentation processes influencing and creating novel plant communities. Management of the environmental consequences of the Three Gorges Project should take into account factors associated with these processes, in order to facilitate vegetation recovery in the reservoir and to conserve biodiversity of the surrounding ecosystems.     

Responses of phytoplankton diversity to physical disturbance under manual operation in a large reservoir, China

In aquatic ecosystems, physical disturbances have been suggested to be one of the main factors influencing phytoplankton structure and diversity. To elucidate whether large-scale artificial operation of a hydroelectric reservoir has potential impacts on phytoplankton diversity, the impact on phytoplankton biodiversity of physical disturbances under artificial operation from May 2007 to April 2008 in tributaries of the Three Gorges Reservoir (TGR), China, was analysed. Two disturbance parameters, i.e. the absolute incremental rates of discharge (R _d,i ) and precipitation (R _p,i ), were created in this study for evaluating physical disturbance intensities during low and high water level periods of the TGR. Results showed that river discharge seemed to be the main factor controlling the phytoplankton diversity in low water level periods (≤151 m), and that precipitation was a potential promoter of the physical disturbance. During the 156-m impoundment process, the species diversity clearly decreased due to the high dilution effect on the phytoplankton communities. At high water level periods (>151 m), the low levels of disturbance eventually allowed the phytoplankton community to approach competitive exclusion in late February 2008. Sharply declining diversity values appeared when the Dinophyta blooms occurred in late March and late April 2008 (Peridinium and Ceratium, respectively).     

Pathogen-Host Associations and Predicted Range Shifts of Human Monkeypox in Response to Climate Change in Central Africa

Climate change is predicted to result in changes in the geographic ranges and local prevalence of infectious diseases, either through direct effects on the pathogen, or indirectly through range shifts in vector and reservoir species. To better understand the occurrence of monkeypox virus (MPXV), an emerging Orthopoxvirus in humans, under contemporary and future climate conditions, we used ecological niche modeling techniques in conjunction with climate and remote-sensing variables. We first created spatially explicit probability distributions of its candidate reservoir species in Africa''s Congo Basin. Reservoir species distributions were subsequently used to model current and projected future distributions of human monkeypox (MPX). Results indicate that forest clearing and climate are significant driving factors of the transmission of MPX from wildlife to humans under current climate conditions. Models under contemporary climate conditions performed well, as indicated by high values for the area under the receiver operator curve (AUC), and tests on spatially randomly and non-randomly omitted test data. Future projections were made on IPCC 4^th Assessment climate change scenarios for 2050 and 2080, ranging from more conservative to more aggressive, and representing the potential variation within which range shifts can be expected to occur. Future projections showed range shifts into regions where MPX has not been recorded previously. Increased suitability for MPX was predicted in eastern Democratic Republic of Congo. Models developed here are useful for identifying areas where environmental conditions may become more suitable for human MPX; targeting candidate reservoir species for future screening efforts; and prioritizing regions for future MPX surveillance efforts.     

层次分析法对南水北调中线水源区的水质评价

层次分析法(AHP)是一种多指标多因素综合评价法,其理论内容深刻而表现形式简单,包括递阶层次结构模型、判断矩阵的建立及其求值、一致性检验和综合指数计算等运算过程.在南水北调中线水源区3个采样点进行了2a的水体浮游植物和9项理化指标的检测,并应用层次分析法通过季节4因素和6项理化指标对水质进行综合评价.结果表明:层次分析综合指数PI在3采样点有差异并且变化灵敏,渠首 (陶岔S1 ) PI=0.5697,水质属于污染;库心 (小太平洋S2 ) PI=0.3619,水质属于尚清洁;丹江入库上游 (大石桥S3 ), PI=0.7755,水质属于中污染;AHP分析结果与实际基本相符.根据结果分析认为:层次分析法做为综合评价法对水质评价有重要性,值得推广应用;丹江口水库是重要的水资源,但目前水质状况并不理想,因此做好水源区的长期生态监测,加强理论和技术研究,改善水质,极为重要.     

水文气候波动下云南太平水库硅藻群落演替的长期特征

在区域气候变暖的背景下,干旱事件引起的水位频繁波动以及流域开发导致的污染物输入均可以直接威胁水库的生态安全.本研究以云南省太平水库为对象,通过对沉积物的物理(粒度、烧失量)、化学(碳、氮元素)、生物(硅藻群落)等代用指标的分析,并结合监测数据和调查资料,重建了该水库1937-2018年的生态环境变化过程,并识别了硅藻群...     

贵州山区新建水库浮游植物群落结构特征

对贵州山区新建水库的浮游植物群落结构特征进行研究,有利于了解同类水库的浮游植物群落演替趋势,还可以评估水华发生的潜在风险,为管理部门提供参考。贵州省六盘水市的观音岩水库和万营水库,分别为2018年和2017年建成蓄水的新建水库,文章以实地调查为基础对两座水库的浮游植物群落结构特征及其与环境因子关系进行了研究。2018年11月至2019年10月间的季度调查显示,两座水库分别检出32种和28种浮游植物,优势种均以硅藻和绿藻为主,藻类平均密度分别为3.46×10⁶和4.79×10⁶ cells/L。RDA分析结果显示,观音岩水库和万营水库浮游植物群落的主要驱动因子相同,均为水温(WT)、总磷(TP)和水体透明度(SD)。总体来说,新建水库在运行初期出现藻类暴发的风险较低,在后续管理中,应着重关注浮游植物密度受温度、外源营养及季节变化的影响。     

Chlorophyll content and factors affecting its spatial distribution in the Middle Volga reservoirs

On the basis of the data obtained during field observations in the summer low water period of 2001, the patterns of chlorophyll distribution and its relation to hydrological and hydrochemical factors in two eutrophic reservoirs of the Middle Volga are studied. The hydrological structure of the Gorky Reservoir, where the Volga water mass dominates, is homogeneous, while in the Cheboksary Reservoir along with the eutrophic Volga waters, the mesotrophic Oka water masses can be distinguished keeping their abiotic and biotic features over a long distance. Phytoplankton in the two contiguous reservoirs with different flow regimens and anthropogenic loads responds differently to the external influence. An autotrophic community in the Gorky Reservoir is more stable and depends little on abiotic factors which account for ∼63% of the explained chlorophyll variation. In the Cheboksary Reservoir under maximal for the Volga cascade flow velocity and anthropogenic load, the development and distribution of phytoplankton are almost completely (R ² = 0.93) controlled by these factors. The trophic state of the reservoirs has not changed as compared to the beginning of the 1990s.     

锑矿废水影响下水库沉积物中细菌群落结构特征研究

【背景】水库沉积物中的微生物是水生态系统的重要组成部分,在沉积物物质循环中起重要作用。【目的】揭示含锑废水影响下水库表层沉积物中细菌群落结构特征及影响因子。【方法】基于Illumina高通量测序技术,对冷水沟水库表层沉积物细菌群落结构进行研究并分析其与沉积物理化性质的相关性;基于FAPROTAX软件对细菌功能进行预测分析。基于重金属污染负荷指数法评价水库重金属污染情况。【结果】高通量测序结果表明冷水沟水库的细菌群落较为丰富,主要由变形菌门(Proteobacteria,40.32%-20.19%)、拟杆菌门(Bacteroidetes,25.89%-4.44%)、脱硫杆菌(Desulfobacter,9.43%-2.02%)等81个门570个属组成。相关性分析表明,不同提取形态的锑及水溶态锑与多个不同分类水平下的细菌群落有显著的相关性。FAPROTAX软件对细菌功能进行预测,结果表明,化能异养功能细菌占优势(占总细菌的14.59%-23.58%),包括化能异养(Chemoheterotrophy)和需氧化能异养(Aerobic Chemoheterotrophy);此外,与碳、氮、硫元...     

Microbial community study in newly established Qingcaosha Reservoir of Shanghai,China

Qingcaosha Reservoir located at Yangtze Estuary of China is a newly constructed and one of the largest tidal reservoirs in the world, which will be an important drinking water source of Shanghai. This study aims at investigating microbial community and its shifts corresponding to different water quality during the test running period of Qingcaosha Reservoir. The results showed lower concentrations of total nitrogen (TN) and total phosphorus (TP) in the reservoir than that in Yangtze Estuary. The number of total cultivable bacteria was significantly lower in the reservoir than that of Yangtze Estuary. The denaturing gradient gel electrophoresis (DGGE) analysis showed that the dominant microbes were α-Proteobacteria, β-Proteobacteria, Flavobacterium, Rheinheimera, Prochlorococcus, and Synechococcus. The quantitative PCR (q-PCR) results revealed significantly higher number of cyanobacteria and Microcystis in the reservoir during summer season. In addition, bacterial abundance positively correlated with TP concentration inside the reservoir. These results indicated that Qingcaosha Reservoir had ability to reduce the TN and TP in influent and improve the water quality overall. However, it also faced the risk of potential cyanobacteria bloom and eutrophication in Qingcaosha Reservoir where phosphorus will be the nutrient limiting factor.     

Acoustic assessment of the fish spatio‐temporal distribution during the initial filling of the Three Gorges Reservoir,Yangtze River (China), from 2006 to 2010

The aim of this study was to quantify the fish fauna in the Three Gorges Dam (TGD) and assess the tendency for change as well as for any spatial and temporal distribution. Two types of echo‐sounder equipment (HTI Model 241 and Simrad EY60) were used to detect the fish density and fish spatio‐temporal distribution. Eight surveys were conducted between 2006 and 2010, with the results showing that fish abundance in the Three Gorges Reservoir (TGR) increased yearly from 15.5 to 123 ind./1000 m³, a change apparently correlated with the corresponding increase in the reservoir water level. Horizontally, fish density increased from the lower reaches to the upper reaches. Fish preferred inhabiting the area around the Zhongxian section during winter and the Chongqing section in spring. Vertically, fish density was highest in the lower layer, followed by the middle layer. The difference in fish density in different water layers observed in spring was not as evident as in the winter. Fish target strength throughout the eight investigations showed a skewed distribution with respect to fish size. The overall increasing tendency of fish density and the spatio‐temporal distribution of fish species were closely related to the water level of the TGR during the impounding period. Other influencing factors included water flow rate, water depth, reservoir shape, habitat type, and protection policy.     

Nitrogen and phosphorus interchange between sediments and overlying water of a wastewater retention pond

Nitrogen and P interchange between the sediments and the overlying water of a simulated retention pond used for wastewater treatment were evaluated under conditions of seasonal temperature fluctuations and varying physico-chemical conditions (exposing floodwater surface to daylight vs. dark and turbulent vs. quiscent floodwater). Natural sediment columns obtained from two types of field retention ponds were used. One type of retention pond consisted of calcareous clay loam sediment while the sediment of second retention pond contained organic soil. Nutrient interchange between sediments and the overlying water was measured once a month over a period of one year. Nitrogen removal rates from floodwater were controlled by the initial floodwater NH ₄ ⁺ and NO ₃ ^? concentration, rate of NH ₄ ⁺ diffusion from the sediments to the overlying water, ammonification in the sediments, NH₃ volatilization and nitrification at the sediment-water interface, and denitrification in the sediments. Under the conditions studied, NH ₄ ⁺ concentrations of the floodwater were in the range of 0.01 to 0.05 µg/ml, while NO ₃ ^? concentrations were in the range of 0.27 to 0.78 µg/ml. Sediments with organic soil were found to be less effective in the removal of floodwater organic N, organic C and P, compared to the sediments with calcareous clay loam. Phosphorus exchange rates were dependent on the capacity of the sediment to adsorb or desorb P. Total P exchange rates were in the range of ?1.04 to 0.34 mg P/m² day. Seasonal temperature fluctuations, turbulent vs. quiscent water conditions or exposing the floodwater surface to daylight or dark had very little effect on N and P exchange rates.     

Population dynamics of autotrophic picoplankton in a southeastern U.S. Reservoir

Reservoirs typically exhibit a gradient along their longitudinal axis in turbidity, nutrient flux, and algal biomass. We utilized these characteristics to examine factors influencing temporal and spatial patterns in abundance, biomass, composition, and production of epilimnetic autotrophic picoplankton (APP) in Sardis Reservoir, Mississippi, USA. Over a 18-month period, APP abundance varied between about 15,000 and 700,000 cells ml⁻¹. Both APP abundance and APP biomass were closely linked to APP production and temperature. On an annual basis, the contribution of APP to total algal biomass and light-standardized production ranged between 15–47%, and 5–40%, respectively. Prokaryotes comprised more than 95% of all APP in summer, but eukaryotes dominated the APP community in winter. During the nutrient-depleted summer period, APP decreased in number but tended to increase in the percentage of total algal biomass and production, from the uplake riverine zone to the downlake lacustrine zone. Only in the second year of the study, when reservoir water residence time was more than four times greater than in the first year, were there significant differences in biomass and productivity of APP between the uplake and downlake regions. We suggest that, particularly in years or at times of the year when water-flow through the reservoir is slow, the importance of APP in Sardis Reservoir reflects a spatial and temporal gradient in nutrient availability.     

Distinct age and landscape influence on two reservoirs under the same climate

With the purpose of finding out whether different landscape occupation could affect water quality in two reservoirs of distinct age and subjected to the same climatic influence, several factors were investigated in a study lasting from January 2000 till December 2001. Total phosphorus, orthophosphate, chlorophyll a concentrations and water colour were determined monthly in winter and biweekly in summer, in two reservoirs located in the Portuguese part of River Douro catchment. Complementarily, variables such as nitrate, ammonium ion and ammonia gas, as well as water temperature, dissolved oxygen, conductivity, and transparency were measured. Trophic state of both reservoirs was assessed by computation of Carlson's Trophic State Index. The potential allochthonous sources of phosphorus and nitrogen to both reservoirs were identified and estimated. Differences between reservoirs were found for conductivity, water temperature, transparency and water colour. According to Carlson's Trophic State Index both reservoirs were classified as meso-eutrophic from winter to the beginning of summer, and as eutrophic from this period onwards. Intrinsic factors such as age of reservoir, organic matter inputs from decomposition of flooded terrestrial vegetation and exposure of littoral sediments to cycles of drying and wetting, as well as extrinsic factors such as grazing and frequent land fires, can explain the trophic state of S. Serrada Reservoir. Allochthonous sources of nutrients originated from agriculture and grazing in the catchment area, and recreational activities in the reservoir probably are the factors with greatest influence on Azibo Reservoir trophic state. Based upon the obtained data, management measures are suggested to prevent further eutrophication and water quality degradation in both reservoirs.     

水分管理调控水稻氮素利用研究进展

水、氮是调控水稻生长发育的两个重要环境因子。通过"以水调氧"增加根际溶氧量(如干湿交替、好氧栽培等)能够提升土壤硝化势和氧化还原电位,刺激土壤氮的矿化作用,使水稻处于NH+4与NO-3混合营养中,并能通过诱导水稻的生理特性及改善根系的吸收功能增强其抗旱性能,提高水稻产量及氮素利用率。光合作用是形成干物质的主要途径,土壤氮水平、氮形态与水稻光合速率紧密相关,提高叶片光合速率将有助于提高水稻的氮素利用率和产量。从稻田水分管理对土壤氮素形态特征、水稻氮吸收利用、光合速率及氮环境效应的影响等方面综述了国内外相关研究进展,并指出进一步的研究方向。     

丹江口水库动库容估算及其变化

丹江口水库库容的动态变化研究,对保障中线工程调水有重要意义.针对丹江口水库库容实测复杂、短期波动明显的问题,选用Landsat和HJ卫星数据,结合库区数字高程模型(DEM)数据,构建了动库容提取的新方法,提取了水库2000-2016年逐月库容动态信息,分析了引起库容动态变化的影响因素及其对调水的影响.结果表明: 在研究期间,丹江口水库最大库容为192.16亿m³,最小库容为79.74亿m³,平均库容为112.04亿m³;南水北调中线一期工程通水后,丹江口水库库容呈逐步增加趋势;从月际平均库容来看,5-10月逐渐增大,10-12月呈波动变化,12月至次年5月逐渐减小.周期性的人为调蓄和气候变化是库容变化的驱动力;在合理调度水库水量下,丹江口水库可满足一期调水需要.     

Determinants of the sex ratio at birth: Review of recent literature

Abstract

Use of contraception by rural Egyptian women who desire no more children is examined within a modified microeconomic framework. Four sets of factors are hypothesized to influence current use of contraception: (1) costs of contraception, ‘(2) factors influencing the slope of the desired family size function, (3) anticipated costs of child rearing and (4) strength of motivation for fertility regulation. Women's education and two measures of psychic costs were found to be important predictors of contraceptive use. Factors affecting the demand for children and thus indirectly influencing the motivation for fertility regulation were also important. Land ownership, cultivating status of the household, and educational expectations for children were significantly related to current use. Strength of motivation, although significant, was less strongly related to use of contraception. The findings suggest women who want no more children, but who are not practicing contraception, are affected by factors influencing both the costs of contraception and the costs of an unwanted child.     

三峡库区消落带植被NPP估算——基于机器学习优化CASA模型

三峡库区蓄水后,其生态效应受到广泛关注。消落带植被固碳量作为衡量库区生态系统健康状态的重要指标,对库区碳循环与生态净化具有重要意义。针对消落带不同高程植被接受光照的时间有所差异,且受河流水位变化影响,传统的CASA模型在计算消落带植被固碳量时,存在对植物的光能利用率计算不够精确等问题。以三峡库区香溪河陡坡消落带为研究区域,提出了一种耦合RBFNN模型（Radial Basis Function Neural Network）与CASA模型（Carnegie-Ames-Stanford approach）的新方法（RBF-CASA）。基于RBFNN建立环境影响因子模型,借助高程数据及植被指数等特征计算适合消落带区域的环境影响因子。结合CASA模型中温度和水分胁迫因子,提高植被在像元尺度上的净初级生产力（Net Primary Productivity,NPP）的估算精度,并对反演结果进行验证。模型验证结果显示：RBF-CASA模型估算值与观测值的决定系数（Coefficient of determination, R²）为0.730（P<0.01, n=32）。对比原始CASA模型,平均绝对误差（Mean absolute error, MAE）降低10.991,均方根误差（Root mean square error, RMSE）降低了23.861,相对均方根误差（Relative root mean square error, RRMSE）降低5.10%,平均绝对百分误差（Mean absolute percentage error, MAPE）降低1.12%。使用提出的RBF-CASA模型在库区水位落干期（7-8月份）进行固碳量估算,结果表明：NPP月均值在66.234-134.144g C/m²之间,NPP随着高程的增加呈现起伏变化,其总量在150-155m之间达到峰值,均值在170m以上区域最高。在2021年9月植被NPP均值为35.883g C/m²,2022年9月植被NPP均值为25.964g C/m²,由于降雨量减少、长江水位下降,在2021-2022年间植被恢复情况较差。研究结果可为库区碳循环、生态净化及生态修复等决策提供科学依据。     

基于生态足迹的大型水电工程建设生态补偿标准评价模型——以三峡工程为例

生态足迹作为重要的生态环境指标,已被广泛应用于可持续性分析中,但在生态补偿领域应用的较少。运用生态足迹思想,构建了6类大型水电工程建设的生态供给足迹与生态需求足迹模型,以此为基础,确立了大型水电工程建设的生态补偿标准评价模型;并进行了三峡工程案例研究。结果表明:(1)三峡工程建设6项正面影响的生态供给足迹为949.96×104hm2/a,换算成总经济价值为619.18×108元/a;三峡工程建设9项负面影响的生态需求足迹为188.98×104hm2/a,换算成总经济损失为123.18×108元/a。(2)发电产品、调蓄洪水和发电环境效益是三峡工程的主要正面影响,三者经济价值占总经济价值的95.06%;水库泥沙淤积和水库淹没是三峡工程的主要负面影响,两者经济损失占总经济损失的85.56%。(3)三峡工程建设的生态补偿标准为123.18×108元/a,水电开发业主、中央政府和地方政府是主要的生态补偿主体,两者承担了95.06%的生态补偿标准额度;河流生态系统和移民是主要的生态补偿对象,两者获得了91.39%的生态补偿额度。通过对比分析发现,构建的模型在三峡工程案例中得到了很好的验证。