香溪河消落带人工构建与自然恢复植物群落的差异性

三峡工程修建后所形成的大幅度、反季节水位消涨节律使得库区消落带植物群落及其生态功能严重退化,积极开展消落带植物群落的生态恢复有利于改善库区的生态环境。以香溪河消落带为例,通过对人工恢复地和自然恢复地植物群落的野外调查,研究了不同恢复模式下植物群落的物种组成与结构、物种多样性以及群落生物量特征,以客观评价不同模式对植物群落恢复的影响。结果显示:(1)人工与自然恢复模式下的消落带均形成了以1年生和多年生草本为主的植物群落,其中人工恢复样地中共有草本48种、灌木6种,自然恢复样地中有草本42种,无灌乔木分布;(2)人工恢复地植物群落的物种多样性略高于自然恢复地,自然恢复地植物群落的物种多样性随海拔梯度的增加呈先增加、后减少的变化趋势,而人工恢复地因在消落带上引入了灌木物种呈先增加、后减少、再增加的趋势,植物群落组成在不同海拔梯度也呈相应的变化;(3)2种恢复模式下植物群落生物量均随着海拔梯度的增加而逐步增加,但人工恢复地草本植物群落的生物量显著高于自然恢复地,其中总平均生物量高出27.5%,海拔145 m及165 m处的生物量分别高出62.7%和69.4%。实验表明,人工恢复通过引入灌木物种和增播草本植物,在一定程度加快了消落带的恢复进程,增强了植物群落的稳定性。     

三峡水库消落区植物群落结构及其季节性变化规律

为揭示三峡水库消落区出露期间植物群落结构特征的季节性变化规律,于2017年4、6和98月,设置了15个调查样地,并根据高程将消落区分为145~155 m、156~165 m和166~175 m等3个区域,并设置未水淹区域（高程176~-185 m）为对照。结果表明,消落区出露时间显著影响着植物群落的组成,随着出露时间的延长,消落区植物群落优势种及其优势度变化规律因植物的生活型不同呈现出相反的变化规律。从4月至8月,优势植物狗牙根、牛鞭草、喜旱莲子草等多年生草本植物优势度下降,鬼针草、苍耳、醴肠、水蓼、野胡萝卜、狗尾草等一年生草本植物优势度增加。而未水淹区植物优势种及其优势度变化规律不会因生活型不同而表现出不同的规律,不同地点的植物群落优势种差异较大,相对来说艾蒿较为优势,其次为小飞蓬。高程也是影响植物群落特征的主要因子,消落区植物群落Shannon-Wiener指数、Margalef指数、Simpson指数、植物高度均值显著低于未水淹区域,随着高程的增加,Shannon-Wiener指数、Margalef指数、Simpson指数生物多样性指数及、植物高度均值呈增加趋势。三峡水库消落区之所以呈现出目前的植物群落分布特征,植物内在的适应机制包括植物本身的冬季耐水淹能力、夏季抗旱能力、抗病虫害能力以及植物的及其繁殖对策、种源扩散对策等是主因,而外界环境条件,包括消落区土层厚度、地形坡度、土壤基质氮磷等营养盐,以及受水淹持续时间、水淹深度、高程、消落区出露时间等是其主要驱动因子。     

小清河流域夏季浮游植物功能群与环境因子的关系

为了解济南地区小清河流域浮游植物群落结构特征,于2015年8月对小清河流域浮游植物群落结构和水环境因子进行了野外调查。通过划分浮游植物功能群以及采用典范对应分析等方法,分析了小清河流域浮游植物群落的组成及结构特征。结果表明:共鉴定出浮游植物68种,各点位种类平均值为21.36种,物种密度平均值为1.49×10⁷ cells/L,香农威纳指数平均值为2.55,均匀度指数平均值为0.58。全流域共划分出浮游植物功能群12类,MP类物种数占主要优势,其中舟形藻属优势明显。典范对应分析结果显示,总氮和总磷是影响小清河流域浮游植物群落结构的主要环境因子。综合分析表明,小清河流域水体呈中度污染。     

环境变化对湿地植物根系的影响研究

湿地生态系统具有独特的水文特征和潜育化土壤环境,湿地植物在生长过程中往往表现出独特的环境适应机制。根系作为植物重要的功能器官,是湿地植物群落与周围环境实现物质循环与能量流动的关键纽带,在发挥植物的生态功能及维持生态平衡中具有重要作用。因此,近年来植物根系生理生态研究越来越受到关注。从湿地植物根系在植物生长及湿地生态系统中的作用出发,综合论述环境因子对湿地植物根系的影响及作用机制,着重评述近年来水分条件、土壤盐分、土壤养分、有毒有害物质以及其他因子对湿地植物根系生理生态特征的影响等方面的研究进展和亟待解决的问题,指出湿地植物根系研究将是湿地生态学的重要研究方向。     

影响草鱼摄食水生植物因素的研究进展

在自然界,草鱼Ctenopharyngodon idella大量摄食使水生植物的生物量下降,抑制植物群落的构建,影响利用水生植物修复水体生态系统。本文通过叙述草鱼消化系统的结构和功能、自身质量和放养密度与摄食行为的关系,以及草鱼摄食植物后产生的生理反应;讨论水温、pH和溶解氧、亚硝酸盐及氨氮含量对草鱼摄食的影响;分析水生植物的物理结构、营养成分和化学成分对草鱼摄食行为影响以及不同生长时期草鱼对水生植物的摄食率,以期为生态修复工程中先锋物种选择或水生植物恢复方法提供技术参考。     

浮游植物群落生态学指标分析的专家系统

本系统利用Ｆｏｘｂａｓｅ高级编程技巧,实现只需对应输入藻类细胞数或个体数与放大倍数,即可对浮游植物种类组成,生物量,优势种,污染指标种,各污染等级示种和营养级别指示种的ｓｈａｎｎｏｎ多样性指数,马加列夫多样性指数,综合指数,硅藻指数,渔产潜力等指标的进行分析,给出水域浮游植物群落生态学指标,为水质分析提供依据。     

水分对湿地生态系统不同植被类型土壤种子库的影响

探讨退化河流湿地生态系统不同植被类型土壤种子库对水分变化的响应机制，了解植物群落的演替规律和退化驱动力，可为退化湿地的保护和生态恢复提供参考。通过水分控制实验（干旱、湿润和积水），在妫水河流域自然湿地生态系统五种不同植被类型的表层土样上开展土壤种子库的萌发实验。结果表明，不同的植被类型对于水分变化的响应模式明显不同。根据其植被特征可分为三类：（1）对于以中旱生植物为主的林下杂类草群落，随着水分的增加其植物种类和数量明显增多。相比较干旱处理，积水处理组植物种类和数量增加的幅度分别为43.8%和249.5%，其中湿生植物明显增多；多样性指数的分析也表明积水处理组其多样性较干旱处理组更高。（2）对于湿生/水生的欧地笋杂类草、芦苇杂类草和芦苇优势种群落，其表现为湿润处理时单位面积物种数和植物密度最低，而干旱和积水处理皆高于湿润处理；多样性水平则呈现随水分增加而降低的趋势。（3）水生的香蒲优势种群落则呈现和林下杂类草群落相反的结果，随水分增加其植物种类明显下降、多样性水平显著降低，但植物数量随水分的增加而呈增加趋势、最大增幅为137.6%。在植物群落组成和相似度方面，本文涉及的五种植被类型皆有其特定的优势植物及结构组成，并和其他植被类型有较高或较低的相似性，并呈现出对于不同水分条件的适应特异性。本研究表明，水分因子在植物群落的发生和演替中起重要作用，是湿地生态系统植被类群演替的重要外在环境因素。     

长江口东滩湿地不同盐沼植被样地内浮游植物群落结构的差异

根据2015年5-12月在长江口东滩盐沼湿地水域采集的浮游植物监测数据,分析了海三棱藨草[Scirpus mariqueter(编号:HS)]、互花米草(Spartina alterniflora)入侵早期(编号:HZ)和互花米草入侵后期阶段(编号:HH)、芦苇[Phragmites australis(编号:LW)]等4种植被样地浮游植物群落结构的时空差异。结果表明,共发现浮游植物64种(或属),隶属4个门。硅藻门种类最多,有48种(或属),占总种类数的73.8%;其次为蓝藻门种类,有10种(或属);绿藻门有6种。优势种为中肋骨条藻(Skeletonema costatum)(Y=0.76)、洛氏菱形藻(Nitzschia lorenziana)(Y=0.03)和近缘斜纹藻(Pleurosigma affine)(Y=0.02)等3种。5-8月盐沼植被区浮游植物的种类数相对较高,而9-12月(秋季至冬初)种类数明显下降。各个植被样地中硅藻的月平均丰度均明显高于其它藻类,而甲藻丰度最低。HS和HZ植被样地中的浮游植物群落的种类数和丰度并无显著性差异(P0.05),HH和LW样地浮游植物的种类数和丰度同样无显著性差异;前2种生境浮游植物的月平均丰度是后2种生境的3.8倍,这主要是由于硅藻的丰度差异较大造成的。从物种丰富度指数(D)来看,两两生境间物种丰富度指数未发现显著性差异(P0.05)。Shannon指数(H')变化趋势类似于均匀度指数(J),5-8月和12月H'值相对较高。从群落聚类和排序结果来看,在空间上4种植被样地浮游植物群落难以区分开;而在时间上大致分为2组[即5-8月(春初至夏末)与9-12月(秋季至冬初)]。总体来说,不同植被样地浮游植物群落动态月份差异较大,同一高程植被样地浮游植物群落差异不显著。研究表明,长江口盐沼植被生境浮游植物群落组成与邻近水体有着较大的不同,具有独特的生态功能。     

松花江野鲤的主要经济性状和遗传特性

从1986年至1990年,在黑龙江水产研究所松浦试验场,用分别来自松花江下游同江江段,嫩江中下游泰来县江桥和兴凯湖的野鲤(分别取名为松花江野鲤,嫩江野鲤和兴凯湖野鲤)后代,进行形态学比较和池塘生长等测定,结果发现松花江野鲤在形态特征上和生产性能上与另两种野鲤有明显差别。根据对体长、头长、体高、尾柄长、背鳍基部长,背鳍前端至吻端的距离、背鳍后端至尾鳍的距离,胸腹鳍距离、腹臀鳍距离、侧线鳞、鳃耙数、背鳍条数等20个性状的比较测定,方差分析和多重比较,松花江野鲤有17个性状与嫩江、兴凯湖野鲤有差异,达到显著的程度。在生产性能上,通过池塘生长对照和抗寒,抗病等测定,松花江野鲤一龄时的体型瞬时增长率比嫩江、兴凯湖野鲤分别快50％,22.4％;相对体重增长率分别快88.7％、29.6％(三个池塘均值)。二龄时,体重瞬时增长率分别比嫩江、兴凯湖野鲤快32.2％、25.6％(二池均值)。三龄时,体重瞬时增长率分别快27.59％、10.25％。池塘饲养成活率,松花江野鲤一龄时分别比嫩江、兴凯湖野鲤高13.8％、8.0％。二龄时分别高8.7％,1.6％。三龄时分别高3.5％,6.5％。由于饲养成活率高,群体产量松花江野鲤也明显高于嫩江和兴凯湖野鲤。     

渠道硬化对养殖场外排水污染物浓度影响分析

在对虾养殖收获季节,对广西钦江农场自然沟渠和硬化沟渠的水生植物群落和外排水污染物浓度变化情况进行了监测。结果表明,自然沟渠水生植物群落以挺水植物为主,优势种类为喜旱莲子草、李氏禾、孔雀稗和水莎草,硬化沟渠破坏了水生植物生境,水生植物种类数、盖度和生物量明显降低。自然沟渠对颗粒态的氮、磷具有明显的拦截作用,从而有效降低外排水中的高锰酸盐指数、TP、TN浓度,而硬化沟渠丧失了这一功能。自然沟渠的水生植物优势种多无经济价值,改造群落结构以促进有效利用,并及时进行清淤,是当前经济技术条件下,沟渠净化的主要发展方向。     

Epidemic disease in a sheep herd with a possible relationship to a pestivirus

In connection with a case of epidemic disease with high morbidity and mortality in a flock of sheep, a pestivirus infection could be diagnosed. Pathological-anatomical abnormalities were very similar to the character of BVD/MD. Scientific findings on pestivirus infections in sheep are discussed.     

Trophic relationships between a native and a nonnative predator in a system of natural lakes

Abstract – Bull trout, a species of char listed as threatened under the US Endangered Species Act, have been displaced from portions of their historic range following the introduction of nonnative lake trout. It has been suggested that competitive exclusion as a result of trophic overlap between bull trout and lake trout may be the causal mechanism associated with displacement of bull trout. This study used stable isotope data to evaluate trophic relationships among native bull trout, nonnative lake trout and other fishes in seven lakes in Glacier National Park (GNP), Montana. Bull trout and lake trout had greater δ¹⁵N values relative to other fishes among lakes (δ¹⁵N ≥ 3.0‰). Lake trout had greater δ¹⁵N values relative to bull trout (δ¹⁵N = +1.0‰). Bull trout had greater δ¹³C values relative to lake trout in six of the seven lakes examined. Although both bull trout and lake trout had greater δ¹⁵N values relative to other fishes within lakes in GNP, differences in δ¹⁵N and δ¹³C between bull trout and lake trout suggest that they are consuming different prey species or similar prey species in different proportions. Therefore, displacement of bull trout as a direct result of complete overlap in food resource use is not anticipated unless diet shifts occur or food resources become limiting. Additionally, future studies should evaluate food habits to identify important prey species and sources of partial dietary overlap between bull trout and lake trout.     

Habitat characteristics affecting occurrence of a fluvial species in a watershed altered by a large reservoir

Flooding river valleys following construction of dams restrict fluvial environments to reaches that were formerly headwaters. Whether remaining habitat is suitable for all life stages of fluvial species is poorly understood. A fluvial species, Arctic grayling Thymallus arcticus, showed a dramatic decline following flooding of the Upper Peace River and the formation of the Williston Reservoir. We related landscape and field site‐specific features with occurrence of juvenile Arctic grayling using an information theoretic approach. For the landscape model, an association was identified between stream order and Arctic grayling occurrence although stream order alone was a poor predictor. A positive association between juvenile Arctic grayling occurrence and distance from the Williston reservoir and stream order, as well as a negative association with water temperature and temperature variance, was deemed important for the field site model. Both modelling approaches indicated size of stream system to be an important influence on occurrence of juvenile grayling in the Williston watershed. River length required for suitable river habitat for salmonids has not previously been identified, but should be factored into future management plans when evaluating the impact of proposed hydroelectric dams and subsequent flooding of river systems.     

The isoelectric point, a key to understanding a variety of biochemical problems: a minireview

We address the importance of the isoelectric point (IEP) of proteins and membrane components such as phospholipids for our understanding and interpretation of isoforms and opposite charge interactions in the formation of complexes. Five examples drawn from the literature are newly approached from the IEP point of view to clarify general principles.     

六边形开口方形人工鱼礁阻力系数数值模拟与模型试验比较研究

为了对4种不同开口大小的六边形开口方形人工鱼礁在4种迎流角度下数值模拟和水槽模型试验的阻力系数进行对比验证,分别利用水槽模型和数值模拟试验方法对4种不同开口比（γ_ty=0.0625,0.14,0.25,0.39）六边形开口方形人工鱼礁在4种迎流角度（θ=0°,15°,30°,45°）状态下的阻力进行测定,并计算两种方法的阻力系数。结果表明：（1）在数值模拟和水槽模型试验中,人工鱼礁模型阻力均随着开口比的增大而减小;礁体迎流角度的变化可改变礁体阻力,且在4种迎流角度下,人工鱼礁阻力在θ=30°时最大。（2）人工鱼礁数值模拟与水槽模型试验中,当θ为15°、30°和45°时,阻力系数均随着开口比的增加而增加,具有明显的线性关系,且阻力系数在迎流角度θ=30°时最大。（3）数值模拟与模型试验阻力的相对误差在0.12%~17.18%,平均误差7.43%;礁体阻力系数的相对误差在0.03%~14.64%,平均误差5.26%。阻力及阻力系数误差均在20%以下。水槽模型试验与数值模拟阻力和阻力系数相关系数R分别为0.99和0.80,P<0.001,具有极强的相关性。因此,利用数值模拟精细化研究人工鱼礁水动力性能是可行的。     

Just a dream

告别凉爽的大连,来到炎热的上海,对于从小生活在这一带的我而言,这样的炎热,似乎再平常不过了.然而今年的这份炎热注定要和以往不同.没有一天好几集的肥皂剧,没有打不完的游戏,没有满冰箱的冷饮,更没有那种想马上开学的冲动.因为,一切都回不去了.以前从未觉得寒暑假是一场梦,而当我现在意识到这个的时候,这个梦却再也不会醒来. 但是,与其说的这么伤感,还不如说,我只是又开始追寻一段新的梦!     

Characterization of a cDNA encoding a homolog of actin-related protein 4 from a marine red alga Porphyra yezoensis

ABSTRACT:   A cDNA ( PyARP4 ) containing an open reading frame for a protein of 573 amino acids was identified in the marine red alga Porphyra yezoensis . The conceptual PyARP4 protein exhibits significant similarity to actin-related protein (ARP) 4 in the terrestrial plant Arabidopsis . Comparison of the deduced amino acid sequence showed moderate sequence identity (30%) to a conventional actin in P. yezoensis , as seen in comparisons between ARP and conventional actins of other organisms. A putative bipartite nuclear localization signal and an actin motif were found within the PyARP4 amino acid sequence. In a phylogenetic analysis, the PyARP4 was found to cluster with the ARP4 of other organisms. The expression level of PyARP4 did not change significantly among four developmental stages of life cycle and was lower than that of a conventional actin. This cDNA therefore may serve as a useful internal standard in gene expression analyses of differentially expressed genes in P. yezoensis .     

Nitrification performance of a propeller-washed bead clarifier supporting a fluidized sand biofilter in a recirculating warmwater fish system

A propeller-wash bead filter (PWBF) and a fluidized sand filter (FSF) on a 28 m³ recirculating system stocked with tilapia maintained favorable water quality at five different feed rates, ranging from 0.9 to 4.5 kg feed per day. TAN removal rates ranged up to about 200 g TAN/m³ of media per day for each of the units. Peak rates of 244 g TAN/m³ of media per day were observed when the recirculating flow was boosted by 20%. Roughly 75% of the removal was accomplished by the fluidized sand filter an observation that is consistent with the difference between the fluidized sand filter volume (0.92 m³) and the bead filter media volume (0.28 m³). The bead filter's primary function was clarification. At the highest daily feed load, over 570 g dry weight of solids were removed during each daily bead filter backwashing event. A 20% increase in flow, at the same daily feed rate, improved solids removal to over 670 g dry weight per bead filter backwash event. The PWBF and FSF combination provided suitable water quality for fish production; however, further increases in feed loading were limited by carbon dioxide buildup and oxygen limitations.