鄂西七姊妹山泥炭藓沼泽植物多样性

以湖北宣恩县七姊妹山泥炭藓沼泽植被为研究对象,对其物种组成、群丛类型、植物群落生物量、物种重要值及多样性特征进行了分析.结果表明,该沼泽物种组成较为丰富,共计41科65属94种;沼泽植被可区分为9个群丛,其中泥炭藓(Sphagnum palustre ssp. palustre)、野灯心草(Juncus sethuensis)和堇菜(Viola verecunda)为9个群丛共有种.在9个群丛中,大理苔草-泥炭藓群丛(Ass.Carex taliensis-Sphagnum palustre ssp.palustre)的生物量最高,亮鞘苔草-泥炭藓群丛(Ass.Carexfargesii-Sphagnum palustre ssp.palustre)的生物量最低;泥炭藓的生物量占其所在群丛总生物量的74.78%-91.18%.泥炭藓的平均盖度为88.6%,在其中7个群丛中,泥炭藓的重要值大于其他物种的重要值.在群丛物种多样性指数中,丰富度指数(R)最高的为西南小叶地笋 庐山蔗草一泥炭藓群丛(Ass.Lycopus coreanus vat.cavaleriei Scirpus lushanensis-Sphagnum palustre ssp.palustre),优势度指数(C)最高的为亮鞘苔草-泥炭藓群丛,多样性指数(H')最高的为西南小叶地笋 野灯心草-泥炭藓群丛(Ass.Lycopus coreanus vat.cavaleriei Juncus setchuensis-Sphagnum paslustre ssp.palustre),均匀度指数(J)最高的为野灯心草 宜昌苔草-泥炭藓群丛(Ass.Juacus setchuensis Carex alliFormis-Sphagnum palustre ssp.palustre).     

湖北省海口湖、太白湖与武山湖水生植物多样性的比较研究

为了探讨人为干扰与淡水湖泊水生植物多样性的关系,比较研究了湖北省海口湖、太白湖与武山湖水生植物多样性的现状和近20a来三湖泊水生植物多样性的变化,讨论了密齿苦草对太白湖人为干扰的适应机制,探讨了武山湖水生植物多样性及其退化水生生态系统恢复的可能途径。主要结论是：（1）海口湖、太白湖、武山湖现各分布有水生植物57种、35种和11种,分别隶属于28科42属、18科30属和6科9属,近20a来三湖泊分别有1种、9种和29种水生植物消失。（2）1999－2000年三湖泊各分布有水生植物群丛类型14个、6个和0个;全湖植被覆盖率分别是96.18%,76.17%和0％;全湖平均单位面积生物量分别为2896g/m^2,177g/m^2和0g/m^2(鲜重）,近20a来其分别下降了12.1%,88.3%和100％;武山湖水生植被已完全消失。（3）所有群丛中,以海口湖的“野菱＋菱群丛”（Trapa incisa Trapa bispinosa Ass.)的群落物种多样性指数最高;密齿苦草群丛（Vallisneria denseserrulata Ass.);菹草群丛（Potamogeton crispus Ass.)和和“野菱＋菱群丛”为海口湖与太白湖所共有,三者的多样性指数均是海口湖显著高于太白湖。水生植物多样性丰富程度的现状是：海口湖＞太白湖＞武山湖,多样性丧失的程度与其所受干扰程度成正相关。（4）密齿苦草对太白湖人为干扰的适应机制是其具有繁殖能力强的地下根状茎和多数地下越冬块茎。（5）武山湖水生植物多样性及该湖退化水生生态系统恢复的关键是消除工厂废水污染的同时,处理好施肥量与透明度的关系、鱼与草的关系。     

长湖水生植物多样性及其变化

研究了湖北省第三大湖泊长湖水生植物多样性的现状及其长期变化,并探讨了多样性丧失的机理及多样性恢复与保护的有效途径。主要结论：(1)长湖现有水生植物98种,多度最大的是微齿眼子菜(Potamogeton maackianus)、密齿苦草(Vallisneria denseserrulata)、野菱(Trapa incisa)、双角菱(T.bispinosa)、菹草(Potamogeton crispus)、紫萍(Spirodela polyrhiza)、穗花狐尾藻(Myriophyllum spicatum)、轮叶黑藻(Hydrilla verticillata)、满江红(Azolla imbricata)。(2)长湖现有水生植物群丛类型14个,群落物种多样性指数最高的是芡实 野菱 双角菱群丛(Euryale ferox Trapa incisa T.bispinosa Ass.),其次为轮叶黑藻 密齿苦草|大茨藻群丛(Hydrilla verticillata Vallisneria denseserrulata Najas marioa Ass.)与竹叶眼子菜 穗花狐尾藻群丛(Potamogeton malaianus Myriophylhum spicatum Ass.)。(3)20年来,已有6种水生植物和7个水生植物群丛类型从长湖消失,植被覆盖率下降了54．85％,全湖平均单位面积生物量下降了69．78％。(4)多样性丧失的主要原因是过度养殖、过度打草和耙捞作业,以及由此导致的湖水透明度的大幅度下降。(5)多样性恢复的有效途径是政府部门的行政干预与经济支持。     

升金湖植物区系及其群落演变

升金湖国家自然保护区是我国重要的湿地自然保护区,通过实地调查,在分析升金湖植物群落现状与变化的基础上,探讨了水产养殖对升金湖植物群落的影响.调查发现升金湖共有水生和湿生维管植物43科94属125种,其中发现圆基愉悦蓼(Polygonum jucundum var. routundum Z. Z. Zhou et Q. Y. Sun)这一新亚种;滩涂植物群落主要为白朗苔 阿齐苔群丛(Ass. Carex brownii Carex argyi )、圆基愉悦蓼群丛(Ass. Polygonum jucundum var. routundum)和蓼子草群丛(Ass. Polygonum cripolitanum);水生植物群落包括菰群丛(Ass. Zizania caduciflora)、菱群丛(Ass. Trpa sp.)、芡群丛(Ass. Euryale ferox)、菹草群丛(Ass. Potamogeton crispus)、金鱼藻群丛(Ass. Ceratophyllum demersum)、聚草 金鱼藻群丛(Ass. Myriophyllum spicatum Ceratophyllum demersum)、聚草 苦草 水车前群丛(Ass. Myriophyllum spicatum Vallisneria natans Ottelia alismoides)等.目前全湖水生植被的盖度仅约30%.通过多年的调查记录对比,升金湖沉水植被严重退化,过度的水产养殖可能是主要因素,保护水生植被刻不容缓.     

鄱阳湖苔草湿地非淹水期CO2释放特征

2009年9月至2010年4月非淹水期,在鄱阳湖南矶湿地国家级自然保护区,选择以灰化苔草为建群种的洲滩湿地,设置土壤-植物系统(TC)、剪除植物地上部分(TJ)2个试验处理(分别代表生态系统和土壤呼吸),利用密闭箱-气相色谱法测定了非淹水期鄱阳湖苔草湿地CO,释放通量.结果表明:苔草湿地生态系统呼吸与土壤呼吸均具有明显的季节变化模式,释放速率变化范围分别为89.57～1243.99和75.30～960.94 mg CO2·m-2·h-1,土壤呼吸占生态系统呼吸的比例为64%(39%～84%);土壤温度是苔草湿地CO2通量的主要控制因子,可以解释呼吸速率80%以上的变异;生态系统呼吸与土壤呼吸的温度敏感性指数(Q10)分别为3.31和2.75,且冬季的Q10值明显高于春秋季节;土壤水分与CO2释放速率之间未达到显著相关;非淹水期,鄱阳湖苔草湿地是大气CO2的汇,其强度为1717.72 g C·m-2.     

西凉湖水生植物多样性研究

研究了江汉湖群西凉湖水生植物多样性的现状及其变化 ,讨论了西凉湖水生植物多样性丧失的原因和保护的途径。主要结果是 :( 1 )西凉湖现有水生植物 3 2科 5 6属 77种 ,优势种类为微齿眼子菜、密齿苦草、轮叶黑藻、菹草、野菱、双角菱、金鱼藻、凤眼莲和菰等。 ( 2 )西凉湖现有水生植物群落类型 1 3个 ,全湖水生植被覆盖率约为 61 %,平均生物量为 1 4 70 .5 g/m2 。 ( 3 )物种多样性指数最高的群落是“凤眼莲 +野菱 +双角菱群丛”(D =0 .8499,H =2 .975 8) ,其次为“菰—凤眼莲群丛”与“野菱 +双角菱群丛”(D =0 .840 1 ,H =2 .82 35 ;D =0 .83 2 4,H =2 .888) ,以微齿眼子菜群丛的多样性指数最低 (D =0 .2 2 81 ,H =0 .782 3 )。 ( 4 )二十年来 ,西凉湖水生植物多样性严重丧失 :植被覆盖率和全湖平均单位面积生物量分别下降了 3 8.80 %与 77.87%,先后有 8种水生植物 (水葱、荸荠、莲子草、乌菱、细果野菱、萍蓬草、睡莲、小眼子菜 )和 4个水生植物群落类型(荇菜群落、乌菱群落、马来眼子菜群落、穗花狐尾藻群落 )从西凉湖消失。 ( 5 )多样性丧失的原因是围网养殖、过度收获水草、耙捞蚌类螺类等人为干扰     

鄱阳湖湿地灰化苔草种群生产力特征及其水文响应

淡水湖泊湿地中,水文条件是影响湿地植物分布和生长发育的关键因素,研究特定湿地植物种群与水文变化之间关系,对于认识湿地植被格局形成及进行湿地生态调控与恢复具有重要意义。选取鄱阳湖湿地洲滩优势植物——灰化苔草(Carex cinerascens)种群作为研究对象,基于野外实地观测数据,研究不同高程带灰化苔草春草种群生产力特征及其对水文变化的响应。结果表明:春草生长季内各高程带灰化苔草种群变化规律基本一致,但其生长发育过程对水文条件产生差异性反应,长期连续水淹和半水淹条件抑制灰化苔草的生长,而间歇性半水淹和未水淹条件则促进灰化苔草伸长生长和生物量积累;生长初期灰化苔草通过储水策略应对水分缺乏形成的干旱胁迫,而生长末期则通过增加干物质含量来应对淹水胁迫;灰化苔草定植与生长发育需要一定的水文条件,淹没期平均水深3.70—2.78 m、淹没频率42.08%—43.17%、平均距湖水面高度-0.23—0.77 m的水文环境更有利于灰化苔草的生长发育。研究结果可为未来鄱阳湖湿地植被保护和湖泊水位调控提供重要参考依据。     

博斯腾湖湖滨湿地植被数量分类与排序

应用双向指示种分析(TWINSPAN)方法对湿地植物群落进行分类,采用除趋势对应分析(DCA)、典范对应分析(CCA)对群落进行排序,以明确博斯腾湖湖滨湿地的主要植物群落类型及影响植被类型变化和分布的主要环境因子。结果表明,博斯腾湖湖滨湿地植被可分为7个主要群丛,分别为长苞香蒲(Ass.Typha angustata)、芦苇+长苞香蒲(Ass.Phragmites australis+Ty.angustata)、芦苇+水烛(Ass.P.australis+Ty.Angustifolia)、多枝柽柳-芦苇(Ass.Tamarix ramosissima-P.australis)、胡杨-多枝柽柳(Ass.Populus euphratica-Ta.ramosissima)、旱柳-多枝柽柳(Ass.Salix matsudana-Ta.ramosissima)和多枝柽柳(Ass.Ta.ramosissima),它们分布于湖滨浅水带、湖滨沼泽带、湖岸乔灌林带和旱生灌丛带;TWINSPAN分类产生的7个主要群丛在DCA排序图上被很好地反映出来。CCA排序与DCA排序结果基本一致,说明土壤含水量和土壤总含盐量是决定该地区植被分布格局的主要环境因子。博斯腾湖湖滨湿地植被种类单一,生态结构简单,水盐动态及其相互作用是影响该地区植被分布的主要因素之一。因此,在对博斯腾湖湖滨湿地进行植被保护与重建过程中,需重点考虑土壤含水量和土壤总含盐量这2个主要环境因子的影响,合理开发、利用水资源,防止土壤盐渍化的发生。     

木论喀斯特常绿落叶阔叶混交林群丛数量分类及稳定性

加深对喀斯特顶极群落植物组成、群落结构和群落分布的认识可以为该区域生物多样性保护和森林管理提供参考。本文基于广西木论喀斯特常绿落叶阔叶混交林25 ha森林动态监测样地地形、土壤和物种组成数据, 采用多元回归树对该群落进行群丛分类, 并分析各群丛多样性和稳定性。结果表明, 群落可分为6个群丛, 分别为群丛I: 长序厚壳桂+栀子皮+香叶树群丛(Ass. Cryptocarya microcarpa + Itoa orientalis + Lindera communis), 群丛II: 长序厚壳桂+灰岩棒柄花+罗伞群丛(Ass. Cryptocarya microcarpa + Cleidion bracteosum + Brassaiopsis glomerulata), 群丛III: 圆果化香树+密花树+齿叶黄皮群丛(Ass. Platycarya longipes + Rapanea neriifolia + Clausena dunniana), 群丛IV: 圆果化香树+滇丁香+齿叶黄皮群丛(Ass. Platycarya longipes + Luculia intermedia + Clausena dunniana), 群丛V: 长序厚壳桂+罗伞+伞花木群丛(Ass. Cryptocarya microcarpa + Brassaiopsis glomerulata + Eurycorymbus cavaleriei), 群丛VI: 小叶栾树+长管越南茜+圆果化香树群丛(Ass. Boniodendron minus + Rubovietnamia aristate + Platycarya longipes)。除群丛I外, 各群丛总体的多样性指数较高。Shannon-Wiener指数、Simpson指数以及Pielou均匀度指数表现出一致的变化趋势: 群丛VI > 群丛V > 群丛IV > 群丛III > 群丛II > 群丛I, 而丰富度则为群丛VI > 群丛IV > 群丛V > 群丛I > 群丛III > 群丛II, 物种多样性在中海拔群丛最高。中上坡部位群丛稳定性最高, 洼地群丛稳定性最低。海拔在群落结构及组成中起重要作用, 可能是影响群落分布的重要因素。     

不同水淹深度对鄱阳湖洲滩湿地植物生长及营养繁殖的影响

水淹深度是影响湿地植物生长和繁殖的关键因子,不同湿地植物对淹水深度存在着不同响应。然而,在水情不断变化的背景下,鄱阳湖洲滩湿地植物种群和群落如何变化还不清楚。为了探究淹水深度对湿地植物生长的影响,并预测鄱阳湖洲滩湿地植被分布的趋势,采用控制实验模拟了不同水淹深度(0、0.5、1 m和2 m)下鄱阳湖湿地3种优势植物(灰化薹草(Carex cinerascens)、南荻(Miscanthus lutarioriparius)和虉草(Phalaris arundinacea))的生长和繁殖情况。实验结果表明:1)水淹对灰化薹草总生物量的影响最显著。遭受水淹时,灰化薹草把大部分的生物量集中在地下部分;随着水淹深度逐渐增加,南荻的生物量逐渐减少;不同深度水淹对虉草生物量没有产生显著影响(P0.05)。就生物量而言,虉草对水淹的适应性强于其他两种植物。2)不同水淹深度下,灰化薹草的株高都显著降低;而南荻只在2 m水淹梯度下株高才显著降低。在枯水年时,下降的水位有利于南荻向较低高程迁移。3)不同深度水淹对灰化薹草的分株没有产生显著影响(P0.05);而虉草在经过2 m水淹后分株数显著高于其他水淹深度。在丰水年时,相比于灰化薹草和南荻,升高的水位对虉草的繁殖影响较小。在一个水位周期性变化的湿地生态系统中,不同深度的水淹对植物的生长及退水后的繁殖产生了严重影响,研究结果为预测水文变化对湿地植被的生存和分布提供了重要的依据。     

两湖平原六个湖泊水生植物多样性的比较研究

为了揭示人为干扰对淡水湖泊水生植物多样性的影响 ,本文采用断面法 ,应用全球定位系统 (GPS)技术与地理信息系统 (GIS)技术 ,比较研究了所受干扰强度各不相同的两湖平原的白莲湖、海口湖 (轻度干扰 )、长湖、西凉湖 (较强度干扰 )、大通湖与武山湖 (重度干扰 )水生植物多样性的现状及其 2 0年来的变化 ,并探讨了人为干扰强度与植物多样性丰富程度及丧失程度间的关系。主要结论是 (1) 2 0 0 1年白莲湖、海口湖、长湖、西凉湖、大通湖与武山湖各分布有水生植物 6 9、 6 7、 98、 77、 5 6和 38种 ,6个湖泊各有水生植物群丛类型 14、 14、 14、 13、 6和 0个 ,植被覆盖率分别为 10 0 %、 96 18%、 6 5 32 %、 6 1 18%、10 6 0 %和 0 % ,全湖平均单位面积生物量分别是 2 2 31g m2 、 2 718g m2 、 1816g m2 、 14 71g m2 、2 5 6g m2 和 0g m2 。 (2 ) 2 0年来 ,6个湖泊各有 1、 1、 6、 7、 9和 2 9种水生植物消失 ,消失的水生植物群丛类型数目分别是 1、 1、 4、 4、 5和 6个 ,水生植被覆盖率分别下降了0 %、 3 82 %、 32 85 %、 37 80 %、 5 9 4 0 %和 91 0 0 %。 (3)多样性丰富程度的现状是白莲湖、海口湖 >长湖、西凉湖 >大通湖、武山湖 ,丰富程度与所受干扰强度成负相关关系 ;多样性丧失程度与所     

Wildfire effects on microbial biomass and diversity in pine forests at three topographic positions

The aim of this study was to determine microbial biomass carbon and diversity at three topographic positions (ridge, middle slope and valley bottom) at varying periods after the occurrence of wildfire. The purpose of this study was to enhance knowledge on the microbiological status of post-fire sites for a better estimate of the success of their restoration. Results showed that the biomass carbon and microbial diversity were affected by fire: the averages of the burnt plots were <50% of those of the unburnt plots. In addition, the biomass carbon at the sites studied 3 years after and 25 years after fire, and 5 months after and 9 years after fire, were not significantly different from each other. On the other hand, the site studied 5 months after fire showed the highest microbial diversity, followed by the ones studied 3, 25, 9 and 6 years after fire. In terms of topographic position, the ridge was shown to be the most affected by fire. These results show that fire can adversely affect the microbial biomass carbon and microbial diversity of the soil, the recovery of which may take a long time.     

Effects of flooding, salinity and herbivory on coastal plant communities, Louisiana, United States

Flooding and salinity stress are predicted to increase in coastal Louisiana as relative sea level rise (RSLR) continues in the Gulf of Mexico region. Although wetland plant species are adapted to these stressors, questions persist as to how marshes may respond to changed abiotic variables caused by RSLR, and how herbivory by native and non-native mammals may affect this response. The effects of altered flooding and salinity on coastal marsh communities were examined in two field experiments that simultaneously manipulated herbivore pressure. Marsh sods subjected to increased or decreased flooding (by lowering or raising sods, respectively), and increased or decreased salinity (by reciprocally transplanting sods between a brackish and fresh marsh), were monitored inside and outside mammalian herbivore exclosures for three growing seasons. Increased flooding stress reduced species numbers and biomass; alleviating flooding stress did not significantly alter species numbers while community biomass increased. Increased salinity reduced species numbers and biomass, more so if herbivores were present. Decreasing salinity had an unexpected effect: herbivores selectively consumed plants transplanted from the higher-salinity site. In plots protected from herbivory, decreased salinity had little effect on species numbers or biomass, but community composition changed. Overall, herbivore pressure further reduced species richness and biomass under conditions of increased flooding and increased salinity, supporting other findings that coastal marsh species can tolerate increasingly stressful conditions unless another factor, e.g., herbivory, is also present. Also, species dropped out of more stressful treatments much faster than they were added when stresses were alleviated, likely due to restrictions on dispersal. The rate at which plant communities will shift as a result of changed abiotic variables will determine if marshes remain viable when subjected to RSLR. Received: 8 April 1998 / Accepted: 15 June 1998     

Community dynamics of Neocallimastigomycetes in the rumen of yak feeding on wheat straw revealed by different primer sets

Anaerobic fungi (Neocallimastigomycetes) play an important role in fermenting lignin-rich plant biomass into sugars in the rumen of animals, representing a very promising enzyme resource to contribute to the conversion of plant biomass into biofuels. However, current studies about their functions mainly focus on limited species, and little is known about the coordination of different members of the anaerobic fungi in the digestion process of plant fibres. In this study, the community composition of anaerobic fungi in the rumens of yaks at five different time points (1, 3, 5, 7.5 and 24 h after feeding wheat straw) was investigated employing a cultivation-independent method using ITS clone libraries. Comparison of five pairs of primers showed that PCR primer sets could have clear amplification bias and therefore potentially affect the interpretation of the resulting fungal community structure; then two primer sets GM1/MNGM2 and ITS1/ITS4 were selected. Among the 398 sequences from 10 clone libraries, 18 operational taxonomic units (OTUs) of Neocallimastigomycetes were obtained, covering five known genera and one yet uncultured lineage. OTUs belonging to the bulbous-type morphotype (Caecomyces- or Cyllamyces-related) and the rhizoidal genus Neocallimastix were abundant and predominantly present, representing 62.7% and 19.3% OTUs respectively. In all the later samples taken from 3 h to 24 Neocallimastigomycetes h after feeding, a relatively stable community composition was revealed: members of Neocallimastix increased to represent 43.4–49.4% and the bulbous-type morphotype declined to represent 39.5–42.7%. This implies a substantial turnover and synergy between bulbous and rhizoidal morphotypes of anaerobic fungi during the process of fibre digestion. Our study provided the first insight into the in vivo temporal change in the anaerobic fungal community, and the role of Neocallimastigomycetes with a bulbous morphotype in the degradation of plant cell wall in the yak rumen.     

The restoration of the destroyed forest vegetation in Yunmeng Mountain,Beijing

The study was carried out in two sample plots which were set in two regions where the vegetation was protected for 8 and 3 years.The results of DCA (Detrended Correspondence Analysis) showed that the vegetation on the north or northwest aspects in Yunmeng Mountain (Quercus liaotungensis coppice and Spiraea trilobata scrubs) has no systematic floristic difference from the vegetation which existed in the same area in 1964 with the approximate aspect under human disturbance, no matter whether they were protected for 8 or 3 years. In south and southeast slopes (Vitex negundo var. heterophylla community), the protected shrublands have larger species diversities than that of the shrublands in 1964. In addition, there is no significant difference between the communities which were protected for different periods of time. However, the number of species in protected area is larger than that in unprotected area. Furthermore, the community which is under a longer period of protection developes larger diversity. The north slopes have more species than the south slopes.The protection is helpful for communities to develope their biomass. The biomass of scrubs on the north slope is much greater than that on the south in the site where the vegetation is protected for 8 years, as well as in the site under 3 years protection. In contrast, due to the larger coverage of the scrubs on north slopes, the biomass of herbage on the south slope is much greater than that on the north slope in both sites. When compared with the biomass of the shrublands in unprotected area, the increase of biomass shows the efficiency of protection. The aboveground biomass of scrubs in both site are 2.8 and 2.2 times greater than that in unprotected area. The ratio of the total aboveground biomass of Site 1, Site 2 and the unprotected area is 2.5:2.2:1 on south aspect.     

Ecological investigations on lichen fields of the Central Namib

Number, geographic location, extent and characteristics of lichen fields were recorded within the Central Namib fog desert. Their occurrence is restricted to stable surfaces in the near coastal belt, while percentage cover changes with exposure, elevation and distance from the coastline. Maximum coverage of 70% was found at a distance of 5 km from the coast near Wlotzkas Baken. The highest biomass rate of 400 mg/m² was measured here at a distance of 1 km from the coast, where Teloschistes capensis appears as cushion growth type. Distribution patterns on hills, riverbeds and polygon structures are described. In general, fruticose and foliose lichens dominate on SW-exposed, ocean-facing habitats. Crustose species dominate on NE-E-exposed plots.Species composition and distribution, particularly the distribution of the fruticose species T. capensis (L. f.) Vain. ex Müll. Arg., were investigated in seventysix plots along twenty W-E transects in one lichen field near Wlotzkas Baken. T. capensis occurs in three different growth types: tuft, cushion and mat. Four zones are distinguished within the above lichen field, each dominated by a growth form indicating various influences of different climatic, geomorphic or biogenic parameters.     

Life at the extreme: meiofauna from three unexplored lakes in the caldera of the Cerro Azul volcano,Galápagos Islands,Ecuador

On Isla Isabela, Galápagos Archipelago, three so far unexplored lakes were investigated in the caldera of Cerro Azul, one of the most active volcanoes in the world. The lakes face recurrent desiccation and eruption events and showed distinct differences in their water chemistry. Thirty cores from the upper 15 cm of sediment indicate distinct differences in the composition of meiobenthic communities between the lakes. In total, 27 different aquatic metazoan species could be distinguished. Numerically, rotifers dominated in two of the lakes, with mean densities up to 4.56 × 10⁶ individuals m⁻² while the third lake was dominated by a gastrotrich of the genus Chaetonotus (0.67 × 10⁶ individuals m⁻²). The largest lake harboured up to 14.4 × 10⁶ nematodes m⁻², which is the highest nematode density thus far reported for a freshwater habitat. The lakes yielded few nematode species (S = 7, N = 887) and calculation of the Shannon–Wiener index (H′) indicated an exceptionally low nematode diversity. The nematode community of one lake was clearly dominated by an undescribed suction-feeding Mesodorylaimus (59.6%), the community of the other lake by the epistrate feeder Achromadora pseudomicoletzkyi (89.3%), whereas the third lake surprisingly contained no nematodes. The benthic nematode biomasses for the two nematode-containing lakes differed by a factor 50. The food webs of the three lakes are presumed to have an exceptionable simply structure.

古尼拟青霉表型多样性及其与活性成分的关系

目的研究表型多样性与活性成分之间的联系。方法研究10株古尼拟青霉菌株的培养特性,观察菌落形态,测定其产孢量和粗蛋白、多糖、甘露醇、麦角甾醇、腺苷等主要活性成分含量。结果A类菌株菌落背面褶皱不平,中央为棕色环状,周边为淡黄色,是生长性状优良、活性成分含量高,适于大规模工业化生产的优质菌株。结论不同菌株具有不同的形态特征,且形态特征与其产孢量及主要活性成分存在一定内在联系。     

稻鸭共育稻田水体藻类动态变化

稻鸭共育技术作为稻田复合种养模式,是有效控制常规稻作生态污染的重要技术途径.通过对不同时期稻田藻类群落种类、密度、生物量及环境因子进行测定,研究稻鸭共育稻田水体藻类动态变化规律.结果表明,稻田藻类群落包括蓝藻门、绿藻门、硅藻门、裸藻门,隐藻门及甲藻门共6门、38属、108种.随着水稻发育进程,藻类优势种单位生物量增加,前期皆以银灰平裂藻、栅藻等为优势种,后期对照以方鼓藻,灿烂颤藻,短小舟形藻等为优势种,而放鸭区优势种皆是裸藻门,包括绿色裸藻,尖尾裸藻,梭形裸藻等.稻鸭共育稻田水体藻类初期有个适应期,在放鸭后15d左右藻类密度及生物量显著下降,之后开始上升.与常规对照相比,稻鸭共育藻类密度及生物量较低,放鸭对稻田水体生态系统的影响主要体现在放鸭45d以后,表现为水体全P增加,全N减少,藻类多样性下降,优势种发生变化.环境因子与藻类相关分析表明,全磷与裸藻生物及藻类总生物量存在显著正相关,相关系数分别为0.697、0.625,而全N与藻类相关性不显著.     

Microbial diversity of topographical gradient profiles in Fushan forest soils of Taiwan

To evaluate the microbial diversity of Fushan forest soils, the variation of soil properties, microbial populations, and soil DNA with soil depth in three sites of different altitude were analyzed. Microbial population, moisture content, total organic carbon (C_org), and total nitrogen (N_tot) decreased with increasing soil depth. The valley site had the lowest microbial populations among the three tested sites due to the low organic matter content. Bacterial population was the highest among the microbial populations. The ratios of cellulolytic microbes to the total bacteria in organic layers were high, implying their roles in the carbon cycle. The microbial biomass carbon (C_mic) and nitrogen (N_mic) contents ranged from 130.5 to 564.1 μg g⁻¹ and from 16.7 to 95.4 μg g⁻¹, respectively. The valley had the lowest C_mic and N_mic. The organic layer had the highest C_mic and N_mic and decreased with soil depth. Analysis using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplicons of 16S rDNA showed that the bacterial diversity of the three sites were very similar to each other in the major bands, and the variation was in the minor bands. However, the patterns in PCR-DGGE profile through gradient horizons were different, indicating the prevalence of specific microbes at different horizons. These results suggest that the microbial diversity in the deeper horizons is not simply the diluted analogs of the surface soils and that some microbes dominate only in the deeper horizons. Topography influenced the quantity and diversity of microbial populations.