生态保护区外斑块对景观连接度的影响评价

快速的城市化过程带来的生境斑块破碎化及损失会影响物种迁移、捕食等生态活动,对生物多样性构成威胁。然而,现有生态保护区可能无法覆盖其内生物的必要活动范围。生态保护区外的生境斑块对于维持生态过程也具有重要作用,因此识别生态保护区外的关键斑块并加以保护非常重要。以北京市延庆区为研究区,划分两种生境斑块,即核心生境斑块和潜在生境斑块,并基于图论构建生境网络。考虑地表覆盖类型、坡度、人类活动等因素构建生境阻力面。结合未来土地利用类型变化的模拟,研究城市化过程对区域生境网络和景观连接度的影响,选用CLUE-S模型模拟土地利用类型变化的格局。结合生境斑块特征和未来城市土地利用变化情况设计了3种未来生境变化情景。利用连接概率指数(PC)和网络连接度变化率(dI)评价不同生境变化情景下生态保护区外潜在生境斑块的景观连接度重要性,判断保护优先顺序,并分析景观格局变化对不同迁移能力物种的影响。结果表明：生态保护区外的全部潜在生境斑块对维持生境整体景观连接度有最大2.15%的影响,单个潜在生境斑块对维持景观连接度有最大0.28%的影响。此外,景观格局及其变化对不同迁移能力物种的影响差异显著,因此需针对保护物种和城市生境特征设计保护方案,研究区需要优先保护大中型斑块和位于关键位置的小型斑块。为了满足对生物多样性保护的需求,建议在区分生境斑块保护优先顺序时考虑生境斑块对景观连接度的贡献和城市化扩展过程的压力。研究为城市生物多样性保护和生境管理提供了方法参考。     

基于网络效能分析的生境网络构建与优化——以苏锡常地区白鹭为例

从网络效能分析出发研究生境网络优化具有重要意义。以快速城市化苏锡常地区为小尺度研究区、苏锡常及周边15个城市为大尺度泛研究区、白鹭为焦点物种,通过采用引入并构建网络效能概念框架、识别和构建不同尺度生境网络、调整网络结构和转换网络结构特性相结合的方法,实现了跨尺度下白鹭生境网络优化。结果表明:1)依据大尺度迁移网络完善小尺度生境网络得到的方案一和改变方案一网络特性得到的方案二均是现状生境网络的优化方案;2)方案二与方案一相比,在平均路径长度值增加、聚类系数值减少、节点度概率分布幂次关系拟合度提高,即小世界特性减弱、无标度特性增强的基础上,测度网络连接度的α、β、γ指数值得到增加,同时新增生境节点和迁移廊道数量更少,具有更好的优化成效;3)从网络效能分析出发,有益于提高生境网络跨尺度下优化方案的可行性,其分析思路既丰富了网络优化的方法论研究,也为提高上位与下位规划空间契合度的实践提供了理论支持。但从网络效能概念框架看,如网络层级分析、其他尺度情景研究、网络质量测度指标等方面还亟待丰富与完善。     

扬州市绿地生态网络构建与优化

快速城市化使得绿地生境斑块日益破碎,连接性不断降低,如何科学合理地构建绿地生态网络,连接破碎生境,对保护生物多样性和区域生态安全具有重要意义。在RS及GIS技术支撑下,通过分析连通性指数确定绿地斑块节点,采用最小耗费距离模型进行潜在廊道模拟,构建扬州市绿地生态网络体系,并基于重力模型和廊道曲度指数对生态网络结构进行定量分析,针对性地提出扬州市生态网络优化建议。结果表明:扬州市域范围内,阈值200 m下的可能连通性指数(PC)最适合作为绿地斑块节点的选择指标;绿地和农业用地为该范围内组成生态网络的优势景观类型;不同绿地斑块间的相互作用差异较大,相互作用较弱的廊道景观阻力大,生境适宜性低,需进一步改善;曲度较大的廊道景观阻力较大,生物流动效能较低,需进一步优化。研究结果可为扬州市绿地系统规划提供科学参考。     

基于生境组团化分析与景观廊道模拟的南京市白鹭生境网络构建与优化

保持生境连通性是全球生物多样性保护面临的主要挑战之一。生境网络构建与优化是一种积极主动的景观策略,但其成效取决于异质性景观背景下生境分布格局与物种响应。以南京市为例、白鹭为目标物种,开展了基于生境组团化分析与景观廊道(LSCorridors)模拟的生境网络构建与优化研究。通过整合生境适宜性评价、干扰度评价、最大熵(MaxEnt)模型模拟,实现了物种生境源地综合识别;利用景观连通性指标与核密度分析,识别了物种生境分布的组团化格局;在最小成本路径(LCPs)的基础上,定义了优化新增型与提升型两类廊道,并从物种感知与适应性变化出发,应用LSCorridors软件模拟了这两类目标优化廊道的多重随机路径及其空间范围。结果表明,南京市白鹭生境斑块共计428个,总面积达31525.75 hm²,主要是林地与水域,具有较为明显的破碎化和局部集聚特征,九大生境组团以南京长江段水域斑块为轴,沿两侧分布,彼此联系比较薄弱;最佳距离阈值4.5 km内,识别LCPs共907条,总长度1548.59 km,平均较短、分布紧凑,主要位于各生境组团内部,但仅少数连接着不同生境组团;确定的8条优化新增型廊道和10条优化提升型廊道,其LSCorridors模拟结果与LCPs存在空间偏差,前者更符合现实进而有益于避免保护低效和促进多类型、差异化的优化措施制定。研究成果能为面向生物多样性保护的南京市生境网络保护以及重点生态廊道的规划实践提供决策参考。     

福建省自然保护区生态网络的构建与优化

自然保护区对维护物种多样性具有重要意义,但城市化的快速发展造成自然保护区不断被蚕食和破坏,保护区日益破碎,生物多样性不断减少.构建生态网络能够有效连接破碎生境,为物种保护提供空间保障.本文基于ArcGIS软件平台,在确定源地斑块和景观阻力面的基础上,采用最小耗费距离模型构建福建省自然保护区潜在生态网络,并基于连通性指数和重力模型对构建网络前后的连通性和廊道重要性进行定量分析和评价,最后提出生态网络优化的措施和对策.结果表明: 林地、草地、湿地是研究区潜在廊道的重要景观构成类型;面积大的生境斑块在网络中的重要性较高;构建网络后,景观整体连通性指数和可能连通性指数显著提高;不同斑块间的相互作用强度差异很大,但相互作用力大的斑块间的廊道在生态网络中的重要性程度较高.本研究结果可为福建省自然保护和规划提供科学参考和依据.     

不同鸟类生境网络复合与优化——以苏锡常地区白鹭、鸳鸯、雉鸡为例

通过复合优化不同焦点物种的生境网络表征多数物种生境网络实现物种多样性保护,具有重要理论价值和实践意义。以苏锡常地区为研究区域,以白鹭、鸳鸯和雉鸡3种鸟类为焦点物种,通过采用生境斑块约束条件模型与最小成本路径法相结合的方法识别出生境网络;从满足集合覆盖问题视角出发,通过采用网络构成要素复合的方法进行网络复合,其中廊道与廊道的复合通过采用评价生态系统服务价值的方法实现;通过采用观测数据为生境斑块和迁移廊道增补依据的方法进行复合生境网络优化。结果表明:生境网络经过复合,廊道总面积、总长度及生态系统服务价值在分别减少了16%、68%和10%的情况下,保持了斑块间的连接度、兼顾到经济效益和生态效益最大化、覆盖了占总数86%以上的75处观测点;复合生境网络经过优化,覆盖了2010年及以后所有84处观测点,廊道总面积、总长度及生态系统服务价值分别增加了19%、21%和27%;说明生境网络复合优化定量分析方法和思路具有可行性,为网络复合研究提供了借鉴。     

基于MSPA与最小路径方法的巴中西部新城生态网络构建

目前快速城市化导致了生境斑块的日益破碎化,景观之间的连通性不断降低。构建生态网络可以连接破碎的生境斑块,增加绿地景观的连通性,对生物多样性保护具有重要意义。以高度景观破碎化的四川省巴中西部新城为研究区,采用形态学空间格局分析(MSPA)方法,提取出对研究区生态网络构建具有重要生态意义的核心区和桥接区两类景观要素,并选用整体连通性(IIC)、可能连通性(PC)和斑块重要性(d I)等景观指数,分别对核心区和桥接区进行景观连接度评价,遴选出对维持景观连通性贡献最大的10个核心区生境斑块作为生态网络的源地,并根据斑块对维持景观连通的重要性程度将其他核心区和桥接区进行类型划分,以此作为景观阻力的赋值依据,融入消费面模型中,最后采用最小路径方法构建了研究区潜在的生态网络,并基于重力模型对重要生态廊道进行了识别与提取,在此基础上有针对性地提出了生态网络优化的对策。研究结果表明,MSPA方法能够科学的辨识出研究区内对生态保护具有重要意义的结构性要素,例如作为物种栖息地的核心区和物种迁移通道的桥接区,这些要素是生态网络的重要组成部分;景观连通性的计算,明确了研究区景观要素的保护重点,为最小路径方法中的景观阻力赋值提供了重要的参考信息;基于MSPA与最小路径方法的生态网络分析框架综合了现有景观结构性要素识别、连通性分析以及物种潜在迁移路径分析等方法,将景观中潜在的生态源地和结构性廊道的连通性作为构建生态网络的重要基础和主要依据,从而使得生态网络的构建更科学。研究结果可为高度破碎化地区生态网络的构建提供重要的参考与依据,对其他地区生态网络的构建也具有一定的借鉴意义。     

基于不同网络构建方法的生境网络优化研究——以苏锡常地区白鹭为例

生境网络在支持物种长期存活中具有重要意义,由于受人类社会经济频繁活动的影响,迫切需要优化。选取城市化快速发展的苏锡常地区为研究区域,以湿地代表性鸟类白鹭为目标物种,利用2000、2010年土地利用/覆被数据,采用两种不同的网络构建方法,识别出恢复或新建生境节点或斑块,以及基于网络连接度并兼顾了集合覆盖问题遴选出重要新增生境节点,得到生境网络优化方案。结果表明:(1)恢复型生境节点对应的生境斑块面积在10—50 hm~2之间,以乔木林地为主;新建型生境节点对应的生境斑块是乔木林地和湖泊水库与河流兼而有之,均满足白鹭生境地类要求;优化的生境网络连接度较高、整体结构状况最好,兼顾了资源有限性下经济效益和生态效益最大化,与历史观测点实际情况较为吻合,可作为优化方案。(2)相同的生境斑块格局受生境格局时空变化、生态过程模拟方法及网络优化评判标准的影响,在采用不同网络构建方法时,会得到不同的网络结构及网络优化结果。采用时空格局变化与不同生态过程模拟相结合的网络优化方法,有助于分析格局-生态过程及网络结构变化情况,其思路为网络优化方法进一步深入研究提供了借鉴。     

黄河口湿地生态网络构建与评价

构建生态网络能够有效连接破碎的生境,对保护物种多样性具有重要意义。以黄河口为研究区域,利用最小耗费距离模型和重力模型构建黄河口湿地“三横两竖”的生态网络框架,并基于景观连通性指数法、廊道土地利用类型分析法和网络结构分析法对黄河口湿地生态网络进行了评价。研究结果表明:(1)通过构建生态网络,生境源地的的IIC和PC分别提高到之前的4.5倍和8.6倍,各生境源地的斑块重要性较为均衡。(2)不同生境源地之间相互关系密切程度随着距离和面积的变化存在差异。(3)黄河口湿地生态网络的α指数为0.4396,β指数为1.8125,γ指数为0.6304,具有较大优化提升空间。(4)草本沼泽和灌丛湿地是生境源地主要景观组成,盐沼湿地、草本沼泽和灌丛湿地是构成生态廊道的优势景观,分别占生态网络景观组成的31.23%、23.86%和17.30%。黄河口湿地生态网络的构建对黄河口湿地生态保护和保护区规划有重要的参考价值。     

济南城市绿地生态网络构建

城市绿地为城市生物多样性保护提供了重要的空间保障.改善与提高城市绿地生态网络的连接对保护城市生物多样性具有重要意义.以济南市为例,在GIS技术的支撑下,在考虑不同绿地斑块间的距离与景观阻力的基础上,采用最小路径方法,定量表征与模拟了研究区的潜在生态廊道,并基于重力模型和网络连接度指数,对绿地斑块间相互作用强度与生态网络结构进行了定量分析与评价.研究结果表明,风景林、滨水绿地和公园绿地是组成研究区生态网络的优势景观类型;济南绿地系统规划中的许多斑块在生态网络中起着"踏脚石"的作用,但占规划绿地面积的比例不高;不同绿地斑块间的相互作用强度差异显著,斑块之间相互作用强的绿地廊道在生态网络中的地位突出,对生物物种的丰富度、迁移与扩散等起着重要作用,而斑块之间相互作用弱的廊道景观阻力大,生境适宜性低,必须在未来的绿地系统规划中加以改善;网络结构越复杂,连接度与闭合度水平越高,对物种的迁移与扩散就越有利.因此,增加绿地斑块,优化绿地空间布局,改善绿地斑块间的连接,完善城市绿地网络是新一轮城市绿地系统规划的关键任务.研究结果可为城市建设者与规划者进行城市绿地系统规划提供科学的依据与参考信息.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Succession in the southern part of the Canadian boreal forest

Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled.     

Hectorella: A member of the betalain-suborderChenopodiineae of the orderCentrospermae

Roots ofHectorella caespitosa Hook. f. were induced to produce a red pigment which was shown to be a betalain and not an anthocyanin. These data indicate thatHectorella belongs to theChenopodiineae, the betalain suborder of theCentrospermae, and excludes alignment with the anthocyanin family theCaryophyllaceae.     

Progress on the genetics of the N2-fixing actinorhizal symbiont Frankia

The actinomycete Frankia is of fundamental and ecological interests for several reasons including its wide distribution, its ability to fix nitrogen, differentiate into sporangium and vesicle (specialized cell for nitrogen-fixation), and to nodulate plants from about 24 genera. Here, we present a review on the genetics performed so far on Frankia. At the end of July 2001, 293 kbp of Frankia DNA sequences were found in the databases. Thirty five percent of these sequences corresponded to full gene or gene cluster sequences. These genes could be divided according to their role into 6 key activities: gene translation (rrnA and tRNA ^pro gene), proteolysis (pcr genes), assimilation of ammonium (glnA and glnII), protection against superoxide ions (sodF), nitrogen fixation (nif cluster), and plasmid replication. We present a review of these genetic islands; their function, expression, localization and particular properties are discussed. A comparative analysis of Frankia nif genes from various strains and species is presented. An improved nomenclature for some of these genes is suggested to avoid conflicts. Frankia plasmids DNA sequences are also presented. The novel trends in Frankia genetics are described.     

The purification of the three trimannosyl-N-acetylchitobiose pentasaccharides from the urine of swainsonine-intoxicated sheep

A simple method for the preparative resolution of three Man₃GlcNAc₂ isomers called Ia, Ib and II has been designed. It consists mainly of the use of concanavalin A-Sepharose which allowed the total purification of Man₃GlcNAc₂-Ia, and then of anion-exchange resin in borate buffer-gradient to separate the Ib and II isomers. The purity of each oligosaccharide was checked by two HPLC methods. The use of these oligosaccharides for different analytical and biosynthetic purposes is discussed, and the unexpected resistance of one of the Man₃GlcNAc₂ alditols to the action of endo--N-acetylglucosaminidase H is noted.     

Evaluation of the Pro-Lab ID ring system for the identification of medically important yeasts

We evaluated 151 coded isolates of medically important yeast species belonging to the genera Candida, Cryptococcus, Geotrichum, Rhodoturula, Saccharomyces and Torulopsis using the newly developed rapid Pro-Lab Identification Ring, PL 960 system (PLID-Ring). All isolates were concurrently identified by the API 20C and conventional procedures comprising macro- and micromorphology, assimilation and fermentation of various carbon and nitrogen compounds. The PLID-Ring system identified isolates of Candida albicans, C. kefyr, C. krusei, C. lusitaniae, C. parapsilosis, Rhodotorula rubra, and Torulopsis glabrata with 100% accuracy in 24 h. This system identified C guilliermondii and S. cerevisiae isolates with an accuracy of 90% and 86%, respectively, while those belonging to Cr. neoformans, T. candida (= C. famata), C. rugosa and C. tropicalis were identified with 38.4%, 50%, 12.5% and 50% accuracy, respectively. Three isolates of Cr. laurentii were not identified by the PLID-Ring system. The overall accuracy of the PLID-Ring system was 81.45% (123 of 151 isolates). However, the system does not include species such as Cr. laurentii in its data base. When these three Cr. laurentii isolates were excluded from the evaluation, the accuracy of the PLID-Ring system increased from 81.45% to 83.1%.     

An ACTH-Like Peptide Immunocortin: Effect on the Activity of Cells from the Rat Adrenal Cortex

The effect of immunocortin, an ACTH-like decapeptide VKKPGSSVKV corresponding to the 11–20 sequence of the variable part of the human IgG1 heavy chain on the content of 11-hydroxycorticosteroids (CS) in rat adrenal glands and blood serum in vivo was studied. An intramuscular injection of immunocortin at a dose of 10 g/kg was found in an hour to induce a twofold decrease in CS content in the adrenal glands and a 1.8-fold increase in the blood serum CS content. At the same time, an immunocortin dose of 100 g/kg exerted practically no effect on the CS content and its dose of 1000 g/kg increased the CS content both in adrenal glands and in blood serum by 1.6 and 2.2 times, respectively. Four hours after the injection of any of the three doses of immunocortin, the CS content in adrenal glands did not differ from the control value, and after 24 h the content decreased threefold. Immunocortin was shown to be bound by the ACTH receptors in the membranes of the rat adrenal cortex with a high affinity and specificity (inhibiting the specific binding of ¹²⁵I-labeled ACTH-(11–24) peptide with K _i of 1.2 nM).     

New and old problems in the taxonomy of the Gelidiales (Rhodophyta)

The order Gelidiales includes over 140 agar-producing taxa. Many species are taxonomically confused; the boundaries of one family and all but four genera recently have been contested, and the controversy over ordinal status has lasted for over 25 years. This study reviews recent developments in the taxonomy of the group and suggests future areas for studies. The order cannot be defined by a few exclusive characters, as intended in the past, but it shows a unique combination of characters. Additional studies on Gelidiella and Acanthopeltis seem advisable to clarify family limits. The segregation of Onikusa and Pterocladiastrum is doubtful. Only three of six characters discriminate Gelidium from Pterocladia. None allows complete generic segregation and all need variability studies. Analysis of nomenclatural types in the light of morphological variation would permit an understanding of species limits in Gelidium and Pterocladia. Similar studies are needed in Gelidiella and Ptilophora.     

Freeliving nematodes from the Salton Sea

Thirteen species, or putative species, of freeliving nematodes are recorded from a variety of habitats in the hypersaline Salton Sea, the largest inland lake in California. This doubles the number of species of multicellular invertebrates known to occur in the lake. All species are referable to known marine genera, and are regarded as having a marine coastal origin. The range of taxa present is representative of the full taxonomic spread found in marine coastal habitats, suggesting that a wide range of marine nematode taxa are capable of adapting to the hypersaline conditions. The broad spectrum of feeding types present suggests that nematodes play a variety of ecological roles within the lake.