Influence of invasive palms on terrestrial arthropod assemblages in desert spring habitat     

Jeffrey G. Holmquist  Jutta Schmidt-Gengenbach  Michèle R. Slaton 《Biological conservation》2011,(1):518-525

Invasive plants can eliminate native flora and ultimately have negative indirect effects on fauna and the functional ecology of ecosystems, but understanding of these cascading effects on arthropod assemblages is poor. Desert spring habitats are small, isolated landscape elements that are literal oases for flora and fauna and support high diversity assemblages; invasive palms can colonize desert springs and form monocultures. In an effort to understand effects of these invasive trees on higher terrestrial trophic levels at springs, we contrasted assemblage structure of terrestrial arthropods in native vegetation versus invasive palm habitat. We sampled arthropods in paired palm and native habitat at 10 springs in Death Valley National Park, California, USA, during both spring and fall growing seasons using suction sampling. The invading palms Phoenix dactylifera L. and Washingtonia filifera (Linden ex André) supported a mean of only one-sixth of the arthropod abundance, one-third of the species richness, and half the family richness of native habitat. Almost all orders were less abundant in palms, and most families and species were either absent or virtually absent in palm habitat. Both live and dead palm leaves were depauperate, and season and block effects were minimal. Impacts of these visually striking invasives clearly go beyond monopolization of ground cover, and invading palms appear capable of reshaping the functional ecology of desert springs. If control efforts are undertaken, we recommend complete removal of palms, because killed but standing “ghost palms” and associated thatch persist for many years and will continue to provide poor arthropod habitat and prevent native plant establishment.  相似文献   

Regrowth and revegetation in temperate Australia presents a conservation challenge for reptile fauna in agricultural landscapes     

Damian R. Michael  Ross B. Cunningham  David B. Lindenmayer 《Biological conservation》2011,(1):407-415

Secondary vegetation, associated with changes in land use, presents a conservation issue in the preservation of biological diversity in agricultural landscapes. We examine the interactive effect of eucalypt regrowth and rock habitat on reptile species richness and assemblage structure in fragmented agricultural landscapes in south-eastern Australia. Zoogeographic and geomorphic factors influenced species richness and community composition. Saxicolous and arboreal species were less abundant in grassy woodland regrowth, whereas Bassian and fossorial species responded positively to forest regrowth (and tree plantings). Regrowth with rock habitat had higher reptile richness, and more old growth-associated taxa, than regrowth without rock habitat. Thus, the presence of saxicolous habitat can reduce the time required for regrowth to attain a climax community structure and elements of old growth fauna. However, in the absence of vegetation management, secondary vegetation can reduce habitat suitability for a broad range of reptiles. In agricultural landscapes historically supporting savannah-like vegetation, habitat manipulation may be necessary to maintain reptile diversity. Furthermore, tree plantings in temperate agricultural landscapes should aim to restore historical vegetation composition and structure, thereby reflecting the habitat requirements of extant species and facilitating evolutionary processes. In grassy woodland ecosystems, this may involve heterogeneous plantings which emulate natural levels of canopy cover and solar penetration. Maintaining biodiversity in agricultural landscapes will therefore involve managing trade-offs to preserve areas of dense regeneration for regrowth-dependant fauna, while at the same time, creating open-canopy environments to enhance habitat for ectothermic organisms.  相似文献   

Determinism versus chance in canopy gap herbaceous species assemblages in temperate Abies-Betula forests     

Xiaowei Qin  Gang Li  Dexiang WangRuiying Liu  Gaihe Yang  Yongzhong FengGuangxin Ren 《Forest Ecology and Management》2011,262(6):1138-1145

It is not known if the species composition of herbaceous plant assemblies within tree-fall gaps is determined stochastically or whether it follows species-specific and environmentally-determined patterns. We applied three methods, fitting species abundance distribution models, comparing community similarities, and testing species-environmental variable association, to evaluate the relative importance of chance and deterministic rules in controlling herbaceous composition within canopy gaps in the Abies-Betula forests of Mt. Taibai, Central China. Herbaceous species abundance within canopy gaps was well fit by a neutral model, showing that relative abundance was qualitatively consistent with stochastic processes. Although species composition in gaps significantly differed from closed canopy sites (ANOSIM, R = 0.509, p = 0.001), there were no significant differences among gaps of different age groups (ANOSIM, R = 0.035, p = 0.191) or gaps of different size groups (ANOSIM, R = 0.089, p = 0.057). Similarly, gaps of similar age and size did not show significantly higher similarity (χ² = 2.30, df = 3, p = 0.513) in species composition than gaps of distinct age or size. Moreover, there were only eight species, including two light-demanding species, confined to larger gaps among the 69 species, and only an additional seven species found more commonly in larger gaps, whereas most herbaceous species were gap size generalists. Canonical correspondence analysis and random permutation tests suggested that only 27% of species with abundance ?5 were associated with environmental variables in gaps. In summary, the species composition in gaps was not constrained significantly by gap traits; rather species were distributed stochastically, likely through by random dispersal and recruitment limitation of species from the surrounding available species pool. Measures that introduce gap disturbance, such as selective harvesting, are still recommended when the maintenance of total biodiversity in forests is a concern.  相似文献   

Short-term effects of a mass coral bleaching event on a reef fish assemblage at Iriomote Island, Japan   总被引：3，自引：0，他引：3  

Mitsuhiko  SANO 《Fisheries Science》2004,70(1):41-46

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High temporal species turnover enhances the complexity of fish assemblages in Amazonian Terra firme streams     

J. I. Mojica  C. Castellanos  J. Lobón-Cerviá 《Ecology of Freshwater Fish》2009,18(4):520-526

Abstract –  The objective of this study was to quantify fish species diversity in Terra firme streams of the Río Amazonas drainage. Fish diversity was quantified as the number of species collected or species richness in two sites of Yahuarcaca stream, a typical, first order tributary of the central Río Amazonas near Leticia (Colombia). The extremely high species richness recorded, 131 and 133 for the two study sites for a total of 171 species, was primarily due to species of low abundance (rare species) mostly with adults <5 cm in total length. The nonasymptotic tendencies of accumulated species richness over time for the 1999 samples at the two study sites and for the combined samples of 1999, 2001 and 2005 at site 2 suggested that the real number of fish species may be still greater. These findings emphasise the importance of long-term sampling designs to quantify species richness in these systems. Terra firme streams actually sustain greater fish richness than previously reported for similar sized streams that in turn, represent a substantial per cent of the total species richness reported for vast areas of the main stem of Río Amazonas including tributaries and lakes. Terra firme streams should be considered critical hotspots for conservation and management efforts which are urgently needed given the rapid development of ornamental fisheries on small streams throughout Río Amazonas drainage.  相似文献   

Distribution and community structure of ichthyoplankton from the northern and central California Current in May 2004–06     

TOBY D. AUTH 《Fisheries Oceanography》2008,17(4):316-331

The distributions, concentrations, and community structure of pelagic larval fishes collected from the central and northern California Current in the northeast Pacific Ocean during May 2004, 2005, and 2006 were analyzed to investigate inter-annual, latitudinal, cross-shelf, and depth-stratified variability. The inter-annual climate-induced variability during the sampling period provided a unique opportunity to observe how larval fish communities adjust to rapidly changing environmental conditions. The 170 depth-stratified samples collected from three cruises yielded 14 819 fish larvae from 56 taxa representing 23 families. Dominant larval taxa were Engraulis mordax , Citharichthys spp., Sebastes spp., and Stenobrachius leucopsarus . Larval concentrations decreased significantly in 2006 from 2004 and 2005 levels following the anomalous oceanic conditions observed in 2005 and decreased water temperature in 2006. Larvae were generally found in higher concentrations at northern (>43°N) versus southern (<43°N) stations, with larval E. mordax and Citharichthys spp. found almost exclusively in the north during all sampled years. Inter-annual variability related to dynamic upwelling intensity was observed in cross-shelf larval distributions, although concentrations of S. leucopsarus larvae consistently increased in the offshore direction, while larval Sebastes spp. were generally found in highest concentrations at intermediate stations along the shelf. Multivariate analyses revealed that latitude, station depth, and sea-surface temperature were the most important factors explaining variability in larval concentrations. The present study shows that the ichthyoplankton community of the central and northern California Current changed dramatically in response to the variable environmental conditions of 2004–06.  相似文献   

Fish abundance and community composition in native and non-native plants following hydrilla colonisation at Lake Izabal, Guatemala     

C. A. BARRIENTOS  & M. S. ALLEN 《Fisheries Management and Ecology》2008,15(2):99-106

Abstract  Fish community composition was assessed among six macrophyte habitats, including hydrilla, Hydrilla verticillata (L.F.) Royle, common native species (bulrush, Scirpus spp., muskgrass, Chara spp., eelgrass, Vallisneria americana Michx. and Illinois pondweed, Potamogeton illinoensis Morong) and no-plants, to assess potential impacts of recent hydrilla colonisation on the littoral fish community at Lake Izabal, Guatemala. Fish biomass was significantly different among habitats, with hydrilla supporting the highest fish biomass. Fish density did not differ significantly among habitats. Total fish species richness was similar (12-15 species) among habitats, but community composition changed with macrophyte presence. Biomass of mojarra, Cichlasoma maculicauda Regan, which supported the most important subsistence fishery at the lake, was significantly different among habitats and had the greatest biomass in the hydrilla habitat. Although hydrilla may adversely affect native plants, lake access and other uses, it provided useful fish habitat and likely was not detrimental to the Lake Izabal fish community composition.  相似文献   

航道整治透水框架群对鱼类集群影响的水声学探测     

郭杰  王珂  段辛斌  陈大庆  房冬梅  刘绍平 《水生态学杂志》2015,36(5):29-35

四面六边透水框架作为工程构造物具有良好防冲促淤功能,在航道整治工程中得到广泛应用。为了探究四面六边透水框架群对鱼类的影响,于2014年5－6月,应用EY60回声探测仪和双频识别声呐（ARIS Explorer 1800）对金城洲透水框架工程区水域进行定点水声学监测,并采集工程区附近的渔获物。结果表明,工程区共捕获鱼类114尾,包含3目、4科、12属、14种,体长均值为（27.29±8.84）cm,95%置信区间为 25.65～28.92 cm。EY60回声探测仪对工程区共监测时长9589 min,鱼的数目12356尾,工程区鱼体的目标强度均值为（-63.24±5.79）dB,95%置信区间为-63.35～-63.15 dB;数据独立性T检验显示,工程区与对照区之间无显著性差异（P>0.05）;通过回声探测仪和双频识别声呐对鱼类出现频次监测,工程淹没区是对照区1.18倍,而工程半淹没区却是对照区的0.85倍;说明处于水下的四面六边透水框架群对鱼类具有一定的诱集作用。  相似文献   

春季和夏季杭州湾北部海域鱼类种群结构分析   总被引：3，自引：0，他引：3  

王淼  洪波  张玉平  孙振中 《水生态学杂志》2016,37(5):75-81

为了解杭州湾北部海域鱼类种群组成及结构特点,利用相对重要性指数(IRI)、Cluster聚类和多元统计等方法对该海域鱼类种群结构进行分析。结果显示,春、夏季杭州湾北部海域共出现鱼类22种,隶属8目、12科、19属,鲈形目占比最高,为50.0%,其次为鲽形目和鲱形目,所占比例各为13.6%,生态类型以海洋性鱼类为主。调查共发现6种鱼类优势种,春季优势种为棘头梅童鱼(Collichthys lucidus)、鮸(Miichthys miiuy)和凤鲚(Coilia mystus),夏季优势种为棘头梅童鱼、白姑鱼(Pennahia argentata)、龙头鱼(Harpodon nehereus)、鮸和焦氏舌鰨(Cynoglossus joyneri)。Cluster聚类和非度量多维标度显示,杭州湾北部海域鱼类种群可分为春季组(Ⅰ组)和夏季组(Ⅱ组),春季组由5月站点组成,夏季组由8月站点组成,组间差异系数达到84.17%。ANOSIM分析表明,春季组和夏季组种群结构差异极显著(R=0.554,P0.01);BIOENV分析表明,春、夏季杭州湾北部鱼类种群结构与温度的相关性最高,相关系数为0.404。研究表明,杭州湾海域仍然是棘头梅童鱼、凤鲚等经济鱼类的产卵场和索饵场,鱼类种群结构的季节变化明显,棘头梅童鱼的生态洄游习性可能是造成种群结构变化的主要原因。  相似文献   

基于流场数值仿真的人工鱼礁组合优化研究   总被引：1，自引：0，他引：1  

林军  章守宇  叶灵娜 《水产学报》2013,37(7):1023-1031

基于特征礁水槽集鱼实验,研究了不同结构人工鱼礁和不同背景速度下黑鲷幼鱼在各流速区段出现频度,以鱼类出现频度高、水平流速为背景速度的0.7倍和0.8倍以下的流场空间体积作为背涡流范围指标,以垂向上升流速为水平来流速度的0.1倍和0.2倍以上的空间体积作为上升流范围指标,基于Fluent、采用大涡模拟法(LES)的湍流模型,进行数值水槽建模,以4种单位鱼礁组合方案为例来分析不同组合流场效应的差异和优劣。研究表明,边长3 m的正方体鱼礁,以20～30个单礁、1～2倍礁距进行五点式、对称型单位鱼礁组合投放为宜,这样既能发挥礁体的协同效应,又能使单位鱼礁的调控范围达到最大化。  相似文献