山西北部地区沙棘群落的数量分类和排序研究

采用双向指示种分析法对山西北部地区沙棘群落进行分类和排序研究,结果将山西北部地区沙棘群落划分为14个群系,并论述了各群系的特征。DCA排序进一步说明了群系的分布格局与水分和土壤的密切关系,结果表明组成沙棘灌丛的种群对群落生境具有指示作用,能客观反映群落的生境特征．     

Facilitative interactions among the pelagic community of temperate migratory terns,tunas and dolphins

We studied habitat and behavioral interactions among the marine community of top pelagic predators over the Atlantic continental shelf, observed from shipboard surveys off the northeastern United States. We hypothesized that foraging seabirds, specifically common terns Sterna hirundo and roseate terns S. dougallii, associate positively with the distribution and abundance of large, easily‐detected subsurface marine predators, as a result of facilitative interactions. Few rigorous tests examine the effect of interspecific interactions on seabird distributions, though many papers note the importance of environmental influences. Fewer, still, assess facilitation, defined as positive interactions among multiple taxa (birds, fish, mammals), where individuals use foraging neighbors for improved prey detection or enhanced prey availability. Our use of spatiotemporal‐structured Bayesian hierarchical models allowed us to test for fine‐scale associations of common and roseate terns with aggregations of tunas and cetaceans, and with standard oceanographic parameters. High tern abundance was linked to relatively high tuna densities and low dolphin densities, as well as high sea surface temperatures, shallow water, and proximity to shore. The fact that terns foraged when in the presence of tunas or relatively dense dolphin pods supports our hypothesis that the mechanism behind this spatial association involves positive interspecific interactions (attraction), a phenomenon that has been described but rarely quantified. This study reveals that community structure depends on static and dynamic covariates alike, ranging from bathymetry to the movement of other guild members. To improve the efficacy of predictive modeling, ecosystem approaches to applied conservation management should integrate not only habitat, but also behavior and community factors into analyses, especially in the case of marine spatial planning.     

Nearshore subtidal community structure compared between inner coast and outer coast sites in Southeast Alaska

Processes that structure subarctic marine communities, particularly in glaciated regions, are not well understood. This understanding is needed as a baseline and to manage these communities in the face of future climate-driven changes. This study investigates two coastal regions of Southeast Alaska with the goals to (a) identify and compare patterns of subtidal community structure for macroalgal, fish, macroinvertebrate (>5?cm), and small epibenthic invertebrate (<5?cm) communities between inner coast and outer coast sites and (b) link patterns of community structure to habitat and environmental parameters. Species assemblage and benthic habitat data were used to compare species diversity and community composition at 6?m and 12?m depths at nine inner coast and nine outer coast sites. Multivariate analysis was applied to reduce environmental variables to major gradients, to resolve community structure, and to relate community structure to habitat and environmental variables. Increased salinity and decreased temperature at outer coast sites compared with inner coast sites were associated with community structure, with greater species diversity at outer coast sites at 6?m depth. Invertebrate community composition was associated with benthic habitat, including crust and coralline algae for macroinvertebrates, and algal cover and substrate for small epibenthic invertebrates. This research suggests that marine communities in glaciated regions are strongly influenced by freshwater input and that future climate-driven changes in freshwater input will likely result in marine community composition changes.     

Metazoan parasite diversity of the endemic South African intertidal klipfish,Clinus superciliosus: Factors influencing parasite community composition

The current trend in marine parasitology research, particularly in South Africa, is to focus on a specific parasite taxon and not on the total parasite community of a specific fish host. However, these records do not always reveal the ecological role of parasites in ecosystems. Thus, the present study aimed to determine which factors influence the parasite community composition of the endemic southern African intertidal klipfish, Clinus superciliosus (n = 75). Metazoan parasites were sampled from four localities (two commercial harbours - west coast; and two relatively pristine localities - southeast coast) along the South African coast. A total of 75 klipfish were examined for parasites, where 30 distinct taxa, representing seven taxonomic groups were found: Acanthocephala (4 taxa), Cestoda (2 taxa), Crustacea (5 taxa), Digenea (11 taxa), Hirudinea (2 taxa), Monogenea (1 taxon) and Nematoda (5 taxa). Results indicated that the main driver of diversity was locality, with the highest diversity on the southeast coast, most likely due to higher water temperatures and upwelling compared to the west coast. The parasite community composition of the klipfish was significantly influenced by water temperature and parasite life cycle. These results emphasise the importance of parasitological surveys including all parasite taxa in hosts from multiple localities and seasons, to better comprehend their ecological role.     

Predicting the constraint effect of environmental characteristics on macroinvertebrate density and diversity using quantile regression mixed model

Various factors, such as habitat availability, competition for space, predation, temperature, nutrient supplies, presence of waterfalls, flow variability and water quality, control the abundance, distribution and productivity of stream-dwelling organisms. Each of these factors can influence the response of the density of organisms to a specific environmental gradient, inflating variability and making difficult to understand the possible causal relationship. In our study, we used quantile regression mixed models and Akaike’s information criterion as an indicator of goodness to examine two different datasets, one belonging to Italy and one belonging to Finland, and to detect the limiting action of selected environmental variables. In the Italian dataset, we studied the relationships among five macroinvertebrate families and three physical habitat characteristics (water velocity, depth and substratum size); in the Finnish dataset the relationships between taxa richness and 16 environmental characteristics (chemical and physical). We found limiting relationships in both datasets and validated all of them on different datasets. These relationships are quantitative and can be used to predict the range of macroinvertebrate densities or taxa richness as a function of environmental characteristics. They can be a tool for management purposes, providing the basis for habitat-based models and for the development of ecological indices.     

Effects of biotic factors on depth selection by salt marsh nekton

Biotic factors such as interactions among co-occurring taxa are frequently cited as important in determining how nekton use habitat, yet their effects have rarely been tested experimentally. We investigated the general hypothesis that depth distributions of five taxa common in salt marsh intertidal creeks are affected by the presence of other taxa. Two experiments were conducted in a pair of large (15 m³), multi-level (20, 40, and 60 cm water depth) flow-through tanks under fairly stable environmental conditions. During the first experiment, when grass shrimp (Palaemonetes spp.), mummichog (Fundulus heteroclitus), white mullet (Mugil curema), spot (Leiostomus xanthurus), and pinfish (Lagodon rhomboides) were each tested alone, the highest proportions of individuals occupied the intermediate and deepest depths. When all taxa were tested together, the distributions of resident creek taxa, mummichog and grass shrimp, shifted to shallower depths, but the distributions of the seasonal transient taxa, white mullet, spot, and pinfish, did not change. A second experiment was conducted to test the effect of predator presence on grass shrimp depth selection. Neither predatory pinfish nor non-predatory white mullet had a strong influence on grass shrimp depth distribution when tested separately, but grass shrimp shifted to shallower depths in the combined presence of both fish. This suggests that a multiple-taxa effect such as increased disturbance or higher encounter frequency influenced the depth selection of grass shrimp. Our results demonstrate that biotic factors are important in shaping distributions of grass shrimp and mummichog in shallow water habitat.     

Measuring Tailing's 'element of chance in pond populations'

SUMMARY. 1. A series of small seasonal pools on a freshwater marsh was used to estimate the element of chance in animal community patterns.
2. The pools were artificially created in 1963. They were all the same age, size, shape, depth and had the same substrate. Other physico-chemical parameters, and the faunas, were sampled. Community assemblages were analysed using multivariate classification and ordination (TWINSPAN and DECORANA). and related to physico-chemical characteristics. Communities correlated with distance of pools from permanent water and annual drying/flooding regimes.
3. TWINSPAN analysis in 1987 was used to identify co-occurring groups of animals and the sets of ponds with which each group was associated. The presence or absence of a taxon from a pool within a set in which it otherwise commonly occurred was used as a measure of the element of chance.
4. The mean occurrence of taxa in pools in which they were expected was 79.6.16.2%. The mean occurrence in pools in which they were not expected was 10.9.10.5% ( n =80).     

Connecting local environmental sequences to global climate patterns: evidence from the hominin-bearing Hadar Formation, Ethiopia

Central to the debate surrounding global climate change and Plio-Pleistocene hominin evolution is the degree to which orbital-scale climate patterns influence low-latitude continental ecosystems and how these influences can be distinguished from regional volcano-tectonic events and local environmental effects. The Pliocene Hadar Formation of Ethiopia preserves a record of hominin paleoenvironments from roughly 3.5 to 2.2 Ma at a temporal resolution relevant to evolutionary change within hominins and other taxa. This study integrates the high-resolution sedimentological and paleontological records at Hadar with climate proxies such as marine core isotope, dust, and sapropel records. Consistent cycling observed both between and within fluvial and lacustrine depositional environments prior to 2.9 Ma at Hadar appears to be predominantly climatic in nature. In contrast a significant change in depositional facies after 2.9 Ma to sequences dominated by conglomerate cut-and-fill cycles indicates a strong tectonic signature related to regional developments in the Main Ethiopian Rift. While specific events seen in marine proxy records may have parallels in the Hadar environmental archive, their overall patterns of high versus low variability may be even more relevant. For example, periods of relatively high-amplitude climate oscillations between 3.15 and 2.95 Ma may be linked to noted size-related morphological changes within the Hadar Australopithecus afarensis lineage and a significant increase in more arid-adapted bovid taxa. Increased aridity in East Africa during this period is also indicated by peaks in eolian dust in the marine core record. Conversely, the dominant lacustrine phase at Hadar ca. 3.3 Ma coincides with the least variable period in several climate proxy records, including marine core foraminifera delta(18)O values and eolian dust concentration. This phase is also coeval with low insolation variability and a very distinct and significant long-term period of low dust percentage in circum-Africa marine cores.     

Bathymetry,water optical properties,and benthic classification of coral reefs using hyperspectral remote sensing imagery

The complexity and heterogeneity of shallow coastal waters over small spatial scales provides a challenging environment for mapping and monitoring benthic habitats using remote sensing imagery. Additionally, changes in coral reef community structure are occurring on unprecedented temporal scales that require large-scale synoptic coverage and monitoring of coral reefs. A variety of sensors and analyses have been employed for monitoring coral reefs: this study applied a spectrum-matching and look-up-table methodology to the analysis of hyperspectral imagery of a shallow coral reef in the Bahamas. In unconstrained retrievals the retrieved bathymetry was on average within 5% of that measured acoustically, and 92% of pixels had retrieved depths within 25% of the acoustic depth. Retrieved absorption coefficients had less than 20% errors observed at blue wavelengths. The reef scale benthic classification derived by analysis of the imagery was consistent with the percent cover of specific coral reef habitat classes obtained by conventional line transects over the reef, and the inversions were robust as the results were similar when the benthic classification retrieval was constrained by measurements of bathymetry or water column optical properties. These results support the use of calibrated hyperspectral imagery for the rapid determination of bathymetry, water optical properties, and the classification of important habitat classes common to coral reefs.     

Evaluating the Applicability of Phi Coefficient in Indicating Habitat Preferences of Forest Soil Fauna Based on a Single Field Study in Subtropical China

Phi coefficient directly depends on the frequencies of occurrence of organisms and has been widely used in vegetation ecology to analyse the associations of organisms with site groups, providing a characterization of ecological preference, but its application in soil ecology remains rare. Based on a single field experiment, this study assessed the applicability of phi coefficient in indicating the habitat preferences of soil fauna, through comparing phi coefficient-induced results with those of ordination methods in charactering soil fauna-habitat(factors) relationships. Eight different habitats of soil fauna were implemented by reciprocal transfer of defaunated soil cores between two types of subtropical forests. Canonical correlation analysis (CCorA) showed that ecological patterns of fauna-habitat relationships and inter-fauna taxa relationships expressed, respectively, by phi coefficients and predicted abundances calculated from partial redundancy analysis (RDA), were extremely similar, and a highly significant relationship between the two datasets was observed (Pillai''s trace statistic = 1.998, P = 0.007). In addition, highly positive correlations between phi coefficients and predicted abundances for Acari, Collembola, Nematode and Hemiptera were observed using linear regression analysis. Quantitative relationships between habitat preferences and soil chemical variables were also obtained by linear regression, which were analogous to the results displayed in a partial RDA biplot. Our results suggest that phi coefficient could be applicable on a local scale in evaluating habitat preferences of soil fauna at coarse taxonomic levels, and that the phi coefficient-induced information, such as ecological preferences and the associated quantitative relationships with habitat factors, will be largely complementary to the results of ordination methods. The application of phi coefficient in soil ecology may extend our knowledge about habitat preferences and distribution-abundance relationships, which will benefit the understanding of biodistributions and variations in community compositions in the soil. Similar studies in other places and scales apart from our local site will be need for further evaluation of phi coefficient.     

Ecological structuring of bacterial and archaeal taxa in surface ocean waters

The Global Ocean Sampling (GOS) expedition is currently the largest and geographically most comprehensive metagenomic dataset, including samples from the Atlantic, Pacific, and Indian Oceans. This study makes use of the wide range of environmental conditions and habitats encompassed within the GOS sites in order to investigate the ecological structuring of bacterial and archaeal taxon ranks. Community structures based on taxonomically classified 16S ribosomal RNA (rRNA) gene fragments at phylum, class, order, family, and genus rank levels were examined using multivariate statistical analysis, and the results were inspected in the context of oceanographic environmental variables and structured habitat classifications. At all taxon rank levels, community structures of neritic, oceanic, estuarine biomes, as well as other exotic biomes (salt marsh, lake, mangrove), were readily distinguishable from each other. A strong structuring of the communities with chlorophyll a concentration and a weaker yet significant structuring with temperature and salinity were observed. Furthermore, there were significant correlations between community structures and habitat classification. These results were used for further investigation of one-to-one relationships between taxa and environment and provided indications for ecological preferences shaped by primary production for both cultured and uncultured bacterial and archaeal clades.     

Different surrogacy approaches for stream macroinvertebrates in discriminating human disturbances in Central China

Due to the difficulty of identifying many taxa of freshwater invertebrates to species, many researchers have assessed the utility of surrogates for species-level identifications (e.g. higher taxa) in bioassessment programs. Here, we examined the efficiency of two different approaches to species surrogacy, one using coarser taxonomic resolution and a second approach based on random aggregation (“Best practicable aggregation of species”, BestAgg), in portraying patterns of stream macroinvertebrates in Central China. The main objectives were: (1) to compare the discriminatory power of biodiversity indices and assemblage structure for different levels of human disturbances based on different taxonomic resolution and on BestAgg; (2) to identify the congruence of assemblage-environment and biodiversity-indices-environment relationships for datasets at the species level versus those at surrogate levels. We found that genus-level and BestAgg datasets accurately reproduced the pattern of species-level communities, whereas family- and order-level datasets did not. Specifically, both genus-level and BestAgg approaches performed almost as well as species-level data in distinguishing sites subjected to different disturbance levels. Most of the environmental variables that were important for species-level assemblages, also emerged as significant when analyzing genera and BestAgg surrogates, as shown by both analyses of indices and assemblage composition according to distance-based ordination models. Our results suggest that genus-level taxonomy, which resulted in the least loss of ecological information relative to species-level identification, is sufficient in studies of community ecology and bioassessment of stream macroinvertebrates in Central China. In addition, the BestAgg approach, which required identification of fewer taxa than genus-level analysis, has a similar ability to depict multivariate patterns of macroinvertebrate assemblages and differentiate different disturbance levels. Applying our results could enhance speed and cost-effectiveness of freshwater biomonitoring and bioassessment programs; however, independent determination of best taxonomic level and BestAgg will be required whenever a new geographic area or habitat type is assessed.     

Green sturgeon physical habitat use in the coastal Pacific Ocean

The green sturgeon (Acipenser medirostris) is a highly migratory, oceanic, anadromous species with a complex life history that makes it vulnerable to species-wide threats in both freshwater and at sea. Green sturgeon population declines have preceded legal protection and curtailment of activities in marine environments deemed to increase its extinction risk. Yet, its marine habitat is poorly understood. We built a statistical model to characterize green sturgeon marine habitat using data from a coastal tracking array located along the Siletz Reef near Newport, Oregon, USA that recorded the passage of 37 acoustically tagged green sturgeon. We classified seafloor physical habitat features with high-resolution bathymetric and backscatter data. We then described the distribution of habitat components and their relationship to green sturgeon presence using ordination and subsequently used generalized linear model selection to identify important habitat components. Finally, we summarized depth and temperature recordings from seven green sturgeon present off the Oregon coast that were fitted with pop-off archival geolocation tags. Our analyses indicated that green sturgeon, on average, spent a longer duration in areas with high seafloor complexity, especially where a greater proportion of the substrate consists of boulders. Green sturgeon in marine habitats are primarily found at depths of 20-60 meters and from 9.5-16.0°C. Many sturgeon in this study were likely migrating in a northward direction, moving deeper, and may have been using complex seafloor habitat because it coincides with the distribution of benthic prey taxa or provides refuge from predators. Identifying important green sturgeon marine habitat is an essential step towards accurately defining the conditions that are necessary for its survival and will eventually yield range-wide, spatially explicit predictions of green sturgeon distribution.     

Multivariate statistical analysis of the Pteridophytic diversity of District Battagram,Khyber Pakhtunkhwa,Pakistan

The Pteridophytes represent a great but poorly explored potential as an ecological indicators. Ecological indicator is a useful tool to link empirical results, models and theories with environmental applications. Habitat diversity, precipitation, moisture and rainfall have a high influence on species richness with altitudinal gradients. From 15 different habitats 45 species belonged to 25 genera and 13 families were documented. The leading family were Pteridaceae with 14 taxa, Dryopteridaceae were the second largest family with 7 taxa, followed by Thylepteridaceae with 6 taxa and Aspleniaceae with 5 taxa. Adiantum capillus-veneris and Diplazium esculentum survive in a wide range of habitats while Pellaea calomelanos have a narrow range of habitat. Five plant associations were sorted out through cluster analysis and two ways indicator species analysis. In Bray Curtis ordination the maximum Regression coefficient were recorded for axis 1 (?10.66) with a variance of 0.61. The response data were compositional and have a gradient of 3.2 SD units long. In DCA ordination maximum Eigenvalue and gradient length were recorded for axis 1. Species grouped on the basis of habitat types and habitats having common species. CCA ordination showed that the plants have a linear relationship with environmental variables. The permutation test results on all axis were pseudo-F = 2.4, P = 0.002 indicating the significance value. CCA ordination showed that the environmental variables had a great impact on the association and distribution of majority of the species.     

Response of fauna in seagrass to habitat edges,patch attributes and hydrodynamics

This study has investigated the taxon‐specific responses of fauna to patch edges, and how these relate to patch attributes (patch size, seagrass biomass and water depth), and hydrodynamics in the seagrass habitat. Faunal abundances were sampled at the edge, 2 m in from the edge, and in the middle of 10 seagrass patches of variable size in Port Phillip Bay, Australia. Five of nine taxa showed edge effects. There were higher abundances at the edge compared with the middle for porcellid harpacticoids, and an increase in abundance from the edge to the middle of the patches for tanaids and isopods. For caprellid and gammarid amphipods, the edge effect varied across patches. Changes in current within the patch and patch size were related to the variability in the edge effect pattern of caprellids. None of the measured environmental variables (seagrass biomass, current and water depth) or patch size had a role in the variable edge effect pattern of gammarid amphipods. At the patch level, the distribution of six of nine taxa in this study, namely isopods, polychaetes, ‘other harpacticoids’, porcellid harpacticoids, cumaceans and gammarid amphipods, was related to differences in average water depth, average seagrass biomass and patch size. Our study indicates that the faunal response to edges cannot be generalized across seagrass habitat, and the implications of habitat area loss will vary depending on the taxon under consideration.     

Community structure of epilithic and endolithic algae and cyanobacteria on cliffs of the Niagara Escarpment

Abstract. In order to understand how communities of rock-inhabiting micro-organisms are spatially organized, rock samples and environmental variables were collected from five cliff sites in Ontario, Canada. Algae and cyanobacteria were extracted from the epilithic zone (rock surface) and endolithic zone (subsurface) of 180 samples, and the frequency of each taxon (genus or larger) was determined. Multivariate statistical analyses were used to determine (1) the variation in community composition on different spatial scales; (2) differences in community composition between surface and subsurface; and (3) the environmental constraints of community structure. 13 taxa of cyanobacteria and 12 taxa of eukaryotic algae were identified in the endolithic zone, and 17 and 14 in the epilithic zone, respectively. The most frequent taxa were similar in both zones, but MANOVA of species frequencies showed significant differences between endolithic and epilithic communities. DCA and CCA showed that geographic-scale variation in community composition was the dominant trend in the data for both surface and subsurface. Cyanobacteria and eukaryotic algae showed a clear separation on the first ordination axis. When the geographic-scale variation was removed in a partial ordination, the separation of organisms by kingdoms disappeared and epi- and endolithic ordinations were no longer similar. Light then appeared to control the endolithic species composition, while other factors, possibly moisture-related, were suggested for the epilithic community. Despite biomass and productivity that varies mostly at scales of < 1m², we conclude here that species composition and its environmental constraints vary at small as well as larger scales.     

Effects of substratum stability on diversity of stream invertebrates during baseflow at two spatial scales

1. The effects of substratum stability on the diversity of stream invertebrates were assessed at two spatial scales in a Japanese stream during baseflow, from May to June 1998. Deposition and erosion were examined separately as distinct elements of substratum stability by a newly developed method using small steel pins. Stream invertebrates were sampled after 28 days of measurement of substratum stability. We also measured physical environmental variables, current velocity and depth, and food resource parameters including periphyton and particulate organic matter (POM) standing crops.
2. At the scale of the habitat patch, the effects of substratum stability on invertebrates were overwhelmed by those of POM standing crop. Moreover, higher taxon richness at high abundance may simply result from a higher likelihood of more taxa being included in samples. Therefore, this small scale revealed no role for substratum stability in explaining spatial pattern of community diversity.
3. At the reach scale ( n =10), taxon richness and evenness peaked at an intermediate level of deposition, whereas invertebrate abundance did not show any significant relationship. This result, and the pattern of relative abundance of common taxa, implies that the diversity of stream invertebrates was determined by subtle substratum movements and by the habitat preference of each taxon.
4. The difference in the determinant of community parameters between the habitat patch and the reach affirm the importance of a cross-scale analysis to choose an appropriate spatial scale for investigating the community structure of stream invertebrates. Prominent effects of substratum stability, particularly the deposition of substratum particles, during baseflow suggest that subtle and constant movement of small substratum particles can contribute to determine the diversity of stream invertebrates.     

Community Structure of Macrobiota and Environmental Parameters in Shallow Water Hydrothermal Vents off Kueishan Island,Taiwan

Hydrothermal vents represent a unique habitat in the marine ecosystem characterized with high water temperature and toxic acidic chemistry. Vents are distributed at depths ranging from a few meters to several thousand meters. The biological communities of shallow-water vents have, however, been insufficiently studied in most biogeographic areas. We attempted to characterize the macrofauna and macroflora community inhabiting the shallow-water vents off Kueishan Island, Taiwan, to identify the main abiotic factors shaping the community structure and the species distribution. We determined that positively buoyant vent fluid exhibits a more pronounced negative impact to species on the surface water than on the bottom layer. Species richness increased with horizontal distance from the vent, and continuing for a distance of 2000 m, indicating that the vent fluid may exert a negative impact over several kilometers. The community structure off Kueishan Island displayed numerous transitions along the horizontal gradient, which were broadly congruent with changes in environmental conditions. Combination of variation in Ca²⁺, Cl^-, temperature, pH and depth were revealed to show the strongest correlation with the change in benthic community structure, suggesting multiple factors of vent fluid were influencing the associated fauna. Only the vent crabs of Kueishan Island may have an obligated relationship with vents and inhabit the vent mouths because other fauna found nearby are opportunistic taxa that are more tolerant to acidic and toxic environments.