长白山劲松林场植物群落的分类和排序

将长白山白河林业局劲松林场的５４块样地用聚类分析法划分成６个植被类群,再用ＰＣ－ＶＴＡＢ程序中经过改进的Ｂｒａｕｎ－Ｂｌａｎｑｕｅｔ学派的植被排表分析法进行综合,产生了鉴别概要表,为各个等级的植被类群筛选出诊断种。此外,还用鉴别种地样地记录进行主成分分析,以验证诊断种的有效性,结果表明,ＰＣ－ＶＴＡＢ中的植被排表分析法是筛选鉴别种的有效方法,而鉴别种以显著地提高植被分析和排序的质量。     

Early Cambrian coelobiontic communities in tectonically unstable crevices developed in Neoproterozoic andesites, Ossa-Morena, southern Spain

A well-preserved biota of Lower Cambrian cavity-dwelling organisms is recorded within fissures in Neoproterozoic andesites in Ossa-Morena (southern Spain). The cavities are unique among described Lower Cambrian coelobiontic communities due to the igneous character of the host rock. Coelobiontic habitat was episodically enlarged by synsedimentary tectonic fracturing reflecting polyphase infill of recurrent facies. The pioneer coelobiontic biota was diverse, and consisted of encrusting stromatolites and thromboids (dominated by Epiphyton and Renalcis), attached to walls and ceilings of the cavities, associated with archaeocyaths. Sponge spicules and chancelloriid sclerites occur as dense clusters indicating in situ growth, death and decay of spiculate sponges and coeloscleritophorans. Other organisms, such as echinoderms, trilobites and brachiopods, are also found within the cavities as reworked skeletons, indicating that they were washed in from the overlying, open seafloor. The main feature of the coelobiontic biota is the dominance of a sessile, chemosynthetic and filter-feeding epibenthos, composed of microbial communities, archaeocyaths, spiculate sponges (demosponges and rarer hexactinellides) and coeloscleritophorans.     

Spatial resolution and location impact group structure in a marine food web

Ecological processes in food webs depend on species interactions. By identifying broad‐scaled interaction patterns, important information on species' ecological roles may be revealed. Here, we use the group model to examine how spatial resolution and proximity influence group structure. We examine a data set from the Barents Sea, with food webs described for both the whole region and 25 subregions. We test how the group structure in the networks differ comparing (1) the regional metaweb to subregions and (2) subregion to subregion. We find that more than half the species in the metaweb change groups when compared to subregions. Between subregions, networks with similar group structure are spatially related. Interestingly, although species overlap is important for similarity in group structure, there are notable exceptions. Our results highlight that species ecological roles vary depending on fine‐scaled differences in the patterns of interactions, and that local network characteristics are important to consider.     

Mapping Dominican transnationalism: narrow and broad transnational practices

This article maps the structure for understanding the Dominican transnational field. By transnational field we refer to a web of linkages that affects the lives of Dominicans in their places of residence in every social field. We find that social boundaries of the nation do not coincide with political ones and the degree of participation in transnational exchanges varies. We suggest that the structure of the transnational social field is better understood by establishing and defining broad and narrow transnational social practices.     

Comparing the conservatism of ecological interactions in plant–pollinator and plant–herbivore networks

Conservatism in species interaction, meaning that related species tend to interact with similar partners, is an important feature of ecological interactions. Studies at community scale highlight variations in conservatism strength depending on the characteristics of the ecological interaction studied. However, the heterogeneity of datasets and methods used prevent to compare results between mutualistic and antagonistic networks. Here we perform such a comparison by taking plant–insect communities as a study case, with data on plant–herbivore and plant–pollinator networks. Our analysis reveals that plants acting as resources for herbivores exhibit the strongest conservatism in species interaction among the four interacting groups. Conservatism levels are similar for insect pollinators, insect herbivores and plants as interacting partners of pollinators, although insect pollinators tend to have a slightly higher conservatism than the two others. Our results thus clearly support the current view that within antagonistic networks, conservatism is stronger for species as resources than for species as consumer. Although the pattern tends to be opposite for plant–pollinator networks, our results suggest that asymmetry in conservatism is much less pronounced between the pollinators and the plant they interact with. We discuss these differences in conservatism strength in relation with the processes structuring plant–insect communities.     

Zooplankton distribution and diversity in a frontal area of the Aegean Sea

This study was carried out in the northern Aegean Sea during late summer and spring. The aim was to examine the spatial and temporal distribution of the zooplankton community across a dynamic frontal area and to investigate how the oceanographic heterogeneity structures the composition of the zooplankton assemblages. The low-salinity and cold Black Sea water coming from the Dardanelles Strait is modified by mixing with the underlying warm and saline Aegean water. These hydrological features result in a pronounced thermohaline front in the northern Aegean Sea throughout the year. In both seasons, zooplankton was collected using both 45 and 200 µm mesh plankton nets. A high abundance of zooplankton was observed in the surface layer at the stations closest to the Dardanelles Strait on the stratified side of the front. The zooplankton distribution and community structure in the northern Aegean Sea were strongly influenced by the hydrological features. The frontal structure acts as a boundary for the zooplankton community. The surface layer at the stratified stations had the lowest copepod diversity, from where it increased with depth and horizontally as the stratification weakened outside of the front. The total abundance of zooplankton collected with the 200 µm net was between two and 20 times lower than samples taken with the 45 µm net. The most pronounced differences were observed for the adults and copepodids of the small genera Oithona, Oncaea and Microsetella. Thus, to manage and understand the transfer of primary production up the food chain in the Aegean Sea, the smaller fraction of copepods should be taken into account in future investigations.     

Facies pattern and genesis of the Jebel Rheris biostromes (Givetian,Eastern Anti-Atlas,Morocco)

Summary During Givetian times, the Jebel Rheris area was situated in a transitional zone at the northern margin of Gondwana, between the emerged Ougnate High in the north and the Mader Basin in the south. A facies pattern developed from stacked or amalgamated coral-stromatoporoid biostromes in the northern near-shore area to an alternating biostrome–crinoidal grainstone succession, which passed over a low angle slope setting towards the south to a pure crinoidal grainstone facies with abundant slumping structures. Finally in the south, a basinal turbiditic facies evolved. In the shallow sea, biostromes probably developed due to the lack of a ‘binder guild’ in the fossil community, which hampered the establishment of mound-like structures, stable enough to resist high-energy storm events. Repeated termination of the coral-stromatoporoid growth is attributed to transgressions. During suitable conditions, colonisation of the sea floor proceeded in three phases: a) cluster settlement; pioneer communities, mostly consisting of tabulate corals and domical to bulbous stromatoporoids, started growing in laterally delimited clusters; b) lateral dispersion; from these centres, settlement prograded laterally, until large areas of the sea-floor were covered; c) vertical accretion; the organisms more and more grew on each other, causing a homogeneous vertical expansion. A significant difference of this up to 200 m thick biostrome—crinoidal grainstone succession compared to continuously growing reefs is the fact that communities repeatedly had to start with the colonisation stage, thus could not reach a mature or climax stage.     

Extended statistical approaches to modelling spatial pattern in biodiversity in northeast New South Wales. II. Community-level modelling

Regional conservation planning can often make more effective use of sparse biological data by linking these data to remotely mapped environmental variables through statistical modelling. While modelling distributions of individual species is the best known and most widely used approach to such modelling, there are many situations in which more information can be extracted from available data by supplementing, or replacing, species-level modelling with modelling of communities or assemblages. This paper provides an overview of approaches to community-level modelling employed in a series of major land-use planning processes in the northeast New South Wales region of Australia, and evaluates how well communities and assemblages derived using these techniques function as surrogates in regional conservation planning. We also outline three new directions that may enhance the effectiveness of community-level modelling by: (1) more closely integrating modelling with traditional ecological mapping (e.g. vegetation mapping); (2) more tightly linking numerical classification and spatial modelling through application of canonical classification techniques; and (3) enhancing the applicability of modelling to data-poor regions through employment of a new technique for modelling spatial pattern in compositional dissimilarity.     

A framework for evaluating sustainability indicators in the real estate industry

The growth in the use of sustainability indicators and ratings in the real estate industry has been accompanied by strong criticism of the most commonly used rating systems designed to evaluate the sustainability performance of real estate developments. Most of these criticisms focus on the content of the different rating systems. A systematic evaluation of the methodologies of sustainability ratings is lacking. This article builds a framework that can be used to evaluate the methodologies of sustainability ratings and applies the evaluation framework to five widely used sustainability ratings for homes and communities (BREAAM, CASBEE, Estidama, Green Star, LEED). The evaluation results highlight three major shortcomings in the rating systems that have been evaluated. First, the systems lack unambiguous definitions of sustainability. They give insufficient explanation of why certain components are included in the ratings and on what basis these components have been accorded their weights. Second, the rating systems put more emphasis on sustainable design than performance, especially for the ratings for communities. Finally, the ratings are generally not responsive to local conditions of a project. Each rating system has its particular strengths and weaknesses and no system is superior on all dimensions. The proposed evaluation framework can be applied to sustainability ratings in different industries and is adaptable depending on stakeholder requirements.     

Impact of a parasitic plant on the zonation of two salt marsh perennials

Animal, fungal, and bacterial consumers can have dramatic effects on the structure of plant communities, often by consuming dominant competitors and indirectly increasing the abundance of inferior competitors. We investigated the role of a consumer plant, the parasite Cuscuta salina, on plant zonation in a western salt marsh. Cuscuta had a strong host species preference in experiments, disproportionally infecting Salicornia virginica, the dominant competitor in most of the marsh. In plots with Cuscuta, which infected 18% of our study area over a 3-year period, Salicornia cover decreased and the cover of Arthrocnemum increased substantially in comparison to plots without Cuscuta. Deep in the Salicornia zone, the cover of Arthrocnemum in Cuscuta-infected plots increased by 558% in 1 year relative to uninfected plots. At the ecotone, the cover of Arthrocnemum in Cuscuta-infected plots increased by only 41% during the same time interval. These data suggest that the relative benefit of a consumer to a less-preferred, subordinate competitor may be strongest where competition is the most asymmetrical as predicted by recent theoretical models. By weakening the competitive dominant, which in the absence of the parasite can create virtual monocultures, Cuscuta enhanced community diversity and altered the ecotone between Salicornia and Arthrocnemum. Cuscuta patches were highly dynamic at the ecotone between Salicornia and Arthrocnemum, and thus the changes we measured in our sample plots were likely to be representative of large portions of the marsh. Our findings emphasize the importance of trophic interactions in salt marsh structure and zonation. Received: 23 April 1997 / Accepted: 10 October 1997