The influence of riparian vegetation on macroinvertebrate community structure and functional organization in six new Guinea streams

Information on the ecology of New Guinea streams is meagre, and data are needed on the trophic basis of aquatic production in rivers such as the Sepik in Papua New Guinea which have low fish yields. This study investigates the relationship between riparian shading (from savanna grassland to primary rainforest), algal and detrital food, and macroinvertebrate abundance and community structure in 6 Sepik River tributary streams. A particular aim was to elucidate macroinvertebrate community responses to changes in riparian conditions. All streams supported diverse benthic communities, but morphospecies richness (overall total 64) was less than in streams on the tropical Asian mainland; population densities of benthic invertebrates, by contrast, were similar to those recorded elsewhere. Low diversity could reflect limited taxonomic penetration, but may result from the absence of major groups (Plecoptera, Heptageniidae, Ephemerellidae, Psephenidae, Megaloptera, etc.) which occur on the Asian mainland. Population densities of all 19 of the most abundant macroinvertebrate taxa varied significantly among the 6 study streams, but community composition in each was broadly similar with dominance by Baetidae and (in order of decreasing importance), Leptophlebiidae, Orthocladiinae, Elmidae and Hydropsychidae. Principal components analysis (PCA) undertaken on counts of abundant macroinvertebrate taxa clearly separated samples taken in two streams from the rest. Both streams contained high detrital standing stocks and one was completely shaded by rainforest. Stepwise multiple-regression analysis indicated that population densities of the majority of abundant taxa (11 out of 19) across streams (10 samples per stream; n = 60) were influenced by algae and/or detritus, although standing stocks of these variables were not clearly related to riparian conditions. When regression analysis was repeated on mean counts of taxa per stream (dependent variables) versus features of each stream as a whole (thus n = 6), % shading and detritus were the independent variables yielding significant regression models most frequently, but pH, total-nitrogen loads and algae were also significant predictors of faunal abundance. Further regression analysis, undertaken separately on samples (n = 10) from each stream, confirmed the ability of algae and detritus to account for significant portions of the variance in macroinvertebrate abundance, but the significance of these variables varied among streams with the consequence that responses of individual taxa to algae or detritus was site-specific.Community functional organization — revealed by investigation of macroinvertebrate functional feeding groups (FFGs) — was rather conservative, and streams were codominated by collector-gatherers (mean across 6 streams = 43%) and grazers (36%), followed by filter-feeders (15%) and predators (7%). The shredder FFG was species-poor and comprised only 0.4% of total macroinvertebrate populations; shredders did not exceed 2% of benthic populations in any stream. PCA of FFG abundance data was characterized by poor separation among streams, although there was some evidence of clustering of samples from unshaded sites. The first 2 PCA axes accounted for 84% of the variation in the data suggesting that the poor separation resulted from the general similarity of FFG representation among streams. Although stepwise multiple-regression analysis indicated that algae and detritus accounted for significant proportions of the variations in population density and relative abundance of some FFGs, the response of community functional organization to changes in riparian conditions and algal and detrital food base was weak — unlike the deterministic responses that may be typical of north-temperate streams.     

Best Linear Unbiased Prediction (BLUP) for regional yield trials: a comparison to additive main effects and multiplicative interaction (AMMI) analysis

Multilocation trials are often used to analyse the adaptability of genotypes in different environments and to find for each environment the genotype that is best adapted; i.e. that is highest yielding in that environment. For this purpose, it is of interest to obtain a reliable estimate of the mean yield of a cultivar in a given environment. This article compares two different statistical estimation procedures for this task: the Additive Main Effects and Multiplicative Interaction (AMMI) analysis and Best Linear Unbiased Prediction (BLUP). A modification of a cross validation procedure commonly used with AMMI is suggested for trials that are laid out as a randomized complete block design. The use of these procedure is exemplified using five faba bean datasets from German registration trails. BLUP was found to outperform AMMI in four of five faba bean datasets.     

Systematic classification of Asian colobines

In order to study the differentiation of Asian colobines, fourteen variables were analysed in one way, on 123 skulls, includingRhinopithecus, Presbytis, Presbytiscus, Pygathrix, andNasalis with both cluster and differentiated functions tests. Information on paleoenvironment changes in China and South-East Asia since late Tertiary have been used to examine the influences of migratory habits and the distribution range in Asian colobines. The cladogram among different Asian colobines genera was made from the results of various analysis. Some new points or revisions were suggested: 1. Following the second migratory way, ancient species of Asian colobines perhaps passed through Xizang along the northern bank of Tethis sea and Heng-Duan Shan regions, across Yunnan into Vietnam, since the ancient continent between Yunnan and Xizang was already located in on eastern bank of Tethis sea. Thus, during the evolution, Asian colobines must have had two original centres, i.e. “Sundaland” and Heng-Duan Shan Chinese regions; 2. Pygatrix possesses a lot of cranial features more similar toPresbytiscus than toRhinopithecus. The small difference from the modification combinesPygatrix with other two genera as shown by Groves (1970), but it is better to putPygatrix andPresbytiscus together as one genus; 3.Nasalis (2n=48) may be the most primitive genus within Asian colobines. Some features shared withRhinopithecus, for example body size, terrestrial activities, limb proportion etc. ...seem to be considered as a common inheritance of symlesiomorphus characters; 4.Rhinopithecus, with reference to cranioface and cranium or to its origin, is a special genus of Asian colobine. It may represent the highest level of evolutionary position within various genera (Peng et al., 1985).     

Natural CO2 springs in Italy: a resource for examining long-term response of vegetation to rising atmospheric CO2 concentrations

It is estimated that more than 100 geothermal CO₂ springs exist in central-western Italy. Eight springs were selected in which the atmospheric CO₂ concentrations were consistently observed to be above the current atmospheric average of 354μmol mol^-1. CO₂ concentration measurements at some of the springs are reported. The springs are described, and their major topographic and vegetational features are reported. Preliminary observations made on natural vegetation growing around the gas vents are then illustrated. An azonal pattern of vegetation distribution occurs around every CO₂ spring regardless of soil type and phytoclimatic areas. This is composed of pioneer populations of a Northern Eurasiatic species (Agrostis canina L.) which is often associated with Scirpus lacustris L. The potential of these sites for studying the long-term response of vegetation to rising atmospheric CO₂ concentrations is discussed.     

Latitudinal gradients of coniferous tree species,vegetation, and climate in the Sierran-Cascade axis of Northern California

Latitudinal gradients of tree species composition along the Sierran/Cascade axis in northern California were explored by comparing forests of Lassen Volcanic and Yosemite National Parks, USA. A calibration procedure based on canonical correspondence analysis predicted a mean rate of elevational displacement of 172.1 m/° latitude for Lassen sites in Yosemite. This is a steep latitudinal gradient compared with other temperate uplands (which average around 100 m/⁰ latitude), but it corresponds with the magnitude of the July mean temperature gradient (143 m/⁰ latitude) and the annual precipitation gradient (230 m/⁰ latitude). Elevational displacement of basal-area weighted species means showed considerable variation. The range for montane species was 20–153 m/⁰ latitude; for subalpine species the range was 142–305 m/⁰ latitude. This disparity is related to differential temperature lapse rates between regions and is reinforced by contrasting biogeographic affinities of montane vs. subalpine species. Whereas it is uniformly hot and dry during the growing season at lower elevations in both regions, growing seasons in the subalpine zone are significantly warmer and drier (at comparable elevations) in Yosemite, the more southerly locale. Furthermore, montane species are principally of Sierran affinity, whereas subalpine are primarily of Pacific Northwestern affinity.     

Soil factors affecting patchiness in community composition of heavy metal-contaminated areas of Western Europe

The vegetation at various sites within two separate areas (Mechernich and Aachen) of the Eifel Mountains, Germany/Belgium, both characterized by elevated concentrations of heavy metals in their soils, was surveyed in order to investigate the relationships between soil chemical attributes and floristic composition. In both areas, the typical heavy metal communities can form distinct zones, clearly separated from the surrounding heavy metal-sensitive vegetation. However, an intergrading of heavy metal-tolerant and-sensitive vegetation types is not uncommon and such overlaps can occupy large areas. In Mechernich, soil toxicity is primarily determined by the effects of lead, which is best expressed in terms of the Pb/Ca ratio rather than the absolute levels of this metal in the soil. Soils of heavy metal-sensitive vegetation types have a low Pb/Ca ratio, whereas it is considerably higher in areas supporting heavy metal vegetation. Zinc appears to exert little influence on the floristic composition of the investigated vegetation types. In Aachen, zinc is the predominant heavy metal determining vegetation development. Absolute zinc levels of soils do not accurately reflect zinc toxicity. Analogous to the role of the Pb/Ca ratio in the Mechernich area, the Zn/Ca ratio not only separates heavy metal-sensitive and highly tolerant vegetation units, but also gives a good indication of the gradient operating between the two vegetation types. Lead is probably only of local importance in influencing species composition.     

川西北甘南云冷杉林的数量分类

 本文应用DCA二维散点非等级制分类和TWINSPAN等级制分类的方法进行了四川西北部和甘肃南部云冷杉林的数量分类,共划分出15个群丛,分属于云杉、冷杉、高山栎和桦木四个群系,并分别讨论了各群丛的特征。用DCA二维散点的非等级制分类与TWINSPAN的等级制分类的方法对于云冷杉植物群落都产生了较好且一致的分类效果。通过TWINSPAN分类的研究,发现了对生境有指示意义的特征种和指示种,主要的植物种类有：圆叶菝契、网状小壁等(冷湿,指示藓类冷杉林和杜鹃冷杉林);小花拂子茅、箭炉樱等(冷旱,指示草类云杉林和箭竹云冷杉林);槭树、铁杉、沛阳花等(暖湿,指示落阔冷杉林和灌木云杉林等);罗氏异燕麦、华西矮卫茅、糙野青茅和狭叶柳兰等(暖旱,指示灌木云杉林和云冷杉疏林)。     

The influence of sampling method on the classification of wetland macroinvertebrate communities

Macroinvertebrate communities sampled by a corer, plankton net and sweep net from five wetlands on the Swan Coastal Plain were compared. The composition of the fauna collected in sweeps and tows was generally similar and differed from that collected in the cores. Cores caught fewer species than tows and sweeps at all wetlands and did not capture fast swimming hemipterans or less abundant taxa. The highest species richness was recorded in sweep samples in four out of the five wetlands. Classification (TWIN-SPAN) and ordination (SSH) of the samples collected in sweeps and tows gave good separation of the wetlands, whereas classification of core samples did not. Coring appeared to be the least suitable sampling method for describing the major components of the macroinvertebrate communities of these wetlands. Plankton tows were useful if the time available for sorting was limited as these samples were free of sediments and generally gave similar results to those obtained with sweeps. Sweeps appeared to be the most useful method for a large classification study as they collected more species and resulted in the best discrimination amongst wetlands.     

分散角质层的分类和命名*

简略讨论了分散角质层对地层学、古生物学和古环境的意义;简述了气孔器的形态学、发生学和形态一发生学的分类;在介绍并讨论了分散角质层的分类原则和命名方法的基础上,提出了新的分类方案.