Weed species diversity and community composition in cropping practices at two intensity levels – a six-year experiment

Alternative cropping practices can be expected to increase the diversity and change the species composition of weed communities. In a six-year field experiment we compared species diversity and species composition in the weed community of cereal fields cultivated by conventional and by low-input cropping methods. In the conventional cropping both mineral fertilizers and herbicides were applied but in the low-input cropping the fertlizer was manure and herbicides were avoided altogether. The level of nitrogen fertilization was higher in conventional cropping. A five-year crop rotation comprising rye, oat-pea, barley and two-year grasslands was used in both cropping methods. We found that the species pool was larger (42 vs 35 species) and the average number of species higher (20.2 vs 13.1 species) in low-input than in conventional cropping. This was the case both in the data pooled across crops and in each crop separately. Herbicides affected species diversity and species composition more than did nitrogen fertilization. Species susceptible to the herbicides applied declined in abundance, which resulted in more skewed dominance patterns in the communities of conventional fields than in those of low-input fields. The crop affected the species composition of weed communities more than did the cropping method. Our results suggest that weed species diversity could be promoted by using low-intensity cropping practices.     

Environmental Lithium Exposure in the North of Chile—I. Natural Water Sources

Lithium as an essential element for human life is still a subject of controversy. However, it is accepted that it does have profound neurological effects and is a valuable treatment for bipolar disease. Generally, it occurs in barely trace amounts in groundwater with few major exceptions. One of these is the Northern area of Chile where all potable water and many of the food stuffs contain high levels of lithium; between 100 and 10,000 times higher than most rivers in North America. Inevitably, the local population has been exposed to these levels in their drinking water for as long as the region has been populated. The present report details lithium levels in all the surface water sources of Northern Chile with comparison to that elsewhere. The implications for the local population are discussed and their situation compared to those exposed to other sources of lithium pollution.     

Effects of changes in tree species composition on water flow dynamics – Model applications and their limitations

Water-plant relations play a key role in the water cycling in terrestrial ecosystems. Consequently, changes in tree species composition may have distinct effects on the water retention capacity as well as on the pattern of streamflow generation. Such changes may result from modified interception properties and transpiration related to differences in canopy properties and root distribution. In order to evaluate the potential hydrological effects of the current silvicultural conversion from monocultural conifer stands into mixed or pure deciduous stands the hydrological model BROOK90 was applied to two forested upland catchments in Germany. The Rotherdbach catchment (9.4 ha, 93 yr-old Norway spruce) is situated in the Eastern Ore Mountains. The Schluchsee catchment (11 ha, 55-yr-old Norway spruce) is located in the higher altitudes of the Black Forest. The calibrated model is capable to describe rather well the temporal variation of streamflow but also the portions of the individual flow components. Data for a beech scenario were adapted for each site using a standard parameter set for deciduous trees provided by BROOK90. The annual discharge in the fictional beech stand at Rotherdbach is 30 to 50% higher compared to spruce with an increase of soil moisture and especially the slow streamflow components. This mainly results from low interception rates during winter time. In contrast, the spruce stand has a permanently higher interception rate. Effects of tree species conversion are moderate at Schluchsee. The annual discharge of a fictional beech stand at Schluchsee is 7 to 14% higher compared to spruce. There in contrast to Rotherdbach, effects of tree species conversion on soil moisture dynamics are small since vertical percolation in the highly permeable soil dominates and precipitation is abundant. Practical forestry will favorably establish mixed beech–spruce rather than pure beech stands. However, it is critical to simulate mixed stands with BROOK90. Therefore, a simple summation of model results from spruce and beech according to their respective area in a fictional mixed stand can only be a first approximation. Advanced hydrological simulation of mixed stand conditions should regard interactions of tree species and spatial parameter distribution. However, this is not yet feasible due to a distinct lack of information. As a consequence, there is a strong need to collect relevant hydrological and ecophysiological data in mixed stands in the future.     

Spatial and temporal variation in the vegetation of dune slacks in relation to the ground water régime

Summary The aim of the study presented here is to determine the relation between the vegetation and the ground water régime in the dune slacks on the island of Voorne. A distinction is made between the spatial and the temporal variation in the vegetation. On the basis of data from a transect the relation between the spatial variation and the water-table is determined. With respect to the temporal variation data recorded on permanent plots were used. Both the variation in space and that in time proved to be related to differences in the ground water régime. The supposition is put forward that the amount of variation in time depends on the height of site relative to the water-table.Contribution to the Symposium of the Working Group on Succession Research on Permanent Plots held at Yerseke, the Netherlands, October 1975.Nomenclature of phanerogams follows Heukels & van Ooststroom 1975, Flora van Nederland, 18e druk Wolters-Noordhoff, Groningen; that of bryophytes Margadant 1959, Mossentabel, 3e druk, Amsterdam.The author is very much indebted to Mr. P.A. Bakker, Society for the Preservation of Nature reserves in the Netherlands, for the use of the 1966 relevé of site 46, and to Mr. W. Smant for his assistance in field work and the preparation of the data.     

Evaluation of species composition and seasonal dynamics of mosquito larvae in the Košice Basin during 2010 and 2011

In six sites in the Ko?ice Basin we collected 17,520 larvae of 15 mosquito species during the seasons (April–August) of 2010 and 2011. They were: Aedes vexans (Meigen, 1830), Ae. cinereus (Meigen, 1818) [or Ae. rossicus (Dolbeskin, Gorickaja & Mitrofanova, 1930], Ochlerotatus geniculatus (Olivier, 1791), Oc. refiki (Medschid, 1928), Oc. rusticus (Rossi, 1790), Oc. sticticus (Meigen, 1838), Oc. punctor (Kirby, 1837), Oc. cataphylla (Dyar, 1916), Oc. cantans (Meigen, 1818)[or Oc. annulipes (Meigen, 1830)], Oc. communis (De Geer, 1776), Oc. flavescens (Müller, 1764), Oc. leucomelas (Meigen, 1804), Culiseta annulata (Schrank, 1776), Culex pipiens (L., 1758) [or Cx. torrentium (Martini, 1925)] and Anopheles maculipennis s.l. The objective of the present research was to identify the mosquito larvae species diversity and compare their distribution and density in urban and suburban localities of the monitored territory.     

The chemical composition of the volatile oil of the leaves of Picea rubens Sarg. and chemotaxonomic correlations with other North American spruce species : Gas-liquid chromatography of terpenes—XIV.

The volatile oil from two populations of red spruce was found to consist mainly of bornyl acetate (55 per cent). Smaller amounts of α- and β-pinene, camphene, 3-carene, myrcene, limonene, α- and β-phellandrene, p-cymene, 1:8-cineole, linalool, camphor, terpinen-4-ol, α-terpineol, borneol, piperitone, citronellyl and geranyl acetate, bisabolene and a mixture of γ- and δ-cadinene (“canadene”) were also isolated. Santene, tricyclene, γ-terpinene, thujone, isothujone and isoborneol were tentatively identified. The leaf oils of the foliage from black spruce (2 trees) white spruce (3 trees) and Colorado spruce (5 trees) were analysed by GLC and the data obtained were compared with those of red spruce. The close phylogenetic relationship of red and black spruce was found to be reflected in the chemical composition of their leaf oils, whereas significant chemical differences were observed with both white and Colorado spruce. Hypothetical pathways for the formation of the terpenes found in spruce leaf oils from a single precursor, such as geranyl pyrophosphate, are discussed. Piperitone, a C-3 oxygenated monoterpene, appears to take an exceptional position in such postulated sequences. Also, not all of the compounds expected from schemes involving carbonium-ion intermediates are found in the spruce leaf oils.     

Explaining the variation in the soil microbial community: do vegetation composition and soil chemistry explain the same or different parts of the microbial variation?

Aim

To assess whether vegetation composition and soil chemistry explain the same or different parts of the variation in the soil microbial community (SMC).

Method

The above and below-ground communities and soil chemical properties were studied along a successional gradient from moorland to deciduous woodland. The SMC was assessed using PLFAs and M-TRFLPs. Using variance partitioning, Co-Correspondence Analysis (CoCA) and Canonical Correspondence Analysis (CCA), the variation (total inertia) in the SMC was partitioned into variation which was uniquely explained by either plant composition or soil chemistry, variation explained by both soil chemistry and plant composition, and unexplained variation.

Results

Plant community composition uniquely explained 30, 13, 16 and 20% of the inertia and soil chemistry uniquely explained 5, 18, 9 and 9% of the inertia in the archaeal TRFLPs, bacterial TRFLPs, fungal TRFLPs and all PLFAs, respectively.

Conclusion

For the first time, variance partitioning was used to include data from a CoCA; although the current limits of such an approach are shown, this study illustrates the potential of such analyses and shows that soil chemistry and plant composition are, in substantial amounts, explaining different parts of the variation within the SMC. This marks an important step in furthering our understanding of the relative importance of different drivers of change in the SMC.     

Cryptogamic epiphytes in primary and recovering upper montane oak forests of Costa Rica – species richness,community composition and ecology

Species richness, community composition and ecology of cryptogamic epiphytes (bryophytes, macrolichens) were studied in upper montane primary, early secondary and late secondary oak forests of the Cordillera de Talamanca, Costa Rica. Canopy trees of Quercus copeyensis were sampled with the aim of getting insight in patterns and processes of epiphyte succession and recovery of diversity in secondary forest following forest clearing. Species richness of cryptogamic epiphytes in secondary and primary forests were nearly the same, showing that primary forests are not necessarily more diverse than secondary forests. High species richness of secondary forests was presumed due to the closed canopy, resulting in permanently high atmospheric humidity in these forests. Similarity in species composition of secondary and primary forests increases with forest age, but after 40 years of succession one third (46 species) of primary forest species had not re-established in the secondary forest. Community composition in primary and secondary forests differed markedly and indicates that a long time is needed for the re-establishment of microhabitats and re-invasion of species and communities adapted to differentiated niches. Genera and species exclusive to primary forests are relevant as indicator taxa and conservation targets. Forty percent (68 species) of all species recorded are restricted to secondary forests, indicating the important contribution of secondary forest diversity to total species richness of the oak forests of Costa Rica.     

Effects of environmental factors on the phytoplankton community in the Gulf of Finland – unattended high frequency measurements and multivariate analyses

We studied life history and secondary production of Cheumatopsyche spp. (Trichoptera: Hydropsychidae) in StroublesCreek, a 3rd order stream near Blacksburg, Virginia to compare lifehistories and production dynamics in two reaches with differentland-uses. The upstream reach was influenced by agriculturalactivities and more annual degree-days accumulated in this sectionof the stream. The downstream reach was surrounded by forest,received less thermal input than the upstream reach, and showedlittle evidence of human disturbance. Differences between the twosites included a shift in dominant taxa and changes in voltinismand production of hydropsychids. Cheumatopsyche pettiti(Banks) was dominant at the upstream site, while C. pettitiand Cheumatopsyche oxa Ross were both abundant downstream.Cheumatopsyche larvae and other aquatic insects had higherdensities at the forested downstream site. C. pettiti wasbivoltine at the upstream site, but C. pettiti and C. oxa were partially bivoltine downstream, with a small summergeneration overlapping with continuous emergence of overwinteringlarvae. Cheumatopsyche production at the two sites inStroubles Creek was higher than in forested, low-order streams ofNorth America, but similar to some values obtained at streams inagricultural areas and large rivers. Production was higher at thedownstream site, but the superior bivoltinism at the upstream sitecounterbalanced, to some extent, the increase in larval densitythat caused higher production downstream. The adjustment in lifehistory and production dynamics, in the two reaches, showed theecological plasticity of Cheumatopsyche and the importance ofhydropsychids in the energy flow of moderately disturbedstreams.     

Fish fauna of the Severn Estuary. Are there long-term changes in abundance and species composition and are the recruitment patterns of the main marine species correlated?

Fish were collected from the intake screens of the Oldbury Power Station in the Severn Estuary in each week between early July 1972 and late June 1977 and at least twice monthly between early January 1996 and late June 1999. The annual catches, after adjustment to a common sampling effort, demonstrate that the abundance of fish at Oldbury was far greater in the 1990s than 1970s, mainly due to marked increases in the numbers of certain marine species, such as sand goby, whiting, bass, thin-lipped grey mullet, herring, sprat and Norway pout. These increases may reflect the great improvement that occurred in the water quality of the Severn Estuary between these decades. The only species that declined markedly in abundance was poor cod. Modest declines in flounder and River lamprey paralleled those occurring elsewhere in the UK. The species composition in the two decades also differed, reflecting changes not only in the relative abundances of the various marine estuarine-opportunistic species, which dominated the ichthyofauna, but also in those of the suite of less abundant species in the estuary. The cyclical changes undergone each year by the species composition of the fish fauna of the Severn Estuary reflect sequential intra-annual changes in the relative abundances of species representing each of the marine, diadromous and freshwater categories. New approaches have been developed to test whether or not large sets of correlations between patterns of recruitment amongst abundant marine species (internal correlations), and between those patterns and salinity and water temperature within the estuary (cross-correlations), were significant. The correlation profile analyses found no evidence that the annual recruitment strengths of these species were either intercorrelated, or correlated with either one or a combination of both of the above environmental variables. Yet, the timings of the recruitment of these species into the estuary were intercorrelated, i.e. a slightly earlier or later than normal immigration by one species in a given year was paralleled by the same trend in other species. However, this association in recruitment times could be linked neither to salinity nor water temperature within the estuary, nor to a combination of these two variables. These results indicate that, while the factors that influence the annual recruitment strengths of the juveniles of different marine species vary, inter-annual differences in the phasing of events that regulate spawning times and/or larval dispersal influence, in the same direction, the times when marine species are recruited into the estuary.     

From introduced species to invader: what determines variation in the success ofCodium fragile ssp.tomentosoides (Chlorophyta) in the North Atlantic Ocean?

The green algaCodium fragile ssp.tomentosoides (Chlorophyta) has been introduced accidentally and successfully from Japan to many shores of the northern and southern hemispheres, including those of the Northeast and Northwest Atlantic Ocean. On most European coasts,Codium occurs regularly but at low abundances in the intertidal zone and is absent from subtidal habitats. In contrast,Codium is extremely abundant in subtidal kelp beds in the Northwest Atlantic Ocean where it often reaches nuisance proportions. This differential success cannot be accounted for by either the properties of the invader or by physico-chemical differences between invaded coasts. A theoretical comparison between two regions on opposite sides of the Atlantic Ocean, i.e. Eastern Nova Scotia, Canada, and south central Britain, illustrates how the resident benthic community may determine the difference in relative abundance ofCodium in subtidal habitats between northeast America and Europe. In this review, low floral species diversity, biological disturbance and facilitation by a previous species invasion are suggested as potential factors for the establishment, success and abundance ofCodium in the Northwest Atlantic Ocean, but these require testing in field experiments.     

Is there chaos in the brain? I. Concepts of nonlinear dynamics and methods of investigation

In the light of results obtained during the last two decades in a number of laboratories, it appears that some of the tools of nonlinear dynamics, first developed and improved for the physical sciences and engineering, are well-suited for studies of biological phenomena. In particular it has become clear that the different regimes of activities undergone by nerve cells, neural assemblies and behavioural patterns, the linkage between them, and their modifications over time, cannot be fully understood in the context of even integrative physiology, without using these new techniques. This report, which is the first of two related papers, is aimed at introducing the non expert to the fundamental aspects of nonlinear dynamics, the most spectacular aspect of which is chaos theory. After a general history and definition of chaos the principles of analysis of time series in phase space and the general properties of chaotic trajectories will be described as will be the classical measures which allow a process to be classified as chaotic in ideal systems and models. We will then proceed to show how these methods need to be adapted for handling experimental time series; the dangers and pitfalls faced when dealing with non stationary and often noisy data will be stressed, and specific criteria for suspecting determinism in neuronal cells and/or assemblies will be described. We will finally address two fundamental questions, namely i) whether and how can one distinguish, deterministic patterns from stochastic ones, and, ii) what is the advantage of chaos over randomness: we will explain why and how the former can be controlled whereas, notoriously, the latter cannot be tamed. In the second paper of the series, results obtained at the level of single cells and their membrane conductances in real neuronal networks and in the study of higher brain functions, will be critically reviewed. It will be shown that the tools of nonlinear dynamics can be irreplaceable for revealing hidden mechanisms subserving, for example, neuronal synchronization and periodic oscillations. The benefits for the brain of adopting chaotic regimes with their wide range of potential behaviours and their aptitude to quickly react to changing conditions will also be considered.     

Epidemiology of tegumentary leishmaniasis in Mérida, Venezuela. I. Diversity and dispersion of phlebotomine species at 3 altitude levels and its possible role in the transmission of the disease

As part of an epidemiological study on leishmaniasis in Merida, Venezuela, the diversity and dispersion of sandflies species found in 15 localities between 175 m and 1,960 m.a.s.l., are presented. From 7,126 collected sandflies (5,132 female and 1,994 male), 24 species were identified, 10 of them recognized as anthropophilic. The relation species-altitude is presented, and the species composition found in human dwellings, periodomestic and sylvatic areas, are recorded. The possible role of the identified species on the transmission of leishmaniasis in the andean region, is discussed.     

The short—term variation of asthma in Brisbane: Its relation to the weather and other factors

In the cooler portions of the six years 1961–1966, there were 22 weeks in which the night attendances for asthma at the Royal Brisbane Hospital Casualty Department were much higher than would be expected from the seasonal and annual variation, 23 weeks in which they were much lower, and 114 intermediate weeks. The high-asthma weeks differed significantly from intermediate weeks in having on the average a greater decrease from the previous week in mean and minimum temperature, dew point, relative humidity and rainfall, and a greater increase in hours of sunshine. There was a significant association with the arrival of a cold dry change. No significant difference was found with smoke density, fungal elements or pollens. In many of the individual high-asthma weeks the increase in asthma occurred within 48 hours after a definite fall in minimum temperature or dew point or both. However, in some of the weeks, particularly in spring, there had not been a cold or dry change, and many cold dry changes were not followed by an increase in asthma. The low-asthma weeks differed significantly from intermediate weeks in having on the average a higher dew point and relative humidity, more rainy days, a lower temperature range and fewer hours of sunshine. This applied particularly to autumn. In autumn and spring, rain was significantly less frequent on days with asthma attendances than on days with none. These relationships are largely the converse of those with high-asthma weeks.

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Zusammenfassung Während der kühleren Jahreszeiten in 6 Jahren (1961–1966) waren 22 Wochen in denen die Anzahl der nächtlichen Einlieferungen wegen Asthma im Royal Brisbane Hospital weit höher war als die erwartete Anzahl, 23 Wochen in denen sie wesentlich geringer war, und 114 Wochen mit einer mittleren Anzahl Fälle. Die Wetterbedingungen während der Wochen mit vielen Asthmafällen waren signifikant unterschieden von denen mit mittlerer Häufigkeit. Im Mittel waren die mittlere und die Minimaltemperatur tiefer als in der vorausgegangenen Woche, es waren weniger Regen, niedrigere Luftfeuchtigkeit und mehr Stunden Sonnenschein. Es bestand eine signifikante Beziehung zu dem Eintreffen kalter trockener Luft. Dagegen bestand keine Beziehung zur Dichte der Luftverunreinigung und der Menge Pilzsporen und Pollen in der Luft. In vielen Wochen trat Asthma innerhalb 48 Stunden nach dem Fall der Temperatur und Feuchtigkeit auf. Während einiger Wochen dagegen, besonders im Frühling, lag dieser Wetterwechsel nicht vor und in vielen Fällen bewirkte der Wechsel keinen Anstieg der Asthmahäufigkeit. Während der Wochen mit niedriger Asthmahäufigkeit waren im Mittel die Feuchtigkeit erhöht, ein geringerer Temperaturwechsel, weniger Regen und weniger Sonnenscheinstunden, besonders im Herbst. Im Herbst und Frühling war signifikant weniger Regen an Tagen mit als an Tagen ohne Asthmameldungen. Diese Beziehungen waren weitgehend umgekehrt von denen in Wochen mit hoher Asthmahäufigkeit.

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Resume Des statistiques de la permanence du \"Royal Brisbane Hospital\" il appert que durant les périodes froides des années 1961 à 1966, on a dénombré 22 semaines pendant lesquelles, la nuit, les entrées d'urgence causées par des crises d'asthme furent beaucoup plus nombreuses que ne le laissaient supposer les variations saisonnières et annuelles. Durant les mêmes laps de temps, on en a décompté 23 pendant lesquelles les crises nocturnes d'asthme étaient moins fréquentes et 114 qui occupent une position intermédiaire. Les semaines à haute fréquence d'asthme présentent des moyennes de température, des minimums journaliers, des points de rosée, des humidités relatives et des précipitations inférieurs et une durée d'insolation supérieure à la normale et cela de façon significative. On a pu déceler une relation significative entre les crises d'asthme et des invasions d'air froid et sec. On n'a par contre pas pu déceler de différences en ce qui concerne le taux de fumée ou le nombre de spores et de grains de pollen. Dans bon nombre de semaines avec de hautes fréquences d'asthme, le déclenchement des crises se produit 48 heures après la chute du minimum de la température ou du point de rosee, voire des 2 ensemble. Pourtant, quelques unes de ces semaines — au printemps surtout — n'ont pas connu d'invasion d'air froid et sec et de nombreuses invasions de ce type ne furent pas suivies d'une augmentation du nombre de crises. Les semaines de faible fréquence se distinguent de façon significative de la classe intermédiaire en ce sens qu'elles présentent en moyenne des points de rosée et une humidité plus élevés, plus de jours avec précipitations, une température plus basse et moins d'heures d'insolation. Ceci est valable surtout en automne. En automne et au printemps, la pluie fut moins fréquente les jours où l'on note des crises d'asthme qu'à ceux où il n'y en a pas. Cette relation est en général inverse à celle que l'on rencontre durant les semaines à haute fréquence de crises d'asthme.

     

Tree population dynamics,stand structure and species composition in the montane virgin forest of Vallibäcken,northern Sweden

The population dynamics of Betula pubescens and Picea abies in a boreal forest near Kvikkjokk, northern Sweden, are governed by a process of storm gap regeneration similar to the gap regeneration described for boreo-nemoral forests. Cumulative age distribution curves, interpreted as static survivorship curves, lead to a simple theory of differential survival based on properties of the species, i.e. shade tolerance and relative growth rate. The theory is sustained by diameter and height distributions and by the spatial distributions of logs and of trees in different life-phases. Species of the field and ground layers respond differentially to gap formation and the ensuing successional stages. Browsing by moose (Alces alces) may prevent tree species, mainly Sorbus aucuparia, Betula pubescens and Pinus sylvestris, from developing into a tree layer. The regeneration ability for tree species growing in a stand at 460 m a.s.l. is limited compared with the regeneration at 330 m a.s.l., and typical storm gap formation involving more than one tree seems to occur rarely if at all, while overthrown trees with exposed rootplates are uncommon. Spruce at 460 m a.s.l. shows also a lower growth rate and a lower height/diameter ratio compared to the lower situated stands.