Consulta: creatorFacets:"Janssen, C.R."
Registros recuperados: 16
Data/hora: 12/06/2024 03:18:01

Stevens Pond: A postglacial pollen diagram from a small Typha Swamp in Northwestern Minnesota, interpreted from pollen indicators and surface samples
Provedor de dados: 16
Autores: Janssen, C.R.
The pollen assemblages of a core in the coniferhardwood formation in northwestern Minnesota are compared with the floristics of the recent vegetation in the region. Percentage levels of the main tree components have been compared first with those from recent surface samples taken at the same short distance from various types of upland forests and second with the regional values of the pollen rain in this area (McAndrews 1966). To that end all the data were recalculated on the basis of special pollen sums. The regional diagram of Stevens Pond shows basically the same assemblage zones as established by McAndrews but without the late-glacial Picea-Populus assemblage zone. The pollen in the following Pinus-Pteridium assemblage zone has been interpreted as...
Tipo: Article / Letter to the editor
Ano: 1967
URL: http://www.repository.naturalis.nl/record/534791

A short life history of Prof. Dr. F.P. Jonker
Provedor de dados: 16
Autores: Janssen, C.R.
This year Prof. Dr. F.P. Jonker, Frits as he is known among his friends, will retire from the formal academic life at the State University of Utrecht: a long and busy life of 49 years, devoted to teaching, administration, and scientific research. Looking back on all these years, one realises the important contributions that Jonker has made to botanical science in general and to palaeobotany in particular, both in The Netherlands and abroad, as well as the impact he has exerted on his surroundings, culminating in the vigorous activities of the Laboratory of Palaeobotany and Palynology at Utrecht. To describe Jonker’s life history is indeed to describe the history of his laboratory. To understand the significance of Jonker and the character of the “lab”, we...
Tipo: Article / Letter to the editor
Ano: 1978
URL: http://www.repository.naturalis.nl/record/534719

Alnus as a disturbing factor in pollen diagrams
Provedor de dados: 16
Autores: Janssen, C.R.
It is commonly accepted that percentages of pollen in a pollen diagram do not express the exact composition of forests in earlier times. This inaccuracy is due to several factors, for instance the different quantities of pollen produced by plants, the distance of transport etc. A pollen diagram tells us only the change in pollen rain on the locality where we collected soil samples. In studying a pollen diagram we find a close relation between the variations in the percentages of a certain species and the area occupied by this species in the vegetation. When the percentage of pollen of a species increases, we conclude generally that the relative area occupied by this species in the vegetation increases too. However, such a connection might be doubted. The...
Tipo: Article / Letter to the editor
Ano: 1959
URL: http://www.repository.naturalis.nl/record/535044

Some Late-Holocene pollen diagrams from the Peel raised bogs (Southern Netherlands)
Provedor de dados: 16
Autores: Janssen, C.R.; Hove, H.A. ten.
Three pollen diagrams from the Peel peatlands, a raised bog area in the southern part of The Netherlands reveal the post-Boreal vegetation history of that region. There are two or three land-occupation phases in the Neolithic and Bronze ages, that show but low values of terrestrial herbs. They are negatively correlated with Ulmus. The Fagus curve starts slightly below the first occupation phase at around 2500 B.C. In the Subatlantic there is an Iron age and a Medieval occupation phase with higher values of terrestrial herbs. Fagus shows two maxima, one at the beginning of our era and another at around 700 A.D. The trend of the pollen curves for bog species is discussed in relation to bog development.
Tipo: Article / Letter to the editor
Ano: 1971
URL: http://www.repository.naturalis.nl/record/534844

Recent pollen spectra from the deciduous and coniferous-deciduous forests of Northeastern Minnesota: a study in pollen dispersal
Provedor de dados: 16
Autores: Janssen, C.R.
Pollen samples were taken along nine transects across local vegetational belts bordering bogs or ponds in overall deciduous and coniferous-deciduous forest regions. Three types of pollen rain are distinguished: local, extralocal, and regional. Local pollen rain is derived from plants that grow at or very close to the sampling point. High local values are common in all sorts of vegetation types: lakes, bogs, marshes, and forests. Extralocal pollen rain is derived largely from trees that grow on the slopes and upland adjacent to the sampling site, but not extensively over larger areas. When excluded from the pollen sum along with the local types, its curves increase slightly, but noticeably, along the transect as the source of dispersal is approached. The...
Tipo: Article / Letter to the editor
Ano: 1966
URL: http://www.repository.naturalis.nl/record/535204

Problems in the recognition of plant communities in pollen diagrams
Provedor de dados: 16
Autores: Janssen, C.R.
In recent years pollen analysis has turned increasingly from historical plant geography towards paleoecology. More and more the main interest lies in a reconstruction of the past vegetation instead of simply floristics of a region. Vegetation as a rule is made up of communities¹) that can be described quantitatively in terms of species composition or qualitatively in terms of structure.
Tipo: Article / Letter to the editor
Ano: 1970
URL: http://www.repository.naturalis.nl/record/535170

Myrtle Lake: a late- and post-glacial pollen diagram from northern Minnesota
Provedor de dados: 16
Autores: Janssen, C.R.
A pollen diagram from a lake in the former bed of the eastern arm of Lake Agassiz in northern Minnesota records a vegetation of spruce forest followed by immigration successively of Pinus banksiana and (or) P. resinosa at 10 000 B.P., then Abies and Pteridium, and still later Alnus. Between 8000 and 7000 B.P. prairie and (or) Quercus savanna prevailed on the uplands, followed by deciduous forests of mainly Quercus, Ostrya virginiana, Fraxinus pennsylvanica, and possibly Populus sp. Slightly later, Pinus strobus migrated into the area, resulting in a gradual decline of pollen of deciduous forest types. Betula pollen, however, rises, and there is an indication of a return to prairie conditions prior to 3000 B.P. During the 8000-7000 B.P. dry interval the...
Tipo: Article / Letter to the editor
Ano: 1969
URL: http://www.repository.naturalis.nl/record/535048

A post-Atlantic pollen sequence from the Tourbière du Tanet (Vosges, France)
Provedor de dados: 16
Autores: Janssen, C.R.; Janssen-Kettlitz, E.L.
The pollen analyse of a raised-bog on the High Vosges crest shows the vegetation regional development since 3200 years. A prehistoric civilization, the Gallo-roman period, the great migrations and the Carolingian period are reflected in the pollen diagram by N.A.P. minima and maxima. A discussion on curves fluctuations of the main A.P. follows.
Tipo: Article / Letter to the editor
Ano: 1972
URL: http://www.repository.naturalis.nl/record/534828

On the lateglacial and postglacial vegetation of South Limburg (Netherlands)
Provedor de dados: 16
Autores: Janssen, C.R.
The present study deals with the late-glacial and post-glacial development of the vegetation in the loess region of South Limburg (Netherlands). In the lateglacial time the continental element in the vegetation (Artemisia) is very pronounced, probably due to the particular soil conditions in South Limburg. The zonation of FIRBAS (1949) has been applied to the South Limburg diagrams. Zone I: Tundra, a temporary amelioration of the climate (Bölling time) can be observed. Zone II: Closed pine forests present (Alleröd time). Zone III: In the lower part of the zone Pinus dominant, afterwards Belula. Zone IV: Decrease of the percentages of the herbs; Pinus dominant in the vegetation; first appearance of Corylus. Zone V: Pinus and Corylus dominant; in the lower...
Tipo: Article / Letter to the editor
Ano: 1960
URL: http://www.repository.naturalis.nl/record/534940

A floristic study of forests and bog vegetation, Northwestern Minnesota
Provedor de dados: 16
Autores: Janssen, C.R.
Single vegetation plots in forests and bogs in the deciduous and coniferoushardwood formation in northwestern Minnesota were studied according to the field methods of the Zürich-Montpellier system. Plots and species were arranged so that the greatest coincidence of occurrences was obtained. Species that show approximately similar amplitudes were united in sociological groups. Plant communities typified by these groups were placed in a hierarchy. The plant communities appear to intergrade but are not completely continuous. Definite concentrations of occurrences remain present in the ordination. Fourteen main types of vegetation are recognized. Their relations to the environment are discussed, and their relations to vegetation in other regions are indicated....
Tipo: Article / Letter to the editor
Ano: 1967
URL: http://www.repository.naturalis.nl/record/534710

First occurrence of the Pontocaspian invader &lt;i&gt;Hemimysis anomala&lt;/i&gt; (Sars, 1907) in Belgium (Crustacea: Mysidacea)
Provedor de dados: 27
Autores: Verslycke, T.; Janssen, C.R.; Lock, K.; Mees, J.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Mysidacea Belgium; Zeeschelde; Galgenweel.
Ano: 2000
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2678

Assessment of ammonia toxicity in contaminated sediments in the upper Scheldt (Belgium): the development and application of toxicity identification evaluation procedures
Provedor de dados: 27
Autores: Van Sprang, P.; Janssen, C.R.; Sabayasachi, M.; Benijts, F.; Persoone, G.
The toxicity of sediment pore waters from 4 sites in the Upper Scheldt war characterized using modified Toxicity Identification Evaluation (TIE) procedures The samples from all locations exhibited acute toxicity to the freshwater crustacean Thamnocephalus platyurus. The IIE approach was conducted using an enlarged battery of fractionation tests. Toxicity was removed or reduced significantly by the cation exchange resins and the air-stripping test at pH 11. Additionally, increased toxicity war observed at higher pH while a reduced toxicity war found at a decreased pH. From these TIE studies, ammonia war identified as the dominant toxic agent.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Metals; River; Toxicants; Water.
Ano: 1996
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7459

Aberrant individuals of &lt;i&gt;Neomysis integer&lt;/i&gt; and other Mysidacea: intersexuality and variable telson morphology
Provedor de dados: 27
Autores: Mees, J.; Fockedey, N.; Dewicke, A.; Janssen, C.R.; Sorbe, J.-C.
Intersexuality in the mysid &lt;i&gt;Neomysis integer&lt;/i&gt; is described from samples collected in the Elbe (north Germany), Eems-Dollard (north Netherlands), Westerschelde (south-west Netherlands) and Gironde (south-west France) estuaries. Individuals which had an irregularly shaped or nearly symmetrically rounded telson, rather than a typically truncated one, were also recorded from the four populations studied. A culture experiment with damaged specimens revealed that all types of abnormal telson morphology found in the field can result from regeneration of damaged parts. It is concluded that both intersexuality and aberrant telson morphology are widespread phenomena among estuarine &lt;i&gt;N. integer&lt;/i&gt; populations. Both abnormalities seem...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Abnormalities Animal morphology Aquatic environment Brackish water Estuaries Estuarine organisms Physiology Mysidacea Neomysis integer (Leach; 1814) [An opossum shrimp].
Ano: 1995
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7470

De grondels (Pisces, Gobiidae) van de Belgische kustwateren en de aangrenzende estuaria
Provedor de dados: 27
Autores: Hamerlynck, O.; Janssen, C.R.
The authors provide a new and simple identification key for the different Gobiidae species in Belgian coastal waters.The key avoids to use the pigmentation pattern, because sexual dimorphism, individual and seasonal variations make this parameter useless for the non-scientist. The general life history of the Gobiidae is described, and each species is shortly treated separately.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Brackishwater fish Check lists Distribution Identification keys Life history Aphia minuta (Risso; 1810) [Transparent goby] Gobiidae [Gobies] Gobius niger Linnaeus; 1758 [Black goby] Pomatoschistus lozanoi [Lozano's goby] Pomatoschistus microps (Kröyer; 1838) [Common goby] Pomatoschistus minutus (Pallas; 1770) [Sand goby] Pomatoschistus pictus (Malm; 1865) [Painted goby] ANE; Belgium.
Ano: 1985
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7023

Pseudo-hormonen, fictie of realiteit?
Provedor de dados: 27
Autores: Dhooge, W.; D'haese, I.; Versonnen, B.; Schellekens, P.; Comhaire, F.; Verstraete, W.; Janssen, C.R.
Tipo: Info:eu-repo/semantics/article
Ano: 1999
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7493

The use of biomarkers in &lt;i&gt;Daphnia magna&lt;/i&gt; testing: 3. Rapid toxicity testing of pure chemicals and sediment pore waters using ingestion and digestive enzyme activity
Provedor de dados: 27
Autores: De Coen, W.M.; Vangheluwe, M.L.; Janssen, C.R.
In this study, 4 rapid (90 min) toxicity tests were developed using ingestion and digestive enzyme activity of &lt;i&gt;Daphnia magna&lt;/i&gt; juveniles. Ingestion activity was assessed using fluorescent labelled latex micro-beads and digestive enzyme activity (trypsin, beta-galactosidase and esterase) was measured in homogenates using chromogenic (N-benzoyl-L-arginine-4-nitroanilide) and fluorogenic (4-methylumbelliferyl-B-D-galactoside and fluorescein diacetate) substrates.All assays and toxicity endpoints were evaluated for their potential use as routine toxicity testing tools for pure chemicals and sediment pore waters. The observed high correlation coefficients (r(2)&gt;0.9) between the short-term toxicity values and the acute toxicity endpoint (24h...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Assimilation; Assimilation; Exposure; Exposure; Filtration; Respiration; Zooplankton; Daphnia magna; Rotifera.
Ano: 1998
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7488