Species turnover in deciduous forest vegetation

Summary Permanent quadrats were marked out in two areas of hardwood forest vegetation in 1969, and listings of their vascular plant species were taken on several occasions over the snow-free seasons of 1969, 1970, 1971 and 1976. Over the period of study, mean numbers of species per m² remained virtually constant, but variations in the species compositions of individual quadrats were such that mean turnover ratios of 0.115 and 0.085, respectively, were computed for the two stands. Between 1969 and 1976 averages of 20% and 14%, respectively, of the species found in individual quadrats were replaced. This was not accomplished by qualitative changes in the floras of the two stands. Rather, it reflects the operation of a system of continuous rearrangements of species in the small quadrats of both sample areas.Taxonomical nomenclature and life-form system used in this study are according to Gleason & Cronquist (1963).William Phillips, Ian Sutherland and Sheila Thompson helped in the field; Professor Keith Wade commented on the material; Abal Sen drafted the diagram; and the research is part of that funded by the National Research Council of Canada.     

Änderungen in der Stickstoffversorgung auf Dauerflächen im Brachland

Summary Starting in 1968 plant succession and nitrogen status in the top soil of an old field was investigated. The soil is a calcareous loam which was sterilized by heating. In the absence of human influence distinct successional stages with characteristic floristical and physiognomical features were observed. During the first six years vegetational development was characterized by competition between therophytes and hemicryptophytes. Agricultural treatments such as annual ploughing (spring, summer) and cutting (autumn) were found to change the trend of the succession.Five years after starting the experiment total nitrogen content in the top soil of the control area had increased slightly, while the ploughed plots persisted in their low values. A comparison of the nitrogen mineralisation between 1970 and 1974 showed decreasing amounts of mineral nitrogen in the later stage (1970: 67 kg N_min/ha/30 weeks; 33 kg N_min/ha/30 weeks). On the other hand, mineral nitrogen supply on the ploughed plots was not significantly different after the five-years-period. It is suggested that in old-field vegetation the external nitrogen cycle of the early therophyte stage changed to an internal one when long-lived hemicryptophytes, rhizome- and root-budding geophytes became dominant.Tables 1 to 4 show the vegetation development under different treatments; the figures represent average cover values per vegetation season using Londo's (1975) scale. Table 5 contains the total nitrogen concentration values in the uppermost of 10 cm of mineral soil, and Table 6 lists the values for soil volume, mean soil temperatures, average water content, and mineral nitrogen supplies for 1970 and 1974.

Contribution to the Symposium of the Working Group for Succession Research on Permanent Plots, held at Yerseke, the Netherlands, October 1975.     

Dynamics of benthic algal vegetation and environment in Dutch estuarine salt marshes studied by means of permanent quadrats

Summary Knowledge of the spatial structure of benthic algal vegetations in salt marshes, consisting of about 100 species of blue-green, green, brown and red algae, formed the basis of a detailed study into the dynamics of the algal mat.The temporal changes in algal vegetations and concomitant processes in their environment were studied in 27 permanent quadrats (PQs), plotted in tidal salt marshes and along brackish inland waters in the SW Netherlands. Once a month vegetation and environment of the PQs were examined over the period March 1968-February 1971. From the Spearman rank-correlation between vegetational and environmental parameters it appeared that in semiterrestrial and terrestrial environments the average number of algal species in a relevé and the average similarity between the species composition of successive relevés obtained from one PQ have a significant positive correlation with the stability of the substrate, and hardly any correlation with fluetuations in soil-moisture content and salinity of the soil moisture and with the maximum cover percentage of the phanerogams.Stable substrates tend to bear stable algal mats, as appeared from quantitative data. Small and moderate fluctuations in soil-moisture content and salinity of the soil moisture have no limiting influence on the algal cover degree. During periods of extremely high salinity and concomitant extremely low soil-moisture contents that coincide with evaporation surpluses, the green algal mat bleaches and decreases in cover in semi-terrestrial and terrestrial environments. Below 20% the soil-moisture content is limiting for the expansion of a mat of green algae (Rhizoclonium riparium, Percursaria percursa, Enteromorpha torta, E. prolifera) and Vaucheria species. The mat desiceates and bleaches but recovers after increase of the soil-moisture content above 20% within one month. Two weeks of severe frost (temperature down to – 10°C) do not influence the cover degree of the algal mat in aquatic branckish PQs, but the cover degree in semi-terrestrial PQs decreases. Short lasting soil-moisture salinities of 130–190 Cl^– have no limiting effect on the expansion of the algal mat.Nomenclature authorities are given in Table 3.Contribution to the Symposium of the Working Group for Succession Research on Permanent Plots, held at Yerseke, The Netherlands, October 1975.Communication No. 163 of the Delta Institute for Hydrobiological Research, Yerseke.     

Fluctuations in a coastal dune grassland due to fluctuations in rainfall: Experimental evidence

Experiments with rainfall on a dune grassland near Oostvoorne, the Netherlands with Festuco-Galietum as the main syntaxon are described. Both increase in rain through additional watering and decrease in rain through catchment are presented to plots belonging to the xerosere and the mesosere. Clear changes in the floristic composition are the result, even after only two years. Typical Festuco-Galietum species are promoted by high rainfall, species of open habitat such as Corynephorus canescens are promoted by drought. The results are discussed against the background of long term permanent plot observations in the area and a relation with rabbit grazing intensity is supposed.Nomenclature of vascular plants follows Heukels-van Ooststroom (1975) Flora van Nederland 18 ed., Woiters-Noordhoff, Groningen; Nomenclature of syntaxa follows Westhoff & den Held (1969). Plantengemeenschappen in Nederland, Thieme, Zutphen.Field work in 1978 was carried out with Frans Bongers and Marc de Lyon, in 1979 with Marc de Lyon, Picter Meeuwissen and Guiljo van Nuland, all then MSc. students at the Division of Geobotany. Their help and the advice of Dr. Peter van der Aart, Institute of Ecological Research, Oostvoorne, are acknowledged.     

Graphical comparison of resemblance measures in phytosociology

A simple graphical method, COREM, is described for the comparison of quantitative resemblance measures. The basis of the method is the ordered comparison case series (OCCAS) composed of relevé pairs ranked in decreasing order of similarity. For a given OCCAS, values of given resemblance functions are calculated and plotted in COREM.Delta resemblance (DR) is defined as the rate of change between two neighbouring relevé pairs in the OCCAS. High mean delta resemblance (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaaGqaai% aa-reacaWFsbaaaaaa!392E!\[\overline DR \]) of a resemblance measure indicates a high power of resolution and small standard deviation (SDDR) is indicative of linearity. A measure of efficiency combines % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaaGqaai% aa-reacaWFsbaaaaaa!392E!\[\overline DR \] and SDDR in the coefficient of variation for delta resemblance (CVDR). An efficient measure shows balanced sensitivity to the common and differential species. With the method COREM locally optimal resemblance measures may be selected for any given set of relevés which produce the sharpest separation of clusters. A reasonable compromise is to use types of measures, such as the similarity ratio (SIM6), Czekanowski coefficient (SIM8), or floristic similarity (SIM9), which have the best chance of being successful in most relevé sets. A study of transformation functions on Braun-Blanquet values with the help of COREM demonstrates that the combined transformation is the most advantageous for clustering. It is shown that standardization by relevés, or conversion to unit sum has undesirable effects.During the preparation of this paper the author was a recipient of a Postgraduate Scholarship, Deutscher Akademischer Austauschdients, Dortmund, KFA Abteilung Algenforschung, Germany. The author would like to thank L. Orlóci, P. Juhász-Nagy and E. van der Maarel for valuable suggestions, and comments.     

Use of lambda phasmids for deletion mapping of non-selectable markers cloned in plasmids

A nonselectable gene carried on a poorly selectable recombinant plasmid has been physically mapped by deletion analysis. Our method involved cloning the plasmid into a coliphage lambda vector and treating the recombinant phage with a chelator. Virtually all particles surviving this treatment carried large deletions within the plasmid insert. Further deletion analysis was done by inserting a selectable lambda sequence into one such deletion derivative and repeating the chelator selection. Chelator selection was also used to isolate deletions constructed in vitro. The deleted phage are readily characterized by restriction mapping, and the gene in question scored after infection of a mutant host strain. These techniques have enabled us to physically assign the cyclopropane fatty acid synthase gene of Escherichia coli to 0.8 kb of a 16-kb segment after characterizing only a small number of isolates. This approach should be generally useful in the mapping of plasmids for which no convenient method exists for selecting or scoring the gene in question.     

Molecular cloning of bovine leukemia virus DNA integrated into the bovine tumor cell genome

The bovine leukemia virus (BLV) DNA harbored in the bovine tumor cell genome was cloned in lambda Charon 4A phage. Using either representative or 3' half-enriched BLV cDNA as a blot hybridization probe, clone lambda BLV-1 was shown to carry 9 kb of the BLV genome, flanked by cellular sequences at both ends. Restriction mapping with twelve endonucleases and hybridization of the DNA fragments to BLV cDNA representing a 3'-end portion of the viral genome revealed the presence and precise location of two long terminal repeats (LTRs) and virus-cell junctions. Thus, lambda BLV-1 appears to contain the complete BLV genome and flanking tumor cellular sequences. The restriction map of the cloned BLV proviral DNA closely resembles that previously reported for unintegrated linear proviral DNA, but differs significantly from that of the integrated provirus of another BLV isolate, the difference occurring preferentially in the putative gag and pol genes.     

Linkage group IV of fish of the genus Xiphophorus (Poeciliidae): Assignment of loci coding for pyruvate kinase-1, glucosephosphate isomerase-1, and isocitrate dehydrogenase-1

Electrophoretic variation ascribable to three enzyme loci, coding for a pyruvate kinase (PK1), a glucose phosphate isomerase (GPI1), and an isocitrate dehydrogenase (IDH1), was observed in three species of fish of the genus Xiphophorus. Electrophoretic patterns in F₁ hybrid heterozygotes confirmed the dimeric structures of GPI and IDH, and indicated a multimeric structure for pyruvate kinase. Variant alleles at the three loci exhibited normal Mendelian segregation in backcross hybrids. Linkage analyses indicate a gene order and estimated recombination of PK1—10%—GPI1—41%—IDH1. No significant interference or sex- or population-specific recombination difference was detected. This group (designated linkage group IV) was shown to assort independently from the nine loci comprising linkage groups I, II, and III and from 23 other informative markers, within the limits of the data. No conclusions with respect to homology of linkage relationships could be reached, due to the presence of presumably duplicated loci in these fish coding for isozymes whose homology with enzymes in other vertebrate species is as yet unestablished.This work was supported in part by Public Health Service Research Grant CA-28909.     

Mapping of the seed storage protein locus Sec-2 in rye

The segregation of the 75K gamma secalin locus (Sec-2) in combination with five interchanges (reciprocal translocations) and two marker genes was analyzed. The translocations involved chromosome arms 1RL, 1RS, 2RL, 2RS, 4RL, 5RL, 5RS, 6RL and 6RS. The gene loci were both on 2R, but the arm was not known. Although the Sec-2 locus was expected to be on chromosome 2RS, no linkage between Sec-2 and any of the markers was found. This is concluded to be the result of exceptionally frequent recombination between Sec-2 and the break point of one of the translocations, which is the only marker in 2RS.