The floodplain grasslands of the Middle Lena-river II. Classification

The grassland vegetation of the Middle Lena valley is described. The syntaxonomy of floodplain grassland vegetation includes 19 associations of five classes (Cleistogenetea squarrosae, Hordeetea brevisubulati Calamagrostietea langsdorffü, Phragmiti-Magnocaricetea, Thero-Salicornietea). An example of a typical Lena-river floodplain ridge-hollow vegetation complex is shown. Most of the syntaxa reflect the peculiarity of the East-Siberian vegetation and are absent from Europe. The geographical distribution of these syntaxa is described. The relation of the vegetation of different parts of the floodplain to the vegetation of the alases of Central Yakutia is discussed.     

Fuzzy set ordination and classification of Serengeti short grasslands,Tanzania

Abstract. Species abundance data from 32 representative stands are used to evaluate the vegetation in the heavily grazed Serengeti short grasslands. The abundant species are: Kyllinga nervosa, Sporobolus ioclados, S. kentro-phyllus and Eustachys paspaloides, all occurring in elevated areas, and Hypoestes forskalei, which is found in the drainage areas. Numerical classification and fuzzy set ordination revealed four main grassland communities associated with a topographic gradient. The communities are considered distinct since their niches, as computed in the community and environmental fuzzy system space are not overlapping. Leaching, erosion and animal disturbance effects correlated with the topographic gradient are found to determine species composition and overall community structure in the grasslands.     

Vegetation-environment relations of a Middle Zambezi floodplain

Detrended correspondence analysis was used to study the relationships between environmental factors and the species composition of vegetation on Zambezi River alluvium downstream of the Kariba hydroelectric dam. Grass, sedge and woody species were recorded in 73 stands in Mana Pools National Park, Zimbabwe. Grass and sedge species composition was related to the soil moisture regime, as indexed by soil texture and flooding frequency. The first woody plant ordination axis was related to a stand development gradient; Acacia albida was a pioneer species on lowlying sandbanks and the woody species richness of stands increased with their height above the Zambezi River. Two-way indicator species analysis identified 7 vegetation types which could be separated on the basis of their topsoil texture and flooding frequency. The types were: sandbanks; young A. albida woodland; A. albida woodland; A. albida dominated mixed woodland; mixed riverine woodland with understory; mixed riverine woodland; and grassland on clay soils.     

The risks of parenthood. I. General theory and applications

Summary We use contemporary life history theory to analyze parental decisions concerned with the defense of offspring, and with the provisioning of offspring in the presence of risk. In achieving the optimal level of parental investment, the parent faces a tradeoff between present and future reproductive success. Our models, which are based on stochastic dynamic programming, lead to predictions of the following kind: (i) offspring will be defended more vigorously as they grow older; (ii) long-lived species will accept fewer risks in caring for offspring than short-lived species; (iii) parents living in permanently riskier environments will defend their offspring more vigorously than parents in less risky environments; (iv) however, temporary increases in risk will result in temporarily less vigorous defense and provisioning of offspring. The models also show that parents and their offspring have different conceptions of the optimal level of parental investment. The flexibility of our modeling approach as a method of analyzing facultative behavior is also emphasized. Finally, we apply the methods of this paper to analyze fledging behavior of Atlantic puffins.     

On the variation explained by ordination and constrained ordination axes

Abstract. Total inertia (TI), the sum of eigenvalues for all ordination axes, is often used as a measure of total variation in a data set. By use of simulated data sets, I demonstrate that lack-of-fit of data to the response model implicit in any eigenvector ordination method results in polynomial distortion ordination axes, with eigenvalues that normally contribute 30–70% to TI (depending on data set properties). The amount of compositional variation extracted on ecologically interpretable ordination axes (structure axes) is thus underestimated by the eigenvalue-to-total-inertia ratio. I recommend that the current use of total inertia as a measure of compositional variation is discontinued. Eigenvalues of structure axes can, however, be used with some caution to indicate their relative importance. I also demonstrate that when the total inertia is partitioned on different sets of explanatory variables and unexplained variation by use of (partial) constrained ordination, (35) 50–85% of the variation ‘unexplained’ by the supplied explanatory variables represents lack-of-fit of data to model. Thus, the common interpretation of ‘unexplained variation’ as random variation (‘noise’) or coenoclinal variation caused by unmeasured explanatory variables, is generally inappropriate. I recommend a change of focus from the variation-explained-to-total inertia ratio and ‘unexplained’ variation to relative amounts of variation explained by different sets of explanatory variables.     

The development of numerical classification and ordination

Summary The paper reviews the constraints and influences which have affected the development of numerical classification and ordination of vegetation.Initial development of ordination techniques and their reception by ecologists was hindered by the mistaken idea that ordination involved acceptance of variation in vegetation as a continuum, as well as by a general suspicion of mathematical approaches.Three distinct approaches to ordination, largely unrecognised at the time, are apparent in earlier work: direct gradient analysis, reduction in dimensionality and path-seeking (catenation) (Dale 1975).Modifications of simple initial techniques made them more efficient at the cost of increased computation. Acceptance of heavier computation as computers increased in capacity and speed turned attention to prineipal component analysis and the superficially similar factor analysis. These have been widely misunderstood largely because they were initially applied in the same way as in the analysis of psychological data, in which different constraints and objectives apply. The initial failure to recognise that principal component analysis involves a preliminary data transformation, the form of which depends on answers to biological, not mathematical, questions, was particularly unfortunate.Principal component analysis has limitations as a technique of ordination resulting from its assumptions of linearity and additivity of plant responses. Attempts to devise more effective techniques raise questions about the practical importance of non-linearity if the objective is data-exploration rather than elucidating the nature of species-response curves and about the adequacy of using simulated data as test data when we do not know how to simulate realistic data.Data-exploration has been more prominent in practical uses of ordination but many methodological developments have concentrated rather on species-response curves.Numerical classification also met obstacles to its acceptance additional to a general aversion to numerical techniques. The first numerical techniques were presented in the context of the relationships of a particular set of data, rather than of a generally valid system, which was the more familiar concept in non-numerical classification.Both numerical and non-numerical classification aim to produce as homogeneous groups as possible. The distinctive contribution of numerical methods is to allow the data to indicate the most efficient criteria of classification; this was an unfamiliar idea.The strategy of classification may be either divisive or agglomerative and either monothetic or polythetic. Choice of strategy in earlier work was not only constrained by computational limitation but may also have been influenced by an author's previous experience of non-numerical classification. As with ordination, the distinction between preliminary data transformation and subsequent analysis was at first not appreciated.Numerical classification has been influenced by parallel numerical developments in formal taxonomy. Because objectives and assumptions are not always the same, this influence has not been altogether helpful.The limitations of real data suggest that developments of technique are at risk of becoming too concerned with refinements of methodology. Increasingly complex methods and increasing availability of programmes for such methods carry the risk that they may be used without adequate understanding of what they do.     

Denitrification potential of a river floodplain during flooding with nitrate-rich water: grasslands versus reedbeds

Denitrification is a major mechanism for nitrogen removal from nitrogen-rich waters, but it requires oxygen-poor conditions. We assessed denitrification rates in nitrate-rich but also oxygen-rich river water during its stay in a floodplain. We measured diurnal oxygen fluctuations in floodwater along the river Rhine, and carried out an experiment to assess denitrification rates during day, evening and night. Denitrification in floodwater and flooded sediment were measured, comparing activity of periphyton and sediment from agricultural grasslands and reedbeds. Floodwater along the river Rhine was oxygen-saturated (> 10 mg O₂/L) during the day, but oxygen largely disappeared during the night (0.4–0.8 mg O₂/L). Independent of oxygen concentrations, denitrification in surface water alone hardly occurred. In flooded sediments, however, denitrification rates were much higher (1.1–1.5 mg N m^–2 h^–1), particularly at dark and oxygen-poor conditions (nighttime). In the experimental jars, reedbed-periphyton bacteria achieved similar denitrification rates as bacteria in sediment, but overall periphyton denitrification was of minor importance when calculated per square meter. Apart from oxygen levels, maximum denitrification appeared to be regulated by nitrate diffusion from water into the sediment, as the maximum quantity of N denitrified in the sediment equalled the quantity of N lossed from the surface water. Assessed 24-hr denitrification rates in the flooded floodplains (c. 15 mg N m^–2 d^–1) were similar in grasslands and reedbeds, and were rather low compared to rates in other floodplains.     

Vegetation development after a large scale restoration of species-rich grasslands in a Central European floodplain

Large scale restoration using local high-diversity seed mixture combined with turf transfer was applied on ex-arable land in the Morava River floodplain in the western Slovakia in the years 1999–2012. The post-restoration vegetation development was recorded during 12 years after the restoration using floristic records per restored polygons with cover estimation in simple 3-degree scale. Temporal changes in species composition were evaluated by gradient analysis and number of characteristic grassland and ruderal species on restored sites was analysed by general linear models. Species composition changed gradually towards the species composition typical for species-rich floodplain grasslands, but the trajectory was not straightforward and several irregularities were observed. They were probably induced by extreme weather events (drought, floods). The decrease in ruderal species and increase in the number of typical floodplain grassland species were observed, when floodplain grassland species permanently outcompeted ruderal species since 8th year after the restoration. However the development in large scale was slower, than expected from previous small-scale experiments, it is evident, that combination of local seed mixture sowing with a turf transfer is a feasible method for the restoration of species-rich floodplain grasslands from arable land.     

The fermentation of L-sorbose by Gluconobacter melanogenus. I. General characteristics of the fermentation

Growing cultures, washed cells, and cell-free preparations of Gluconobacter melanogecnus IFO 3293 converted L -sorbose to 2-keto-L -gulonic acid, to D -sorbitol (which was metabolized further) and to 5-keto-D -fructose.     

Vegetation patterns of floodplain meadows along the climatic gradient at the Middle Elbe River

Central European floodplain meadows are characterised by flooding mainly in winter/spring and dry conditions over the summer. They harbour many rare and endangered plant species. We studied the vegetation of floodplain meadows along the regional climatic gradient of the Middle Elbe River. This gradient exhibits rather continental conditions in the south-east and oceanic conditions in the north-west. We aimed at detecting the influence of climate on the vegetation of floodplain meadows along this gradient.