Search

An index measuring interaction importance ( Iimp) was proposed in a paper published on 2010 by the Journal of Ecology. This index, now widely used by researchers, has been claimed to symmetrically range in the interval (−1, 1), with negative values for competition and positive values for facilitation., Here, the index properties are carefully analysed, and it is demonstrated that Iimp can never exceed the value of 0.5 in facilitation., Several years have passed since its publication, yet nobody has corrected the inexact index range, and several researchers continue to inaccurately refer to it. Overlooking this lack of symmetry could potentially lead to biased conclusions., Synthesis. Iimp cannot be treated as a symmetric index for negative and positive interactions. This is only the last of several concerns discussed in literature: current approaches to measuring interaction importance still need to be debated and analysed in depth. [ABSTRACT FROM AUTHOR]

The article studies the ecology of shingle beach plants. The author mentions some of the relevant papers on shingle beaches as a plant habitat, or on their vegetation. Each of the two principal factors, beach composition and shingle mobility, is continuously variable in itself as well as interacting with other factors such as local topography, climate and water supply, and the whole is influenced by time and by past history, according to the author. The author says that the material of shingle beaches consists of two components, the shingle or coarse fraction and the matrix or fine fraction.

This account presents information on all aspects of the biology of Viscum album L. (Mistletoe) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of Britain and Ireland: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation.Viscum album is a widespread obligate hemiparasite on a wide range of angiosperm and gymnosperm trees. Once thought to take just water and nutrients from its host via a haustorium, it is now suggested to also take carbon. Heavy infestations can reduce host vitality through prolific water use and carbon removal.Flowers are highly reduced but are primarily pollinated by flies, ants and bees. Seeds are dispersed by birds. Removal of the epicarp is necessary for successful seedling establishment, and seeds have a sticky viscin coat, adhering it to the host bark. Vegetative spread also happens under the bark of its host resulting in densities of >700 Mistletoe plants per host.Viscum album is a lowland species, most frequent in open human‐made habitats extending into woodlands in Europe. It has been widely planted for folklore use centred around Christmas. Despite conservation concerns following removal of Mistletoe‐laden old orchards, the species is thriving and needs control in some areas. Viscotoxins and lectins in leaves and shoots have been widely used in herbal medicine and now potentially in complementary cancer therapy. [ABSTRACT FROM AUTHOR]

The article reports on the acquisition of the journal "The Plant World" by the Ecological Society of America in the U.S. It says that the acquired journal bears the title "Ecology". The acquisition made the journal as the organ of the Society and will publish papers both on plant and animal ecology. Furthermore, the Plant World journal has always published several ecological papers, and its successor, the Ecology journal may now be expected to become one of the main outlets for American ecological work.

Global change threatens plant diversity and disrupts its interrelationship with ecosystem structure and function. This disruption in turn undermines confidence in the knowledge ecologists produce, and whether it will translate into multidisciplinary research settings or guide the effective management of natural lands.To address this challenge, ecology needs to consider the interactions between different levels of biological hierarchy, especially how they feedback on, and are mediated by, plant diversity. Doing so will require conducting empirical work and developing theory that simultaneously considers multiple disciplinary perspectives and units of study.Here we advocate the use of common gardens to integrate ecology, evolutionary biology and ecosystem science through an explicit focus on simultaneous measurement of response variables at multiple levels of biological organization. This approach will provide opportunities to evaluate assumptions important to prediction, such as space‐for‐time substitution, and tackle the integration of physicochemical and eco‐evolutionary foundations to understanding plants and ecosystems.Synthesis. We summarize the large body of research on Sonoran Desert winter annuals to demonstrate how experimental designs that employ common gardens to integrate processes across scales hold special promise. This includes refining trait‐based theories of plant strategies, providing insight into ecosystem responses to global change and collaborating effectively with other scientific disciplines. [ABSTRACT FROM AUTHOR]

The article offers information about several conventions of the British Ecological Society in Great Britain. The symposium titled "The Water Relations of Plants," organized by the Society on April 5-8, 1961, was attended by 112 members and overseas visitors. The meeting of the Tropical Ecology Group of the Society on April 6, 1961 in the Department of Botany was attended by 55 members which was arranged by P. W. Richards. The 1961 Summer Meeting was centered on the Departments of Botany and Zoology which was participated by 35 members who joined in the excursions by several local members. Various topics are also mentioned on each of the events.

The article reports that the hump-back relationship between diversity and productivity is one of the well-known patterns in ecology that have defied unequivocal explanation. Their model also casts new light on data where relationship between richness and productivity is monotonic. Finally, it should be noted that symmetry of competition is an inherent property of the resource contested and is not easily changed by natural selection.

The article discusses a study which investigated the species of Sargassum found along the coasts of the Danish West Indies with remarks upon the floating forms of the Sargasso Sea. The Sargassum species include Sargassum vulgare, found on both exposed and sheltered places. The second part of the study deals with the floating Sargassum found in the Sargasso Sea, which are referred to as Sargassum natans and a coarser form which the author called Sargassum hystrix. The biology, affinities and origin of the floating pelagic gulfweed forms are also discussed.

This account presents information on all aspects of the biology of Silene suecica (Lodd.) Greuter & Burdet ( Lychnis alpina L.) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation., Silene suecica is native to the British flora, being found in just two confirmed localities (one in north-west England and the other in Scotland) on open fell-field and rocky outcrop habitats. It occurs on acid to neutral soil in Britain and elsewhere its circum-arctic range. It often indicates elevated concentrations of copper or other heavy metals, whose presence in the soil restricts the growth of other species; therefore, S. suecica is perceived as a stress-tolerant, competition-avoiding species. Nonetheless, it also grows in more or less closed alpine grassland in Europe; in North America and Greenland, it is known from tundra, rocky barrens, gulleys and river outwashes, grassy slopes and sea cliffs., Silene suecica is a (semi-)rosette plant with a strong taproot, with no capacity for vegetative spread. The main perennating organ is the slightly lignified rootstock/taproot. The rosette has winter-green leaves; after flowering the rosette leaves die, but new lateral rosettes may be produced in the following year. The longevity of the species is between 3 and 10 years, with the time of first flowering depending on rosette size. Plants that have flowered may die (semelparous individuals), but some are iteroparous and flower again on lateral shoots., Silene suecica produces protandrous hermaphrodite flowers, but self-pollination may occur. In Scotland about 10% of all plants flower in any year. Pollination is by a range of insects, including flies and bees. Capsules produce up to 80 seeds (mean = 30)., Silene suecica has probably not declined in the British Isles and, in fact, a slight population expansion in permanent plots was observed in Scotland in the early 1990s. Nonetheless, it remains classed as vulnerable to extinction because of its restricted distribution. Both of its British locations are protected as SSSI and SAC ( Natura 2000) within national parks. It is common in many countries within its distribution range. [ABSTRACT FROM AUTHOR]

1. This account presents information on all aspects of the biology of Primula veris that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and diseases, history and conservation. 2. Primula veris is a distylous, perennial rosette hemicryptophyte, mostly found in well-drained, herb-rich meadows and grasslands, in scrub or woodland rides and edges, and on calcareous cliffs. It occurs on base-rich loams or clays, on limestone, and sometimes in dunes. 3. Native to the British Isles, it is characteristic of many mesotrophic and calcicolous lowland grassland communities, but it also extends into upland valleys in northern England and Scotland. In Ireland it is also native and most abundant in the central plain. Primula veris occurs throughout the temperate areas of Europe as far east as the Russian border. 4. Primula veris is a shade-intolerant species that shows reduced performance and flowering under shade or increased competition. The species is not able to penetrate anoxic soil layers and is therefore mostly absent from locations that are characterized by a high water table. It has a well-developed drought tolerance. 5. Primula veris is an obligate outbreeder which entirely depends on foraging insects for successful pollination. Although the species shows heterostyly, with two reciprocal morphs (pin and thrum), only relatively low levels of intermorph pollination have been reported. Seed dispersal is restricted to a few centimetres from maternal plants, whereas pollen flow is wider, but still limited to a few metres from parental plants. Both are factors that contribute to a significantly fine-scale spatial genetic structure and small neighbourhood size. 6. At several locations throughout the British Isles, P. veris occurs together with P. elatior and especially P. vulgaris. The hybrid P. veris ×  P. vulgaris =  P. ×  polyantha occurs frequently in mixed populations, whereas the hybrid P. veris ×  P. elatior =  P. ×  media has been rarely reported in Britain. 7. Although P. veris is still a widespread grassland herb, it is less abundant in the British Isles and continental Europe than before. This decline can be attributed to changes in land-use practices, such as the loss of traditional hay–meadow management, the loss of grazing and an increase of ploughing, in combination with ongoing destruction and nutrient enrichment of permanent grasslands. However, from 1980 onwards the species has increased substantially in many areas of the UK, largely because its seeds are included in wildflower seed-mixtures that are sown on new or upgraded road and motorway verges, embankments and urban conservation areas. [ABSTRACT FROM AUTHOR]

1. Invading species typically need to overcome multiple limiting factors simultaneously in order to become established, and understanding how such factors interact to regulate the invasion process remains a major challenge in ecology. 2. We used the invasion of marine algal communities by the seaweed Sargassum muticum as a study system to experimentally investigate the independent and interactive effects of disturbance and propagule pressure in the short term. Based on our experimental results, we parameterized an integrodifference equation model, which we used to examine how disturbances created by different benthic herbivores influence the longer term invasion success of S. muticum. 3. Our experimental results demonstrate that in this system neither disturbance nor propagule input alone was sufficient to maximize invasion success. Rather, the interaction between these processes was critical for understanding how the S. muticum invasion is regulated in the short term. 4. The model showed that both the size and spatial arrangement of herbivore disturbances had a major impact on how disturbance facilitated the invasion, by jointly determining how much space-limitation was alleviated and how readily disturbed areas could be reached by dispersing propagules. 5. Synthesis. Both the short-term experiment and the long-term model show that S. muticum invasion success is co-regulated by disturbance and propagule pressure. Our results underscore the importance of considering interactive effects when making predictions about invasion success. [ABSTRACT FROM AUTHOR]

1. The Mediterranean region has been invaded by a wide range of introduced plant species which differ greatly in their ecology, morphology and human utilization. In order to identify a suite of traits which characterize invasiveness, recent studies have advocated the use of evolutionary relationships to unravel highly confounded influences. 2. This study attempts to identify an evolutionary component to invasiveness and other complex invasion-related traits in the Mediterranean alien flora using an autocorrelation technique, the ‘phylogenetic association test’. I compared a traditional hierarchical taxonomy with the recent phylogeny of the Angiosperm Phylogeny Group. 3. Invasiveness did not have a significant phylogenetic component. Any weak clustering was generally at the genus level. 4. Several associated ‘meta-traits’ (high introduction frequency, adaptation to several habitat types and favourability for different modes of introduction), exhibited stronger phylogenetic components. Although each of these conveys some of the attributes of invasiveness, their clustering patterns differed considerably, suggesting that they arise from independent evolutionary pressures. Furthermore, within each meta-trait, different clusters may have been selected for different reasons. 5. Other reasons for the lack of a detectable evolutionary component to invasiveness are discussed. Firstly, the results of our test simulations suggested that incorrect phylogeny could result in a moderate degree of error. Secondly, over evolutionary time, complex or stochastic events such as ecosystem change could radically alter the adaptive advantages of particular traits. 6. Synthesis. Since invasiveness has little phylogenetic component, I argue that it is less likely to be predictable from as yet unidentified traits in any simple way. Although trait syndromes could develop without leaving a phylogenetic pattern, its absence probably indicates that the dominant selective forces are responses to short-term ecological shifts, and a greater mechanistic understanding of these is needed. [ABSTRACT FROM AUTHOR]

1. Tropical plants express multiple defensive traits that enable them to resist, deter or escape herbivores. In this study, we approached plant defensive adaptations by focusing on variation and interaction between sets of plant defensive strategies from a community perspective. 2. We compared two sites: the aseasonal Amazonian forest of Yasuni, Ecuador, and the seasonal forest of Barro Colorado National Monument (BCNM), Panama. We suggest that differences in ant abundance between these sites influence the divergence, local assembly and interaction of chemical and indirect ant-mediated defences in 18 tree species of the genus Inga (Fabaceae: Mimosoideae). 3. Relative ant abundance and visitation to extra floral nectaries were significantly higher at Yasuni than at BCNM. Correspondingly, Yasuni Ingas had low leaf extract bioactivity compared with BCNM Ingas, suggesting that Yasuni Ingas rely more on indirect ant defences, while BCNM Ingas rely more on chemical defences. 4. Yasuni Ingas varied widely in their ant visitation and extract bioactivity, and the strategies were negatively correlated in a trade-off like pattern. In comparison, BCNM Ingas had a positive correlation and little variation in their ant visitation, suggesting that their defence ecology was driven by environmental characteristics other than ants. 5. An experiment planting the same Inga species at both sites supported the prediction of higher herbivore pressure at Yasuni than at BCNM. However, leaf damage to naturally occurring Ingas was similar between sites, suggesting that the adaptations at the two sites were equally effective. Damage levels were also similar among species with contrasting defensive strategies, suggesting that ant and chemical strategies were also equally effective at a single site. 6. Synthesis. While tropical forests are thought to be a cradle of specialized interactions that promote diversification and allow the coexistence of a large number of species, the observed divergence in the defence ecology of Inga between these two sites suggests that general community characteristics can also promote diversity by favouring local and geographical diversity in defensive solutions. [ABSTRACT FROM AUTHOR]

1 Small and isolated populations of species are susceptible to loss of genetic diversity, owing to random genetic drift and inbreeding. This loss of diversity may reduce the evolutionary potential to adapt to changing environments, and may cause immediate loss of fitness (cf. inbreeding depression). Together with other population size-dependent stochastic processes, this may lead to increased probabilities of population extinction. 2 This set of processes and theories forms the core of conservation genetics and has developed into the conservation genetics paradigm. Many empirical studies have concentrated on the relationship between population size and genetic diversity, and in many cases evidence was found that small populations of plants do indeed have lower levels of genetic diversity and increased homozygosity. Although less empirical attention has been given to the relationship between low genetic diversity, fitness and, in particular, evolutionary potential, the paradigm is now widely accepted. 3 Here we present five areas of the paradigm which could be refined, i.e. the ‘rough’ edges of the conservation genetics paradigm. 4 Treating population size and isolation not as interchangeable parameters but as separate parameters affecting population genetics in different ways could allow more accurate predictions of the effects of landscape fragmentation on the genetic diversity and viability of populations. 5 There is evidence that inbreeding depression may be a genotype-specific phenomenon, rather than a population parameter. This sheds new light on the link between population inbreeding depression and the expected increased probability of extinction. 6 Modern eco-genomics offers the opportunity to study the population genetics of functional genes, to the extent that the role of selection can be distinguished from the effects of drift, and allowing improved insights into the effects of loss of genetic diversity on evolutionary potential. 7 Incorporating multispecies considerations may result in the generally accepted notion that small populations are at peril being called into question. For instance, small populations may be less capable of sustaining parasites or herbivores. 8 Comparative studies of endangered, common and invasive species may be a valuable approach to developing conservation biology from a phenomenological case study discipline into one investigating the general principles of what sustains biodiversity. 9 The issues discussed set an agenda for further research within conservation genetics and may lead to a further refinement of our understanding and prediction of the genetic effects of habitat fragmentation. They also underline the need to integrate ecological and genetic approaches to the conservation of biodiversity, rather than regarding them as opposites. [ABSTRACT FROM AUTHOR]

1 This review brings into focus what is known about the response of the herbaceous layer of forest ecosystems to increasing nitrogen deposition. The emphasis on forests in general is important for two reasons. First, forests often occupy areas receiving high rates of atmospheric deposition of N. Second, compared with herb-dominated communities, about which much is known regarding response to excess N, forests generally display greater biological and structural complexity. The more specific focus on the herbaceous layer – here defined as all vascular (herbaceous and woody) plants ≤ 1 m in height – is warranted because most of the species diversity of forests occurs in the herb layer. 2 Most responses of forest ecosystems to N saturation, defined here as ecosystem supply of N exceeding ecosystem demand for N, can be characterized by two complementary hypotheses, each emphasizing different facets of ecosystem structure and function. One focuses on ecosystem processes, such as net primary productivity, whereas the other addresses seasonal patterns of concentrations of in stream water. Although neither hypothesis considers the effects of chronically elevated N deposition on forest herbs, both share a prediction – a dramatic increase in availability of – that is relevant to forest herb response. Such a shift towards dominance has important implications for changes in herbaceous layer dynamics. For example, increases in soil pools can increase invasibility by exotic species. Also, because preferential use of vs. can be highly species-specific among forest herbs, predominance of availability can bring about further changes in herb layer species composition. Also important to forest herbs is the tendency for enhanced mobility of to increase mobility and decrease availability of essential cations, such as Ca2+. 3 The response of plant species of the herbaceous layer of forest ecosystems to excess N availability can arise from N-mediated changes in several processes. Here I identify six – competition, herbivory, mycorrhizal infection, disease, species invasions and exotic earthworm activity – and discuss how they respond to excess N and how this response affects the herb layer of forests. With the exception of the activity of exotic earthworms (which is correlated with, but not necessarily caused by, high N deposition), there is compelling evidence that all processes respond sensitively to N deposition and that this response generally leads to drastic shifts in species composition and decreases in biodiversity of forest herb communities. 4 A hypothesis is suggested – the nitrogen homogeneity hypothesis – that predicts loss of biodiversity in forest ecosystems experiencing chronically elevated N deposition. This hypothesis is based on the decrease in spatial heterogeneity of N availability that is typically high in forest soils under N-limited conditions. [ABSTRACT FROM AUTHOR]

1 The effects of hybridization on the abundance of parental taxa depends on their relative frequency, the viability of hybrid offspring and the degree of ecological differentiation among parental and hybrid taxa. Habitat overlap can facilitate competition for suitable sites and threaten the persistence of parental taxa, especially those in small populations. 2 Here we examine ecological differentiation between the endangered North American red mulberry ( Morus rubra), introduced white mulberry ( M. alba) and red × white hybrids in a reciprocal transplant experiment. Fitness of red, white and hybrid mulberry was estimated as survival and above-ground biomass of seedling and juvenile life stages, transplanted into open (white habitat) and shaded (red habitat) forest environments. In addition, all taxa, including reciprocal hybrids (R × W, W × R), were compared in a common garden in full sun. 3 In the reciprocal transplant study, red mulberry was consistently less fit than white and hybrid mulberry regardless of transplant habitat; F1 hybrids were as fit as white mulberry. In the common garden, red mulberry and hybrids with red mothers had lower fitness than white mulberry and hybrids with white mothers. Reciprocal hybrid crosses differed significantly with respect to survival and cumulative fitness, but not biomass. 4 Red mulberry is not ecologically differentiated from white or hybrid mulberry in the three transplant environments examined; rather, it is consistently the least fit taxon. Therefore, all else being equal, hybridization with white mulberry and the subsequent presence of hybrids will place red mulberry at a strong disadvantage during establishment. 5 The results highlight the potential effect of hybridization by introduced species on the abundance of native species, particularly at the northern extremes of its geographical range, where populations are small and native environments may be degraded or at the limits of ecological tolerance. [ABSTRACT FROM AUTHOR]

1 Global change and emerging concepts in ecology and evolution are leading to a growing interest in phenotypic plasticity (PP), the environmentally contingent trait expression observed in a given genotype. The need to quantify PP in a simple manner in comparative ecological studies has resulted in the prevalence of various indices instead of the classic approaches, i.e. a comparison of slopes in the norms of reactions (trait vs. environment plots). 2 The objectives of this study were: (i) to review the most common methods for quantitative estimation of PP; (ii) to apply them to a specific case study of growth and shoot–root allocation responses to irradiance in seedlings of four woody species grown at 1%, 6%, 20% and 100% full sunlight; and (iii) to propose new methods of estimating PP. 3 The 17 different plasticity indices analysed rendered disparate results, with cross-overs in species PP rankings. Statistical comparisons of PP among species were not possible with most of the indices due to the lack of confidence intervals. The non-linear responses of the traits made the use of the slope of the reaction norm to quantify PP unrealistic, and raised awareness on values derived from studies that consider just two environments. 4 We propose an alternative approach to quantify PP based on phenotypic distances among individuals of a given species exposed to different environments, which is summarized in a relative distance plasticity index (RDPI) that allows for statistical comparisons of PP between species (or populations within species). RDPI was significantly correlated with 12 out of the 17 PP indices analysed. An index including the environmental range leading to the different phenotypes (environmentally standardized plasticity index, ESPI), and thus expressing plasticity per unit of environmental change, is also proposed. 5 The new indexes can statistically segregate and unambiguously rank species according to their PP, which can foster a better understanding of plant ecology and evolution, particularly when common protocols are used by different investigators. [ABSTRACT FROM AUTHOR]

1 Host–pathogen interactions in isolated populations may result in the adaptation of pathogens to local hosts. However, results of earlier studies of local adaptation in plant–pathogen systems have been contradictory and it has been suggested that specific, species characteristics, for example distribution, dispersal and the degree of pathogen dependence on the host, are important for the outcome of host–pathogen interactions. In addition, the scale of the study may influence whether or not local adaptation is found. 2 We argue that local adaptation of the pathogen to the host can be expected in a system where: (i) the pathogen is host-specific with a short generation time compared with the host; (ii) populations are isolated, allowing localized evolution to occur; and (iii) the study is performed on a geographical scale exceeding the maximum dispersal range of the interacting species. 3 To test these predictions we examined the within- and among-population variation in resistance and virulence of the plant–pathogen system Salix triandra– Melampsora amygdalinae. The pathogen occurs throughout the whole distribution range of the host, and the area of interest consists of highly isolated, small natural populations. 4 Resistance and virulence differed both within and between populations and all clones showed a unique resistance pattern. We conclude that M. amygdalinae is locally adapted to the host S. triandra as all pathogen populations have a higher probability of infecting sympatric than allopatric hosts. Furthermore, high resistance in the host population was accompanied by a high virulence in the pathogen population, suggesting that high resistance levels in a host population may select for more virulent pathogen populations, or vice versa. 5 The nature of host–pathogen interactions differs among systems, and the dynamics of the interaction between S. triandra and M. amygdalinae is governed by characteristics that have resulted in the evolution of local adaptation. 6 Thus, when studying local adaptation of pathogens to their hosts it is important to consider the biology, as well as the scale of dispersal and spatial distribution of both host and pathogen. [ABSTRACT FROM AUTHOR]

1 This account reviews information on all aspects of the biology of Rubus vestitus that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, hervbivores and disease, history, and conservation. 2 Rubus vestitus is a widespread member of the series Vestiti, one of 11 rather ill-defined series of largely apomictic microspecies in the section Glandulosus of Rubus subg. Rubus. Each of the series represents a main node in the spectrum of variation within this section. Its species (usually with those from sections Rubus and Corylifolii) are commonly included in the Rubus fruticosus L. aggregate (brambles or blackberries). More than 320 microspecies have been recognized in this aggregate in Britain. 3 Rubus vestitus is typical of shady woodlands, wood margins, scrub and hedgebanks. Often abundant on calcareous or clay soils, it is rarer on acid soils of heaths and moors. 4 Rubus vestitus is placed in its ecological context, relative to the other widespread and important bramble species in Britain. Where possible, information specific to R. vestitus is provided but much of the relevant literature does not distinguish it within the broader R. fruticosus agg. As this is the first account of a bramble in the Biological Flora of the British Isles, an inclusive approach incorporates data for the species aggregate where appropriate (e.g. in lists of pollinators and phytophagous insects). [ABSTRACT FROM AUTHOR]

1 We measured and modelled the dispersal of a wind-dispersed herb, the leafless hawk's beard (Crepis praemorsa, Asteraceae), using a combination of measurement techniques, selected empirical models and mechanistic models originally developed for trees.2 Dispersal was measured by releasing individual seeds and by placing seed traps around an experimentally created point source of seeding plants. Dispersal distances varied considerably between the experiments. In the seed releases, dispersal distances were positively related to horizontal wind speed (linear regression,P < 0.001) and, under favourable conditions, many seeds dispersed over several metres, with a few at> 30 m.3 Four empirical models (the inverse power (IP), the negative exponential (NE), Bullock&Clarke's mixed model (MIX) and Clarket al.'s 2Dt model) were fitted to the data. IP and NE models often failed to accommodate the shape of the empirical distribution of dispersal distances, and the MIX model, although extremely flexible, tended to overfit the data. The 2Dt model was, however, flexible and realistic in each experiment. Nevertheless, the parameter values for all of the empirical models varied dramatically between experiments; no set of parameter values predicted the observed dispersal distances under all conditions.4 Two mechanistic models (Greene&Johnson's analytical model (GJ) and Nathanet al.'s individual-based simulation model (NSN)), originally developed for trees, were parameterized using independent data and parameter values from the literature. Although the NSN model provided a poor fit for the seed trap experiment, it performed almost as well as the best empirical models in the seed release experiments. Its predictions were further improved by including convection, and predicted dispersal> 30 m corresponded closely with our observations. The prediction of low (< 1%) dispersal> 200 m requires further... [ABSTRACT FROM AUTHOR]

Presents several books related to biology. "Dynamic Changes in Terrestrial Ecosystems: Patterns of Change, Techniques for Study and Applications to Management," edited by R. O. Slatyer; "Man and the Boreal Forest," edited by C. O. Tamm; "Plant Population Biology at the Crossroads."

(1) Spectral analysis is a relatively untried method for the analysis of data from a line of contiguous quadrats. Conventional block-size analyses are shown to be related to square waves. In spectral analysis square waves are replaced by sine waves. (2) These methods and Mead's test are compared with conventional methods, using artificial and field data. Spectral analysis performed reliably and gave a good indication of the type of departure from a random pattern. Mead's test proved sensitive but hard to interpret, often contradicting other methods. (3) It is argued that standardization should not be used with methods based on variances. [ABSTRACT FROM AUTHOR]

(1) Principal components analysis of incidence (presence and absence) data produces a horseshoe effect. A new method, called step-across, is described which removes this effect. (2) From a matrix of joint occurrences, distances are found directly for all positive values. Distances for zero joint occurrences are found from the shortest network distance. The complete distance matrix is then analysed by Gower's principal coordinates technique. (3) The method can be used on both the rows and columns of an incidence matrix. It is illustrated with artificial data and with data on euphausiids from the Indian Ocean. [ABSTRACT FROM AUTHOR]

(1) In grasslands in Uganda dominated by Hyparrhenia filipendula and Themeda triandra, biomass of shoots increases to about 0.5–0.7 kg m-2 in the rainy season without grazing, and to about half this value with grazing. Maximum leaf-area index in ungrazed grassland generally does not exceed 3.0, Biomass of roots varies seasonally from 0.5 to 2.0 kg m-2. (2) In this grassland, and in grassland dominated by Sporobolus pyramidalis and Chloris gayana, the quantities of dry matter which can be harvested by successive monthly cuts at 5 or 20 cm above the ground vary from almost nothing in dry seasons to the equivalent of 4 or 2 gm-2 per day dry matter production respectively in rainy seasons, (3) These values are for grassland not grazed by large animals; with grazing the rates are approximately halved, and the differences provide estimates of the rates of natural grazing. (4) The mean values for the rate of grazing throughout the year are of the same order of magnitude as values calculated from estimates of the energy requirements of the biomass of large mammals on the sites, (5) Monthly production of dry matter and protein are significantly correlated with rainfall, giving regression constants of 6.8 g m-2 dry matter and 0.56 g m-2 protein per month per cm of rain. [ABSTRACT FROM AUTHOR]

Focuses on the biological flora of the British Isles. Identification of common Cynoglossum species; Composition and habitat of individual plants; Height of flowering stalk.

Characterizes the biological flora of the British Isles. Geographical and altitudinal distribution of plants in the area; Climatic and topographical limitations.

The article highlights a study of the ecology of Hordeum murinum L. in Great Britain. It notes that a punched card technique is described for the analysis of distribution maps. It mentions that the technique allows analysis of complex patterns, the data are amenable to statistical analysis and use is made of negative information. It reports that the distribution of Hordeum murinum and Reseda luteola is shown to be correlated with climate and with the distribution of urban land. It also discusses some of the problems of analysis of distribution patterns using visual comparison and the punched card technique.

This article presents a study which investigated the relation between mean square and block size in the analysis of similar plant patterns. Models of basic patterns have been prepared and the analysis of these suggests that the starting point for sampling is of importance. If the series starts towards the centre of a clump there is a strong possibility that the indicated peak mean square will be one block size smaller than the actual. A new method of field sampling is suggested which involves taking a slightly larger series of samples, and performing a number of analyses.

The article presents the study on edaphic ecotypes in Euphorbia thymifolia L. The three populations within the red ecotype of Euphorbia thymifolia L. have showed very diverse responses to calcium in the soil, in regard to their growth performance under competitive and non-competitive conditions. Mella soil was also found to be highly calcareous compared to Indian soil. The differences recognized in the growth and the yield of the three populations are maintained when grown on a neutral substratum.

The article outlines the biology of Andropogon (A.) gayanus Kunth, a member of the tribe Andropogoneae and the sub-family Panicoideae within the family Gramineae. It has three varieties, namely A. gayanus, A. squamulatus and A. isquamulatus and they are distributed throughout most of the tropical and subtropical savannas of Africa south of the Sahara. The known locations of the species lie between 400 millimeter (mm) and the 1500 mm annual isohyets. The morphology and anatomy, and phenology of A. gayanus are discussed.

The article offers information on the use of plant-to-neighbor distance for the detection of intraspecific competition. The plants are competing with one another may manifest two ways, including the distance between any plant and its nearest neighbor will be positively correlated with the sum of their sizes, and there may be a lower limit to the distance between any plant and its nearest neighbor. Accordingly, each successful plant may have around it its own territory within which no new colonizers can establish. It is stated that weak competition might produce result unsuccessful competitors would be stunted. Moreover, it also discusses the detection of regularity within dense clumps by the usual methods of examining pattern.

The article investigates the effect of controlled environmental conditions, such as water regime, soil type and associated species, on the distribution of closely related species. Five Rumex species were used in the study including R. crispus, R. obtusifolius, R. sanguineus, R. conglomeratus and R. hydrolapathum. Results showed that water regime and soil type have the same pattern of response for all species except for R. sanguineus. Findings showed that interspecific interference is more powerful in flower suppression than intraspecific interference.

The article offers information on the multivariate methods in plant ecology. Association-analysis in plant communities was conducted using the method developed by D. W. Goodall in 1953. Goodall developed the utility of interspecific associations for sorting quadrants into groups is based on definition of a homogeneous unit of vegetation as one in which all species-associations are indeterminate or non-significant. Details related to the ecological information obtained from two heathland communities are presented, followed by discussion on the conclusion that a method by Goodall is likely to prove a very useful tool in primary survey.

The article offers information on the dune system and vegetation in Braunton Burrows, North Devon. The seaward part of the Burrows is a composed of dunes featuring different land types, including sand-hills, crests to landwards, as well slacks between the high dunes. A variety of plant habitat is found within the dune systems. Botanists has been studying the rich flora found in the dunes. Mobile dunes are prominent feature at the Burrows. It is mentioned that the vegetation and topography is directly connected to the opposing winds and of stabilization by plants of the sand surface.

A biography of Sir Arthur George Tansley, writer of biology books, is presented. He was born in London, Great Britain, on August 15, 1871, and studied at several private schools, the Highgate School, and later on enrolled at the University College, London and the University of Cambridge. Tansley was married to Edith Chick and had written several books including "Practical Plant Ecology" and "The New Psychology and its relation to life."

The article discusses the effect of quadrat size on the estimation of the Neyman type A series and Thomas series parameters. Both the Neyman and Thomas distributions are preferred in theoretical contagious distributions commonly applied to plant and insect populations. Both series are based on two assumptions that assume that plants occur in randomly distributed centers and that the number of seedlings or vegetative shoots per cluster is also random. Several conclusions were drawn from assumptions on plant distribution according to the models based from both the Neyman and Thomas series and on clusters appearing not very small and not visibly distinct. One of the conclusions include the size chosen for the quadrats substantially affects the result.

The article presents a memorandum released by the British Ecological Society related to botanical nomenclature and taxonomy. The Council of the British Ecological Society decided that names used, should be in agreement with the International Rules of Botanical Nomenclature. Details related to the nomenclature of biological flora are also presented. Moreover, a definition of terms is provided by the author, which lists intraspecific units in taxonomy. This is to prevent contributors from using the terms, such as ecotype, variety and species, in a different meaning.

The article presents reviews of the periodical "The Journal of Animal Ecology," November 1942, Vol. 11, No. 2 issue,as well as five articles by M. C. Rayner related to the mycorrhizal relations of Pinus and the book "The Reproductive Capacity of Plants," by E. J. Salisbury. This issue of "The Journal of Animal Ecology" presents population studies related to land mammals. Rayner's studies on the other hand, deal with the associations of mycorrhiza with Pinus, specifically focusing on its species: P. sylvestris, P. laricis, P. pinaster and P. contorta. Lastly, the book by Salisbury tackles on plant biology.

The article discusses the studies made on the biology of the Bristol Channel and Severn Estuary in England. It presents a description of an inquiry made on the physical features and the fauna of the estuary starting above Gloucester to Ilfracombe. It is noted that mud of Severn water is high, which increases in winter, while the mud zone remains constant. The highest turbidity takes place more on saline water during summer than in winter but there is more silt in winter than in summer. Moreover, the floods from fresh-water in winter push the salt water to the sea. The animals from Ilfracombe to Gloucester has also been studied and it dies out rapidly above Avonmouth.

The article presents a discussion about climatic classification based for East African biology. The article provides a brief introduction and knowledge about the relevant characteristics of East Africa. It explores the classifications of climate using Köppen system and derivatives, functions of rainfall, evaporation, and temperature, and months with a defined climatic ratios. The article is also supplemented with details regarding the importance of mist and cloud, meteorology, and precipitation.

The article talks about the concepts and criteria used for the recognition of biotic communities. These concepts describe the fundamental use of the ecological units established by Clements and Shelford, which are used by many American and British authors. The definitions of the concepts, including association abstract, abstract communities and associes abstract, are offered. The subdivisions of the biotic formation (biome), which includes the perennial nucleus, seasonal societies of communities, and intradiel communities, are discussed.

The article describes the relict method in dynamic ecology. It discusses ecological methods for the field and the indicator method and its applications. A relict is defined as a community or fragment of one that has survived some change, often to become an integral part of the existing vegetation. It offers information on the nature of relicts, shrinkage of climaxes and utilisation and interpretation. The two kinds of relict communities re those due to climatic pulsations and those produced by human coactions. It stresses the importance when applying the relict method to the interpretation of a particular climax to realise that the structure of the latter is a mosaic of climatic, seral and coactive effects.

The article focuses on the standardization of descriptions for plant communities. Descriptive ecology should be aimed at discovering the causal relations that determine the character and structure of the communities being studied to be able to advance knowledge. There are several schools of thought in ecology, including floristic, physiognomic, edaphic and successional, each dominated by a specific direction of approach and produced systems of classifications. Several features and characteristics should be regarded as essential to the proper diagnosis and delimitation of vegetation units.

The article examines the faunistic ecology of streams. The structure of a fauna is investigated. Many of the organisms which have been considered as the almost entire source of food of fish, such as Limnaea peregra, Gammarus pulex and Ephemera spp., have been found to contribute either no part or very little part of the total fauna. The presence of peaty water is noticed especially during heavy rains. The foregoing account of the stream-bed indicates a general succession of conditions in passing down a stream.

The article discusses the climatic cycles and treegrowths in the U.S. It highlights the ecologist interest in the correlation of treegrowth rainfall. According to that author, in dry climates, the ring thickness is proportional to the amount of rainfall in the year with an accuracy of seventy percent. It says that the trees were tabulated in groups of 10 or more, but a remarkable correspondence exists between individual trees of each group. It also says that double rings in the arid regions were found to be correlated with deficient winter snowfall, so that the tree had not enough water to continue forming its summer wood, and passed to forming autumn wood before the summer rains enabled it to start a fresh zone of wide elements.

The article addresses the principles of ecology using illustrations of animals. Ecology refers to the branch of general physiology which deals with the organism as a whole, with its general life processes as distinguished from the more special physiology of organs. The reason for the difficulty in ecological work is the lack of knowledge of physiological life histories. Ecology can be divided into individual ecology or the ecology of individuals or particular species, and when several species belonging to one genus are treated it is usually called aggregated ecology.