Plant Distribution (plant + distribution)

Distribution by Scientific Domains


Selected Abstracts


Distribution of aquatic vascular plants in lowland rivers: separating the effects of local environmental conditions, longitudinal connectivity and river basin isolation

FRESHWATER BIOLOGY, Issue 3 2005
BENOÎT O. L. DEMARS
Summary 1. Changes in species distributions along rivers have rarely been observed independently of changes in environmental conditions and meaningful comparison between different catchments is made difficult by the limited geographical distribution of species. This study presents a new approach to quantify the effect of the spatial structure of lowland river networks on aquatic plant distribution and to explore the potential underlying processes using species life-history characteristics. 2. Twenty-five species of aquatic vascular plants recorded in 62 sites across five calcareous river basins were used to investigate (i) the temporal turnover of plant species, (ii) the habitat utilisation of species, (iii) the trade-offs between different plant life-history characteristics and (iv) the relationship between species life-history characteristics and habitat utilisation. 3. The annual plant turnover within a 3-year period was, although significant, extremely low. It suggests that results from spatial surveys conducted over 3 years should not be undermined by temporal changes. 4. Spatial connectivity along and between rivers was more important than in-channel physical characteristics in shaping species assemblages. Neither chemical factors (ammonium, phosphate) nor extrinsic biotic competitors (filamentous green algae) significantly influenced plant distribution. 5. The most common combinations of life-history characteristics were neither related to environmental conditions nor to spatial isolation. Instead, they could reflect natural selection processes associated with larger scales than those considered in this study. 6. Plant distribution was most strongly related to the dispersal and regeneration abilities of the plants, supporting the hypotheses relating to longitudinal connectivity. The hypothesis that different growth forms would be associated with different in-channel physical features was not verified. As expected, there were no substantial differences in plant life-history characteristics between river basins. [source]


Sex in Space: Pollination among Spatially Isolated Plants

BIOTROPICA, Issue 2 2004
Jaboury Ghazoul
ABSTRACT Plant distributions are changing at unprecedented rates, primarily due to habitat clearance and the spread of alien invasive species. Landscape pattern and local density can affect plant sexual processes, particularly those mediated by biotic vectors, by acting on the composition and behavior of pollinators and seed dispersers. Ecologists are now grappling with the likely effects of these altered processes on future forest composition as existing plant reproductive mutualisms break down or adjust to new spatial circumstances. Here, we introduce five papers that address pollinator responses and pollination outcomes in a variety of human-dominated landscapes and emphasize the need to better understand the dynamic nature of plant,pollinator interactions. [source]


Present and potential distribution of invasive garlic mustard (Alliaria petiolata) in North America

DIVERSITY AND DISTRIBUTIONS, Issue 4 2002
Erik Welk
Abstract. This paper demonstrates the use of a bioclimatic model mapped over geographical regions as a tool for spatially refined risk assessment for the establishment of non-indigenous plants with invasive behaviour. Drawing on the relationship between plant distribution and climate, the approach uses gridded spatial interpolated monthly means of temperature and precipitation linked with accurate maps of general native distribution ranges to predict the long-term potential of a plant species to invade a certain region. The ascertained potential for establishment is illustrated by the example of garlic mustard (Alliaria petiolata[M. Bieb.] Cavara & Grande) in North America. The first step is to calculate and visualize the number of populated grid cells along climatic gradients in frequency diagrams for the general native distribution range. Interpretations of the response curves recorded are used for assessing apparent climatic range boundaries. Modelling was gradually optimized based on the results of experience-based interpretations and by examining omission and over-representation errors. The obtained climatic model of the range of A. petiolata shows considerable congruencies with its mapped, native Eurasian range. Degrees of climatic similarity between North America and the native range of A. petiolata were calculated with the help of GIS methodology and were used to assess the regionally different likelihood of establishment in North America of the invasive species under consideration. [source]


Vegetation,environment relationships along El-Salam Canal, Egypt

ENVIRONMETRICS, Issue 3 2001
Mamdouh S. Serag
Abstract The bank and open water vegetation along El-Salam Canal in north-eastern Egypt were studied in relation to the prevailing environmental factors. The hypothesis that terresterial and aquatic species would show different downstream patterns of species richness was tested by sampling species composition and environmental variables along 80,km of the canal. Species richness was highest in the first 30,km of the canal. The downstream decrease in species richness exhibits interpretable downstream patterns. Total species richness increased with increasing organic matter in the soil and decreased with both increasing soil and water salinity along the gradient. The indicator species of TWINSPAN analysis are: Azolla filiculoides, Echinochloa stagnina, Eichhornia crassipes and Saccharum spontaneum (cluster I); Ceratophyllum demersum, Ludwigia stolonifera and Typha domingensis (cluster II); Potamogeton pectinatus and Phragmites australis (cluster III); Tamarix nilotica and Suaeda vera (cluster IV). The environmental factors influencing the vegetation clusters were analysed using canonical correspondence analysis ordination (CCA). The water salinity, total nitrogen and total phosphorus appeared to be the most important factors controlling the abundance of aquatic plant distribution along the canal. The shoreline vegetation is mainly controlled by salinity, K+ and organic carbon of the soil. Water analysis indicated that the salinity of the water increases southwards and the minimum salinity of the water (0.78,mS/cm) was recorded at the intake of the canal. The maximum value (7.5,mS/cm) of water salinity was recorded near the Suez Canal. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Distribution of aquatic vascular plants in lowland rivers: separating the effects of local environmental conditions, longitudinal connectivity and river basin isolation

FRESHWATER BIOLOGY, Issue 3 2005
BENOÎT O. L. DEMARS
Summary 1. Changes in species distributions along rivers have rarely been observed independently of changes in environmental conditions and meaningful comparison between different catchments is made difficult by the limited geographical distribution of species. This study presents a new approach to quantify the effect of the spatial structure of lowland river networks on aquatic plant distribution and to explore the potential underlying processes using species life-history characteristics. 2. Twenty-five species of aquatic vascular plants recorded in 62 sites across five calcareous river basins were used to investigate (i) the temporal turnover of plant species, (ii) the habitat utilisation of species, (iii) the trade-offs between different plant life-history characteristics and (iv) the relationship between species life-history characteristics and habitat utilisation. 3. The annual plant turnover within a 3-year period was, although significant, extremely low. It suggests that results from spatial surveys conducted over 3 years should not be undermined by temporal changes. 4. Spatial connectivity along and between rivers was more important than in-channel physical characteristics in shaping species assemblages. Neither chemical factors (ammonium, phosphate) nor extrinsic biotic competitors (filamentous green algae) significantly influenced plant distribution. 5. The most common combinations of life-history characteristics were neither related to environmental conditions nor to spatial isolation. Instead, they could reflect natural selection processes associated with larger scales than those considered in this study. 6. Plant distribution was most strongly related to the dispersal and regeneration abilities of the plants, supporting the hypotheses relating to longitudinal connectivity. The hypothesis that different growth forms would be associated with different in-channel physical features was not verified. As expected, there were no substantial differences in plant life-history characteristics between river basins. [source]


PLANT COLONIZATION IN CONDESA NIVATION HOLLOW, SIERRA DE GUADARRAMA (SPANISH CENTRAL SYSTEM)

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2009
JULIO MUÑOZ JIMÉNEZ
ABSTRACT. The purpose of this study was to determine plant distribution at a nivation hollow located in a Mediterranean high mountain area and to analyse the effects of snow cover, wind exposure, proximity to moisture and the characteristics of the substrate on the vegetation. We analyse these factors and interpret concurrent effects due to recent climate change. The nivation hollow, called Ventisquero de la Condesa, is located at 2258 m a.s.l., 40°47,10,N and 3°58,35,W, in the Sierra de Guadarrama (Madrid, Spain). We established 579 small sample plots in the study area, and grouped them into 29 transects where snow duration, wind exposure, availability of meltwater, geomorphologic instability and surface rockiness were examined directly and indirectly. The types of plants and the number of individuals per species were registered for each plot to establish ecological affinities among the 28 distinguishable species. Six showed the highest level of chionophily while nine showed the lowest adaptation to snow cover duration. A statistical study incorporating other variables applied in the research revealed that wind exposure, moisture capture and the intensity of geomorphologic dynamics have a highly significant correlation with nivation, while surface rockiness is a virtually independent factor. Due to environmental changes caused by recent global warming, several plant species, especially adapted to survival in snow conditions, coexist in the hollow with saxicolous plants that have invaded the site from adjacent grass and shrublands. [source]


The effect of small gaps in California annual grassland on above-ground biomass production

GRASS & FORAGE SCIENCE, Issue 4 2001
J. S. Fehmi
Small gaps and clumped species distributions are common in grasslands. In California annual grasslands, patches of Lolium multiflorum Lam. and Bromus hordeaceus L. are often separated by gaps. These gaps potentially limit the productivity and associated resource use of these grasslands. The effect that differences in spatial aggregation, gap distribution and species mixing on 20-cm-diameter plots has on overall forage production by these two grasses was tested. There were three levels of aggregation: whole plots planted; half planted/half empty; two opposing quarters planted/two empty. Each species was planted in each distribution, and they were combined as mixed, half L. multiflorum/half B. hordeaceus and two quarters L. multiflorum/two quarters B. hordeaceus (nine treatments). Plant aggregation had no significant effect on above-ground production of whole plots, but individual tillers near gaps were significantly larger than others. Plasticity in the growth of individual annual grasses effectively buffered against variation in average productivity resulting from variations in plant distribution. There were significant (P < 0·001) differences in forage production as a result of the species the plots contained. Plots containing only L. multiflorum produced 4053 kg of dry matter (DM) ha,1, B. hordeaceus plots produced 2448 kg of DM ha,1, and plots containing both species produced 4712 kg of DM ha,1. At small scales, spatial distribution was less important than species composition in determining annual grassland productivity. [source]


ORIGINAL ARTICLE: Towards an understanding of the Holocene distribution of Fagus sylvatica L.

JOURNAL OF BIOGEOGRAPHY, Issue 1 2007
Thomas Giesecke
Abstract Aim, Understanding the driving forces and mechanisms of changes in past plant distribution and abundance will help assess the biological consequences of future climate change scenarios. The aim of this paper is to investigate whether modelled patterns of climate parameters 6000 years ago can account for the European distribution of Fagus sylvatica at that time. Consideration is also given to the role of non-climatic parameters as driving forces of the Holocene spread and population expansion of F. sylvatica. Location, Europe. Methods, European distributions were simulated using a physiologically-based bioclimatic model (STASH) driven by three different atmospheric general circulation model (AGCM) outputs for 6000 years ago. Results, The three simulations generally showed F. sylvatica to have potentially been as widespread 6000 years ago as it is today, which gives a profound mismatch with pollen-based reconstructions of the F. sylvatica distribution at that time. The results indicate that drier conditions during the growing season 6000 years ago could have caused a restriction of the range in the south. Poorer growth conditions with consequently reduced competitive ability were modelled for large parts of France. Main conclusions, Consideration of the entire European range of F. sylvatica showed that no single driving force could account for the observed distributional limits 6000 years ago, or the pattern of spread during the Holocene. Climatic factors, particularly drought during the growing season, are the likely major determinants of the potential range. Climatic factors are regionally moderated by competition, disturbance effects and the intrinsically slow rate of population increase of F. sylvatica. Dynamic vegetation modelling is needed to account for potentially important competitive interactions and their relationship with changing climate. We identify uncertainties in the climate and pollen data, as well as the bioclimatic model, which suggest that the current study does not identify whether or not climate determined the distribution of F. sylvatica 6000 years ago. Pollen data are better suited for comparison with relative abundance gradients rather than absolute distributional limits. These uncertainties from a study of the past, where we have information about plant distribution and abundance, argue for extreme caution in making forecasts for the future using equilibrium models. [source]


Restriction of the upper distribution of New England cobble beach plants by wave-related disturbance

JOURNAL OF ECOLOGY, Issue 5 2000
Coleman W. Kennedy
Summary 1,The New England cobble beach plant community is an intertidal assemblage of halophytic forbs found exclusively behind fringing beds of the grass Spartina alterniflora. The purpose of this study was to determine the life stage and factors that limit the upper (landward) distribution of cobble beach plants in Narragansett Bay, Rhode Island, USA. 2,Seed traps and soil samples above the community border contained large numbers of seeds and buried seedlings of three cobble beach species, indicating that seed supply and germination do not limit vertical plant distribution. Experimentally added seeds of four species germinated above the community border, but seedlings did not emerge suggesting that seedling emergence is the proximate life stage limiting population and community distribution. 3,Measures of wave disturbance (cobble movement and change in cobble depth) indicated that substrate instability is substantially greater above than within the community, probably due to the lack of buffering by the S. alterniflora bed at higher tidal heights. 4,A second seed addition experiment demonstrated that seedlings of Suaeda linearis, a common cobble beach forb, are only able to emerge and grow into reproductive adults above the community border when the substrate there is artificially stabilized. Seedling transplants and glasshouse manipulations demonstrated that neither herbivores nor soil quality limited seedling emergence. 5,Overall, the vertical restriction of habitat modification by S. alterniflora appears to result in substrate instability at higher tidal elevations sufficient to prevent seedling emergence and limit the vertical distribution of cobble beach plants. [source]


Groundwater input affecting plant distribution by controlling ammonium and iron availability

JOURNAL OF VEGETATION SCIENCE, Issue 4 2006
Esther C.H.E.T. Lucassen
Abstract Question: How does groundwater input affect plant distribution in Alnus glutinosa (black alder) carrs? Location: Alder carrs along the river Meuse, SE Netherlands. Methods: Three types of site, characterized by groundwater flow, were sampled in 17 A. glutinosa carrs. Vegetation and abiotic data (soil and water chemistry) were collected and analysed using a Canonical Correspondence Analysis. Based on the results, a laboratory experiment tested the effect of groundwater input (Ca2+) on pore water chemistry (NH4+ availability). Results: Environmental factors indicating groundwater input (Ca2+ and Fe2+), correlating with the NH+4 concentration in the pore water, best explained the variation in plant distribution. NH4+ availability was determined by Ca2+ input via the groundwater and subsequent competition for exchange sites in the sediment. As a result, nutrient-poor seepage locations fully fed by groundwater were dominated by small iron resistant plants such as Caltha palustris and Equisetum fluviatile. More nutrient-rich locations, fed by a combination of groundwater and surface water, allowed the growth of taller iron resistant plant species such as Carex paniculata. Nutrient-rich locations with stagnating surface water were hardly fed by groundwater, allowing the occurrence of fast growing and less iron tolerant wetland grasses such as Glyceria fluitans and G. maxima. Conclusion: Groundwater input affects plant composition in A. glutinosa carrs along the river Meuse by determining nutrient availability (ammonium) and concentrations of toxic iron. [source]


Are nutrient availability and acidity-alkalinity gradients related in Sphagnum-dominated peatlands?

JOURNAL OF VEGETATION SCIENCE, Issue 4 2002
L. Bragazza
Pignatti (1982) for vascular plants; Frahm & Frey (1987) for bryophytes Abstract. Gradients in acidity-alkalinity and nutrient availability were studied in 2 Sphagnum -dominated peatlands on the southeastern Italian Alps. Decreasing concentrations of most mineral elements (Ca2+, Mg2+, Mn2+, Al3+ and Si4+) in pore water indicated a progressively lower influx of mineral-soil water from the slightly minerotrophic conditions in the peatland margins to ombrogenous conditions in the central part of the peatlands. This was paralleled by decreasing concentrations of ash, bulk density, Ca, Fe and, partly, Mn in the peat. The nutrient gradient, as defined by pore water concentrations of N and P, was largely independent of the acidity- alkalinity gradient: NO3- and PO43- had similar concentrations throughout the gradient, whereas NH4+ concentrations increased with increasing pore-water pH. In contrast, the peat nutrient gradient coincided with the acidity-alkalinity gradient, with total concentrations of N and P decreasing from the margin to the centre. Bryophytes and vascular plants had different responses along the acidity-alkalinity gradient and the nutrient gradient. Bryophyte distribution reflected the acidity-alkalinity gradient both in pore water and in peat. Vascular plant distribution was mainly influenced by variations in nutrient availability. [source]


Stream order controls geomorphic heterogeneity and plant distribution in a savanna landscape

AUSTRAL ECOLOGY, Issue 2 2009
LESEGO KHOMO
Abstract We posed the question: does viewing a savanna as a network of streams linked to a matrix of terrestrial hillslopes provide a useful framework to research and understand plant distribution in these landscapes? Our study area, the Phugwane River network, lies in the semi-arid savanna of Kruger National Park, South Africa. We examined changes in hillslope geomorphology from first-, third- and fifth-order hillslopes with regression equations. The distribution of geomorphic boundaries was enumerated by moving window analysis and the relationship between geomorphology and plant distribution was explored through ordination. First-order hillslopes had a simple geomorphology, fewer geomorphic boundaries and a relatively homogeneous plant assemblage. By contrast, fifth-order hillslopes were more complex in geomorphology, with more boundaries and a relatively heterogeneous vegetation pattern. Stream order classification of a savanna drainage network resulted in landscape units distinguishable by geomorphology, geomorphic boundaries and vegetation pattern. Therefore, the drainage network is a useful template to expose and organize the complexity in savanna landscapes into easily managed and researched units. This perspective should inform a shift from single-scale phytosociological views of homogeneous vegetation units towards multi-scale conceptualizations of savannas as water dependent ecosystems. [source]


A multi-scale test for dispersal filters in an island plant community

ECOGRAPHY, Issue 4 2005
Kevin C. Burns
Constraints on plant distributions resulting from seed limitation (i.e. dispersal filters) were evaluated on two scales of ecological organization on islands off the coast of British Columbia, Canada. First, island plant communities were separated into groups based on fruit morphology, and patterns in species diversity were compared between fruit-type groups. Second, abundance patterns in several common fleshy-fruited, woody angiosperm species were compared to species-specific patterns in seed dispersal by birds. Results from community-level analyses showed evidence for dispersal filters. Dry-fruited species were rare on islands, despite being common on the mainland. Island plant communities were instead dominated by fleshy-fruited species. Patterns in seed dispersal were consistent with differences in diversity, as birds dispersed thousands of fleshy-fruited seeds out to islands, while dry fruited species showed no evidence of mainland-island dispersal. Results from population-level analyses showed no evidence for dispersal filters. Population sizes of common fleshy-fruited species were unrelated to island isolation, as were rates of seed dispersal. Therefore, island isolation distances were not large enough to impose constraints on species' distributions resulting from seed limitation. Rates of seed dispersal were also unrelated to island area. However, several species increased in abundance with island area, indicating post-dispersal processes also help to shape species distributions. Overall results suggest that seed dispersal processes play an important role in determining the diversity and distribution of plants on islands. At the community-level, dry-fruited species were seed limited and island communities were instead dominated by fleshy-fruited species. At the population-level, common fleshy-fruited species were not seed limited and showed few differences in distribution among islands. Therefore, although evidence for dispersal filters was observed, their effects on plant distributions were scale-dependent. [source]


Ecological implications of plants' ability to tell the time

ECOLOGY LETTERS, Issue 6 2009
Víctor Resco
Abstract The circadian clock (the endogenous mechanism that anticipates diurnal cycles) acts as a central coordinator of plant activity. At the molecular and organism level, it regulates key traits for plant fitness, including seed germination, gas exchange, growth and flowering, among others. In this article, we explore current evidence on the effect of the clock for the scales of interest to ecologists. We begin by synthesizing available knowledge on the effect of the clock on biosphere,atmosphere interactions and observe that, at least in the systems where it has been tested, the clock regulates gas exchange from the leaf to the ecosystem level, and we discuss its implications for estimates of the carbon balance. Then, we analyse whether incorporating the action of the clock may help in elucidating the effects of climate change on plant distributions. Circadian rhythms are involved in regulating the range of temperatures a species can survive and affects plant interactions. Finally, we review the involvement of the clock in key phenological events, such as flowering time and seed germination. Because the clock may act as a common mechanism affecting many of the diverse branches of ecology, our ultimate goal is to stimulate further research into this pressing, yet unexplored, topic. [source]


Pronounced drought tolerance characterizes the early life stages of the epiphytic bromeliad Tillandsia flexuosa

FUNCTIONAL ECOLOGY, Issue 3 2009
Maaike Y. Bader
Summary 1Germination and seedling performance may set the limits for plant distributions, particularly in stressful habitats. Stressful conditions at these early stages may be avoided by opportunistic germination and growth, or may be tolerated. Many epiphytic plants are frequently exposed to severe drought. Adult epiphytes endure such dry periods in various ways, but little is known about strategies employed during germination and early life. 2Epiphyte seedlings could show either opportunistic fast growth to quickly attain the benefits of being larger or inherently slow growth and early drought tolerance. Here we address the question: which of these strategies characterizes the early life stages of the epiphytic bromeliad Tillandsia flexuosa, a species typical for dry tropical habitats? 3We studied growth and drought tolerance of germinating seeds, of the emerging seedlings and of 2-month-old seedlings under controlled conditions. Additionally, we studied drought hardening in 6-month-old seedlings. 4Germination of T. flexuosa was reduced by intermittent dry periods. However, compared to the congeneric T. fasciculata, which typically occurs in wetter habitats, the depression of germination by drought was small. Seedling growth was fastest at intermediate moisture levels: both prolonged drought and continuous moisture depressed growth. Prolonged drought had a less negative effect on drought-hardened seedlings than on previously well-watered seedlings. After a 3-week drought treatment the previously well-watered seedlings had lost their growth advantage entirely. Had drought continued, they would have probably been starved, indicated by the low level of their non-structural carbohydrate pool. 5Tillandsia flexuosa employs a stress-tolerance strategy both during germination and during the seedling stage. In its epiphytic habitat this strategy is clearly adaptive, considering the predictable briefness of moisture availability throughout the year and the low competition pressure that allows the very slow growth typically seen in adults and seedlings. These conditions characterize not only the dry-forest habitat of T. flexuosa, but all exposed epiphytic growing sites, so we expect this early stress-tolerance to be common among epiphytes in general. Still, a lower stress tolerance in species from wetter habitats may at least partly explain why T. flexuosa shares its dry-forest habitat with so few other vascular epiphytes. [source]


Using species distribution models to identify suitable areas for biofuel feedstock production

GCB BIOENERGY, Issue 2 2010
JASON M. EVANS
Abstract The 2007 Energy Independence and Security Act mandates a five-fold increase in US biofuel production by 2022. Given this ambitious policy target, there is a need for spatially explicit estimates of landscape suitability for growing biofuel feedstocks. We developed a suitability modeling approach for two major US biofuel crops, corn (Zea mays) and switchgrass (Panicum virgatum), based upon the use of two presence-only species distribution models (SDMs): maximum entropy (Maxent) and support vector machines (SVM). SDMs are commonly used for modeling animal and plant distributions in natural environments, but have rarely been used to develop landscape models for cultivated crops. AUC, Kappa, and correlation measures derived from test data indicate that SVM slightly outperformed Maxent in modeling US corn production, although both models produced significantly accurate results. When compared with results from a mechanistic switchgrass model recently developed by Oak Ridge National Laboratory (ORNL), SVM results showed higher correlation than Maxent results with models fit using county-scale point inputs of switchgrass production derived from expert opinion estimates. However, Maxent results for an alternative switchgrass model developed with point inputs from research trial sites showed higher correlation to the ORNL model than the corresponding results obtained from SVM. Further analysis indicates that both modeling approaches were effective in predicting county-scale increases in corn production from 2006 to 2007, a time period in which US corn production increased by 24%. We conclude that presence-only methods are a powerful first-cut tool for estimating relative land suitability across geographic regions in which candidate biofuel feedstocks can be grown, and may also provide important insight into potential land-use change patterns likely to be associated with increased biofuel demand. [source]


The effect of past changes in inter-annual temperature variability on tree distribution limits

JOURNAL OF BIOGEOGRAPHY, Issue 7 2010
Thomas Giesecke
Abstract Aim, The northern limits of temperate broadleaved species in Fennoscanndia are controlled by their requirements for summer warmth for successful regeneration and growth as well as by the detrimental effects of winter cold on plant tissue. However, occurrences of meteorological conditions with detrimental effects on individual species are rare events rather than a reflection of average conditions. We explore the effect of changes in inter-annual temperature variability on the abundances of the tree species Tilia cordata, Quercus robur and Ulmus glabra near their distribution limits using a process-based model of ecosystem dynamics. Location, A site in central Sweden and a site in southern Finland were used as examples for the ecotone between boreal and temperate forests in Fennoscandia. The Finnish site was selected because of the availability of varve-thickness data. Methods, The dynamic vegetation model LPJ-GUESS was run with four scenarios of inter-annual temperature forcing for the last 10,000 years. In one scenario the variability in the thickness of summer and winter varves from the annually laminated lake in Finland was used as a proxy for past inter-annual temperature variability. Two scenarios were devised to explore systematically the effect of stepwise changes in the variance and shape parameter of a probability distribution. All variability scenarios were run both with and without the long-term trend in Holocene temperature change predicted by an atmospheric general circulation model. Results, Directional changes in inter-annual temperature variability have significant effects on simulated tree distribution limits through time. Variations in inter-annual temperature variability alone are shown to alter vegetation composition by magnitudes similar to the magnitude of changes driven by variation in mean temperatures. Main conclusions, The varve data indicate that inter-annual climate variability has changed in the past. The model results show that past changes in species abundance can be explained by changes in the inter-annual variability of climate parameters as well as by mean climate. Because inter-annual climatic variability is predicted to change in the future, this component of climate change should be taken into account both when making projections of future plant distributions and when interpreting vegetation history. [source]


Pollen,plant,climate relationships in sub-Saharan Africa

JOURNAL OF BIOGEOGRAPHY, Issue 3 2007
Julie Watrin
Abstract Aim, To demonstrate that incorporating the bioclimatic range of possible contributor plants leads to improved accuracy in interpreting the palaeoclimatic record of taxonomically complex pollen types. Location, North Tropical Africa. Methods, The geographical ranges of selected African plants were extracted from the literature and geo-referenced. These plant ranges were compared with the pollen percentages obtained from a network of surface sediments. Climate-response surfaces were graphed for each pollen taxon and each corresponding plant species. Results, Several patterns can be identified, including taxa for which the pollen and plant distributions coincide, and others where the range limits diverge. Some pollen types display a reduced climate range compared with that of the corresponding plant species, due to low pollen production and/or dispersal. For other taxa, corresponding to high pollen producers such as pioneer taxa, pollen types display a larger climatic envelope than that of the corresponding plants. The number of species contained in a pollen taxon is an important factor, as the botanical species included in a taxon may have different geographical and climate distributions. Main conclusions, The comparison between pollen and plant distributions is an essential step towards more precise vegetation and climate reconstructions in Africa, as it identifies taxa that have a high correspondence between pollen and plant distribution patterns. Our method is a useful tool to reassess biome reconstructions in Africa and to characterize accurately the vegetation and climate conditions at a regional scale, from pollen data. [source]


Digitization and geo-referencing of botanical distribution maps

JOURNAL OF BIOGEOGRAPHY, Issue 7 2002
Christian A. Schölzel
Aim In many fields of research, valuable information is stored in atlases and maps which are only available as printed media. Scientists who are interested in computational analysis often seek to digitize the data to make it accessible for numerical calculations. In this paper, an approach using the example of digitizing distribution maps taken from plant-taxonomic atlases is described. For this purpose, a software tool has been built for application in the Sonderforschungsbereich 350 `Interactions between and Modelling of Continental Geosystems' at the University of Bonn. Its functionality has to be simple in use and capable of transforming fields drawn on geographical maps into grid data even where the type of map projection is unknown. Location As an example, plant distributions over Europe and Asia have been digitized. Methods To achieve this aim through an objective statistical analysis, the local deterministic approximation has been used for geo-referencing. Results For this reason the development of a new software tool was required. Although there is a large market for related software from Geographical Information Systems (GIS), none of the available GIS-programs appeared to be capable of geo-referencing maps with unidentified projections. Rather than to give a product comparison, this paper aims on the methodology and mathematical formalism. Main conclusions The developed algorithm is a handy tool to capture data from maps based on obscure projections. Valuable historical maps, which are problematic for standard GIS-programs, can be made accessible for modern research work. [source]


Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2009
R. J. BUTLER
Abstract Palaeobiologists frequently attempt to identify examples of co-evolutionary interactions over extended geological timescales. These hypotheses are often intuitively appealing, as co-evolution is so prevalent in extant ecosystems, and are easy to formulate; however, they are much more difficult to test than their modern analogues. Among the more intriguing deep time co-evolutionary scenarios are those that relate changes in Cretaceous dinosaur faunas to the primary radiation of flowering plants. Demonstration of temporal congruence between the diversifications of co-evolving groups is necessary to establish whether co-evolution could have occurred in such cases, but is insufficient to prove whether it actually did take place. Diversity patterns do, however, provide a means for falsifying such hypotheses. We have compiled a new database of Cretaceous dinosaur and plant distributions from information in the primary literature. This is used as the basis for plotting taxonomic diversity and occurrence curves for herbivorous dinosaurs (Sauropodomorpha, Stegosauria, Ankylosauria, Ornithopoda, Ceratopsia, Pachycephalosauria and herbivorous theropods) and major groups of plants (angiosperms, Bennettitales, cycads, cycadophytes, conifers, Filicales and Ginkgoales) that co-occur in dinosaur-bearing formations. Pairwise statistical comparisons were made between various floral and faunal groups to test for any significant similarities in the shapes of their diversity curves through time. We show that, with one possible exception, diversity patterns for major groups of herbivorous dinosaurs are not positively correlated with angiosperm diversity. In other words, at the level of major clades, there is no support for any diffuse co-evolutionary relationship between herbivorous dinosaurs and flowering plants. The diversification of Late Cretaceous pachycephalosaurs (excluding the problematic taxon Stenopelix) shows a positive correlation, but this might be spuriously related to poor sampling in the Turonian,Santonian interval. Stegosauria shows a significant negative correlation with flowering plants and a significant positive correlation with the nonflowering cycadophytes (cycads, Bennettitales). This interesting pattern is worthy of further investigation, and it reflects the decline of both stegosaurs and cycadophytes during the Early Cretaceous. [source]


Labour Market Regimes and Worker Recruitment and Retention in the European Union: Plant Comparisons

BRITISH JOURNAL OF INDUSTRIAL RELATIONS, Issue 4 2001
Jane Morton
We analyse worker recruitment and retention outcomes, contrasting production worker skill profiles in the UK subsidiaries of five multinationals with, in each case, a matched plant in another EU state. From personnel records we build up plant distributions of worker pay, age, schooling, prior experience and tenure. We find evidence of local management discretion, with differences in unit labour costs and in recruitment/retention outcomes between the matched subsidiaries. UK plants have a ,hire and fire' environment and a less skilled worker mix. Such outcomes can be linked to the UK's lower labour costs and less regulated labour market. [source]