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Development Patterns (development + pattern)
Selected AbstractsEARLY DEVELOPMENT PATTERN OF THE BROWN ALGA ECTOCARPUS SILICULOSUS (ECTOCARPALES, PHAEOPHYCEAE) SPOROPHYTE,JOURNAL OF PHYCOLOGY, Issue 5 2008Aude Le Bail The distant phylogenetic position of brown macroalgae from the other multicellular phyla offers the opportunity to study novel and alternative developmental processes involved in the establishment of multicellularity. At present, however, very little information is available about developmental patterning in this group. Ectocarpus siliculosus (Dillwyn) Lyngb. has uniseriate filaments and displays one of the simplest architectures in the Phaeophyceae. The aim of this study was to decipher the morphogenetic steps that lead to the development of the Ectocarpus sporophyte. We carried out a detailed morphometric study of the events that occurred between gamete germination and the 100-cell stage. This analysis was performed on two ecologically distant isolates to assess plasticity in developmental patterning within this species. Cell sizes were measured in both isolates, allowing the definition of two main cell types based on their shape (round and elongated). On average, the filament is composed of about 40% round cells, which are present in the central region of the filament, but different combinations of the two cell types within filaments were observed and quantified. Young sporophytes grew apically, with elongated cells progressively differentiating into round cells. Secondary filaments emerged preferentially on round cells, primarily from the older central cells. Statistical analyses showed that the pattern of branching was regulated to ensure a stereotyped architecture. This description of the developmental patterning during the growth of the E. siliculosus sporophyte will serve as a base for more detailed studies of development, in this species and in brown algae in general. [source] A context- and role-driven scientific workflow development patternCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2008Wanchun Dou Abstract Scientific workflow execution often demands data-centric and computation-intensive collaboration efforts, which is typically different from the process-centric workflow execution with fixed execution specifications. Scientific workflow execution often challenges the traditional workflow development strategy in dynamic context management and role definition. In view of this observation, application context spectrums are firstly distinguished from different profiles of scientific workflow development. Then, a role enactment strategy is proposed for enabling workflow execution in certain application context. They jointly enhance the validity of a scientific workflow development through clearly articulating the correlation between computational subjects and computational objects engaged in scientific workflow system. Furthermore, a novel context- and role-driven scientific workflow development pattern is proposed for enacting a scientific workflow system on the Grid. Finally, a case study is presented to demonstrate the generic natures of the methods in this paper. Copyright © 2008 John Wiley & Sons, Ltd. [source] Some aspects of spiralian developmentACTA ZOOLOGICA, Issue 1 2010Claus Nielsen Abstract Nielsen, C. 2010. Some aspects of spiralian development. ,Acta Zoologica (Stockholm) 91: 20,28 Spiralian development is not only a characteristic early cleavage pattern, with shifting orientations of the cleavage planes, but also highly conserved cell lineages, where the origin of several organs can be traced back to identifiable cells in the lineage. These patterns are well documented in annelids, molluscs, nemertines, and platyhelminths and are considered ancestral of a bilaterian clade including these phyla. Spiral cleavage has not been documented in ecdysozoans, and no trace of the spiral development pattern is seen in phoronids and brachiopods. Origin of the spatial organization in spiralian embryos is puzzling, but much of the information appears to be encoded in the developing oocyte. Fertilization and "pseudofertilization" apparently provides the information defining the secondary, anterior-posterior body axis in many species. The central nervous system consists of three components: an apical organ, derived from the apical blastomeres 1a111 -1d111, which degenerates before or at metamorphosis; the cerebral ganglia derived from other blastomeres of the first micromere quartet and retained in the adult as a preoral part of the brain; and the originally circumblastoporal nerve cord, which has become differentiated into a perioral part of the brain, the paired or secondarily fused ventral nerve cords, and a small perianal nerve ring. [source] Rural tourism development in ChinaINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 5 2009Shunli Gao Abstract This paper provides an overview and brief evaluation of China's rural tourism. Beginning with the form of poverty alleviation through tourism, China's rural tourism has undergone over 20 years of development and exhibited some unique features in its development pattern, scale and business operational models in accordance with China's political, social and economic systems. Government plays a decisive role in developing rural tourism in China. However, rural tourism has been valued mainly as an economic means for rural development during the country's modernisation process. Overlooking rurality as an essential issue in rural tourism may lead development to a wrong direction, which could jeopardise the sustainability of the industry. Copyright © 2008 John Wiley & Sons, Ltd. [source] Perinephric angiomyolipoma: A unique development pattern surrounding the kidneyINTERNATIONAL JOURNAL OF UROLOGY, Issue 3 2005WATARU OBARA Abstract, We report a case of a 31-year-old man with extrarenal angiomyolipoma of the perinephric space. He presented with asymptomatic macrohematuria. Computed tomography of the abdomen revealed a large perinephric mass which was separated from the right kidney and its unique growth appeared to have surrounded the kidney. Extrarenal angiomyolipomas of the perinephric fat are rare and they should be considered in the differential diagnosis of a retroperitoneal mass where asymptomatic macrohematuria was presented at the onset. [source] Simulations of virtual plants reveal a role for SERRATE in the response of leaf development to light in Arabidopsis thalianaNEW PHYTOLOGIST, Issue 3 2007Karine Chenu Summary ,,The SERRATE gene (SE) was shown to determine leaf organogenesis and morphogenesis patterning in Arabidopsis thaliana. The se-1 mutant was used here to investigate the role of SE in leaf development in response to incident light. Virtual plants were modelled to analyse the phenotypes induced by this mutation. ,,Plants were grown under various levels of incident light. The amount of light absorbed by the plant was estimated by combining detailed characterizations of the radiative environment and virtual plant simulations. ,,Four major changes in leaf development were induced by the se-1 mutation. Two constitutive leaf growth variables were modified, with a lower initial expansion rate and a higher duration of expansion. Two original responses to a reduced incident light were identified, concerning the leaf-initiation rate and the duration of leaf expansion. ,,The se-1 mutation dramatically affects both changes in the leaf development pattern and the response to reduced incident light. Virtual plants helped to reveal the combined effects of the multiple changes induced by this mutation. [source] Urban pattern and land cover variation in the greater Toronto areaTHE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 1 2007TENLEY CONWAY Recent epistemological shifts in environmental geography have created a space to consider the interactions between ecological and urban systems more seriously. While openness to thinking about urban ecosystems has increased in recent years, there remain fundamental gaps in our knowledge. For example, recent research has examined the impact of urban,rural gradients on ecological conditions, but major voids exist regarding the relationship between urban development patterns and land cover heterogeneity, particularly for new forms of urbanization. This article attempts to address some of these gaps by examining the relationship between urban pattern and land cover in the greater Toronto area (GTA). In particular, measures of urban pattern that reflect aspects of development density, grain and function, as well as socio-economic characteristics, are systematically analyzed in relation to land cover heterogeneity. The regression analysis shows that multiple components of urban development pattern and socio-economic conditions are correlated with vegetated land covers, while urban density variables are not related. These results indicate more detailed representations of urban pattern should be incorporated into future human,environmental interaction studies in cities. Les changements épistémologiques récents en géographie environnementale ont créé un espace dans lequel les interactions entre les systèmes écologiques et urbains sont considérées plus sérieusement. Par contre, bien qu'il existe depuis quelques temps plus de possibilités pour réfléchir aux écosystèmes urbains, des questions fondamentales subsistent. Par exemple, des recherches récentes se sont penchées sur l'impact des gradients urbain-ruraux sur les conditions écologiques. Toutefois, des lacunes importantes demeurent en ce qui concerne les liens entre les modèles de développement urbain et l'hétérogénéité de la couverture des sols, notamment en ce qui a trait aux nouvelles formes d'urbanisation. Cet article aborde certaines de ces lacunes en examinant les liens entre le modèle urbain et la couverture des sols dans la région du Grand Toronto (RGT). En particulier, des mesures du modèle urbain reflétant des aspects de la densité de développement, la texture et la fonction, ainsi que les caractéristiques socio-économiques sont systématiquement analysées par rapport à l'hétérogénéité de la couverture des sols. L'analyse de régression montre une corrélation entre plusieurs composantes du modèle de développement urbain et des conditions socio-économiques, d'une part, et le type de couverture végétale des sols, d'autre part. Les variables utilisées pour la densité urbaine ne sont pas reliées. Ces résultats font ressortir que des représentations plus détaillées du modèle urbain devraient être intégrées aux études ultérieures consacrées aux interactions humain-environnement en milieu urbain. [source] Enantiornithine Bird with Diapsidian Skull and Its Dental Development in the Early Cretaceous in Liaoning, ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2004GONG Enpu Abstract A large number of enantiornithine birds are discovered from the Early Cretaceous Jiufutang Formation in western Liaoning, China. They are all small-sized birds with a few small teeth. The enantiornithine bird from the Jiufutang Formation in the Shangheshou area, Chaoyang, Liaoning Province reported in this paper is the largest individual known in all enantiornithine birds of the Early Cretaceous. However, its teeth possess a feature of pseudoheterodont. Some different development stages of the new teeth substitute the earlier stages and the stages of development are preserved in this specimen. This development pattern is similar to that of Archaeopteryx and alligator but not dinosaur. A well-developed postorbital was also preserved in the skull, which was a diapsidian skull like that of Confuciusornis. Additionally, the distinctive preservation of its prefrontal distinguishes it from other enantiornithine birds of the Early Cretaceous. [source] Cyclone disaster vulnerability and response experiences in coastal BangladeshDISASTERS, Issue 4 2010Edris Alam For generations, cyclones and tidal surges have frequently devastated lives and property in coastal and island Bangladesh. This study explores vulnerability to cyclone hazards using first-hand coping recollections from prior to, during and after these events. Qualitative field data suggest that, beyond extreme cyclone forces, localised vulnerability is defined in terms of response processes, infrastructure, socially uneven exposure, settlement development patterns, and livelihoods. Prior to cyclones, religious activities increase and people try to save food and valuable possessions. Those in dispersed settlements who fail to reach cyclone shelters take refuge in thatched-roof houses and big-branch trees. However, women and children are affected more despite the modification of traditional hierarchies during cyclone periods. Instinctive survival strategies and intra-community cooperation improve coping post cyclone. This study recommends that disaster reduction programmes encourage cyclone mitigation while being aware of localised realities, endogenous risk analyses, and coping and adaptation of affected communities (as active survivors rather than helpless victims). [source] Impacts of Argentine ants on mealybugs and their natural enemies in California's coastal vineyardsECOLOGICAL ENTOMOLOGY, Issue 6 2007KENT M. DAANE Abstract 1.,The Argentine ant, Linepithema humile, tends honeydew-excreting homopterans and can disrupt the activity of their natural enemies. This mutualism is often cited for increases in homopteran densities; however, the ant's impact on natural enemies may be only one of several effects of ant tending that alters insect densities. To test for the variable impacts of ants, mealybug and natural enemy densities were monitored on ant-tended and ant-excluded vines in two California vineyard regions. 2.,Ant tending increased densities of the obscure mealybug, Pseudococcus viburni, and lowered densities of its encyrtid parasitoids Pseudaphycus flavidulus and Leptomastix epona. Differences in parasitoid recovery rates suggest that P. flavidulus was better able to forage on ant-tended vines than L. epona. 3.,Densities of a coccinellid predator, Cryptolaemus montrouzieri, were higher on ant-tended vines, where there were more mealybugs. Together with behavioural observations, the results showed that this predator can forage in patches of ant-tended mealybugs, and that it effectively mimics mealybugs to avoid disturbance by ants. 4.,Ant tending increased densities of the grape mealybug, Pseudococcus maritimus, by increasing the number of surviving first-instar mealybugs. Parasitoids were nearly absent from the vineyard infested with P. maritimus. Therefore, ants improved either mealybug habitat or fitness. 5.,There was no difference in mealybug distribution or seasonal development patterns on ant-tended and ant-excluded vines, indicating that ants did not move mealybugs to better feeding locations or create a spatial refuge from natural enemies. 6.,Results showed that while Argentine ants were clearly associated with increased mealybug densities, it is not a simple matter of disrupting natural enemies. Instead, ant tending includes benefits independent of the effect on natural enemies. Moreover, the effects on different natural enemy species varied, as some species thrive in the presence of ants. [source] Trouble on the reef: the imperative for managing vulnerable and valuable fisheriesFISH AND FISHERIES, Issue 3 2005Yvonne Sadovy Abstract Reef fishes are significant socially, nutritionally and economically, yet biologically they are vulnerable to both over-exploitation and degradation of their habitat. Their importance in the tropics for living conditions, human health, food security and economic development is enormous, with millions of people and hundreds of thousands of communities directly dependent, and many more indirectly so. Reef fish fisheries are also critical safety valves in times of economic or social hardship or disturbance, and are more efficient, less wasteful and support far more livelihoods per tonne produced than industrial scale fisheries. Yet, relative to other fisheries globally, those associated with coral reefs are under-managed, under-funded, under-monitored, and as a consequence, poorly understood or little regarded by national governments. Even among non-governmental organizations, which are increasingly active in tropical marine issues, there is typically little focus on reef-associated resources, the interest being more on biodiversity per se or protection of coral reef habitat. This essay explores the background and history to this situation, examines fishery trends over the last 30 years, and charts a possible way forward given the current realities of funding, capacity, development patterns and scientific understanding of coral reef ecosystems. The luxury live reef food-fish trade is used throughout as a case study because it exemplifies many of the problems and challenges of attaining sustainable use of coral reef-associated resources. The thesis developed is that sustaining reef fish fisheries and conserving biodiversity can be complementary, rather than contradictory, in terms of yield from reef systems. I identify changes in perspectives needed to move forward, suggest that we must be cautious of ,fashionable' solutions or apparent ,quick fixes', and argue that fundamental decisions must be made concerning the short and long-term values of coral reef-associated resources, particularly fish, for food and cash and regarding alternative sources of protein. Not to address the problems will inevitably lead to growing poverty, hardship and social unrest in many areas. [source] Conditional Probabilistic Population Projections: An Application to Climate ChangeINTERNATIONAL STATISTICAL REVIEW, Issue 2 2004Brian C. O'Neill Summary Future changes in population size, composition, and spatial distribution are key factors in the analysis of climate change, and their future evolution is highly uncertain. In climate change analyses, population uncertainty has traditionally been accounted for by using alternative scenarios spanning a range of outcomes. This paper illustrates how conditional probabilistic projections offer a means of combining probabilistic approaches with the scenario-based approach typically employed in the development of greenhouse gas emissions projections. The illustration combines a set of emissions scenarios developed by the Intergovernmental Panel on Climate Change (IPCC) with existing probabilistic population projections from IIASA. Results demonstrate that conditional probabilistic projections have the potential to account more fully for uncertainty in emissions within conditional storylines about future development patterns, to provide a context for judging the consistency of individual scenarios with a given storyline, and to provide insight into relative likelihoods across storylines, at least from a demographic perspective. They may also serve as a step toward more comprehensive quantification of uncertainty in emissions projections. Résumé Les changements futurs dans la taille, la composition et la distribution spatiale de la population sont des facteurs cels dans l'analyse du changement climatique, et leur évolution future est très incertaine. Dans les analyses du changement climatique, on tient traditionnellement compte de l'incertitude sur la population en utilisant des sénarios alternatifs couvrant un éventail de résultats. Cet article illustre comment des projections à probabilité conditionnelle permettent de combiner les approches probabilistes avec l'approche basée sur des scénarios, typiquement employée dans les travaux de projections d'émissions de gaz à effet de serre. La présentation combine un ensemble de scénarios d'émissions développé par le Panel Intergouvernemental sur le changement climatique (IPCC) avec des projections de population probabilistes existantes de l'IIASA. Les résultats démontrent que les projections à probabilité conditionnelle peuvent expliquer plus complètement l'incertitude sur les émissions dans le cadre de scénarios conditionnels des modèles de développement futurs, qu'elles peuvent permettre de juger de la cohérence de scénarios individuels avec un scénario donné, et de fournir une idée des vraisemblances relatives dans les scénarios, au moins d'un point de vue démographique. Ils peuvent aussi servir d'étape vers une quantification plus précise de l'incertitude dans les projections d'émissions. [source] Aspects of the reproductive biology and breeding management of Asian and African elephants Elephas maximus and Loxodonta africanaINTERNATIONAL ZOO YEARBOOK, Issue 1 2006T. B. HILDEBRANDT Elephants possess many unique qualities, including some that relate directly to their reproductive biology. Thus, comparative studies on elephants provide valuable information to the growing biological database for extant mammals. Left undisturbed, Asian Elephas maximus and African Loxodonta Africana elephants reproduce well in the wild. It is ironic then that most captive populations face possible,extinction'because of historically poor reproductive performance. Some of the problems with breeding elephants in captivity are logistical but others, like ovarian and uterine pathologies and bull infertility, have management-related aetiology. Through advances in endocrine monitoring and ultrasound imaging techniques, we are beginning to understand some of the complex mechanisms controlling reproductive function in elephants. Several reproductive characteristics appear to be unique to the taxon, such as luteal steroidogenic function, follicular development patterns, pituitary gonadotrophin secretion, a 22 month-long gestation and musth (in ,,). One example is the,double LH surge'occurring 3 weeks apart during the follicular or non-luteal phase of the cycle, with only the second surge inducing ovulation. These qualities have at times both enhanced and hampered efforts to understand and control reproduction. We have learned that techniques developed for domestic or laboratory species are not always directly applicable to elephants. However, the recent success of artificial insemination based on new ultrasound and endocrine methodology offers hope that establishing selfsustaining populations is possible. This paper reviews our current knowledge of elephant reproduction and how it is being used to aid species conservation for maximal reproductive efficiency and enhancement of genetic management. [source] Postpubertal Architectural Developmental Patterns Differ Between the L3 Vertebra and Proximal Tibia in Three Inbred Strains of Mice,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2008Helen R Buie Abstract An understanding of normal microarchitectural bone development patterns of common murine models is needed. Longitudinal, structural, and mineralization trends were evaluated by in vivo ,CT over 12 time points from 6,48 wk of age at the vertebra and tibia of C3H/HeN, C57BL/6, and BALB/C mice. Longitudinal growth occurred rapidly until 8,10 wk, slowed as the growth plate bridged, and fused at 8,10 mo. Structural augmentation occurred through formation of trabeculae at the growth plate and thickening of existing ones. In the vertebrae, BV/TV increased rapidly until 12 wk in all strains. Between 12 and 32 wk, the architecture was stable with BV/TV deviating <1.1%, 1.6%, and 3.4% for the C57BL/6, BALB/C, and C3H/HeN mice. In contrast, the tibial architecture changed continuously but more moderately for BV/TV and TbTh compared with the vertebra and with comparable or larger changes for TbN and TbSp. Age-related trabecular deterioration (decreased BV/TV and TbN; increased TbSp and structure model index) was evident at both sites at 32 wk. In all strains, the cortex continued to develop after trabecular values peaked. The temporal plateau of BMD was variable across mouse strains and site, whereas tissue mineral density was attained at ,6 mo for all sites and strains. Geometric changes at the tibial diaphysis occurred rapidly until 8,10 wk, providing the C57BL/6 mice and C3H/HeN mice with the highest torsional and compressive rigidity, respectively. In summary, key skeletal development milestones were identified, and architectural topology at the vertebra was found to be more stable than at the tibia. [source] Early development of the digestive tract (pharynx and gut) in the embryos and pre-larvae of the European sea bass Dicentrarchus labraxJOURNAL OF FISH BIOLOGY, Issue 6 2009E. Sucré The European sea bass Dicentrarchus labrax is a marine teleost important in Mediterranean aquaculture. The development of the entire digestive tract of D. labrax, including the pharynx, was investigated from early embryonic development to day 5 post hatching (dph), when the mouth opens. The digestive tract is initialized at stage 12 somites independently from two distinct infoldings of the endodermal sheet. In the pharyngeal region, the anterior infolding forms the pharynx and the first gill slits at stage 25 somites. The other three gill arches and slits are formed between 1 and 5 dph. Posteriorly, in the gut tube region, a posterior infolding forms the foregut, midgut and hindgut. The anus opens before hatching, at stage 28 somites. Associated organs (liver, pancreas and gall bladder) are all discernable from 3 dph. Some aspects of the development of the two independent initial infoldings seem original compared with data in the literature. These results are discussed and compared with embryonic and post-embryonic development patterns in other teleosts. [source] THE ASSOCIATION BETWEEN URBAN SPRAWL AND OBESITY: IS IT A TWO-WAY STREET?JOURNAL OF REGIONAL SCIENCE, Issue 5 2007Andrew J. Plantinga ABSTRACT We empirically examine the relationship between obesity and urban development patterns where individuals reside. Previous analyses treat urban form as exogenous to weight, and find higher body mass indices (BMI) among residents of areas with sprawl patterns of development. Using samples of recent movers, we find that the causality runs in both directions. Individuals who move to denser locations lose weight. As well, BMI is a determinant of the choice of a dense or sprawling location. In sum, while moving to a dense area results in weight loss, such locations are unlikely to be selected by individuals with high BMI. [source] Shellfish aquaculture and First Nations' sovereignty: The quest for sustainable development in contested sea spaceNATURAL RESOURCES FORUM, Issue 2 2010Alyssa L. Joyce Abstract Aquaculture tenures or leases have become an increasingly important management tool for regulating access rights to coastal and offshore marine habitat. Tenure, as a form of private property rights to marine space, is generally considered a prerequisite for aquaculture development, as are the associated exclusive access rights which provide necessary incentives for producers to invest in infrastructure. The shellfish industry in British Columbia (BC), Canada, is presented as a case study of a transition from a primarily common property wild fishery to a rights-based system for aquaculture. In BC, seafood production has grown substantially during the past two decades as a result of aquaculture production. However, despite the inherent economic advantages of the tenuring system for increasing seafood production, rights to aquaculture sites in BC remain highly controversial, particularly in response to environmental concerns and infringements on Aboriginal territorial claims. Shellfish farming has, to-date, been far less controversial than salmon farming; however, shellfish aquaculture has not been uniformly adopted across the province, and analyses of industry capacity or economic opportunities for coastal communities have failed to adequately explain development patterns. This paper, which identifies perceptions of the risks and benefits of the shellfish aquaculture tenuring system, presents the results of 56 interviews conducted with individuals involved in shellfish production in BC. Results indicate that heightened perceptions of risk about shellfish aquaculture tenuring are related to unresolved Aboriginal territorial claims, economic dependence on wild shellfish resources, as well as place-based values favouring access to wild resources. Underlying values and cultural understandings also strongly shape public perceptions of the risks of aquaculture, and as such, influence local decisions to either accept or resist industry growth. In this case, interviewees' risk perceptions were found to be more important indicators of the potential for industry expansion than studies of capacity or economic cost-benefit analyses. [source] ENDOGENOUS HEALTH CARE, LIFE EXPECTANCY AND ECONOMIC GROWTHPACIFIC ECONOMIC REVIEW, Issue 1 2010Michael C. M. Leung We study the endogenous relationship between health care, life expectancy and output in a neoclassical growth model. Although health care directly diverts resources away from goods production, it prolongs life expectancy, which in turn leads to higher savings and, hence, capital formation through a private annuity market. We show that savings and health care are complements in equilibrium, with both rising with economic development. Our model is therefore consistent with several observed stylized development patterns across countries. Moreover, through the longevity-enhancing channel, health care and health production technology are found by simulation to be growth and welfare promoting. [source] Local Institutions and the Politics of Urban GrowthAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 3 2009Mark Lubell This article uses a political market framework to analyze how the structure of local political institutions affects the relative political influence of development and environmental interests in the context of urban growth. Using panel data from 406 Florida cities from 1998 to 2003, the empirical analysis finds important interaction effects between the structure of city executive branch institutions and interest group variables. The economic and political forces driving urban growth do not operate identically in all cities,they vary as a function of institutional context. Institutional structure helps determine which interest groups have their preferences reflected in local land-use changes and development patterns. The resulting patterns suggest a "sustainability paradox" wherein richer, environmental interests push for the preservation of environmental amenities while at the same time accelerating the number of residential units built in a community. [source] Urban pattern and land cover variation in the greater Toronto areaTHE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 1 2007TENLEY CONWAY Recent epistemological shifts in environmental geography have created a space to consider the interactions between ecological and urban systems more seriously. While openness to thinking about urban ecosystems has increased in recent years, there remain fundamental gaps in our knowledge. For example, recent research has examined the impact of urban,rural gradients on ecological conditions, but major voids exist regarding the relationship between urban development patterns and land cover heterogeneity, particularly for new forms of urbanization. This article attempts to address some of these gaps by examining the relationship between urban pattern and land cover in the greater Toronto area (GTA). In particular, measures of urban pattern that reflect aspects of development density, grain and function, as well as socio-economic characteristics, are systematically analyzed in relation to land cover heterogeneity. The regression analysis shows that multiple components of urban development pattern and socio-economic conditions are correlated with vegetated land covers, while urban density variables are not related. These results indicate more detailed representations of urban pattern should be incorporated into future human,environmental interaction studies in cities. Les changements épistémologiques récents en géographie environnementale ont créé un espace dans lequel les interactions entre les systèmes écologiques et urbains sont considérées plus sérieusement. Par contre, bien qu'il existe depuis quelques temps plus de possibilités pour réfléchir aux écosystèmes urbains, des questions fondamentales subsistent. Par exemple, des recherches récentes se sont penchées sur l'impact des gradients urbain-ruraux sur les conditions écologiques. Toutefois, des lacunes importantes demeurent en ce qui concerne les liens entre les modèles de développement urbain et l'hétérogénéité de la couverture des sols, notamment en ce qui a trait aux nouvelles formes d'urbanisation. Cet article aborde certaines de ces lacunes en examinant les liens entre le modèle urbain et la couverture des sols dans la région du Grand Toronto (RGT). En particulier, des mesures du modèle urbain reflétant des aspects de la densité de développement, la texture et la fonction, ainsi que les caractéristiques socio-économiques sont systématiquement analysées par rapport à l'hétérogénéité de la couverture des sols. L'analyse de régression montre une corrélation entre plusieurs composantes du modèle de développement urbain et des conditions socio-économiques, d'une part, et le type de couverture végétale des sols, d'autre part. Les variables utilisées pour la densité urbaine ne sont pas reliées. Ces résultats font ressortir que des représentations plus détaillées du modèle urbain devraient être intégrées aux études ultérieures consacrées aux interactions humain-environnement en milieu urbain. [source] Influence of fire severity on stand development of Araucaria araucana,Nothofagus pumilio stands in the Andean cordillera of south-central ChileAUSTRAL ECOLOGY, Issue 6 2010MAURO E. GONZÁLEZ Abstract Fire is the prevalent disturbance in the Araucaria,Nothofagus forested landscape in south-central Chile. Although both surface and stand-replacing fires are known to characterize these ecosystems, the variability of fire severity in shaping forest structure has not previously been investigated in Araucaria,Nothofagus forests. Age structures of 16 stands, in which the ages of approximately 650 trees were determined, indicate that variability in fire severity and frequency is key to explaining the mosaic of forest patches across the Araucaria,Nothofagus landscape. High levels of tree mortality in moderate- to high-severity fires followed by new establishment of Nothofagus pumilio typically result in stands characterized by one or two cohorts of this species. Large Araucaria trees are highly resistant to fire, and this species typically survives moderate- to high-severity fires either as dispersed individuals or as small groups of multi-aged trees. Small post-fire cohorts of Araucaria may establish, depending on seed availability and the effects of subsequent fires. Araucaria's great longevity (often >700 years) and resistance to fire allow some individuals to survive fires that kill and then trigger new Nothofagus cohorts. Even in relatively mesic habitats, where fires are less frequent, the oldest Araucaria,Nothofagus pumilio stands originated after high-severity fires. Overall, stand development patterns of subalpine Araucaria,N. pumilio forests are largely controlled by moderate- to high-severity fires, and therefore tree regeneration dynamics is strongly dominated by a catastrophic regeneration mode. [source] Comparative Analysis of Sequence Characteristics among Different Superimposed Stages of the Chelif Basin, AlgeriaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 6 2009ZHANG Yuanfu Abstract: Superimposed basins were investigated with respect to tectonic evolution, sediment deposition and petroleum characteristics within a single superposition stage generally. The comparative study was seldom seen. Sequence characteristics were compared for two different superimposed stages , an expanding rifting stage and a depression-foreland transition stage , in the Chelif Basin during the Miocene in this paper. A model and mechanism for sequence evolution of superimposed basins in different dynamic situations are discussed with respect to sequence similarities and differences. The compared characters include sequence thickness, sequence boundaries and system tracts, as well as sediment deposition within sequences and sequence development patterns. Finally, some typical features of sequence development concomitant with changes of superimposed stages in the Chelif Basin are discussed. [source] Land Market Interactions between Heterogeneous Agents in a Heterogeneous Landscape,Tracing the Macro-Scale Effects of Individual Trade-Offs between Environmental Amenities and DisamenitiesCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 4 2009Tatiana Filatova Heterogeneity in both the spatial environment and economic agents is a crucial driver of land market dynamics. We present an agent-based land market model where land from agriculture use is transferred into urban. The model combines the microeconomic demand, supply, and bidding foundations of spatial economics models with the spatial heterogeneity of spatial econometric models in a single methodological platform. Heterogeneous agents exchange heterogeneous spatial goods via simulated bilateral market interactions. We model a coastal city where both coastal amenities and flooding or erosion disamenities drive land market outcomes, facilitating separate analysis of the effects of each driver on land rents and land development patterns. We also analyze the implications of homogeneous versus heterogeneous but unbiased flood risk perceptions. Since buyers with low risk perceptions drive market outcomes, spatial development under heterogeneous risk perceptions differs qualitatively, with more expansion into risky areas. Our results highlight the shortcomings of policy models based on representative agent assumptions and the importance of including agent-level data in empirical modeling. L'hétérogénéité de l'environnement spatial et des agents économiques constitue un élément moteur crucial de la dynamique du marché foncier. Nous présentons un modèle multi-agent du marché foncier dans lequel des terres agricoles ont été transférées pour des fins urbaines. Le modèle combine les fondements microéconomiques de la demande, de l'offre et des enchères de modèles de l'économie spatiale avec l'hétérogénéité spatiale des modèles de l'économétrie spatiale dans une plateforme méthodologique unique. Les agents hétérogènes échangent des biens hétérogènes par le biais du jeu des forces du marché bilatéral simulé. Nous avons modélisé une ville côtière où les agréments côtiers et les désagréments causés par les inondations ou l'érosion influent sur le marché foncier, facilitant l'analyse individuelle des effets de chaque élément moteur sur les loyers fonciers et les modèles d'aménagement de terrain. Nous avons également analysé les répercussions des perceptions homogènes et hétérogènes mais non biaisées à l'égard du risque d'inondation. Étant donné que les acquéreurs qui ont de faibles perceptions du risque motivent les effets du marché, le développement spatial selon des perceptions hétérogènes à l'égard du risque varie qualitativement, avec plus d'expansion dans les zones à risque. Nos résultats ont mis en lumière les lacunes des modèles de politiques fondés sur les hypothèses d'un agent représentatif et l'importance d'inclure des données sur l'hétérogénéité des agents dans la modélisation empirique. [source] | ||||||||||||||||||||||