Is there a need for a theory of urban ecology?

Although urban ecosystems are governed by the same ecological “laws” as rural ecosystems, the relative importance of certain ecological patterns and processes differs between the two types of ecosystems. For instance, as compared to rural areas, urban habitats are usually more islandlike, more often represent early successional stages, and are more easily invaded by alien species. All these features are results of the intense human influence on urban landscapes. The question then arises whether a distinct theory of urban ecology is needed for understanding ecological patterns and processes in the urban setting. The answer is no, because urban ecosystems can be successfully studied using existing ecological theories, such as the metapopulation theory. However, due to the intense human presence, approaches that include the human aspect are useful in studying urban systems. For instance, the “human ecosystem model,” which emphasizes human impact by identifying social components with connections to ecology, is a useful approach in urban studies. This model, combined with the urban–rural gradient approach, forms an effective tool for studying key ecological features of urban ecosystems. Better understanding of these features would increase our ability to predict changes that land use causes in urban ecosystems, and would help to integrate ecology better into urban planning

Management in relation to disturbance in the boreal forest

http://www.elsevier.com/locate/issn/03781127Disturbances and the consequent habitat heterogeneity are natural features of the boreal forest. Natural disturbances occurring at the level of populations, communities and ecosystems (meters to kilometers and years to hundreds of years), that is, at the `meso-scale' may provide useful guidelines for forest management. This approach is based on the assumption that species are adapted to the disturbance regime of the forest-type that they occupy. However, natural disturbance and human-caused disturbance, such as clear-cutting, may differ substantially in their ecological effects. Potential differences occur on several scales. On the stand scale, removal or destruction of important habitat structures, such as coarse woody debris, during traditional clear-cutting may affect species. On the landscape scale, fragmentation may cause local extinctions and hamper the recolonization of maturing sites by old-growth specialists. The effect of these differences on boreal biota needs to be assessed. On the stand scale, the degree of recovery (resilience) of populations and communities after human-caused disturbance versus natural disturbance, that is, the succession process, could be a useful criterion when developing new forestry methods. On the landscape scale, it is important to maintain enough patches of suitable habitat for the old-growth species in order to prevent local extinctions and to promote recolonizations. Natural landscapes could be used as a reference here. In conclusion, although possibilities of matching forestry with maintenance of taiga biota through development of harvesting methods that mimic natural disturbance seem reasonably good, there is an urgent need to establish criteria for the assessment of the success or failure of such methods. The resilience of forest ecosystems as re¯ected in population changes of surrogate taxa after disturbance could be used to guide management

Bounded LTL Model Checking with Stable Models

In this paper bounded model checking of asynchronous concurrent systems is introduced as a promising application area for answer set programming. As the model of asynchronous systems a generalisation of communicating automata, 1-safe Petri nets, are used. It is shown how a 1-safe Petri net and a requirement on the behaviour of the net can be translated into a logic program such that the bounded model checking problem for the net can be solved by computing stable models of the corresponding program. The use of the stable model semantics leads to compact encodings of bounded reachability and deadlock detection tasks as well as the more general problem of bounded model checking of linear temporal logic. Correctness proofs of the devised translations are given, and some experimental results using the translation and the Smodels system are presented.Comment: 32 pages, to appear in Theory and Practice of Logic Programmin

A systematic mapping study of crunch time in video game development

Abstract. Crunch time means heavy overtime work, which usually happens before deadlines when development is behind schedule. It is common in game development and causes stress and social harm to developers. The purpose of this thesis was to study how crunch time is discussed in scientific literature by finding the trends and gaps using a systematic mapping study research method. The main research question was: How is crunch time in video game development discussed in scientific literature? Three assisting research questions were used to help with answering the main research question: How are the causes for crunch time in video game development discussed in the literature? How are the effects for crunch time in video game development discussed in the literature? How are the solutions for crunch time in video game development discussed in the literature? A search string was defined along with inclusion and exclusion criteria in a way that the resulting papers could best be used to answer the research questions. A total of 36 relevant, primary studies were included for this study after conducting the search on Google Scholar and applying the inclusion and exclusion criteria. The papers were categorised based on their contributions to the causes, effects and solutions related to crunch time. These papers were used as the source material for this research. It was found that the number of studies is increasing and the most common contribution of these studies is presenting the causes of crunch time. The most common causes presented were cultural, planning and process, and structural causes. Health and social effects were the most common effects. Process changes and no-crunch policies were the most common types of solutions to crunch time. The main contribution of this study was presenting an overview of how crunch time is discussed in scientific literature. It can be used by researchers to determine what kind of research might be necessary. The study could also be useful for game developers and managers in deciding what actions to take to avoid crunch time. This study found that there are gaps in the literature regarding solutions to crunch time, but often the causes seem to imply solutions. This study suggested that more research into feature creep and structural changes to the game development companies could be useful for learning how to reduce crunch time

Impactful contributions of usability practitioners to open source software projects:a multiple case study

Abstract. Open source software (OSS) has been described as being designed by and for technically advanced users. As OSS has been gaining popularity among non-technical users, concern about its usability has been raised, as it is difficult for technically-minded developers to design for average users. Hiring usability experts to represent the needs of average users has been used in commercial software development as an effective solution for improving usability. It has been also suggested as a way of addressing the usability issues of OSS, but it has been observed that it is often difficult for usability experts to contribute to OSS so that their work has a major impact on the usability of the software. In this thesis, a multiple case study of four usability interventions was conducted. The cases were a part of a larger research program called UKKOSS, which aims to test ways how usability experts can meaningfully contribute to OSS by conducting usability interventions, where student teams act as usability practitioners who enter OSS projects and carry out usability work on them. This study examined how OSS developers reacted to four of those usability interventions by examining the data gathered during those interventions. The analysed data included documents, such as summary reports, communication logs, project plans, and reports on the conducted usability activities. The larger goal of studying these cases was to gather information on how usability practitioners can conduct impactful usability work on OSS projects. The outcomes of the cases were examined through the lens of prior research, and the factors that may have contributed to the success of the cases were examined through cross-case analysis. The developers welcomed the usability work of the usability teams in generally all of the four cases, but the actual impacts the interventions had varied from none of the suggested usability changes being implemented to most of them being implemented to the software. The outcomes of the most successful cases suggest that an approach where usability practitioners implement their suggested changes themselves after discussing about them with the core developers, establishing trust with the developers by contacting them via voice call or video conferencing instead of using only asynchronous communication, and making usability reports as persuasive as possible by including user testing metrics which strengthen the validity of the issues, should be studied further to evaluate if they can have a positive effect on the impact of the work of usability practitioners. The main contributions of this research were supporting the prior research on the obstacles faced by usability experts entering OSS projects by supporting it with empirical evidence and proposing new areas of research on the subject based on the outcomes of the cases

An Entailment Relation for Reasoning on the Web

Reasoning on the Web is receiving an increasing attention because of emerging fields such as Web adaption and Semantic Web. Indeed, the advanced functionalities striven for in these fields call for reasoning capabilities. Reasoning on the Web, however, is usually done using existing techniques rarely fitting the Web. As a consequence, additional data processing like data conversion from Web formats (e.g. XML or HTML) into some other formats (e.g. classical logic terms and formulas) is often needed and aspects of the Web (e.g. its inherent inconsistency) are neglected. This article first gives requirements for an entailment tuned to reasoning on the Web. Then, it describes how classical logic’s entailment can be modified so as to enforce these requirements. Finally, it discusses how the proposed entailment can be used in applying logic programming to reasoning on the Web

Carabid beetle and spider assemblages along a forested urban–rural gradient in southern Finland

To investigate the effects of urbanization on carabid beetles (Carabidae) and ground dwelling spiders (Araneae) a study was completed along a 20 kmurban–rural forest gradient in the Helsinki–Espoo area of southern Finland. To study changes in assemblage structure, abundance and species richness, these taxa were collected in the year 2000 using pitfall traps, which had been placed in four forest sites within each of the urban, suburban and rural zones.We expected to find changes in the abundances and species richnesses in the two taxa across the urban–rural gradient, but did not find any. Our second and third hypotheses, stating that generalist species and small-bodied species should gain dominance along the gradient from rural to urban sites, were partly supported as carabid specialists were more characteristic of suburban and rural environments whereas generalists were more likely to be collected from rural areas compared to suburban or urban sites. Furthermore, medium to large-sized carabid individuals were more likely to be collected in the rural sites compared to urban forests. We found no evidence for significant changes in spider abundance or species richness across the urban–rural gradient in relation to body size or habitat specialization. We suggest that urbanization does not have significant effects on the total abundances and species richnesses in these two taxa. However, individual species responded differently to urbanization, and there were significant differences in the specialization and body sizes of carabids across the gradient

Ecology and urban planning

Urban areas harbour diverse nature ranging from semi-natural habitats to wastelands, parks and other highly human-in¯uenced biotopes with their associated species assemblages. Maintenance of this urban biodiversity for the residents and for its intrinsic value in the face of increasing population and expanding cities requires that ecological knowledge should be better integrated into urban planning. To achieve this goal understanding of ecological patterns and processes in urban ecosystems is needed. The ®rst step in the necessary urban ecological research is to ®nd out what kind of nature exists in cities. Second, knowledge about ecological processes important in urban nature is required. Although ecological processes in cities are the same as in rural areas, some of them, such as invasion by alien species, are more prevalent in urban than in rural conditions. Third, based on ecological knowledge, management schemes maintaining the diversity of urban nature should be designed. These procedures should also include protection of urban nature, e.g. in urban national parks. Finally, as ecology alone cannot provide the complex information about human in¯uence on urban ecosystems, interdisciplinary research involving natural and social sciences is imperative for a holistic approach to integrating ecology into the process of urban planning

Cloud-base vertical velocity statistics: a comparison between an atmospheric mesoscale model and remote sensing observations

The statistics of cloud-base vertical velocity simulated by the non-hydrostatic mesoscale model AROME are compared with Cloudnet remote sensing observations at two locations: the ARM SGP site in Central Oklahoma, and the DWD observatory at Lindenberg, Germany. The results show that, as expected, AROME significantly underestimates the variability of vertical velocity at cloud-base compared to observations at their nominal resolution; the standard deviation of vertical velocity in the model is typically 4-6 times smaller than observed, and even more during the winter at Lindenberg. Averaging the observations to the horizontal scale corresponding to the physical grid spacing of AROME (2.5 km) explains 70-80% of the underestimation by the model. Further averaging of the observations in the horizontal is required to match the model values for the standard deviation in vertical velocity. This indicates an effective horizontal resolution for the AROME model of at least 4 times the physically-defined grid spacing. The results illustrate the need for special treatment of sub-grid scale variability of vertical velocities in kilometer-scale atmospheric models, if processes such as aerosol-cloud interactions are to be included in the future