6809 research outputs found
Sort by
Tropical Zoology
No full textTropical Zoology is an international journal publishing original papers in the fields of experimental and descriptive zoology concerning tropical areas, with particular attention to the Afrotropical Region. Review papers are welcome. A book review is included. As a rule, the yearly volume comprises four on-line and two printed issues
Habitat determinants of the threatened sahel tortoise centrochelys sulcata at two spatial scales
No full textThe African Spurred Tortoise (Centrochelys sulcata), the second largest tortoise species in the world, is threatened with extinction because of a variety of threats, including habitat loss. Because details of habitat use for this species have not been published for wild populations of this species, we conducted this study to qualify and quantify habitat selection at two spatial scales in Burkina Faso and Niger (West Africa). Tortoises were active above-ground almost exclusively in August, during the peak of the wet season. We surveyed seven potential habitat types but the majority of adult and juvenile tortoises were observed in only two, dry river beds (locally named kori) and stabilized dunes. We used GIS (Geographical Information System) to map the known distribution of the African Spurred Tortoise in both countries in relation to the availability of kori. The habitat preference of African Spurred Tortoises widely overlaps with the occurrence of kori (and not permanent rivers or other water bodies) in the landscape. We discuss the biological and ecological reasons explaining the results, as well as the conservation consequences
Mapping the Lisbon potential foodshed in Ribatejo e Oeste: A suitability and yield model for assessing the potential for localized food production
No full textResearch on food planning has been recently proposed in North American and European planning to account for how cities might change their food provision to respond to the rising demands for a more sustainable and ethical food system. The purpose of this paper was to evaluate the agro-ecological potential of the Lisbon city region, Ribatejo e Oeste, to increase its Regional Food Self-Reliance (RFSR), through adopting demand restraint and food system relocalization approaches to food system sustainability. Three new diet scenarios were considered: meat-based, plant-base and strict vegetarian, defined in accordance with healthy dietary patterns. We used agro-climatic and agro-edaphic agricultural suitability models to evaluate the agro-ecological potential for RFSR, and proposed the use of Foodshed Landscape Plans within a landscape planning methodology. Results showed the extent of local food production that could improve food self-reliance, with 72%, 76%, 84% of total food needs in the meat-based, plant-based, and strict vegetarian scenarios, respectively. Thus, food system transformation by means of relocalization, is therefore ecologically feasible and would ensure the sustainable use of the ecological basis of food security. Additionally, a dietary transition would imply significant land sparing, which strengthens the demand restraint perspective for a transition to food system sustainability
Arabic word processing and morphology induction through adaptive memory self-organisation strategies
No full textAim of the present study is to model the human mental lexicon, by focussing on storage and processing dynamics, as lexical organisation relies on the process of input recoding and adaptive strategies for long-term memory organisation. A fundamental issue in word processing is represented by the emergence of the morphological organisation level in the lexicon, based on paradigmatic relations between fully-stored word forms. Morphology induction can be defined as the task of perceiving and identifying morphological formatives within morphologically complex word forms, as a function of the dynamic interaction between lexical representations and distribution and degrees of regularity in lexical data. In the computational framework we propose here (TSOMs), based on Self-Organising Maps with Hebbian connections defined over a temporal layer, the identification/perception of surface morphological relations involves the alignment of recoded representations of morphologically-related input words. Facing a non-concatenative morphology such as the Arabic inflectional system prompts a reappraisal of morphology induction through adaptive organisation strategies, which affect both lexical representations and long-term storage. We will show how a strongly adaptive self-organisation during training is conducive to emergent relations between word forms, which are concurrently, redundantly and competitively stored in human mental lexicon, and to generalising knowledge of stored words to unknown forms
Dysfunctions of the basal ganglia-cerebellar-thalamo-cortical system produce motor tics in Tourette syndrome
No full textMotor tics are a cardinal feature of Tourette syndrome and are traditionally associated with an excess of striatal dopamine in the basal ganglia. Recent evidence increasingly supports a more articulated view where cerebellum and cortex, working closely in concert with basal ganglia, are also involved in tic production. Building on such evidence, this article proposes a computational model of the basal ganglia-cerebellar-thalamo-cortical system to study how motor tics are generated in Tourette syndrome. In particular, the model: (i) reproduces the main results of recent experiments about the involvement of the basal ganglia-cerebellar-thalamo-cortical system in tic generation; (ii) suggests an explanation of the system-level mechanisms underlying motor tic production: in this respect, the model predicts that the interplay between dopaminergic signal and cortical activity contributes to triggering the tic event and that the recently discovered basal ganglia-cerebellar anatomical pathway may support the involvement of the cerebellum in tic production; (iii) furnishes predictions on the amount of tics generated when striatal dopamine increases and when the cortex is externally stimulated. These predictions could be important in identifying new brain target areas for future therapies. Finally, the model represents the first computational attempt to study the role of the recently discovered basal ganglia-cerebellar anatomical links. Studying this non-cortex-mediated basal ganglia-cerebellar interaction could radically change our perspective about how these areas interact with each other and with the cortex. Overall, the model also shows the utility of casting Tourette syndrome within a system-level perspective rather than viewing it as related to the dysfunction of a single brain area
r.pi: A grass GIS package for semi-automatic spatial pattern analysis of remotely sensed land cover data.
No full text1. Analysing the changing spatial patterns of landscapes due to climate change or anthropogenic impact is important for various disciplines. Land cover change and its resulting modification of spatial patterns in the landscape influence various geographical or ecological parameters. Changing formerly continuous into discontinuous ecosystems due to land cover conversion causes isolated fragments in the landscape. Maintaining the connectivity of a fragmented landscape is relevant for, e.g. in nutrient cycle, water-runoff or species population persistence. 2. Satellite imagery derived land cover can be used to analyse continuously the changing spatial arrangement of land cover types. However, analyses are computer intensive and require robust and efficient processing routines. 3. We developed a patch-based spatial analysis system (r.pi) integrated natively into a Free and Open Source GIS (grass gis) to be able to analyse large amounts of satellite derived land cover data in a semi-automatic manner, and to ensure high reproducibility and robustness. 4. Various established and newly developed indices for spatial pattern analysis are provided in this program, to derive further meaningful information like spatial configuration, patch irreplaceability or connectivity of fragments based on a dispersal model approach
Linear multi-task learning for predicting soil properties using field spectroscopy
No full textField spectroscopy has been suggested to be an efficient method for predicting soil properties using quantitative mathematical models in a rapid and non-destructive manner. Traditional multivariate regression algorithms usually regard the modeling of each soil property as a single task, which means only one response variable is considered as the output during modeling. Therefore, these algorithms are less suitable for the prediction of several key soil properties with low concentrations or unobvious spectral absorption signals. In the current study, we investigated the performance of a linear multi-task learning (LMTL) algorithm based on a regularized dirty model for modeling and predicting several key soil properties using field spectroscopy (350-2500 nm) as an integrated approach. We tested seven key soil properties including available nitrogen (N), phosphorus (P) and potassium (K), pH, water content (WC), organic matter (OM), and electrical conductivity (EC) in drylands. The model performances of LMTL models were compared with the commonly used single-task algorithm of the partial least squares regression (PLS-R). Our results show that the LMTL models outperformed the PLS-R models with the advantage of shared features; the ratio of performance to deviation (RPD) values in the validation set improved by 10.24%, 4.93%, 25.77%, 11.76%, 6.74%, 53.13%, and 3.15% for N, P, K, pH, WC, OM, and EC, respectively. The best prediction was obtained for OM with RPD = 2.29, indicating high accuracy (RPD > 2). The prediction results of N, P, WC, and pH were categorized as of moderate accuracy (1.4 < RPD < 2), while K and EC were categorized as of poor accuracy (RPD < 1.4). However, the explanatory power of the LMTL models was moderate due to fewer features being selected by the regularization algorithm of the LMTL approach, which should be further studied in the soil spectral analysis. Our results highlight the use of LMTL in field spectroscopy analysis that can improve the generalization performance of regression models for predicting soil properties
Citizen science for assessing ecosystem services: Status, challenges and opportunities
No full textCitizen science approaches provide opportunities to support ecosystem service assessments. To evaluate the recent trends, challenges and opportunities of utilizing citizen science in ecosystem service studies we conducted a systematic literature and project review. We reviewed the range of ecosystem services and formats of participation in citizen science in 17 peer-reviewed scientific publications and 102 ongoing or finished citizen science projects, out of over 500 screened publications and over 1400 screened projects. We found that citizen science is predominantly applied in assessing regulating and cultural services. The assessments were often performed by using proxy indicators that only implicitly provide information on ecosystem services. Direct assessments of ecosystem services are still rare. Participation formats mostly comprise contributory citizen science projects that focus on volunteered data collection. However, there is potential to increase citizen involvement in comprehensive ecosystem service assessments, including the development of research questions, design, data analysis and dissemination of findings. Levels of involvement could be enhanced to strengthen strategic knowledge on the environment, scientific literacy and the empowerment of citizens in helping to inform and monitor policies and management efforts related to ecosystem services. We provide an outlook how to better operationalise citizen science approaches to assess ecosystem services
Comparing pixel and object based approaches to map an understorey invasive shrub in tropical mixed forests.
No full textThe establishment of invasive alien species in varied habitats across the world is now recognized as a genuine threat to the preservation of biodiversity. Specifically, plant invasions in understory tropical forests are detrimental to the persistence of healthy ecosystems. Monitoring such invasions using Very High Resolution (VHR) satellite remote sensing has been shown to be valuable in designing management interventions for conservation of native habitats. Object-based classification methods are very helpful in identifying invasive plants in various habitats, by their inherent nature of imitating the ability of the human brain in pattern recognition. However, these methods have not been tested adequately in dense tropical mixed forests where invasion occurs in the understorey. This study compares a pixel-based and object-based classification method for mapping the understorey invasive shrub Lantana camara (Lantana) in a tropical mixed forest habitat in the Western Ghats biodiversity hotspot in India. Overall, a hierarchical approach of mapping top canopy at first, and then further processing for the understorey shrub, using measures such as texture and vegetation indices proved effective in separating out Lantana from other cover types. In the first method, we implement a simple parametric supervised classification for mapping cover types, and then process within these types for Lantana delineation. In the second method, we use an object-based segmentation algorithm to map cover types, and then perform further processing for separating Lantana. The improved ability of the object-based approach to delineate structurally distinct objects with characteristic spectral and spatial characteristics of their own, as well as with reference to their surroundings, allows for much flexibility in identifying invasive understorey shrubs among the complex vegetation of the tropical forest than that provided by the parametric classifier. Conservation practices in tropical mixed forests can benefit greatly by adopting methods which use high resolution remotely sensed data and advanced techniques to monitor the patterns and effective functioning of native ecosystems by periodically mapping disturbances such as invasion
Valutazione del rischio ambientale della presenza di microinquinanti nel lago Maggiore, di Lugano e in altri laghi subalpini
No full textNot availableLa contaminazione da DDx, PCB, PBDE, Hg (mercurio) e As (arsenico) nei sedimenti e in organismi acquatici appartenenti a differenti livelli trofici (zooplancton, molluschi e pesci) ? stata analizzata nel Lago Maggiore e nel Lago di Lugano, due laghi subalpini profondi. Scopo dell\u27analisi ? stato evidenziare l\u27esistenza di sorgenti puntuali di contaminazione nei due ecosistemi lacustri, analizzare i trend temporali e spaziali e valutare le criticit? in termini di superamenti di soglie di tossicit? o qualit? (Sediment Quality Guidelines - SQG - di MacDonald et al. (2000) per i sedimenti, i Quality Standards della Direttiva 2013/39/UE - QS - per il biota). Sono stati considerati i dati prodotti nell\u27ambito del Progetto CIPAIS (Commissione Internazionale per la Protezione delle Acque Italosvizzere) "Indagini sulle sostanze pericolose" nei due laghi relativi al periodo 2001-2015