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Savannah Ecosystem (savannah + ecosystem)
Selected AbstractsSeasonal variation in reproductive behaviour of bushbuck (Tragelaphus scriptus Pallas, 1766) in an equatorial savannah ecosystemAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Ann Apio Abstract While several authors suggest that bushbuck (Tragelaphus scriptus Pallas) from tropical areas with an approximately bimodal rainfall pattern breed throughout the year, there is also a report of seasonal breeding in this species. In this study, we provide indirect evidence of seasonality in reproduction by analysing behavioural data (e.g. rates of mixed-sex sightings) in a population of bushbuck inhabiting an equatorial savannah ecosystem in western Uganda. Observation rates of mixed-sex sightings were correlated with rainfall patterns. We suggest that peaks in reproductive behaviour following the wet season may be advantageous if calves are born during the next wet season, when fresh vegetation is available. Résumé Alors que plusieurs auteurs suggèrent que le bushbuck (Tragelaphus scriptus Pallas) des régions tropicales qui ont un régime de pluies à peu près bimodal se reproduisent tout au long de l'année, il y a aussi un rapport signalant une reproduction saisonnière chez cette espèce. Dans la présente étude, nous apportons des preuves indirectes d'une saisonnalité de la reproduction par l'analyse des données comportementales (e.g. taux d'observations de sexes mélangés) dans une population de bushbucks habitant dans un écosystème de savane équatoriale, dans l'ouest de l'Ouganda. Les taux d'observations de groupes mélangés étaient liés aux chutes de pluies. Nous suggérons que les pics observés dans le comportement reproducteur en fonction de la saison des pluies peuvent être bénéfiques si les jeunes naissent durant la saison des pluies suivante, lorsque la végétation fraîche est abondante. [source] Environmental parameters and anthropogenic effects predicting the spatial distribution of wild ungulates in the Akagera savannah ecosystemAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Christiane Averbeck Abstract Savannah areas affected by human activities such as livestock keeping and agriculture are often characterized by shifts in landscape structuring, with a predominance of few(er) habitat types. This is typically accompanied by pronounced changes in the communities of ungulates. The aim of this study was to find out whether shifts in ungulate communities in Lake Mburo National Park (LMNP) are primarily predicted by an alteration in the composition of the preferred habitat types or if more complex interactions between habitat changes and the prevalence of ungulates occur. Monthly road counts were used to establish the number of eleven ungulate species in LMNP and adjacent unprotected Ankole Ranching Scheme. The common duiker (Sylvicapra grimmia campbelliae Gray, 1843) was found in more abundance in disturbed areas, while showing a significant change in habitat use. Common duiker tended to use the vegetation type otherwise used by the bushbuck (Tragelaphus scriptus dama Neumann, 1902). Our results support the claim that the occurrence of ungulates is not only directly affected by the availability of ,suitable' habitats, but behavioural plasticity and competitive exclusion also need to be considered. Résumé Les zones de savane touchées par des activités humaines telles que l'élevage de bétail et l'agriculture se caractérisent souvent par des évolutions de la structure du paysage, avec une prédominance d'un (plus) petit nombre de types d'habitats. Cela s'accompagne généralement de changements marqués chez les communautés d'ongulés. Le but de cette étude était de voir si l'on peut s'attendre à des évolutions des communautés d'ongulés dans le Parc National du Lac Mburo du seul fait d'une altération de la composition des types d'habitats préférés ou s'il y a des interactions plus complexes entre les changements de l'habitat et la prévalence des ongulés. Nous avons eu recours à des comptages routiers mensuels pour établir le nombre d'ongulés de onze espèces dans le Parc National du Lac Mburo et dans l'Ankole Ranching Scheme voisin, nonprotégé. Le sylvicapre de Grimm (Sylvicapra grimmia campbelliae Gray, 1843) fut observé en plus grand nombre dans les zones perturbées, et manifestait un changement significatif de l'utilisation de son habitat. Cette espèce avait tendance à utiliser le type de végétation normalement utilisé par le bushbuck (Tragelaphus scriptus dama Neumann, 1902). Nos résultats soutiennent l'affirmation selon laquelle la présence des ongulés n'est pas directement affectée seulement par la disponibilité d'habitats « appropriés », mais qu'il faut aussi envisager une certaine plasticité comportementale et des compétitions menant à des exclusions. [source] The Wildlife Picture Index: monitoring top trophic levelsANIMAL CONSERVATION, Issue 4 2010T. G. O'Brien Abstract Although recent biodiversity loss has been compared with cataclysmic mass extinctions, we still possess few indicators that can assess the extent or location of biodiversity loss on a global scale. The Convention on Biological Diversity (CBD) has mandated development of indicators that can meet the needs of monitoring biodiversity by 2010. To date, many indicators rely on unwarranted assumptions, secondary data, expert opinion and retrospective time series. We present a new biodiversity indicator, the Wildlife Picture Index (WPI) that targets medium and large-sized terrestrial birds and mammals in forested and savannah ecosystems that. The WPI is a composite indicator based on the geometric mean of relative occupancy estimates derived from camera trap sampling at a landscape scale. It has been designed to meet the needs of a CBD indicator while avoiding many of the pitfalls that characterize some CBD indicators. We present an example using 8 years of camera trap data from Bukit Barisan Selatan National Park, Indonesia to show that the WPI is capable of detecting changes in the rate of loss of biodiversity, a key requirement of a CBD indicator. We conclude that the WPI should be effective at monitoring top trophic levels in forest and savannah ecosystems using primary data and can fill the gap in knowledge about trends in tropical biodiversity. [source] Arthropod responses to experimental fire regimes in an Australian tropical savannah: ordinal-level analysisAUSTRAL ECOLOGY, Issue 2 2000Alan N. Andersen Abstract Fire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long-term effect on ordinal-level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal-level resilience also occurs in Australia's tropical savannahs. The data are from a multidisciplinary, landscape-scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15,20 km2 compartments subjected to one of three fire regimes, each with three replicates: ,early' (annual fires lit early in the dry season), ,late' (annual fires lit late in the dry season), and ,unburnt' (fires absent during the five-year experimental period 1990,94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated-measures ANOVA. There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass-layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal-level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia. [source] | ||||||||||