bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐existence and niche segregation of three small bovid species in southern Mozambique
Authors: Prins Herbert H.T. , De Boer Willem F. , Van Oeveren Herman , Correia Augusto , Mafuca Jorge , Olff Han 
Published: May 2006

AbstractNiche segregation among three small antelopes – red duiker, common duiker and suni – was investigated in a coastal savanna woodland/forest mosaic. It was expected that these similar‐sized concentrate selectors would show differentiation in diet choice to decrease competition. Diet composition did not vary significantly among the different vegetation types. For all three antelope species, the number of dietary items was large, with a minimum of 70 different food items per species. Dietary specialization was low, with only 10% of the food items being exclusively used by each of the species. The ranks of food items were positively correlated among species in the wet season, but not in the dry season. Diet breadth significantly decreased in the dry season. The use of exclusive species was significantly larger in the dry season with lowest values recorded for the common duiker. Diet overlap in the wet season was considerable, but significantly decreased in the dry season, the time of food scarcity. The dry season data showed evidence for niche segregation, although this was not based on displacement. As niche segregation in the dry season was coupled to a random apportionment of diet items among antelope species, it cannot be interpreted as the result of competitive displacement.
Observations on limnological conditions associated with a fish kill of Oreochromis niloticus in Lake Chivero following collapse of an algal bloom
Authors: Mhlanga Lindah , Day Jenny , Chimbari Moses , Siziba Nqobizitha , Cronberg Gertrud 
Published: May 2006

AbstractPossible causes of deaths of Oreochromis niloticus in Lake Chivero were examined in relation to changes in limnological conditions monitored over a 25‐month period. The fish deaths coincided with the collapse of an algal bloom that had developed and builtup in the lake for 8 months. Chlorophyll a and dissolved oxygen increased to average concentrations of 42.4 μg l−1 and 10.9 mg l−1 respectively prior to the collapse of the bloom. Dissolved oxygen decreased when the bloom started to die off and coincided with the fish deaths when the average surface dissolved oxygen concentration in the lake was 3.9 mg l−1 and was at a depth of 5 m <2 mg l−1. Mortality probably resulted from depressed oxygen levels caused by the high oxygen demand from the massive algal die‐off and released algal toxins. This is the first time that die‐off of algae has been linked to fish‐kills in Lake Chivero as occurs in other hypereutrophic systems.
The influence of forest variation and possible effects of poaching on duiker abundance at Ngogo, Kibale National Park, Uganda
Authors: Lwanga Jeremiah S. 
Published: May 2006

AbstractDuikers were censused at the Ngogo study area, Kibale National Park, Uganda, between July 2002 and August 2004. Censuses were conducted along three transects, of which, two (colonizing forests 1 and 2) were located in colonizing forests naturally replacing anthropogenic grasslands and one in old growth forest. Colonizing forest 1 was more prone to poaching than both colonizing forest 2 and the old growth forest that were closest to the research camp. Duikers that were actually sighted were identified to species, red or blue. However, on some occasions, duikers were detected by alarm calls and/or movements as they fled; these were simply recorded as duikers. Duiker abundance, regardless of species or mode of detection, was higher in colonizing forest 2 than colonizing forest 1 and the old growth forest. However, when the analysis was restricted only to duikers that were sighted, and hence identified to species, red duiker abundance was highest in colonizing forest 2 followed by the old growth forest and was lowest in colonizing forest 1; all these differences were significant. Blue duiker abundance was lowest in the old growth forest despite its proximity to the research camp; however, this was only significantly lower than in colonizing forest 2. Apart from colonizing forest 1, red duikers were significantly more abundant than blue duikers in the other two forest sections. This study suggests that forests colonizing anthropogenic grasslands may support more duikers than old growth forests; poaching in colonizing forest 1 has a severe impact on the duiker population and, red duikers are affected more severely by poaching than blue duikers.
Reproductive ecology of three endangered African violet (Saintpaulia H. Wendl.) species in the East Usambara Mountains, Tanzania
Authors: Kolehmainen Johanna K. , Mutikainen Pia 
Published: May 2006

AbstractKnowledge of the reproductive biology of endangered plants is essential for their effective conservation. It also provides important information for understanding the evolutionary processes that affect speciation, thus helping the definition of proper units for conservation in endangered plants with problematic taxonomy. We studied the reproductive potential and possibility for hybridization in the endangered genus Saintpaulia (Gesneriaceae) by examining flowering phenology, flower and seed production and pollination of three sympatric cross‐compatible Saintpaulia species in the East Usambara Mts., Tanzania. The synchrony observed in flowering in S. confusa and S. difficilis may enable hybridization between these two species, whereas partial phenological separation may contribute to the integrity of S. grotei. Although the level of flower abortion is high in S. confusa, each pollinated flower yields about 1000 seeds. Saintpaulia confusa produces fruits following both self‐ and cross‐pollination but spontaneous self‐pollination seems not to occur. Thus, seed production depends on sufficient pollinator service. Floral heteromorphy (i.e. enantiostyly) and bee pollination are likely to further enhance cross‐pollination, suggesting that the genus predominantly outcrosses. Thus, Saintpaulia populations are likely to suffer from negative effects of inbreeding if they become small and isolated.
Foraging ecology of roan antelope: key resources during critical periods
Authors: Knoop Marie‐Claire , Owen‐Smith Norman 
Published: May 2006

AbstractThe use of landscape zones and grass species by roan antelope, a species threatened with local extirpation within South Africa's Kruger National Park, were investigated. Plant‐based observations of grazing were made within a 300 ha enclosure in the roan range, where 40 roan antelope were confined at high density in the absence of other grazers. The study spanned the dry seasons of two years, one with average rainfall and one with low rainfall. We recorded changes in the extent of grazing of different grass species, height differences between grazed and ungrazed tillers and intensity of cropping per tuft. In the average year, the grazing pressure in the bottomland grassland was twice that in the upland savanna, with two tall grass species bearing the brunt of the grazing through the dry season. Two highly palatable upland grasses were also extensively grazed by the mid dry season. In the dry year, the extent of grazing in the upland exceeded that in the bottomland, and several upland grass species little used the previous year became heavily grazed. Roan antelope appeared to be separated ecologically from more common grazers by their selective use of tall grasses growing in the drainage line grassland during the critical dry season months. However, their grazing expansion into the upland savanna during the dry year potentially brought them into competition with these grazers. Nevertheless, their population performance did not suffer despite the high‐density conditions. Heightened predation pressure following an influx of these grazers, rather than resource limitation, appeared to be primarily responsible for the drastic decline of this species in the park.
Encroachment of woody plants and its impact on pastoral livestock production in the Borana lowlands, southern Oromia, Ethiopia
Authors: Dalle Gemedo , Maass Brigitte L. , Isselstein Johannes 
Published: May 2006

AbstractEncroachment of woody plants has been among the major threats to the livelihoods of Borana pastoralists and their ecosystem. An approach that integrated vegetation survey and pastoralists’ perception was followed to study the impacts of encroachment of woody plants in the Borana lowlands, Ethiopia. Density of woody species was determined in 192 plots of 500 m2. Canopy cover of woody plants was estimated in 123 quadrates of 400 m2. Pastoralists’ perception was assessed through group discussions and a semi‐structured questionnaire. Results showed that plant density was 3014 woody plants ha−1. Cover of woody plants was 52%, indicating an increasing trend from ≤40% cover reported in the early 1990s. It was concluded that the increase of woody plants density and cover has crossed the critical threshold and has entered into the encroached condition. Principal components analysis (PCA) and redundancy analysis (RDA) also showed that woody plants were negatively correlated with herbaceous biomass. Commiphora africana, Acacia melliphera, A. drepanolobium, A. brevispica and Lannea rivae were among the dominant encroachers. RDA revealed that soil nutrients were positively correlated with woody plants density and cover. The pastoralists perceived that encroachment of woody plants had decreased the production of their grazingland. A ban on fire was perceived as the major factor that caused encroachment of woody plants. Re‐utilization of fire and strengthening of traditional rangeland management strategies are recommended.
Bud banks of perennial savanna grasses in Botswana
Authors: Hartnett David C. , Setshogo Moffat P. , Dalgleish Harmony J. 
Published: May 2006

AbstractThree semi‐arid savanna grasses in Botswana (Stipagrostis uniplumis,Eragrostis lehmanniana, andAristida stipitata) were sampled to quantify their belowground bud banks during the dormant season and to estimate their relative allocation to vegetative and sexual reproduction. Bud banks of these African perennial caespitose grasses were also compared with four perennial caespitose grasses of semi‐arid North American grasslands. The three African grasses each maintained approximately two buds per tiller and showed a high percentage (88–99%) of tillers producing seed. OnlyE. lehmannianaproduced new aerial tillers from axillary buds at elevated nodes on the stem as well as from the belowground bud bank. Compared with species of North American grasslands, these African grasses produced fewer belowground buds but showed a much higher percentage of tillers producing seed. These patterns indicate relatively greater belowground meristem limitation, lower allocation to vegetative reproduction (tillering) and higher allocation to seed reproduction in these African grasses, although studies of more species are needed to assess the generality of this pattern. The management of savannas in ways that favour the maintenance of a reserve population of belowground buds may increase the ability of grasses to respond to pulses of resource availability, increase their compensatory growth capacity following grazing or drought, and decrease the invasibility of these plant communities by exotic species, whereas maintaining allocation to sexual reproduction may be important for conserving genetic variation and enhancing their capacity to adapt to environmental change.
Afromontane old‐field vegetation: secondary succession and the return of indigenous species
Authors: Karlowski Ursula 
Published: May 2006

AbstractSouth‐west Uganda primarily holds afromontane forests within three protected areas: Mgahinga Gorilla National Park, Echuya Forest Reserve and Bwindi Impenetrable National Park. All forests contain portions of old‐field vegetation. The central question of this study, then, is whether and how natural regeneration of afromontane vegetation would take place. A successional pathway consisting of nine plant communities was found for the first 2 years after cessation of agricultural use. A return of afromontane species despite of an initial dominance of neophytes, a diversification of life form spectra and a growing importance of endozoochory with time belonged to the conspicuous characteristics of this secondary succession. To obtain an insight into the role of birds and buffaloes as possible vectors for seed input, I examined their faeces with regard to germinable seeds. Both, bird faeces, as well as buffalo faeces contained germinable seeds originating from the forest flora. Thus, animal dispersal from the forest into the regenerating zones could be documented. The regeneration potential of the soil‐seed bank seems to be limited in its time scale, and only an initial regeneration capacity could be found. A further progressive succession into a secondary afromontane forest depends on an input of diaspores from undisturbed forest sites. Zoochory appears to be one of the most important dispersal mechanisms.
Modelling interactions between fold–thrust belt deformation, foreland flexure and surface mass transport
Authors: Simpson Guy D. H. 
Published: May 2006

ABSTRACTInteractions between fold and thrust belt deformation, foreland flexure and surface mass transport are investigated using a newly developed mathematical model incorporating fully dynamic coupling between mechanics and surface processes. The mechanical model is two dimensional (plane strain) and includes an elasto‐visco‐plastic rheology. The evolving model is flexurally compensated using an elastic beam formulation. Erosion and deposition at the surface are treated in a simple manner using a linear diffusion equation. The model is solved with the finite element method using a Lagrangian scheme with marker particles. Because the model is particle based, it enables straightforward tracking of stratigraphy and exhumation paths and it can sustain very large strain. It is thus ideally suited to study deformation, erosion and sedimentation in fold–thrust belts and foreland basins.The model is used to investigate how fold–thrust deformation and foreland basin development is influenced by the non‐dimensional parameter , which can be interpreted as the ratio of the deformation time scale to the time scale for surface processes. Large values of imply that the rate of surface mass transport is significantly greater than the rate of deformation. When , the rates of surface processes are so slow that one observes a classic propagating fold–thrust belt with well‐developed wedge top basins and a largely underfilled foreland flexural depression. Increasing causes (1) deposition to shift progressively from the wedge top into the foredeep, which deepens and may eventually become filled, (2) widespread exhumation of the fold–thrust belt, (3) reduced rates of frontal thrust propagation and possible attainment of a steady‐state orogen width and (4) change in the style and dynamics of deformation. Together, these effects indicate that erosion and sedimentation, rather than passively responding to tectonics, play an active and dynamic role in the development of fold–thrust belts and foreland basins. Results demonstrate that regional differences in the relative rates of surface processes (e.g. because of different climatic settings) may lead to fold–thrust belts and foreland basins with markedly different characteristics. Results also imply that variations in the efficiency of surface processes through time (e.g., because of climate change or the emergence of orogens above sea level) may cause major temporal changes in orogen and basin dynamics.
Use of40Ar/39Ar K‐feldspar thermochronology in basin thermal history reconstruction: an example from the Big Lake Suite granites, Warburton Basin, South Australia
Authors: McLaren Sandra , James Dunlap W. 
Published: May 2006

ABSTRACTThe potential use of40Ar/39Ar thermochronologic data from K‐feldspars in reconstructing basin thermal history has been evaluated using the example of the Warburton/Cooper/Eromanga Basin, Australia's largest onshore oil‐ and gas‐producing basin. Results from40Ar/39Ar step‐heating experiments reveal details of the evolution of the basin system, including the following: (1) the operation of high geothermal gradient regimes during the earliest basin evolution, suggesting that basin formation was active rather than passive; (2) slow cooling from a Permo‐Triassic temperature peak of at least 250–300°C; (3) a rise in thermal gradients to contemporary bottom hole temperatures in the last 5–10 Myr; and (4) spatially variable recrystallization events between 100 and 50 Ma and at around 20 Ma. Initial microstructural observations serve as a useful predictor of the quality and nature of the obtainable age information. Data from ‘pristine’ K‐feldspars may constrain the peak temperature conditions experienced in the basin, the basin's early thermal history and also any recent changes in thermal gradient. Contrasting data from texturally modified K‐feldspars may constrain times of thermal transients and/or fluid flow, with the preferred interpretation that K‐feldspars recrystallize in response to such events. The Warburton/Cooper/Eromanga Basin example suggests that the40Ar/39Ar technique may serve as a useful adjunct to apatite and zircon fission track analysis and conventional organic maturation indices in basin thermal history analysis.
Sub‐surface precipitation of salts in supercritical seawater
Authors: Hovland Martin , Kuznetsova Tatyana , Rueslåtten Håkon , Kvamme Bjørn , Johnsen Hans Konrad , Fladmark Gunnar E. , Hebach Andreas 
Published: May 2006

ABSTRACTExtremely low solubility of typical seawater salts within certain supercritical sections of their pressure–temperature composition space is a proven experimental fact. Its consequences are often referred to as either ‘shock crystallization’ or ‘out‐salting’. Our alternative model for the formation of salt deposits hypothesizes that high temperatures and pressures characteristic for the high heat‐flow zones of tectonically active basins may bring submarine brines into the out‐salting regions and result in the accumulation of geological‐scale salt depositions.To confirm the laboratory observations, molecular‐scale simulations (molecular dynamics) have been employed to study structural changes in a model seawater system where temperature increased from ambient to near‐critical and supercritical. Fluid properties and phase transition regions extracted from the simulations were then used as input parameters for a reservoir simulator program to model out‐salting in a simple hydrothermal geological system. Both numerical simulations and laboratory experiments confirm that supercritical out‐salting is a viable process of geological significance for the formation and accumulation of evaporites. We suggest two regions where hydrothermally associated salts may be depositing today: Atlantis II Deep, in the Red Sea, and Lake Asale, Ethiopia.
Interleukin (IL)-4 and IL-13 up-regulate monocyte chemoattractant protein-1 expression in human bronchial epithelial cells: involvement of p38 mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2 and Janus kinase-2 but not c-Jun NH2-terminal kinase 1/2 signalling pathways
Authors: Ip W K , Wong C K , Lam C W K 
Published: May 2006

SummaryThe Th2 cytokines interleukin (IL)-4 and IL-13 and chemokine monocyte chemoattractant protein-1 (MCP-1) are significantly involved in bronchial hyperreactivity (BHR) and remodelling in allergic asthma. Although IL-4 and IL-13 can regulate a number of chemokines from bronchial epithelium, their regulatory effect on the expression of MCP-1 is as yet unproved. We aim to investigate the intracellular signalling mechanisms of IL-4 and IL-13 regulating the expression and secretion of MCP-1 from human bronchial epithelial cells. BEAS-2B cells, derived from a human bronchial epithelial cell line, were activated with or without IL-4 and/or IL-13 for different time intervals. MCP-1 gene expression and protein secretion were measured by reverse transcription–polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Activation of signalling molecules p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK) and Janus kinase-2 (JAK-2) was accessed by Western blotting. IL-4 and IL-13 were found to up-regulate gene expression and significantly increase the release of MCP-1 from BEAS-2B cells. Both cytokines could activate p38 MAPK, ERK and JAK-2, but not JNK activity. Inhibition of p38 MAPK, ERK and JAK-2 activities by pretreating the cells with their corresponding inhibitors SB203580, PD98059 and AG490, respectively, significantly suppressed IL-4- and IL-13-induced MCP-1 production in BEAS-2B cells. Together, the above results illustrate that the activation of p38 MAPK, ERK and JAK-2 but not JNK is crucial for IL-4- and IL-13-induced MCP-1 release in human bronchial epithelial cells. Our findings may provide insight into the future development of more effective therapeutic agents for treating allergic asthma.
Immunostimulatory oligodeoxynucleotide fromBifidobacterium longumsuppresses Th2 immune responses in a murine model
Authors: Takahashi N , Kitazawa H , Iwabuchi N , Xiao J Z , Miyaji K , Iwatsuki K , Saito T 
Published: May 2006

SummaryWe have reported previously that novel immunostimulatory sequence (ISS) oligodeoxynucleotide (ODN) BL07S from a probiotic strain of Bifidobacterium longum inhibited immunoglobulin (Ig) E production in vitro. However, whether ISS-ODNs from probiotics regulate T helper type 2 (Th2)-polarized immune reactions in vivo remains unclear. To evaluate the inhibitory effects of ODN BL07S on type I allergic response, BALB/c mice were injected with or without ODN BL07S in the presence of ovalbumin (OVA) on days 0 and 14. Serum Ig levels (IgE, IgG1 and IgG2a) and cytokine levels (interferon (IFN)-γ, interleukin (IL)-12, IL-4, IL-5, IL-10 and IL-13) were investigated in splenocyte cultures from days 14–28. Production of OVA-specific and total IgE were significantly suppressed by administration of ODN BL07S, but not by ODN BL06S, a non-ISS-ODN. Compared to controls, ODN BL07S induced significantly lower levels of Th2 cytokines (IL-4 and IL-5) in splenocyte cultures, and significantly higher levels of serum OVA-specific IgG2a. These effects of ODN BL07S on modulation of Th2 immune response were dose-dependent. The present results demonstrate that ODN BL07S from genomic DNA of B. longum BB536 prevents antigen-induced Th2 immune responses in vivo, suggesting that ISS-ODNs from probiotics might be useful in preventing allergic disease.