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139 results for “savannahs”
Burned areas dataset for the enclaves of grasslands and savannah of the Mapinguari National Park (Amazonas, Brazil)
<p><span>The present dataset includes annual mapping of fire scars for the enclaves of grasslands and savannah of the Mapinguari National Park (Amazonas, Brazil), at 30-meter spatial resolution, for the period 2000-2023. The enclave areas occupy a total of 241,000 hectares.</span></p> <p><span>The detection of burned areas was carried out using Burned Area Mapping (BAMS) algorithm (Bastarrika et al, 2014), followed by the performance of visual supervision processes and the use of active fire products to optimize the detection date of each fire event. The algorithm is applied to the Surface Reflectance series of Landsat (TM, ETM+, OLI and OLI-2) – Collection II, accessed using Google Earth Engine (Gorelick et al, 2017). Data from active fire products MCD14DL V006, VIIRS-NPP, VIIRS-NOA20 and GOES16, as well as burned area data from product MCD64A1 v006, were used to optimize the detection date of each fire scar.</span></p> <p><span>_________________________________________________________________________________________________________</span></p> <p><span>July 08, 2023 – The version 1.0 includes the period 2000-2023, with a total of 356,688.5 hectares of fire affected areas, distributed across 453 fire scars.</span></p> <p><span>_________________________________________________________________________________________________________</span></p> <p><span>The files available include: </span></p> <p><span>i) “fire_scars_dataset.rar”: annual burned areas vector files, in shapefile format (*.shp), projected at WGS84 UTM 20S. Each observation is an individual fire scar, with his attribute table indicating:</span></p> <p><span>- ID: Identification number for each;</span></p> <p><span>- area_ha - area of each fire scar, calculated in hectares.</span></p> <p><span>- date - detection date of the fire scar</span></p> <p><span>- date_preci - precision flag of the fire detection date:</span></p> <p><span>0 - fire date detected using only Landsat data</span></p> <p><span>1 - fire date optimized based on active fires dataset (MCD14DL V006; VIIRS-NPP; VIIRS-NOA20; or GOES16)</span></p> <p><span>ii) “enclaves_Mapinguari_National_Park.rar”: vector file of study area location, in shapefile format (*.shp), projected at WGS84 UTM 20S. Includes 8 enclaves of grasslands and savannah situated inside Mapinguari National Park.</span></p> <p><span>iii) “dataset_description.pdf”: description of the dataset.</span></p> <p><span>_________________________________________________________________________________________________________</span></p> <p><span>We thank the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq) and the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBIO) (process number 126772/2022-3) for the grant conceded to the second and third authors.</span></p> <p><span>_________________________________________________________________________________________________________</span></p> <p> </p> <p><span>References</span></p> <p> </p> <p><span>Bastarrika, Aitor, Maite Alvarado, Karmele Artano, Maria Pilar Martinez, Amaia Mesanza, Leyre Torre, Rubén Ramo, and Emilio Chuvieco. 2014. “BAMS: A Tool for Supervised Burned Area Mapping Using Landsat Data.” Remote Sensing 6: 12360–80. https://doi.org/10.3390/rs61212360.</span></p> <p><span>Gorelick, Noel, Matt Hancher, Mike Dixon, Simon Ilyushchenko, David Thau, and Rebecca Moore. 2017. “Google Earth Engine: Planetary-Scale Geospatial Analysis for Everyone.” Remote Sensing of Environment 202: 18–27. https://doi.org/10.1016/j.rse.2017.06.031.</span></p>
Fig. 3 in Ants found on acacia of the genus Vachellia and other savannah trees at Mkomazi Game Reserve, Tanzania with the description of a new species Hymenoptera: Formicidae
Fig. 3. Insect sampling by pyrethrum knock-down spraying.
FIGURE 3 in Local effects of deforestation on stream fish assemblages in the Amazon-Savannah transitional area
FIGURE 3 | Box-and-whiskers plots of the five metrics comprising the Physical Integrity Index.
TABLE 1 in Nesting evidence, density and vocalisations in a resident population of Savannah Sparrow Passerculus sandwichensis wetmorei in Guatemala
<p>TABLE 1 Mean (± SD) and range of signal characteristics of songs of breeding Savannah Sparrows <i>Passerculus sandwichensis wetmorei</i> in PRM Todos Santos Cuchumatán, dpto. Huehuetenango, Guatemala, in June 2016, <i>n</i> = 37 songs of four males.</p><table><thead><tr><th><b>Song section (see Fig. 5)</b></th><th><b>Duration (seconds)</b></th><th><b>Peak frequency (kHz)</b></th></tr></thead><tbody><tr><th>Entire song (<i>n</i> = 37)</th><td>2.5 ± 0.3 (2.1–3.1)</td><td></td></tr><tr><th>Introduction:</th><td></td><td></td></tr><tr><th><i>Chip</i> note (<i>n</i> = 97)</th><td>0.06 ± 0.01 (0.04–0.12)</td><td>7.906 ± 202 (6.938 –8.250)</td></tr><tr><th>Middle section:</th><td></td><td></td></tr><tr><th>Descending whistle (DW1) (<i>n</i> = 37)</th><td>0.10 ± 0.01 (0.08–0.11)</td><td>6.927 ± 132 (6.750 –7.125)</td></tr><tr><th>Trill (n = 37)</th><td>0.05 ± 0.01 (0.03–0.06)</td><td>6.471 ± 1.268 (4.125 –7.500)</td></tr><tr><th>Double <i>ch</i> note (<i>n</i> = 37)</th><td>0.08 ± 0.004 (0.07–0.10)</td><td>5.063 ± 378 (3.188 –5.625)</td></tr><tr><th>Dominant section:</th><td></td><td></td></tr><tr><th>Buzz (<i>n</i> = 37)</th><td>0.60 ± 0.06 (0.5–0.8)</td><td>6.456 ± 646 (4.688 –6.938)</td></tr><tr><th>Terminal section:</th><td></td><td></td></tr><tr><th>Descending whistle (DW2) (<i>n</i> = 37)</th><td>0.08 ± 0.005 (0.07–0.09)</td><td>7.566 ± 222 (7.313 –8.063)</td></tr><tr><th>Trill-whistle (n = 37)</th><td>0.29 ± 0.07 (0.16 – 0.39)</td><td>4.074 ± 355 (3.375 –4.313)</td></tr></tbody></table>
Savannah River NERP songbird tissue, insect, and fruit isotope database
Many temperate passerine bird species switch from diets of mostly invertebrates in the spring and summer to diets that include fruit and seeds in the fall and winter. However, relatively few studies have quantified diet composition or the extent of seasonal shifts during the non-breeding period, particularly among species and across communities with both residents and migrants. We measured carbon and nitrogen stable isotope values in food items (fruits, C3 and C4 seeds, and insects from various trophic levels and plant communities) and in multiple tissues (feathers and plasma/whole blood) from 11 species of songbirds wintering in the southeastern U.S. We combined these diet and tissue values with empirically derived discrimination factors and used concentration-dependent mixing models to quantify seasonal diet shifts. We also validated mixing model results with data from fecal samples. Diets in this bird community, as delineated N and C isotopic space, diverged in the fall and winter relative to the summer as consumption of fruits and seeds increased. Across this songbird community, estimated contributions of fruit to plasma/whole blood increased from 16.2 ± 7.5% in the fall (mean ± SD; range: 4–26%) to 21.7 ± 10.3% (range: 9–37%) in the winter, while contributions of seeds increased from 29.4 ± 2.6% (range: 28–32%) in the fall to 36.6 ± 4.8% (range: 32–42%) in the winter. Fecal data showed qualitatively similar trends to mixing models, but consistently estimated higher contributions of fruit. Our work indicates that fruits and seeds constitute substantial sources of sustenance for non-breeding songbirds, there is considerable separation of resource use among species in the fall and winter, and fecal estimates of contributions to songbird tissues should be interpreted cautiously.
Savannah River Stemmed (312a587)
**Savannah River Stemmed spear point** Location: Doerschuk site (31Mg22), Montgomery County, North Carolina. Period: Late Archaic (3000-1000 BC). Material: metavolcanic rock. Dimensions: length, 103.3 mm; width, 34.9 mm; thickness, 14.3 mm. Notes: Catalog no. 312a587, North Carolina Archaeological Collection, Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. Illustrated in *The Formative Cultures of the Carolina Piedmont,* by Joffre L. Coe, Transactions of the American Philosophical Society vol. 54, pt. 5, 1964, Figure 38. Model by Abigail Gancz and Steve Davis. Source: Objaverse 1.0 / Sketchfab
Savannah River Stemmed (301a86-2)
**Savannah River Stemmed spear point** Location: Doerschuk site (31Mg22), Montgomery County, North Carolina. Period: Late Archaic (3000-1000 BC). Material: metavolcanic rock. Dimensions: length, 94.8 mm; width, 46.4 mm; thickness, 11.8 mm. Notes: Catalog no. 301a86-2, North Carolina Archaeological Collection, Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. Illustrated in *The Formative Cultures of the Carolina Piedmont,* by Joffre L. Coe, Transactions of the American Philosophical Society vol. 54, pt. 5, 1964, Figure 38. Model by Abigail Gancz and Steve Davis. Source: Objaverse 1.0 / Sketchfab
Data from: Spatial transitions in tree cover are associated with soil hydrology, but not with grass biomass, fire frequency, or herbivore biomass in Serengeti savannahs
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Data from: The burning question: does fire affect habitat selection and forage preference of the black rhinoceros Diceros bicornis in East African savannahs?
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Data from: Passive acoustic monitoring provides reliable under-estimates of population size and longevity in wild Savannah Sparrows
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Abandoned pastures and restored savannahs have distinct patterns of plant-soil feedback and nutrient cycling compared with native Brazilian savannahs.
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Savannah River NERP songbird tissue, insect, and fruit isotope database
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Development and validation of an environmental fragility index (EFI) for the neotropical savannah biome. Supplementary Material 2.
<p>Supplementary Material 2: scatterplots of lrbs vs index component variables</p>
Data from: Strong population genetic structuring in an annual fish, Nothobranchius furzeri, suggests multiple savannah refugia in southern Mozambique
Background: Intraspecific genetic variation of African fauna has been signific antly affected by pronounced climatic fluctuations in Plio-Pleistocene, but, with the exception of large mammals, very limited empirical data on diversity of natural populations are available for savanna-dwelling animals. Nothobranchius furzeri is an annual fish from south-eastern Africa, inhabiting discrete temporary savannah pools outside main river alluvia. Their dispersal is limited and population processes affecting its genetic structure are likely a combination of those affecting terrestrial and aquatic taxa. N. furzeri is a model taxon in ageing research and several populations of known geographical origin are used in laboratory studies. Here, we analysed the genetic structure, diversity, historical demography and temporal patterns of divergence in natural populations of N. furzeri across its entire distribution range. Results: Genetic structure and historical demography of N. furzeri were analysed using a combination of mitochondrial (partial cytochrome b sequences, 687 bp) and nuclear (13 microsatellites) markers in 693 fish from 36 populations. Genetic markers consistently demonstrated strong population structuring and suggested two main genetic groups associated with river basins. The split was dated to the Pliocene (>2 Mya). The northern group inhabits savannah pools across the basin of the intermittent river Chefu in south-western Mozambique and eastern Zimbabwe. The southern group (from southernmost Mozambique) is subdivided, with the River Limpopo forming a barrier (maximum divergence time 1 Mya). A strong habitat fragmentation (isolated temporary pools) is reflected in significant genetic structuring even between adjacent pools, with a major influence of genetic drift and significant isolation-by-distance. Analysis of historical demography revealed that the expansion of both groups is ongoing, supported by frequent founder effects in marginal parts of the range and evidence of secondary contact between Chefu and Limpopo populations. Conclusions: We demonstrated: (1) ancient (pre-Pleistocene) divergence between the two main N. furzeri lineages, their recent secondary contact and lack of reproductive isolation; (2) important genetic structuring attributed to the fragmented nature of their environment and isolation-by-distance, suggesting that dispersal is limited, occurs over short distances and is not directly associated with river routes; (3) an apparent role of the River Limpopo as a barrier to dispersal and gene flow.
Data from: Synergistic effects of fire and elephants on arboreal animals in an African savannah
1. Disturbance is a crucial determinant of animal abundance, distribution and community structure in many ecosystems, but the ways in which multiple disturbance types interact remain poorly understood. The effects of multiple-disturbance interactions can be additive, subadditive or super-additive (synergistic). Synergistic effects in particular can accelerate ecological change; thus, characterizing such synergies, the conditions under which they arise, and how long they persist has been identified as a major goal of ecology. 2. We factorially manipulated two principal sources of disturbance in African savannas, fire and elephants, and measured their independent and interactive effects on the numerically dominant vertebrate (the arboreal gekkonid lizard Lygodactylus keniensis) and invertebrate (a guild of symbiotic Acacia ants) animal species in a semi-arid Kenyan savanna. 3. Elephant exclusion alone (minus fire) had negligible effects on gecko density. Fire alone (minus elephants) had negligible effects on gecko density after 4 months, but increased gecko density twofold after 16 months, likely because the decay of fire-damaged woody biomass created refuges and nest sites for geckos. In the presence of elephants, fire increased gecko density nearly threefold within 4 months of the experimental burn; this occurred because fire increased the incidence of elephant damage to trees, which in turn improved microhabitat quality for geckos. However, this synergistic positive effect of fire and elephants attenuated over the ensuing year, such that only the main effect of fire was evident after 16 months. 4. Fire also altered the structure of symbiotic plant-ant assemblages occupying the dominant tree species (Acacia drepanolobium); this influenced gecko habitat selection but did not explain the synergistic effect of fire and elephants. However, fire-driven shifts in plant-ant occupancy may have indirectly mediated this effect by increasing trees' susceptibility to elephant damage. 5. Our findings confirm the importance of fire × elephant interactions in structuring arboreal wildlife populations. Where habitat modification by megaherbivores facilitates co-occurring species, fire may amplify these effects in the short term by increasing the frequency or intensity of herbivory, leading to synergy. In the longer term, tree mortality due to both top kill by fire and toppling by large herbivores may reduce overall microhabitat availability, eliminating the synergy.
Data from: Geographic population structure of the African malaria vector Anopheles gambiae suggests a role for the forest-savannah biome transition as a barrier to gene flow
The primary Afrotropical malaria mosquito vector Anopheles gambiae sensu stricto has a complex population structure. In western Africa, this species is split into two molecular forms and displays local and regional variation in chromosomal arrangements and behaviours. To investigate patterns of macro-geographic population substructure, 25 An. gambiae samples from 12 African countries were genotyped at 13 microsatellite loci. This analysis detected the presence of additional population structuring, with the M-form being subdivided into distinct west, central and southern African genetic clusters. These clusters are coincident with the central African rainforest belt and northern and southern savannah biomes, which suggests restrictions to gene flow associated with the transition between these biomes. By contrast geographically patterned population substructure appears much weaker within the S-form.
Data from: The roles of joint tissues and jaw muscles in palatal biomechanics of the Savannah monitor (Varanus exanthematicus) and their significance for cranial kinesis
Many vertebrates exhibit cranial kinesis, or movement between bones of the skull other than at the jaw joint. Many kinetic species possess a particular suite of features to accomplish this movement, including flexible cranial joints and protractor musculature. Whereas the skeletal anatomy of these kinetic systems is well understood, how these joints are biomechanically loaded, how different soft tissues affect joint loading and kinetic capacity, and how the protractor musculature loads the skull remain poorly understood. Here we developed a Finite Element Model of the savannah monitor, Varanus exanthematicus, a modestly kinetic lizard, to better elucidate the roles of soft tissue in mobile joints and protractor musculature on cranial loading. We described the 3D resultants of jaw muscles and histology of palatobasal, otic and jaw joints. We tested the effects of joint tissue types, bite point, and muscle loads to evaluate the biomechanical role of muscles have on the palate and braincase. We found the jaw muscles have significant mediolateral components and resultants that can impart stability across palatocranial joints. We found articular tissues affect the magnitude of strains experienced across the palatobasal and otic joints. We found that without protractor muscle loading, the palate, quadrate and braincase experience higher strains suggesting this muscle helps insulate the braincase and palatoquadrate from high loads. Finally, we found the cross-sectional properties of the bones of Varanus exanthematicus is well suited for performing under torsional loads. These findings suggest that torsion may be a significant driver in the evolution of cranial kinesis in lepidosaurs.
Data from: The future distribution of the savannah biome: model-based and biogeographic contingency
The extent of the savanna biome is expected to be profoundly altered by climatic change and increasing atmospheric CO2 concentrations. Contrasting projections are given when using different modelling approaches to estimate future distributions. Furthermore, biogeographic variation within savannas in plant function and structure is expected to lead to divergent responses to global change. Hence the use of a single model with a single savanna tree type will likely lead to biased projections. Here we compare and contrast projections of South American, African, and Australian savanna distributions from a physiologically-based statistical distribution model - the Thornley transport resistance model (TTR-SDM) - and three versions of a dynamic vegetation model (DVM) designed and parameterized separately for specific continents. We show that attempting to extrapolate any continent-specific model globally biases projections. By 2070 all DVMs generally project a decrease in the extent of savannas at their boundary with forests, whereas the TTR-SDM projects a decrease in savannas at their boundary with aridlands and grasslands. This difference is driven by forest and woodland expansion in response to rising atmospheric CO2 concentrations in DVMs, unaccounted for by the TTR-SDM. We suggest that the most suitable models of the savanna biome for future development are individual-based dynamic vegetation models designed for specific biogeographic regions.
Data from: Rapid plastic breeding response to rain matches peak prey abundance in a tropical savannah bird
1. Changes in climate are shifting the timing of life cycle events in the natural world. Compared to northern-temperate areas, these effects are relatively poorly understood in tropical and southern regions, where there is limited information on how timing of breeding and food availability are affected by climatic factors, and where patterns of breeding activity are more unpredictable within and between years. 2. Combining a new statistical modelling approach with 5 years of continuous individual-based monitoring of a monsoonal tropical insectivorous bird, we quantified (i) the proximate climatic drivers at two trophic levels: timing of breeding and abundance of arthropod prey; (ii) the effect of climate variation on reproductive output and (iii) the role of individual plasticity. 3. Rainfall was identified as the main determinant of phenology at both trophic levels. Throughout the year, likelihood of egg laying increased very rapidly in response to even small amounts of rain during the preceding 0-3 weeks. Adult body mass and male sperm storage also increased rapidly after rain, suggesting high breeding preparedness. Additionally, females were flexible, since they were more likely to nest if their previous attempt was longer ago and unsuccessful. Arthropod abundance also increased after rainfall, but more slowly, with a peak around 10 weeks. Therefore, the peak food availability coincided with the presence of dependent fledglings. 4. Fitness benefits of nesting after more rain appeared to be linked to offspring quantity rather than quality: nest attempts following higher rainfall produced larger clutches, but showed no improvement in nestling mass or relative fledging success. The response of clutch size to rainfall was plastic, since repeated sampling showed that individual females laid larger clutches after more rain, possibly mediated by improved body mass. 5. Rapid, individually flexible breeding in response to rainfall and slower increase in arthropod abundance also as a response to rainfall, might buffer insectivorous species living in tropical seasonal environments from climate-change induced phenological trophic mismatches.
Data from: Mechanisms of plant–plant interactions: concealment from herbivores is more important than abiotic-stress mediation in an African savannah
Recent work on facilitative plant–plant interactions has emphasized the importance of neighbours' amelioration of abiotic stress, but the facilitative effects of neighbours in reducing plant apparency to herbivores have received less attention. Whereas theory on stress reduction predicts that competition should be more important in less stressful conditions, with facilitation becoming more important in harsh environments, apparency theory suggests that facilitation should be greater in the presence of herbivores, where it is disadvantageous to be conspicuous regardless of abiotic stress level. We tested the relative strength of neighbours' stress reduction versus apparency reduction on survival, growth, reproduction and lifetime fitness of Hibiscus meyeri, a common forb in central Kenya, using neighbour removals conducted inside and outside large-herbivore exclosures replicated in arid and mesic sites. In the absence of herbivores, neighbours competed with H. meyeri in mesic areas and facilitated H. meyeri in arid areas, as predicted by stress-reduction mechanisms. By contrast, neighbours facilitated H. meyeri in the presence of herbivory, regardless of aridity level, consistent with plant apparency. Our results show that the facilitative effects arising from plant apparency are stronger than the effects arising from abiotic stress reduction in this system, suggesting that plant-apparency effects may be particularly important in systems with extant large-herbivore communities.
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Allen Brain Atlas
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OpenNeuro
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