Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 547
Filtrar
1.
Environ Monit Assess ; 196(11): 1048, 2024 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-39395067

RESUMO

Integrated pest management (IPM) is a sustainable approach for minimizing the negative impacts of pests on crops while reducing reliance on synthetic pesticides. This study was conducted in Kwara State Nigeria in 2023, to investigate the effects of implementation of IPM practices on the occurrence of pesticide residues in okra cultivated by the farmers in Kwara State, Nigeria, and identify the factors affecting the use of IPM practices for pest control in okra production. A sample of 245 okra farmers was selected across 4 agricultural zones of Kwara State using a multistage sampling technique. Additionally, okra samples were collected from the farmers of each community of the local government areas. The data collected from the farmers were analyzed using descriptive and inferential statistics including frequency count, percentage, mean, standard deviation, and Pearson product moment correlation (PPMC). The collected okra samples were taken to the laboratory for pesticide residue extraction and analysis was performed using gas chromatography (GC)-mass spectrometer (MS). The results showed that most okra producers in Kwara State were smallholder farmers who, despite practicing IPM, had limited knowledge of the technology. Some pesticide residues were detected in okra, out of which two were present in quantities above the maximum residue limit, while others were below the maximum residue limit. Therefore, this study recommends that the government should improve extension services in the State by providing adequate funds and training extension agents who can provide comprehensive training to farmers on the types and application of IPM as an eco-friendly technology for preventing pesticide residue in okra.


Assuntos
Abelmoschus , Agricultura , Fazendeiros , Controle de Pragas , Resíduos de Praguicidas , Controle de Pragas/métodos , Nigéria , Abelmoschus/química , Resíduos de Praguicidas/análise , Agricultura/métodos , Monitoramento Ambiental , Produtos Agrícolas
2.
Environ Entomol ; 2024 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-39418123

RESUMO

Termite mounds are a ubiquitous feature of savanna ecosystems, yet the mechanisms by which termites (Blattodea: Termitoidae) mitigate the challenges posed by seasonal drought and flooding through mound construction remain insufficiently explored. This study investigates the material properties, water retention capabilities, and resistance to raindrop penetration across three distinct layers of Globitermes sulphureus (Haviland, 1898) (Blattodea: Termitidae) nests. Our findings reveal a pronounced diversification and specialization of materials and functions across these layers. Specifically, the outer layer has decreased moisture permeability, the middle layer has enhanced resistance to water penetration, and the innermost layer has a high capacity for water retention. The integration of these functionally specialized layers provides a compelling evidence for explaining how these termites are able to adapt to the fluctuating environmental conditions characteristic of savanna ecosystems. Furthermore, this highlights the nest's buffering capability against environmental stressors. The complexity of this construction, marked by a level of self-organization rarely observed in the animal kingdom, underscores a significant instance of architectural ingenuity among non-human builders.

3.
Proc Biol Sci ; 291(2033): 20241120, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39471853

RESUMO

Forest expansion into savanna is a pervasive phenomenon in West and Central Africa, warranting comparative studies under diverse environmental conditions. We collected vegetation data from the woody and grassy components within 73 plots of 0.16 ha distributed along a successional gradient from humid savanna to forest in Central Africa. We associated spatially collocated edaphic parameters and fire frequency derived from remote sensing to investigate their combined influence on the vegetation. Soil texture was more influential in shaping savanna structure and species distribution than soil fertility, with clay-rich soils promoting higher grass productivity and fire frequency. Savanna featuring woody aboveground biomass surpassing 40 Mg ha-1 could escape the grass-fire feedback loop, by depressing grass biomass below 4 Mg ha-1. This thicker woody layer also favoured the establishment of fire-tolerant forest pioneers, which synergically contributed to the expansion of forests. Conversely, savannas below this fire suppression threshold sustained a balance between trees and grasses through the grass-fire feedback mechanism. This hysteresis loop, particularly pronounced on clayey soils, suggests that the contrast between grassy savanna and young forests might represent alternative ecosystem states, although savannas with low woody biomass remained vulnerable to forest edge encroachment.


Assuntos
Florestas , Pradaria , Solo , Solo/química , África Central , Árvores , Biomassa , Poaceae/fisiologia , Incêndios , Ecossistema
4.
Ann Bot ; 2024 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-39383257

RESUMO

BACKGROUND AND AIMS: Anthropogenic disturbances are causing a co-occurring increase in biotic (ungulate herbivory) and abiotic (drought) stressors, threatening plant reproduction in oak-dominated ecosystems. However, we wonder whether herbivory could compensate for the adverse impact of drought by reducing evapotranspiration. Thus, we investigate the isolated and joint effects of herbivory and drought on oak seedlings of two contrasting Mediterranean species that differ in leaf habit and drought resistance. METHODS: California oak seedlings from the evergreen, and more drought-resistant, Quercus agrifolia and the deciduous Q. lobata (n=387) were assigned to a fully crossed factorial design with herbivory and drought as stress factors. Seedlings were assigned in a greenhouse to 3-4 clipping levels simulating herbivory and 3-4 watering levels, depending on the species. We measured survival, growth, and leaf attributes (chlorophyll, secondary metabolites, leaf area and weight) once a month (May-Sep) and harvested above- and below-ground biomass at the end of the growing season. KEY RESULTS: For both oak species, simulated herbivory enhanced seedling survival during severe drought or delayed its adverse effects, probably due to reduced transpiration resulting from herbivory-induced leaf area reduction and compensatory root growth. Seedlings from the deciduous, and less drought-resistant species, benefitted from herbivory at lower levels of water stress, suggesting different response across species. We also found complex interactions between herbivory and drought on their impact on leaf attributes. In contrast to chlorophyll content which was not affected by herbivory, anthocyanins increased with herbivory - although water stress reduced differences in anthocyanins due to herbivory. CONCLUSIONS: Herbivory seems to facilitate Mediterranean oak seedlings to withstand summer drought, potentially alleviating a key bottleneck in the oak recruitment process. Our study highlights the need to consider ontogenetic stages and species-specific traits in understanding complex relationships between herbivory and drought stressors for the persistence and restoration of multi-species oak savannas.

5.
PhytoKeys ; 246: 265-276, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39319030

RESUMO

Tapinavillosa (Gesneriaceae) was published by George Gardner in 1842, based on material he collected in Serra de Natividade (Tocantins, Brazil) in 1840. The species is now recognized as Goyaziavillosa (Gardner) R.A. Howard. Since Gardner's travels in Central Brazil, this species had not been collected again and the taxon was considered as possibly extinct. After a long time, we report the discovery of two new populations of G.villosa in the municipality of Palmas and in the Estação Ecológica Serra Geral do Tocantins, ca. 200 and 100 km north of the Serra de Natividade, respectively. The newly collected materials allow us to better characterize the morphology and infer the phylogenetic placement of this poorly-known species. Here we demonstrate that G.villosa is closely related to G.rupicola in a clade including Goyazia and Mandirola species, and provide an updated description of the species, including field images, photographic plate, information on its distribution and habitat, and a taxonomic key for the species of Goyazia.

6.
Sci Rep ; 14(1): 22261, 2024 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-39333645

RESUMO

The hand is a versatile structure that performs numerous tasks, ranging from exertion of great force such as grip, pinch and torque to execution of precise fine motor skills. The aim of current study was to undertake a preliminary study on hand dimensions as potential predictors of female populations native to the forest and savanna zones of Ghana. A total of one hundred (100) female students aged between 17 and 24 years were recruited into this study, comprising of 53 native to the forest zone and 47 native to savanna zone of Ghana between 12th June to 27th July, 2023 at the Department of Anatomy, School of Medicine and Dentistry, Kwame Nkrumah University of Science and Technology. Statistically significant positive correlation was observed between left hand length and right hand length (R = 0.923, p = 0.000). From the binary regression model, it could be speculated that left-hand breadth could predict female populations native to the savanna zone (LHB: ß = - 2.37, Expß = 0.09, p = 0.014). However, right-hand breadth and length and left hand length did not show any potential of prediction (RHB: ß = 0.900, Expß = 2.460, p = 0.410; RHL: ß = 0.168, Expß = 1.683, p = 0.803; LHL: ß = - 0.300, Expß = 0.741, p = 0.656). The study therefore may speculate that left handbreadth could have the potential to differentiate female populations native to savanna zone from females native to forest zone in Ghana.


Assuntos
Florestas , Pradaria , Mãos , Humanos , Feminino , Gana , Adulto Jovem , Mãos/anatomia & histologia , Mãos/fisiologia , Adolescente , Adulto
7.
Glob Chang Biol ; 30(9): e17509, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39323398

RESUMO

Monitoring the changes of ecosystem functioning is pivotal for understanding the global carbon cycle. Despite its size and contribution to the global carbon cycle, Africa is largely understudied in regard to ongoing changes of its ecosystem functioning and their responses to climate change. One of the reasons is the lack of long-term in situ data. Here, we use eddy covariance to quantify the net ecosystem exchange (NEE) and its components-gross primary production (GPP) and ecosystem respiration (Reco) for years 2010-2022 for a Sahelian semiarid savanna to study trends in the fluxes. Significant negative trends were found for NEE (12.7 ± 2.8 g C m2 year-1), GPP (39.6 ± 7.9 g C m2 year-1), and Reco (32.2 ± 8.9 g C m2 year-1). We found that NEE decreased by 60% over the study period, and this decrease was mainly caused by stronger negative trends in rainy season GPP than in Reco. Additionally, we observed strong increasing trends in vapor pressure deficit, but no trends in rainfall or soil water content. Thus, a proposed explanation for the decrease in carbon sink strength is increasing atmospheric dryness. The warming climate in the Sahel, coupled with increasing evaporative demand, may thus lead to decreased GPP levels across this biome, and lowering its CO2 sequestration.


Assuntos
Sequestro de Carbono , Mudança Climática , Pradaria , Estações do Ano , Ciclo do Carbono , Solo/química , Chuva
8.
Ecol Appl ; 34(7): e3025, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39166511

RESUMO

Fire is a powerful tool for conservation management at a landscape scale, but a rigorous evidence base is often lacking for understanding its impacts on biodiversity in different biomes. Fire-induced changes to habitat openness have been identified as an underlying driver of responses of faunal communities, including for ants. However, most studies of the impacts of fire on ant communities consider only epigeic (foraging on the soil surface) species, which may not reflect the responses of species inhabiting other vertical strata. Here, we examine how the responses of ant communities vary among vertical strata in a highly fire-prone biome. We use a long-term field experiment to quantify the effects of fire on the abundance, richness, and composition of ant assemblages of four vertical strata (subterranean, leaf litter, epigeic, and arboreal) in an Australian tropical savanna. We first document the extent to which each stratum harbors distinct assemblages. We then assess how the assemblage of each stratum responds to three fire-related predictors: fire frequency, fire activity, and vegetation cover. Each stratum harbored a distinct ant assemblage and showed different responses to fire. Leaf litter and epigeic ants were most sensitive to fire because it directly affects their microhabitats, but they showed contrasting negative and positive responses, respectively. Subterranean ants were the least sensitive because of the insulating effects of soil. Our results show that co-occurring species of the same taxonomic group differ in the strength and direction of their response to fire depending on the stratum they inhabit. As such, effective fire management for biodiversity conservation should consider species in all vertical strata.


Assuntos
Formigas , Incêndios , Formigas/fisiologia , Animais , Biodiversidade
9.
Mov Ecol ; 12(1): 57, 2024 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-39187857

RESUMO

BACKGROUND: Animal movement arises from complex interactions between animals and their heterogeneous environment. To better understand the movement process, it can be divided into behavioural, temporal and spatial components. Although methods exist to address those various components, it remains challenging to integrate them in a single movement analysis. METHODS: We present an analytic workflow that integrates the behavioural, temporal and spatial components of the movement process and their interactions, which also allows for the assessment of the relative importance of those components. We construct a daily cyclic covariate to represent temporally cyclic movement patterns, such as diel variation in activity, and combine the three components in a multi-modal Hidden Markov Model framework using existing methods and R functions. We compare the trends and statistical fits of models that include or exclude any of the behavioural, spatial and temporal components, and perform variance partitioning on the model predictions that included all components to assess their relative importance to the movement process, both in isolation and in interaction. RESULTS: We apply our workflow to a case study on the movements of plains zebra, blue wildebeest and eland antelope in a South African reserve. Behavioural modes impacted movement the most, followed by diel rhythms and then the spatial environment (viz. tree cover and terrain slope). Interactions between the components often explained more of the movement variation than the marginal effect of the spatial environment did on its own. Omitting components from the analysis led either to the inability to detect relationships between input and response variables, resulting in overgeneralisations when drawing conclusions about the movement process, or to detections of questionable relationships that appeared to be spurious. CONCLUSIONS: Our analytic workflow can be used to integrate the behavioural, temporal and spatial components of the movement process and quantify their relative contributions, thereby preventing incomplete or overly generic ecological interpretations. We demonstrate that understanding the drivers of animal movement, and ultimately the ecological phenomena that emerge from it, critically depends on considering the various components of the movement process, and especially the interactions between them.

10.
Interface Focus ; 14(4): 20230078, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39165392

RESUMO

Anthropogenic activities around local villages in mesic savanna landscapes of West Africa have resulted in soil improvement and forest establishment outside their climatic zones. Such unique 'forest islands' have been reported to provide ecosystem services including biodiversity conservation. However, the science underpinning their formations is limitedly studied. In 2015 and with funding support from the Royal Society-DFID (now FCDO), we set out to investigate the biogeochemistry of the forest islands in comparison with adjacent natural savanna and farmlands across 11 locations in Burkina Faso, Ghana and Nigeria. Our results showed that the forest islands do not differ significantly from the adjoining ecosystems in soil mineralogy implying that their formation was anthropogenically driven. We observed greater soil organic carbon and nutrient distributions in the forest islands, which also had more stable macro (>500 µm) and meso-aggregates (500-250 µm) than the adjoining agricultural lands. We found that soil micro-aggregate (250-53 µm) stability was climate (precipitation) driven in the West African ecosystems while meso- and macro-aggregate stability was land-use driven. In one of the unique forest islands we studied in the Mole National Park of Ghana, we found its mineral-associated organic carbon over 40% greater than the adjoining natural savanna with potential implications for the achievement of the global initiative of the '4p1000' in West Africa. We conclude that the North-South-South research collaboration has established clearly, the science underlying the age-long West African forest island phenomenon and has, among many successes, led to capacity building of young scientists driving cutting-edge research in climate change adaptation and food systems transformation in the sub-region.

11.
J Environ Manage ; 365: 121576, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38955045

RESUMO

Savannas and grasslands have lost almost 50% of their original cover worldwide. Therefore, the development of methods and information on open-canopy ecosystem restoration is urgent for the inclusion of these ecosystems into global and regional priorities. In the Brazilian savanna, the most diverse savanna in the world, restoration efforts focused on open ecosystems have been virtually absent, but have increased in the last 10 years. Such efforts are frequently threatened by invasive exotic grasses (IEG) that invade and dominate areas excluding native species, oftentimes aided by altered soil conditions. Long-term studies of savanna restoration trajectories are rare. In this study, we surveyed 22 savanna restoration areas established two to ten years before the study with similar restoration methods to assess their current status. We show that the current restoration methods are successful in establishing native species and allowing species turnover but they are threatened by IEG. Restoration success varies and is affected by soil conditions, IEG landscape cover and post-sowing weeding. Despite that, the simultaneous introduction of different plant functional groups allows turnover from fast to slow-growing plants. Establishing savanna native species is possible at an operational scale with current knowledge and techniques. However, native species establishment fails to prevent IEG reinfestation, which needs to be managed in restoration efforts in the Brazilian savanna.


Assuntos
Conservação dos Recursos Naturais , Pradaria , Brasil , Poaceae/crescimento & desenvolvimento , Ecossistema , Espécies Introduzidas
12.
New Phytol ; 243(5): 1660-1669, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38982706

RESUMO

Ecologists are being challenged to predict how ecosystems will respond to climate changes. According to the Multi-Colored World (MCW) hypothesis, climate impacts may not manifest because consumers such as fire and herbivory can override the influence of climate on ecosystem state. One MCW interpretation is that climate determinism fails because alternative ecosystem states (AES) are possible at some locations in climate space. We evaluated theoretical and empirical evidence for the proposition that forest and savanna are AES in Africa. We found that maps which infer where AES zones are located were contradictory. Moreover, data from longitudinal and experimental studies provide inconclusive evidence for AES. That is, although the forest-savanna AES proposition is theoretically sound, the existing evidence is not yet convincing. We conclude by making the case that the AES proposition has such fundamental consequences for designing management actions to mitigate and adapt to climate change in the savanna-forest domain that it needs a more robust evidence base before it is used to prescribe management actions.


Assuntos
Florestas , Pradaria , África , Mudança Climática , Ecossistema
13.
Am J Biol Anthropol ; 185(3): e25007, 2024 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-39056239

RESUMO

OBJECTIVES: Many early fossil hominins are associated with savanna-mosaic paleohabitats, and high sexual dimorphism that may reflect differences in positional behavior between sexes. However, reconstructions of hominin behavior and the selective pressures they faced in an open habitat are limited by a lack of studies of extant apes living in contemporary, analogous habitats. Here, we describe adult chimpanzee positional behavior in the savanna-mosaic habitat of the Issa Valley, Tanzania, to test whether Issa chimpanzees show larger sex-differences in positional behavior than their forest-dwelling counterparts. MATERIALS AND METHODS: We quantified and compared adult locomotor and postural behavior across sexes (6 females, 7 males) in the riparian forest (closed) and miombo woodland (open) vegetation types at Issa Valley (13,743 focal observations). We then compared our results to published data of chimpanzee communities living in more forested habitats. RESULTS: Issa females and males both spent less time arboreally in open vegetation and showed similar locomotor and postural behavior on the same substrates, notably using a high level of suspensory locomotion when arboreal. Females were, however, more arboreal than males during locomotor behavior, as well as compared with females from other communities. Issa males behaved similarly to males from other communities. CONCLUSION: Results suggest that open habitats do not elicit less arboreal behaviors in either sex, and may even select for suspensory locomotion to effectively navigate an open canopy. An open habitat may, however, increase sex differences in positional behavior by driving female arboreality. We suggest this is because of higher energetic demands and predator pressures associated with open vegetation, which are likely exaggerated for reproducing females. These results have implications for the interpretation of how sexual dimorphism may influence reconstructions of hominin positional behavior.


Assuntos
Ecossistema , Locomoção , Pan troglodytes , Caracteres Sexuais , Animais , Pan troglodytes/fisiologia , Feminino , Tanzânia , Masculino , Locomoção/fisiologia , Postura/fisiologia , Comportamento Animal/fisiologia , Florestas , Antropologia Física
14.
AoB Plants ; 16(3): plae032, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38883565

RESUMO

Forest and landscape restoration is one of the main strategies for overcoming the environmental crisis. This activity is particularly relevant for biodiversity-rich areas threatened by deforestation, such as tropical forests. Efficient long-term restoration requires understanding the composition and genetic structure of native populations, as well as the factors that influence these genetic components. This is because these populations serve as the seed sources and, therefore, the gene reservoirs for areas under restoration. In the present study, we investigated the influence of environmental, climatic and spatial distance factors on the genetic patterns of Plathymenia reticulata, aiming to support seed translocation strategies for restoration areas. We collected plant samples from nine populations of P. reticulata in the state of Bahia, Brazil, located in areas of Atlantic Forest and Savanna, across four climatic types, and genotyped them using nine nuclear and three chloroplast microsatellite markers. The populations of P. reticulata evaluated generally showed low to moderate genotypic variability and low haplotypic diversity. The populations within the Savanna phytophysiognomy showed values above average for six of the eight evaluated genetic diversity parameters. Using this classification based on phytophysiognomy demonstrated a high predictive power for genetic differentiation in P. reticulata. Furthermore, the interplay of climate, soil and geographic distance influenced the spread of alleles across the landscape. Based on our findings, we propose seed translocation, taking into account the biome, with restricted use of seed sources acquired or collected from the same environment as the areas to be restored (Savanna or Atlantic Forest).

15.
Glob Chang Biol ; 30(6): e17340, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38840515

RESUMO

Grassy ecosystems cover more than 40% of the world's terrestrial surface, supporting crucial ecosystem services and unique biodiversity. These ecosystems have experienced major losses from conversion to agriculture with the remaining fragments threatened by global change. Woody plant encroachment, the increase in woody cover threatening grassy ecosystems, is a major global change symptom, shifting the composition, structure, and function of plant communities with concomitant effects on all biodiversity. To identify generalisable impacts of encroachment on biodiversity, we urgently need broad-scale studies on how species respond to woody cover change. Here, we make use of bird atlas, woody cover change data (between 2007 and 2016) and species traits, to assess: (1) population trends and woody cover responses using dynamic occupancy models; (2) how outcomes relate to habitat, diet and nesting traits; and (3) predictions of future occupancy trends, for 191 abundant, southern African bird species. We found that: (1) 63% (121) of species showed a decline in occupancy, with 18% (34) of species' declines correlated with increasing woody cover (i.e. losers). Only 2% (4) of species showed increasing population trends linked with increased woody cover (i.e. winners); (2) Open habitat specialist, invertivorous, ground nesting birds were the most frequent losers, however, we found no definitive evidence that the selected traits could predict outcomes; and (3) We predict open habitat loser species will take on average 52 years to experience 50% population declines with current rates of encroachment. Our results bring attention to concerning region-wide declining bird population trends and highlight woody plant encroachment as an important driver of bird population dynamics. Importantly, these findings should encourage improved management and restoration of our remaining grassy ecosystems. Furthermore, our findings show the importance of lands beyond protected areas for biodiversity, and the urgent need to mitigate the impacts of woody plant encroachment on bird biodiversity.


Assuntos
Biodiversidade , Aves , Ecossistema , Dinâmica Populacional , Animais , Aves/fisiologia , Conservação dos Recursos Naturais , África do Sul
16.
Animals (Basel) ; 14(11)2024 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-38891624

RESUMO

We explored the ecological and historical factors that led to formation of the unique guild of native and introduced mammalian herbivores between 5 and 1000 kg in northern Australia. Following the disappearance of large native herbivores about 46 kya, and until the arrival of Europeans and their livestock, the only herbivorous mammals were mid-sized endemic marsupial macropods, which continued to utilise the same vegetation as their much larger former neighbours. Only one species of contemporary native herbivore has an adult bodyweight approaching 100 kg, and for the past 150-200 years, the total biomass of introduced domestic and wild vertebrate herbivores has massively exceeded that of native herbivorous species. We conclude that the current guild of native and introduced mammalian herbivores differentially utilises the landscape ecologically. However, climate- and anthropogenically related changes due to fire, drought, flooding, predation and introduced weeds are likely to have significant impacts on the trajectory of their relative ecological roles and populations. Given their differing ecological and dietary characteristics, against this backdrop, it is unclear what the potential impact of the dispersal of deer species could have in northern Australia. We hence focus on whether sufficient knowledge exists against which the potential impacts of the range expansion of three deer species can be adequately assessed and have found a dearth of supporting evidence to inform appropriate sustainable management. We identify suitable research required to fill the identified knowledge gaps.

17.
Plant Biol (Stuttg) ; 2024 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-38940062

RESUMO

In fire-prone ecosystems, plant traits are influenced by the fire regime, thus reproduction and establishment can be altered by this disturbance. Changes in fire frequency and history can therefore influence seed and germination traits. We investigated the effects of short-term fire exclusion on seed and germination traits of species from tropical open savannas. Seeds from 27 species were collected from two areas with distinct fire histories: recently and frequently burned (RB) or unburned for 5 to 7 years (E). Seeds from both areas underwent germination trials under optimal conditions for 30 days. Also, 10 species were exposed to high temperature treatments (100 or 200 °C) and seed and germination traits measured. Comparisons were then made for each trait, analysing each species separately, between the two areas. Approximately 85% of species studied had at least one of their germination traits altered in the RB area compared to the E area. Clear differences included lower viability and faster germination in seeds from RB areas. Seed traits of 70% of measured species differed between the two areas. Our results show species-specific trait response to different fire histories. For example, faster germination and lower viability of seeds from RB plots suggest selection for faster maturing individuals and differences in resourcing, respectively, under a regime of frequent fire. This study provides insights into fire effects on regeneration responses of tropical savanna species and also points to the need for more studies evaluating the effects of fire history on seed traits.

18.
Ecol Lett ; 27(6): e14450, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38857323

RESUMO

Fire and herbivory interact to alter ecosystems and carbon cycling. In savannas, herbivores can reduce fire activity by removing grass biomass, but the size of these effects and what regulates them remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density. We show that, broadly across African savannas, grazing herbivores substantially reduce both herbaceous biomass and fire activity. The size of these effects was strongly associated with grazing herbivore densities, and surprisingly, was mostly consistent across different environments. A one-zebra increase in herbivore biomass density (~100 kg/km2 of metabolic biomass) resulted in a ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage point reduction in burned area. Our results indicate that fire models can be improved by incorporating grazing effects on grass biomass.


Assuntos
Biomassa , Incêndios , Pradaria , Herbivoria , Animais , Poaceae/fisiologia , África
19.
Oecologia ; 205(2): 411-422, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38898337

RESUMO

The interplay of positive and negative species interactions controls species assembly in communities. Dryland plant communities, such as savannas, are important to global biodiversity and ecosystem functioning. Sandhill oaks in xeric savannas of the southeastern United States can facilitate longleaf pine by enhancing seedling survival, but the effects of oaks on recruitment and growth of longleaf pine have not been examined. We censused, mapped, and monitored nine contiguous hectares of longleaf pine in a xeric savanna to quantify oak-pine facilitation, and to examine other factors impacting recruitment, such as vegetation cover and longleaf pine tree density. We found that newly recruited seedlings and grass stage longleaf pines were more abundant in oak-dominated areas where densities were 230% (newly recruited seedlings) and 360% (grass stage) greater from lowest to highest oak neighborhood densities. Longleaf pine also grew faster under higher oak density. Longleaf pine recruitment was lowest under longleaf pine canopies. Mortality of grass stage and bolt stage longleaf pine was low (~1.0% yr-1) in the census interval without fire. Overall, our findings highlight the complex interactions between pines and oaks-two economically and ecologically important genera globally. Xeric oaks should be incorporated as a management option for conservation and restoration of longleaf pine ecosystems.


Assuntos
Ecossistema , Pradaria , Pinus , Quercus , Plântula , Pinus/crescimento & desenvolvimento , Quercus/crescimento & desenvolvimento , Plântula/crescimento & desenvolvimento
20.
Front Vet Sci ; 11: 1399392, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38803804

RESUMO

Introduction: Foot health is crucial for elephants, as pathological lesions of the feet are a leading cause of euthanasia in captive elephants, which are endangered species. Proper treatment of the feet, particularly in conditions affecting the digits and the digital cushion, requires a thorough understanding of the underlying anatomy. However, only limited literature exists due to the small population and the epidemiological foot diseases which often precludes many deceased elephants from scientific study. The aim of this study was to provide a detailed anatomical description of the blood supply to the African elephant's hindfoot. Methods: The healthy right hindlimb of a 19-year-old deceased female African savanna elephant was examined using computed tomography. Following a native sequence, 48 mL of barium-based contrast agent was injected into the caudal and cranial tibial arteries, and a subsequent scan was performed. The images were processed with 3D Slicer software. Results: The medial and lateral plantar arteries run in a symmetrical pattern. They each have a dorsal and a plantar branch, which reach the plantar skin before turning toward the axial plane of the sole to reach the digital cushion from the proximal direction. An accurate 3D model of the arteries and the bones of the foot, a set of labeled images and an animation of the blood supply have been created for ease of understanding. Discussion: In contrast to domestic ungulates, the digital cushion of the hindlimb is supplied differently from that of the forelimb. The lack of large vessels in its deeper layers indicates a slow regeneration time. This novel anatomical information may be useful in the planning of surgical interventions and in emergency medical procedures.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA