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An increasing human-elephant conflict? Impact of African elephant on cultivated cashew trees. EUR J WILDLIFE RES 2023. [DOI: 10.1007/s10344-022-01629-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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2
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Abraham JO, Goldberg ER, Botha J, Staver AC. Heterogeneity in African savanna elephant distributions and their impacts on trees in Kruger National Park, South Africa. Ecol Evol 2021; 11:5624-5634. [PMID: 34026034 PMCID: PMC8131780 DOI: 10.1002/ece3.7465] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/01/2021] [Accepted: 03/04/2021] [Indexed: 11/30/2022] Open
Abstract
Though elephants are a major cause of savanna tree mortality and threaten vulnerable tree species, managing their impact remains difficult, in part because relatively little is known about how elephant impacts are distributed throughout space.This is exacerbated by uncertainty about what determines the distribution of elephants themselves, as well as whether the distribution of elephants is even informative for understanding the distribution of their impacts.To better understand the factors that underlie elephant impacts, we modeled elephant distributions and their damage to trees with respect to soil properties, water availability, and vegetation in Kruger National Park, South Africa, using structural equation modeling.We found that bull elephants and mixed herds differed markedly in their distributions, with bull elephants concentrating in sparsely treed basaltic sites close to artificial waterholes and mixed herds aggregating around permanent rivers, particularly in areas with little grass.Surprisingly, we also found that the distribution of elephant impacts, while highly heterogeneous, was largely unrelated to the distribution of elephants themselves, with damage concentrated instead in densely treed areas and particularly on basaltic soils.Results underscore the importance of surface water for elephants but suggest that elephant water dependence operates together with other landscape factors, particularly vegetation community composition and historical management interventions, to influence elephant distributions.
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Affiliation(s)
- Joel O. Abraham
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
- Present address:
Department of Ecology and Evolutionary BiologyPrinceton UniversityPrincetonNJUSA
| | - Emily R. Goldberg
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
- Present address:
Department of Mechanical EngineeringUniversity of MinnesotaMinneapolisMNUSA
| | - Judith Botha
- Scientific ServicesKruger National ParkSkukuzaSouth Africa
| | - A. Carla Staver
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
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Young TP, Kimuyu DM, Odadi WO, Wells HBM, Wolf AA. Naïve plant communities and individuals may initially suffer in the face of reintroduced megafauna: An experimental exploration of rewilding from an African savanna rangeland. PLoS One 2021; 16:e0248855. [PMID: 33822786 PMCID: PMC8023473 DOI: 10.1371/journal.pone.0248855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/06/2021] [Indexed: 12/04/2022] Open
Abstract
Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individual plants, adjust to the absence of herbivores in ways that can ill-prepare them for the return of these herbivores. Three lines of evidence suggest that these "naïve" individuals, populations, and communities are likely to initially suffer from herbivore rewilding. First, plots protected from wild herbivores for the past 25 years have developed rich diversity of woody plants that are absent from unfenced plots, and presumably would disappear upon rewilding. Second, individuals of the dominant tree in this system, Acacia drepanolobium, greatly reduce their defences in the absence of browsers, and the sudden arrival of these herbivores (in this case, through a temporary fence break), resulted in far greater elephant damage than for their conspecifics in adjacent plots that had been continually exposed to herbivory. Third, the removal of herbivores favoured the most palatable grass species, and a large number of rarer species, which presumably would be at risk from herbivore re-introduction. In summary, the native communities that we observe in defaunated landscapes may be very different from their pre-defaunation states, and we are likely to see some large changes to these plant communities upon rewilding with large herbivores, including potential reductions in plant diversity. Lastly, our experimental manipulation of cattle represents an additional test of the role of livestock in rewilding. Cattle are in many ways ecologically dissimilar to wildlife (in particular their greater densities), but in other ways they may serve as ecological surrogates for wildlife, which could buffer ecosystems from some of the ecological costs of rewilding. More fundamentally, African savannah ecosystems represent a challenge to traditional Western definitions of "wilderness" as ecosystems free of human impacts. We support the suggestion that as we "rewild" our biodiversity landscapes, we redefine "wildness" in the 21st Century to be inclusive of (low impact, and sometimes traditional) human practices that are compatible with the sustainability of native (and re-introduced) biodiversity.
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Affiliation(s)
- Truman P. Young
- Department of Plant Sciences and Ecology Graduate Group, University of California, Davis, Davis, CA, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Duncan M. Kimuyu
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Wilfred O. Odadi
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Egerton University, Egerton, Kenya
| | - Harry B. M. Wells
- Sustainability Research Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
- Lolldaiga Hills Research Programme, Nanyuki, Kenya
| | - Amelia A. Wolf
- Department of Integrative Biology, University of Texas, Austin, TX, United States of America
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Demography of baobab (Adansonia digitata L.) population in different land uses in the semi-arid areas of Tanzania. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01372] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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5
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Mass sterilization of a common palm species by elephants in Kruger National Park, South Africa. Sci Rep 2020; 10:11719. [PMID: 32678201 PMCID: PMC7366642 DOI: 10.1038/s41598-020-68679-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/15/2020] [Indexed: 11/08/2022] Open
Abstract
Chronic herbivory by elephants rarely eliminates any species of woody savanna plants because these plants are typically vigorous basal resprouters after damage by fire or herbivory. In some instances, resprouting after elephant herbivory even increases stem numbers per unit area compared to protected areas. It is thus difficult to know whether an area has been severely degraded by elephant herbivory or not because although trees may be severely reduced in size, they will still be present and may even be relatively dense. By using an elephant exclosure in the Kruger National Park, South Africa, we demonstrate that this resprouting ability masks the fact that entire populations of a widespread African palm, Hyphaene petersiana, are prevented from reaching sexual maturity by chronic elephant herbivory. Besides sterilizing these palms and thus preventing their evolution and seed dispersal, the absence of the palm fruits, flowers and tall stems has other negative biodiversity impacts on their associated fauna. We suggest that to determine sustainable elephant impacts on savanna plants, conservation managers also use the reproductive condition of savanna plants rather than their presence, height or stem density.
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Msalilwa UL, Munishi LK, Makule EE, Ndakidemi PA. Pinpointing baobab (
Adansonia digitata
[Linn. 1759]) population hotspots in the semi‐arid areas of Tanzania. Afr J Ecol 2019. [DOI: 10.1111/aje.12709] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Upendo L. Msalilwa
- Department of Sustainable Agriculture, Biodiversity, and Ecosystem Management The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
- Centre for Research, Agricultural Advancement, Teaching Excellence and Sustainability (CREATES) in Food and Nutrition Security The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
| | - Linus K. Munishi
- Department of Sustainable Agriculture, Biodiversity, and Ecosystem Management The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
- Centre for Research, Agricultural Advancement, Teaching Excellence and Sustainability (CREATES) in Food and Nutrition Security The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
| | - Edna E. Makule
- Centre for Research, Agricultural Advancement, Teaching Excellence and Sustainability (CREATES) in Food and Nutrition Security The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
- Department of Food and Nutritional Sciences The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
| | - Patrick A. Ndakidemi
- Department of Sustainable Agriculture, Biodiversity, and Ecosystem Management The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
- Centre for Research, Agricultural Advancement, Teaching Excellence and Sustainability (CREATES) in Food and Nutrition Security The Nelson Mandela African Institution of Science and Technology Arusha Tanzania
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7
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Watson LH, Cameron MJ, Iifo F. Elephant herbivory of knob‐thorn (
Senegalia nigrescens
) and ivory palm (
Hyphaene petersiana
) in Bwabwata National Park, Caprivi, Namibia: The role of ivory palm as a biotic refuge. Afr J Ecol 2019. [DOI: 10.1111/aje.12681] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Laurence H. Watson
- Nature Conservation Program Nelson Mandela University George South Africa
| | - Michael J. Cameron
- Nature Conservation Program Nelson Mandela University George South Africa
| | - Fillemon Iifo
- Directorate of Scientific Services – CITES Office Ministry of Environment and Tourism Windhoek Namibia
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Davies AB, Asner GP. Elephants limit aboveground carbon gains in African savannas. GLOBAL CHANGE BIOLOGY 2019; 25:1368-1382. [PMID: 30723962 DOI: 10.1111/gcb.14585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 12/20/2018] [Indexed: 06/09/2023]
Abstract
Understanding the drivers of vegetation carbon dynamics is essential for climate change mitigation and effective policy formulation. However, most efforts focus on abiotic drivers of plant biomass change, with little consideration for functional roles performed by animals, particularly at landscape scales. We combined repeat airborne Light Detection and Ranging with measurements of elephant densities, abiotic factors, and exclusion experiments to determine the relative importance of drivers of change in aboveground woody vegetation carbon stocks in Kruger National Park, South Africa. Despite a growing elephant population, aboveground carbon density (ACD) increased across most of the landscape over the 6-year study period, but at fine scales, bull elephant density was the most important factor determining carbon stock change, with ACD losses recorded only where bull densities exceeded 0.5 bulls/km2 . Effects of bull elephants were, however, spatially restricted and landscape dependent, being especially pronounced along rivers, at mid-elevations, and on steeper slopes. In contrast, elephant herds and abiotic drivers had a comparatively small influence on the direction or magnitude of carbon stock change. Our findings demonstrate that animals can have a substantive influence on regional-scale carbon dynamics and warrant consideration in carbon cycling models and policy formulation aimed at carbon management and climate change mitigation.
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Affiliation(s)
- Andrew B Davies
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona
| | - Gregory P Asner
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California
- Center for Global Discovery and Conservation Science, Arizona State University, Tempe, Arizona
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9
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Lisao K, Geldenhuys C, Chirwa P. Assessment of the African baobab (Adansonia digitata L.) populations in Namibia: Implications for conservation. Glob Ecol Conserv 2018. [DOI: 10.1016/j.gecco.2018.e00386] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
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10
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Davies AB, Gaylard A, Asner GP. Megafaunal effects on vegetation structure throughout a densely wooded African landscape. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2018; 28:398-408. [PMID: 29178395 DOI: 10.1002/eap.1655] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/05/2017] [Accepted: 11/07/2017] [Indexed: 06/07/2023]
Abstract
Megafauna strongly affect vegetation structure and composition, often leading to management concern. However, the extent of their influence across large scales and varying ecosystems remains largely unknown. Using high resolution airborne Light Detection and Ranging (LiDAR), we investigated landscape-scale changes in vegetation height and three-dimensional (3D) structure across landscapes of varying elephant densities and presence over time, and in response to surface water distribution and terrain variability in the heavily managed thicket biome of the Addo Elephant National Park, South Africa. Elephants caused up to a fourfold reduction in vegetation height and altered the vertical profile, but increased vegetation height variability. Vegetation height also increased with elevation and distance from water, particularly in areas that elephants had long occupied at high densities. Slope had opposing effects on vegetation height, with height increasing with slope in areas long exposed to elephants, but decreasing where elephants had only recently been granted access. Our results suggest that elephants are the primary agents of vegetation change in this ecosystem, but that the strength of their effects varies across the landscape, enabling management to use water and terrain as mitigation tools. We further highlight the necessity of landscape-level experimental studies on megafaunal effects to untangle mechanisms and establish causality.
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Affiliation(s)
- Andrew B Davies
- Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, California, 94305, USA
| | - Angela Gaylard
- Scientific Services, South African National Parks, Knysna, South Africa
| | - Gregory P Asner
- Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, California, 94305, USA
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11
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Williams HF, Bartholomew DC, Amakobe B, Githiru M. Environmental factors affecting the distribution of African elephants in the Kasigau wildlife corridor, SE Kenya. Afr J Ecol 2017. [DOI: 10.1111/aje.12442] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Harry F. Williams
- Centre for Ecology and Conservation; University of Exeter; Penryn Cornwall UK
- Wildlife Works; Voi Kenya
| | | | | | - Mwangi Githiru
- Wildlife Works; Voi Kenya
- Department of Zoology; National Museums of Kenya; Nairobi Kenya
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12
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Ndoro O, Mashapa C, Kativu S, Gandiwa E. A comparative assessment of baobab density in northern Mana Pools National Park, Zimbabwe. Afr J Ecol 2014. [DOI: 10.1111/aje.12189] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Onias Ndoro
- Tropical Resource Ecology Programme; University of Zimbabwe; PO Box MP 167 Mount Pleasant Harare Zimbabwe
| | - Clayton Mashapa
- Tropical Resource Ecology Programme; University of Zimbabwe; PO Box MP 167 Mount Pleasant Harare Zimbabwe
| | - Shakkie Kativu
- Tropical Resource Ecology Programme; University of Zimbabwe; PO Box MP 167 Mount Pleasant Harare Zimbabwe
| | - Edson Gandiwa
- School of Wildlife, Ecology and Conservation; Chinhoyi University of Technology; Private Bag 7724 Chinhoyi Zimbabwe
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13
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Stevens N, Seal CE, Archibald S, Bond W. Increasing temperatures can improve seedling establishment in arid-adapted savanna trees. Oecologia 2014; 175:1029-40. [PMID: 24805202 DOI: 10.1007/s00442-014-2958-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/17/2014] [Indexed: 10/25/2022]
Abstract
Plant species are shifting their ranges in response to global climate change, thus intensifying the need to predict such changes accurately. As the environmental requirements controlling plant distribution act differently at each developmental stage, there is a need to acquire a demographic-specific understanding of the factors which determine these distributions. Here we investigated the germination niche of two common savanna species Acacia nigrescens and Colophospermum mopane, with the aims to disentangle the direct and indirect effects of temperature on seed germination and establishment and to explore the impact of higher temperatures on the establishment success of savanna trees. Under laboratory conditions, we used thermal gradient plates to determine the thermal germination niche of both species, and a water stress experiment was conducted on C. mopane to account for water-temperature interactions. Using these data we parameterised a soil-moisture model to determine germination and establishment success under field conditions at current and future temperatures (+4 °C). Based on this model, higher future temperatures will not limit germination directly, but they will reduce the number of germination events by reducing the time window of suitable available soil water. Conversely, warmer conditions will accelerate the rate of radicle extension and increase the frequency of seedling establishment events. An additional advantage of higher temperatures is that fewer seeds will germinate, resulting in slower seed bank depletion when successful seedling establishment events do occur.
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Affiliation(s)
- Nicola Stevens
- Natural Resources and the Environment, CSIR, PO Box 395, Pretoria, South Africa,
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14
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Pittiglio C, Skidmore AK, van Gils HAMJ, McCall MK, Prins HHT. Smallholder farms as stepping stone corridors for crop-raiding elephant in northern Tanzania: integration of Bayesian expert system and network simulator. AMBIO 2014; 43:149-161. [PMID: 23999851 PMCID: PMC3906473 DOI: 10.1007/s13280-013-0437-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 03/30/2013] [Accepted: 08/07/2013] [Indexed: 06/02/2023]
Abstract
Crop-raiding elephants affect local livelihoods, undermining conservation efforts. Yet, crop-raiding patterns are poorly understood, making prediction and protection difficult. We hypothesized that raiding elephants use corridors between daytime refuges and farmland. Elephant counts, crop-raiding records, household surveys, Bayesian expert system, and least-cost path simulation were used to predict four alternative categories of daily corridors: (1) footpaths, (2) dry river beds, (3) stepping stones along scattered small farms, and (4) trajectories of shortest distance to refuges. The corridor alignments were compared in terms of their minimum cumulative resistance to elephant movement and related to crop-raiding zones quantified by a kernel density function. The "stepping stone" corridors predicted the crop-raiding patterns. Elephant presence was confirmed along these corridors, demonstrating that small farms located between refuges and contiguous farmland increase habitat connectivity for elephant. Our analysis successfully predicted elephant occurrence in farmland where daytime counts failed to detect nocturnal presence. These results have conservation management implications.
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Affiliation(s)
- Claudia Pittiglio
- Department of Natural Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands,
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15
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Kassa BD, Fandohan B, Azihou AF, Assogbadjo AE, Oduor AM, Kidjo FC, Babatoundé S, Liu J, Glèlè Kakaï R. Survey ofLoxodonta africana(Elephantidae)-caused bark injury onAdansonia digitata(Malavaceae) within Pendjari Biosphere Reserve, Benin. Afr J Ecol 2013. [DOI: 10.1111/aje.12131] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Barthelemy D. Kassa
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
| | - Belarmain Fandohan
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
- Université d'Agriculture de Kétou; BP 95 Cotonou République du Bénin
- International Ecosystem Management Partnership (IEMP); United Nations Environment Programme (UNEP); c/o Institute of Geographic Sciences and Natural Resources Research; Chinese Academy of Sciences; No. 11A Datun Rd. Beijing 100101 China
| | - Akomian F. Azihou
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
| | - Achille E. Assogbadjo
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
| | - Ayub M.O. Oduor
- International Ecosystem Management Partnership (IEMP); United Nations Environment Programme (UNEP); c/o Institute of Geographic Sciences and Natural Resources Research; Chinese Academy of Sciences; No. 11A Datun Rd. Beijing 100101 China
| | - Ferdinand C. Kidjo
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
| | - Séverin Babatoundé
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
| | - Jian Liu
- International Ecosystem Management Partnership (IEMP); United Nations Environment Programme (UNEP); c/o Institute of Geographic Sciences and Natural Resources Research; Chinese Academy of Sciences; No. 11A Datun Rd. Beijing 100101 China
| | - Romain Glèlè Kakaï
- Laboratoire d'Ecologie Appliquée; Université d'Abomey Calavi; 01 BP 526 Cotonou République du Bénin
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16
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Abundance and Structure of African Baobab (Adansonia digitata) across Different Soil Types in Gonarezhou National Park, Zimbabwe. ACTA ACUST UNITED AC 2013. [DOI: 10.1155/2013/874713] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This study investigated the abundance and structure of African baobab (Adansonia digitata) across soil group strata in Gonarezhou National Park, Zimbabwe. The study was based on a stratified random sampling design composed of the following soil group substrates: (i) granophyres, (ii) malvernia, and (iii) rhyolite. Belt transects of 0.3×0.1 km were randomly laid across soil group. Baobab abundance and population structure were determined from the density and size class distribution, respectively. There were significant differences in plant height and plant density across Gonarezhou soil groups. Study sites on granophyres derived soil group indicated viable abundance and recruitment of baobab population. Whereas the study highlighted a concern over the unbalanced size structure distribution of baobab population on malvernia derived soil group, our results indicated that baobabs are in danger of extirpation on malvernia derived soil group. Baobab community in Gonarezhou tends to occur more densely along environmental gradient of soil group type as influenced by the underlying geological soil substrate of granophyres. Malvernia derived soil group is likely less ideal for baobab recruitment.
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17
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Shrader AM, Bell C, Bertolli L, Ward D. Forest or the trees: At what scale do elephants make foraging decisions? ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2012. [DOI: 10.1016/j.actao.2011.09.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Maclean JE, Goheen JR, Doak DF, Palmer TM, Young TP. Cryptic herbivores mediate the strength and form of ungulate impacts on a long-lived savanna tree. Ecology 2011; 92:1626-36. [PMID: 21905429 DOI: 10.1890/10-2097.1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Plant populations are regulated by a diverse array of herbivores that impose demographic filters throughout their life cycle. Few studies, however, simultaneously quantify the impacts of multiple herbivore guilds on the lifetime performance or population growth rate of plants. In African savannas, large ungulates (such as elephants) are widely regarded as important drivers of woody plant population dynamics, while the potential impacts of smaller, more cryptic herbivores (such as rodents) have largely been ignored. We combined a large-scale ungulate exclusion experiment with a five-year manipulation of rodent densities to quantify the impacts of three herbivore guilds (wild ungulates, domestic cattle, and rodents) on all life stages of a widespread savanna tree. We utilized demographic modeling to reveal the overall role of each guild in regulating tree population dynamics, and to elucidate the importance of different demographic hurdles in driving population growth under contrasting consumer communities. We found that wild ungulates dramatically reduced population growth, shifting the population trajectory from increase to decline, but that the mechanisms driving these effects were strongly mediated by rodents. The impact of wild ungulates on population growth was predominantly driven by their negative effect on tree reproduction when rodents were excluded, and on adult tree survival when rodents were present. By limiting seedling survival, rodents also reduced population growth; however, this effect was strongly dampened where wild ungulates were present. We suggest that these complex interactions between disparate consumer guilds can have important consequences for the population demography of long-lived species, and that the effects of a single consumer group are often likely to vary dramatically depending on the larger community in which interactions are embedded.
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Affiliation(s)
- Janet E Maclean
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
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19
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Sanchez AC, Osborne PE, Haq N. Climate change and the African baobab (Adansonia digitata L.): the need for better conservation strategies. Afr J Ecol 2011. [DOI: 10.1111/j.1365-2028.2011.01257.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Mason GJ, Veasey JS. How should the psychological well-being of zoo elephants be objectively investigated? Zoo Biol 2010; 29:237-55. [DOI: 10.1002/zoo.20256] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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21
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Parker DM, Bernard RTF. Levels of aloe mortality with and without elephants in the Thicket Biome of South Africa. Afr J Ecol 2009. [DOI: 10.1111/j.1365-2028.2008.01025.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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