Browsing by Author "Clark, Connie J"
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Item Open Access Above-ground biomass and structure of 260 African tropical forests.(Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 2013-01) Lewis, Simon L; Sonké, Bonaventure; Sunderland, Terry; Begne, Serge K; Lopez-Gonzalez, Gabriela; van der Heijden, Geertje MF; Phillips, Oliver L; Affum-Baffoe, Kofi; Baker, Timothy R; Banin, Lindsay; Bastin, Jean-François; Beeckman, Hans; Boeckx, Pascal; Bogaert, Jan; De Cannière, Charles; Chezeaux, Eric; Clark, Connie J; Collins, Murray; Djagbletey, Gloria; Djuikouo, Marie Noël K; Droissart, Vincent; Doucet, Jean-Louis; Ewango, Cornielle EN; Fauset, Sophie; Feldpausch, Ted R; Foli, Ernest G; Gillet, Jean-François; Hamilton, Alan C; Harris, David J; Hart, Terese B; de Haulleville, Thales; Hladik, Annette; Hufkens, Koen; Huygens, Dries; Jeanmart, Philippe; Jeffery, Kathryn J; Kearsley, Elizabeth; Leal, Miguel E; Lloyd, Jon; Lovett, Jon C; Makana, Jean-Remy; Malhi, Yadvinder; Marshall, Andrew R; Ojo, Lucas; Peh, Kelvin S-H; Pickavance, Georgia; Poulsen, John R; Reitsma, Jan M; Sheil, Douglas; Simo, Murielle; Steppe, Kathy; Taedoumg, Hermann E; Talbot, Joey; Taplin, James RD; Taylor, David; Thomas, Sean C; Toirambe, Benjamin; Verbeeck, Hans; Vleminckx, Jason; White, Lee JT; Willcock, Simon; Woell, Hannsjorg; Zemagho, LiseWe report above-ground biomass (AGB), basal area, stem density and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries. Mean AGB is 395.7 Mg dry mass ha⁻¹ (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha⁻¹) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo- compared with neotropical forests. However, mean stem density is low (426 ± 11 stems ha⁻¹ greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationships with C : N ratio (suggesting a positive soil phosphorus-AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes.Item Open Access African forest elephant movements depend on time scale and individual behavior.(Scientific reports, 2021-06-16) Beirne, Christopher; Houslay, Thomas M; Morkel, Peter; Clark, Connie J; Fay, Mike; Okouyi, Joseph; White, Lee JT; Poulsen, John RThe critically endangered African forest elephant (Loxodonta cyclotis) plays a vital role in maintaining the structure and composition of Afrotropical forests, but basic information is lacking regarding the drivers of elephant movement and behavior at landscape scales. We use GPS location data from 96 individuals throughout Gabon to determine how five movement behaviors vary at different scales, how they are influenced by anthropogenic and environmental covariates, and to assess evidence for behavioral syndromes-elephants which share suites of similar movement traits. Elephants show some evidence of behavioral syndromes along an 'idler' to 'explorer' axis-individuals that move more have larger home ranges and engage in more 'exploratory' movements. However, within these groups, forest elephants express remarkable inter-individual variation in movement behaviours. This variation highlights that no two elephants are the same and creates challenges for practitioners aiming to design conservation initiatives.Item Open Access Correlations between physical and chemical defences in plants: tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?(The New phytologist, 2013-04) Moles, Angela T; Peco, Begoña; Wallis, Ian R; Foley, William J; Poore, Alistair GB; Seabloom, Eric W; Vesk, Peter A; Bisigato, Alejandro J; Cella-Pizarro, Lucrecia; Clark, Connie J; Cohen, Philippe S; Cornwell, William K; Edwards, Will; Ejrnaes, Rasmus; Gonzales-Ojeda, Therany; Graae, Bente J; Hay, Gregory; Lumbwe, Fainess C; Magaña-Rodríguez, Benjamín; Moore, Ben D; Peri, Pablo L; Poulsen, John R; Stegen, James C; Veldtman, Ruan; von Zeipel, Hugo; Andrew, Nigel R; Boulter, Sarah L; Borer, Elizabeth T; Cornelissen, Johannes HC; Farji-Brener, Alejandro G; DeGabriel, Jane L; Jurado, Enrique; Kyhn, Line A; Low, Bill; Mulder, Christa PH; Reardon-Smith, Kathryn; Rodríguez-Velázquez, Jorge; De Fortier, An; Zheng, Zheng; Blendinger, Pedro G; Enquist, Brian J; Facelli, Jose M; Knight, Tiffany; Majer, Jonathan D; Martínez-Ramos, Miguel; McQuillan, Peter; Hui, Francis KCMost plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.Item Open Access Diversity and carbon storage across the tropical forest biome.(Sci Rep, 2017-01-17) Sullivan, Martin JP; Talbot, Joey; Lewis, Simon L; Phillips, Oliver L; Qie, Lan; Begne, Serge K; Chave, Jerôme; Cuni-Sanchez, Aida; Hubau, Wannes; Lopez-Gonzalez, Gabriela; Miles, Lera; Monteagudo-Mendoza, Abel; Sonké, Bonaventure; Sunderland, Terry; Ter Steege, Hans; White, Lee JT; Affum-Baffoe, Kofi; Aiba, Shin-Ichiro; de Almeida, Everton Cristo; de Oliveira, Edmar Almeida; Alvarez-Loayza, Patricia; Dávila, Esteban Álvarez; Andrade, Ana; Aragão, Luiz EOC; Ashton, Peter; Aymard C, Gerardo A; Baker, Timothy R; Balinga, Michael; Banin, Lindsay F; Baraloto, Christopher; Bastin, Jean-Francois; Berry, Nicholas; Bogaert, Jan; Bonal, Damien; Bongers, Frans; Brienen, Roel; Camargo, José Luís C; Cerón, Carlos; Moscoso, Victor Chama; Chezeaux, Eric; Clark, Connie J; Pacheco, Álvaro Cogollo; Comiskey, James A; Valverde, Fernando Cornejo; Coronado, Eurídice N Honorio; Dargie, Greta; Davies, Stuart J; De Canniere, Charles; Djuikouo K, Marie Noel; Doucet, Jean-Louis; Erwin, Terry L; Espejo, Javier Silva; Ewango, Corneille EN; Fauset, Sophie; Feldpausch, Ted R; Herrera, Rafael; Gilpin, Martin; Gloor, Emanuel; Hall, Jefferson S; Harris, David J; Hart, Terese B; Kartawinata, Kuswata; Kho, Lip Khoon; Kitayama, Kanehiro; Laurance, Susan GW; Laurance, William F; Leal, Miguel E; Lovejoy, Thomas; Lovett, Jon C; Lukasu, Faustin Mpanya; Makana, Jean-Remy; Malhi, Yadvinder; Maracahipes, Leandro; Marimon, Beatriz S; Junior, Ben Hur Marimon; Marshall, Andrew R; Morandi, Paulo S; Mukendi, John Tshibamba; Mukinzi, Jaques; Nilus, Reuben; Vargas, Percy Núñez; Camacho, Nadir C Pallqui; Pardo, Guido; Peña-Claros, Marielos; Pétronelli, Pascal; Pickavance, Georgia C; Poulsen, Axel Dalberg; Poulsen, John R; Primack, Richard B; Priyadi, Hari; Quesada, Carlos A; Reitsma, Jan; Réjou-Méchain, Maxime; Restrepo, Zorayda; Rutishauser, Ervan; Salim, Kamariah Abu; Salomão, Rafael P; Samsoedin, Ismayadi; Sheil, Douglas; Sierra, Rodrigo; Silveira, Marcos; Slik, JW Ferry; Steel, Lisa; Taedoumg, Hermann; Tan, Sylvester; Terborgh, John W; Thomas, Sean C; Toledo, Marisol; Umunay, Peter M; Gamarra, Luis Valenzuela; Vieira, Ima Célia Guimarães; Vos, Vincent A; Wang, Ophelia; Willcock, Simon; Zemagho, LiseTropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1 ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity.Item Open Access Ecological erosion of an Afrotropical forest and potential consequences for tree recruitment and forest biomass(Biological Conservation, 2013) Poulsen, John R; Clark, Connie J; Palmer, Todd MUnprecedented rates of logging and hunting threaten to transform the remaining primary tropical forest into a degraded mosaic, emptied of wildlife. Defaunation is expected to interrupt plant-animal interactions with cascading effects for forest structure, composition, and ecosystem services. In a Central African forest first logged 35years ago, we evaluated this process of ecological erosion in 30 study sites distributed across forest disturbed by logging and hunting, logging alone, and neither logging nor hunting. Both logging and hunting tended to reduce abundances of large mammals, together shifting the relative abundance of the animal community towards squirrels and small birds. Through a series of experiments, we evaluated the effects of logging and hunting on seed dispersal, seed predation and herbivory. We demonstrate that complete defaunation is not necessary to significantly alter the strength of plant-animal interactions. Hunting reduced the mean dispersal distances of nine mammal-dispersed tree species by 22%. Rates of seed predation were similar among forest types, but hunted forest had significantly lower rates of herbivory that we attribute to the lower abundance of meso-herbivores. Hunted forest also had significantly lower above-ground biomass (301Mgha-1) than the logged only (358Mgha-1) and undisturbed (455Mgha-1) forest types, but similar numbers of tree species and individuals. Lower biomass in hunted forest is likely attributable to significantly lower wood densities at small tree size classes (<40cm). We hypothesize that over time the human-mediated modification of plant-animal interactions can alter the composition of the forest to have a higher proportion of fast-growing, low wood density tree species, diminishing the long-term potential for carbon storage. © 2013 Elsevier Ltd.Item Open Access Experimental manipulation of seed shadows of an Afrotropical tree determines drivers of recruitment.(Ecology, 2012-03) Poulsen, John R; Clark, Connie J; Bolker, Benjamin MThe loss of animals in tropical forests may alter seed dispersal patterns and reduce seedling recruitment of tree species, but direct experimental evidence is scarce. We manipulated dispersal patterns of Manilkara mabokeensis, a monkey-dispersed tree, to assess the extent to which spatial distributions of seeds drive seedling recruitment. Based on the natural seed shadow, we created seed distributions with seeds deposited under the canopy ("no dispersal"), with declining density from the tree ("natural dispersal"), and at uniform densities ("good dispersal"). These distributions mimicked dispersal patterns that could occur with the extirpation of monkeys, low levels of hunting, and high rates of seed dispersal. We monitored seedling emergence and survival for 18 months and recorded the number of leaves and damage to leaves. "Good dispersal" increased seedling survival by 26%, and "no dispersal" decreased survival by 78%, relative to "natural dispersal." Using a mixed-effects survival model, we decoupled the distance and density components of the seed shadow: seedling survival depended on the seed density, but not on the distance from the tree. Although community seedling diversity tended to decrease with longer dispersal distances, we found no conclusive evidence that patterns of seed dispersal influence the diversity of the seedling community. Local seed dispersal does affect seedling recruitment and survival, with better dispersal resulting in higher seedling recruitment; hence the loss of dispersal services that comes with the reduction or extirpation of seed dispersers will decrease regeneration of some tree species.Item Open Access Forest elephant movement and habitat use in a tropical forest-grassland mosaic in Gabon.(PloS one, 2018-01) Mills, Emily C; Poulsen, John R; Fay, J Michael; Morkel, Peter; Clark, Connie J; Meier, Amelia; Beirne, Christopher; White, Lee JTPoaching of forest elephants (Loxodonta cyclotis) for ivory has decimated their populations in Central Africa. Studying elephant movement can provide insight into habitat and resource use to reveal where, when, and why they move and guide conservation efforts. We fitted 17 forest elephants with global positioning system (GPS) collars in 2015 and 2016 in the tropical forest-grassland mosaic of the Wonga Wongué Presidential Reserve (WW), Gabon. Using the location data, we quantified movement distances, home ranges, and habitat use to examine the environmental drivers of elephant movements and predict where elephants occur spatially and temporally. Forest elephants, on average, traveled 2,840 km annually and had home ranges of 713 km2, with males covering significantly larger home ranges than females. Forest elephants demonstrated both daily and seasonal movement patterns. Daily, they moved between forest and grassland at dawn and dusk. Seasonally, they spent proportionally more time in grassland than forest during the short-wet season when grasses recruit. Forest elephants also traveled faster during the short-wet season when fruit availability was greatest, likely reflecting long, direct movements to preferred fruiting tree species. Forest elephants tended to select areas with high tree and shrub density that afford cover and browse. When villages occurred in their home ranges elephants spent a disproportionate amount of time near them, particularly in the dry season, probably for access to agricultural crops and preferred habitat. Given the importance of the grassland habitat for elephants, maintenance of the forest-grassland matrix is a conservation priority in WW. Law enforcement, outreach, and education should focus on areas of potential human-elephant conflict near villages along the borders of the reserve. GPS-tracking should be extended into multi-use areas in the peripheries of protected areas to evaluate the effects of human disturbance on elephant movements and to maintain connectivity among elephant populations in Gabon.Item Open Access Long-term thermal sensitivity of Earth's tropical forests.(Science (New York, N.Y.), 2020-05-21) Sullivan, Martin JP; Lewis, Simon L; Affum-Baffoe, Kofi; Castilho, Carolina; Costa, Flávia; Sanchez, Aida Cuni; Ewango, Corneille EN; Hubau, Wannes; Marimon, Beatriz; Monteagudo-Mendoza, Abel; Qie, Lan; Sonké, Bonaventure; Martinez, Rodolfo Vasquez; Baker, Timothy R; Brienen, Roel JW; Feldpausch, Ted R; Galbraith, David; Gloor, Manuel; Malhi, Yadvinder; Aiba, Shin-Ichiro; Alexiades, Miguel N; Almeida, Everton C; de Oliveira, Edmar Almeida; Dávila, Esteban Álvarez; Loayza, Patricia Alvarez; Andrade, Ana; Vieira, Simone Aparecida; Aragão, Luiz EOC; Araujo-Murakami, Alejandro; Arets, Eric JMM; Arroyo, Luzmila; Ashton, Peter; Aymard C, Gerardo; Baccaro, Fabrício B; Banin, Lindsay F; Baraloto, Christopher; Camargo, Plínio Barbosa; Barlow, Jos; Barroso, Jorcely; Bastin, Jean-François; Batterman, Sarah A; Beeckman, Hans; Begne, Serge K; Bennett, Amy C; Berenguer, Erika; Berry, Nicholas; Blanc, Lilian; Boeckx, Pascal; Bogaert, Jan; Bonal, Damien; Bongers, Frans; Bradford, Matt; Brearley, Francis Q; Brncic, Terry; Brown, Foster; Burban, Benoit; Camargo, José Luís; Castro, Wendeson; Céron, Carlos; Ribeiro, Sabina Cerruto; Moscoso, Victor Chama; Chave, Jerôme; Chezeaux, Eric; Clark, Connie J; de Souza, Fernanda Coelho; Collins, Murray; Comiskey, James A; Valverde, Fernando Cornejo; Medina, Massiel Corrales; da Costa, Lola; Dančák, Martin; Dargie, Greta C; Davies, Stuart; Cardozo, Nallaret Davila; de Haulleville, Thales; de Medeiros, Marcelo Brilhante; Del Aguila Pasquel, Jhon; Derroire, Géraldine; Di Fiore, Anthony; Doucet, Jean-Louis; Dourdain, Aurélie; Droissart, Vincent; Duque, Luisa Fernanda; Ekoungoulou, Romeo; Elias, Fernando; Erwin, Terry; Esquivel-Muelbert, Adriane; Fauset, Sophie; Ferreira, Joice; Llampazo, Gerardo Flores; Foli, Ernest; Ford, Andrew; Gilpin, Martin; Hall, Jefferson S; Hamer, Keith C; Hamilton, Alan C; Harris, David J; Hart, Terese B; Hédl, Radim; Herault, Bruno; Herrera, Rafael; Higuchi, Niro; Hladik, Annette; Coronado, Eurídice Honorio; Huamantupa-Chuquimaco, Isau; Huasco, Walter Huaraca; Jeffery, Kathryn J; Jimenez-Rojas, Eliana; Kalamandeen, Michelle; Djuikouo, Marie Noël Kamdem; Kearsley, Elizabeth; Umetsu, Ricardo Keichi; Kho, Lip Khoon; Killeen, Timothy; Kitayama, Kanehiro; Klitgaard, Bente; Koch, Alexander; Labrière, Nicolas; Laurance, William; Laurance, Susan; Leal, Miguel E; Levesley, Aurora; Lima, Adriano JN; Lisingo, Janvier; Lopes, Aline P; Lopez-Gonzalez, Gabriela; Lovejoy, Tom; Lovett, Jon C; Lowe, Richard; Magnusson, William E; Malumbres-Olarte, Jagoba; Manzatto, Ângelo Gilberto; Marimon, Ben Hur; Marshall, Andrew R; Marthews, Toby; de Almeida Reis, Simone Matias; Maycock, Colin; Melgaço, Karina; Mendoza, Casimiro; Metali, Faizah; Mihindou, Vianet; Milliken, William; Mitchard, Edward TA; Morandi, Paulo S; Mossman, Hannah L; Nagy, Laszlo; Nascimento, Henrique; Neill, David; Nilus, Reuben; Vargas, Percy Núñez; Palacios, Walter; Camacho, Nadir Pallqui; Peacock, Julie; Pendry, Colin; Peñuela Mora, Maria Cristina; Pickavance, Georgia C; Pipoly, John; Pitman, Nigel; Playfair, Maureen; Poorter, Lourens; Poulsen, John R; Poulsen, Axel Dalberg; Preziosi, Richard; Prieto, Adriana; Primack, Richard B; Ramírez-Angulo, Hirma; Reitsma, Jan; Réjou-Méchain, Maxime; Correa, Zorayda Restrepo; de Sousa, Thaiane Rodrigues; Bayona, Lily Rodriguez; Roopsind, Anand; Rudas, Agustín; Rutishauser, Ervan; Abu Salim, Kamariah; Salomão, Rafael P; Schietti, Juliana; Sheil, Douglas; Silva, Richarlly C; Espejo, Javier Silva; Valeria, Camila Silva; Silveira, Marcos; Simo-Droissart, Murielle; Simon, Marcelo Fragomeni; Singh, James; Soto Shareva, Yahn Carlos; Stahl, Clement; Stropp, Juliana; Sukri, Rahayu; Sunderland, Terry; Svátek, Martin; Swaine, Michael D; Swamy, Varun; Taedoumg, Hermann; Talbot, Joey; Taplin, James; Taylor, David; Ter Steege, Hans; Terborgh, John; Thomas, Raquel; Thomas, Sean C; Torres-Lezama, Armando; Umunay, Peter; Gamarra, Luis Valenzuela; van der Heijden, Geertje; van der Hout, Peter; van der Meer, Peter; van Nieuwstadt, Mark; Verbeeck, Hans; Vernimmen, Ronald; Vicentini, Alberto; Vieira, Ima Célia Guimarães; Torre, Emilio Vilanova; Vleminckx, Jason; Vos, Vincent; Wang, Ophelia; White, Lee JT; Willcock, Simon; Woods, John T; Wortel, Verginia; Young, Kenneth; Zagt, Roderick; Zemagho, Lise; Zuidema, Pieter A; Zwerts, Joeri A; Phillips, Oliver LThe sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (-9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate.Item Open Access Low-intensity logging and hunting have long-term effects on seed dispersal but not fecundity in Afrotropical forests.(AoB PLANTS, 2019-02) Nuñez, Chase L; Clark, James S; Clark, Connie J; Poulsen, John RHunting and logging, ubiquitous human disturbances in tropical forests, have the potential to alter the ecological processes that govern population recruitment and community composition. Hunting-induced declines in populations of seed-dispersing animals are expected to reduce dispersal of the tree species that rely on them, resulting in potentially greater distance- and density-dependent mortality. At the same time, selective logging may alter competitive interactions among tree species, releasing remaining trees from light, nutrient or space limitations. Taken together, these disturbances may alter the community composition of tropical forests, with implications for carbon storage, biodiversity conservation and ecosystem function. To evaluate the effects of hunting and logging on tree fecundity and seed dispersal, we use 3 years of seed rain data from a large-scale observational experiment in previously logged, hunted and protected forests in northern Republic of Congo (Brazzaville). We find that low-intensity logging had a meaningful long-term effect on species-specific seed dispersal distances, though the direction and magnitude varied and was not congruent within dispersal vector. Tree fecundity increased with tree diameter, but did not differ appreciably across disturbance regimes. The species-specific dispersal responses to logging in this study point towards the long-lasting toll of disturbance on ecological function and highlight the necessity of conserving intact forest.Item Open Access Poaching empties critical Central African wilderness of forest elephants.(Curr Biol, 2017-02-20) Poulsen, John R; Koerner, Sally E; Moore, Sarah; Medjibe, Vincent P; Blake, Stephen; Clark, Connie J; Akou, Mark Ella; Fay, Michael; Meier, Amelia; Okouyi, Joseph; Rosin, Cooper; White, Lee JTElephant populations are in peril everywhere, but forest elephants in Central Africa have sustained alarming losses in the last decade [1]. Large, remote protected areas are thought to best safeguard forest elephants by supporting large populations buffered from habitat fragmentation, edge effects and human pressures. One such area, the Minkébé National Park (MNP), Gabon, was created chiefly for its reputation of harboring a large elephant population. MNP held the highest densities of elephants in Central Africa at the turn of the century, and was considered a critical sanctuary for forest elephants because of its relatively large size and isolation. We assessed population change in the park and its surroundings between 2004 and 2014. Using two independent modeling approaches, we estimated a 78-81% decline in elephant numbers over ten years - a loss of more than 25,000 elephants. While poaching occurs from within Gabon, cross-border poaching largely drove the precipitous drop in elephant numbers. With nearly 50% of forest elephants in Central Africa thought to reside in Gabon [1], their loss from the park is a considerable setback for the preservation of the species.Item Open Access Resistance of African tropical forests to an extreme climate anomaly.(Proceedings of the National Academy of Sciences of the United States of America, 2021-05) Bennett, Amy C; Dargie, Greta C; Cuni-Sanchez, Aida; Tshibamba Mukendi, John; Hubau, Wannes; Mukinzi, Jacques M; Phillips, Oliver L; Malhi, Yadvinder; Sullivan, Martin JP; Cooper, Declan LM; Adu-Bredu, Stephen; Affum-Baffoe, Kofi; Amani, Christian A; Banin, Lindsay F; Beeckman, Hans; Begne, Serge K; Bocko, Yannick E; Boeckx, Pascal; Bogaert, Jan; Brncic, Terry; Chezeaux, Eric; Clark, Connie J; Daniels, Armandu K; de Haulleville, Thales; Djuikouo Kamdem, Marie-Noël; Doucet, Jean-Louis; Evouna Ondo, Fidèle; Ewango, Corneille EN; Feldpausch, Ted R; Foli, Ernest G; Gonmadje, Christelle; Hall, Jefferson S; Hardy, Olivier J; Harris, David J; Ifo, Suspense A; Jeffery, Kathryn J; Kearsley, Elizabeth; Leal, Miguel; Levesley, Aurora; Makana, Jean-Remy; Mbayu Lukasu, Faustin; Medjibe, Vincent P; Mihindu, Vianet; Moore, Sam; Nssi Begone, Natacha; Pickavance, Georgia C; Poulsen, John R; Reitsma, Jan; Sonké, Bonaventure; Sunderland, Terry CH; Taedoumg, Hermann; Talbot, Joey; Tuagben, Darlington S; Umunay, Peter M; Verbeeck, Hans; Vleminckx, Jason; White, Lee JT; Woell, Hannsjoerg; Woods, John T; Zemagho, Lise; Lewis, Simon LThe responses of tropical forests to environmental change are critical uncertainties in predicting the future impacts of climate change. The positive phase of the 2015-2016 El Niño Southern Oscillation resulted in unprecedented heat and low precipitation in the tropics with substantial impacts on the global carbon cycle. The role of African tropical forests is uncertain as their responses to short-term drought and temperature anomalies have yet to be determined using on-the-ground measurements. African tropical forests may be particularly sensitive because they exist in relatively dry conditions compared with Amazonian or Asian forests, or they may be more resistant because of an abundance of drought-adapted species. Here, we report responses of structurally intact old-growth lowland tropical forests inventoried within the African Tropical Rainforest Observatory Network (AfriTRON). We use 100 long-term inventory plots from six countries each measured at least twice prior to and once following the 2015-2016 El Niño event. These plots experienced the highest temperatures and driest conditions on record. The record temperature did not significantly reduce carbon gains from tree growth or significantly increase carbon losses from tree mortality, but the record drought did significantly decrease net carbon uptake. Overall, the long-term biomass increase of these forests was reduced due to the El Niño event, but these plots remained a live biomass carbon sink (0.51 ± 0.40 Mg C ha-1 y-1) despite extreme environmental conditions. Our analyses, while limited to African tropical forests, suggest they may be more resistant to climatic extremes than Amazonian and Asian forests.Item Open Access Roles of seed and establishment limitation in determining patterns of afrotropical tree recruitment.(PloS one, 2013-01) Clark, Connie J; Poulsen, John R; Levey, Doug JQuantifying the relative importance of the multiple processes that limit recruitment may hold the key to understanding tropical tree diversity. Here we couple theoretical models with a large-scale, multi-species seed-sowing experiment to assess the degree to which seed and establishment limitation shape patterns of tropical tree seedling recruitment in a central African forest. Of five randomly selected species (Pancovia laurentii, Staudtia kamerunensis, Manilkara mabokeensis, Myrianthus arboreas, and Entandophragma utile), seedling establishment and survival were low (means of 16% and 6% at 3 and 24 months, respectively), and seedling density increased with seed augmentation. Seedling recruitment was best explained by species identity and the interaction of site-by-species, suggesting recruitment probabilities vary among species and sites, and supporting the role of niche-based mechanisms. Although seed augmentation enhanced initial seedling density, environmental filtering and post-establishment mortality strongly limited seedling recruitment. The relative importance of seed and establishment limitation changed with seed and seedling density and through time. The arrival of seeds most strongly affected local recruitment when seeds were nearly absent from a site (∼ 1 seed m(2)), but was also important when seeds arrived in extremely high densities, overwhelming niche-based mortality factors. The strength of seed limitation and density-independent mortality decreased significantly over time, while density-dependent mortality showed the opposite trend. The varying strengths of seed and establishment limitation as a function of juvenile density and time emphasize the need to evaluate their roles through later stages of a tree's life cycle.Item Open Access Vertebrate community composition and diversity declines along a defaunation gradient radiating from rural villages in Gabon(Journal of Applied Ecology, 2017-06-01) Koerner, Sally E; Poulsen, John R; Blanchard, Emily J; Okouyi, Joseph; Clark, Connie J© 2016 The Authors. Journal of Applied Ecology © 2016 British Ecological Society Anthropocene defaunation is the global phenomenon of human-induced animal biodiversity loss. Understanding the patterns and process of defaunation is critical to predict outcomes for wildlife populations and cascading consequences for ecosystem function and human welfare. We investigated a defaunation gradient in north-eastern Gabon by establishing 24 transects at varying distances (2–30 km) to rural villages and surveying the abundance and composition of vertebrate communities. Distance from village was positively correlated with observations of hunting (shotgun shells, campfires, hunters), making it a good proxy for hunting pressure. Species diversity declined significantly with proximity to village, with mammal richness increasing by roughly 1·5 species every 10 km travelled away from a village. Compared to forest far from villages, the wildlife community near villages consisted of higher abundances of large birds and rodents and lower abundances of large mammals like monkeys and ungulates. Distance to nearest village emerged as a key driver of the relative abundance of five of the six taxonomic guilds, indicating that the top-down force of hunting strongly influences large vertebrate community composition and structure. Several measures of vegetation structure also explained animal abundance, but these varied across taxonomic guilds. Forest elephants were the exception: no measured variable or combination of variables explained variation in elephant abundances. Synthesis and applications. Hunting is concentrated within 10 km around villages, creating a hunting halo characterized by heavily altered animal communities composed of relatively small-bodied species. Although the strongest anthropogenic effects are relatively distance-limited, the linear increase in species richness shown here even at distances 30 km from villages suggests that hunting may have altered vertebrate abundances across the entire landscape. Central African forests store > 25% of the carbon in tropical forests and are home to 3000 endemic species, but roughly 53% of the region lies within the village hunting halo. Resource management strategies should take into account this hunting-induced spatial variation in animal communities. Near villages, resource management should focus on sustainable community-led hunting programmes that provide long-term supplies of wild meat to rural people. Resource management far from villages should focus on law enforcement and promoting industry practices that maintain remote tracts of land to preserve ecosystem services like carbon storage and biodiversity.