Megafaunal influences on tree recruitment in African equatorial forests

The forests of central Africa are distinct from counterpart forests in Amazonia by having fewer trees ≥ 10 cm dbh ha^?1, especially small trees < 20 cm dbh, and in having sapling cohorts with less diversity than canopy trees. We tested four hypotheses to investigate whether herbivory, in particular, browsing by forest elephants, could be a factor in these differences. We found that the density of small saplings and diversity of large saplings were inversely associated with local density of elephants. We then tested the hypothesis that steep slopes might serve as refugia from elephant foraging, but found that elephants routinely forage on slopes with an inclination of less than ca 30 deg. Nevertheless, the diversity of small trees (≥ 10 cm, < 20 cm dbh) was higher on slopes than on paired level‐ground sites. The incidence of break scars on saplings ≥ 2 cm dbh and < 6 cm dbh was greater (107/100 stems) on level ground than on slopes (77/100 stems), although high variability precluded statistical significance. After correcting for background breakage not caused by elephants, an estimated 71% of breaks on level ground and 43% of breaks on slopes were attributable to elephants. Liana loads borne by trees at different sites were highly variable and unrelated to slope. Apparently, disturbances are more critical to liana development than herbivory. Elephants, along with other large mammals such as gorillas, duikers, red river hogs and rodents, appear to act as powerful filters on the tree recruitment process in African forests that still retain intact megafaunal communities.     

Seed dispersal kernel of the largest surviving megaherbivore—the African savanna elephant

Owing to the late Pleistocene extinctions, the megafauna of Europe, Australia and the Americas disappeared, and with them the dispersal service they offered megafaunal fruit. The African savanna elephant, the largest remaining megaherbivore, offers valuable insights into the seed dispersal services provided by extinct megafauna in prehistoric times. Elephant seed dispersal studies have for the most part concentrated on African and Asian forest elephants. African savanna elephants are morphologically distinct from their forest counterparts. Like the forest elephants they consume large quantities of fruit from a large number of tree species. Despite this little is known of the savanna trees that rely on elephants for their dispersal or the spatial scale at which these seeds are dispersed. We combined information from feeding trials conducted on four park elephants with field telemetry data from 38 collared elephants collected over an 8‐year period in APNR/Kruger National Park to assess the seed dispersal service provided by savanna elephants. This study provides the first detailed account of the spatial scale at which African savanna elephants disperse seeds. Our mechanistic model predicts that 50 percent of seeds are carried over 2.5 km, and distances up to 65 km are achievable in maximum gut passage time. These findings suggest the savanna elephant as the longest distance terrestrial vertebrate disperser yet investigated. Maintaining their ecological role as a seed disperser may prove a significant factor in the conservation of large‐fruited tree diversity within the savannas. These results suggest that extinct megafauna offered a functionally unique dispersal service to megafaunal fruit.     

Assessing the effects of elephant foraging on the structure and diversity of an Afrotropical forest

African forest elephants (Loxodonta cyclotis) are ecosystem engineers that browse and damage large quantities of vegetation during their foraging and movement. Though elephant trail networks and clearings are conspicuous features of many African forests, the consequences of elephant foraging for forest structure and diversity are poorly documented. In this study in northeastern Gabon, we compare stem size, stem density, proportional damage, species diversity, and species relative abundance of seedlings and saplings in the vicinity of seven tree species that produce elephant-preferred fruits (“elephant trees”) relative to control trees that do not. Across 34 survey trees, with a combined census area of 2.04 ha, we recorded data on 26,128 woody stems in three sizes classes. Compared with control trees, the area around elephant trees had the following: (a) a significantly greater proportion of damaged seedlings and a marginally greater proportion of damaged saplings (with 82% and 24% greater odds of damage, respectively); (b) no significant difference in stem density or species diversity; and (c) a significantly greater relative abundance of seedlings of elephant tree species. Increasing distance away from focal elephant trees was associated with significantly reduced sapling stem damage, significantly increased sapling stem density, and significantly increased sapling species diversity. Considered in sum, our results suggest that elephants can affect the structure and diversity of Afrotropical forests through their foraging activities, with some variation based on location and plant size class. Developing a more complete understanding of elephants’ ecological effects will require continued research, ideally with manipulative experiments.     

The African rainforest: odd man out or megafaunal landscape? African and Amazonian forests compared

Africa has been called the ‘odd man out’ because the hectare‐scale tree diversity of African equatorial forests is lower than that of forests in other parts of the tropics. Low diversity has been attributed to the smaller area of the African forest and a history of drought, fire and contraction. Several facts shed doubt on this interpretation. The current area of the central African forest is roughly 2 million km². Even during periods of Pleistocene contraction, numerous moist refugia remained, including 6 posited for Gabon, a country the size of the U. S. state of Colorado. The gamma‐diversity of Gabon is high, implying higher alpha diversities. Finally, tree diversities on small islands in the Solomons and Fiji archipelagos are twice those prevalent in Gabonese forests, suggesting that historical contractions may not have been sufficient to reduce diversity to its current level. To place the African situation in perspective, we compared tree stands in Gabon and the Peruvian Amazon. Peruvian forests contained a mean of 618 trees ≥ 10 cm dbh per ha vs 377 for Gabon, or 64% more. Peruvian forests contained relatively more small trees (≥ 10, <20 cm dbh) and many fewer large trees (≥ 20 cm dbh) than Gabonese forests. These structural differences were consistent across 10 Gabonese and 10 Peruvian sites and transcended local gradients in climate and geology, suggesting that they are intrinsic to the two continents. Tree species diversity in Perú is concentrated in the small tree class (≥ 10, <20 cm dbh), whereas it is highest in the larger tree classes in Gabon. Alpha diversity is apparently lower relative to gamma diversity in Africa than it is in Amazonian Perú , implying higher beta diversity. The densities of small plants (<1 m tall) are similar in Gabonese and Peruvian forests; the observed structural differences develop later at the sapling and small tree stages. Explaining the low hectare‐scale diversity of African forests thus reduces to understanding why the density and diversity of small trees is so anomalously low.     

Characteristics of snags and forest structure in southern mistbelt forests of the Amatole region,South Africa

Standing dead trees (or snags) are an important component of forest ecosystems, especially for tree cavity‐nesting vertebrate species, but their prevalence in South African forests remains under studied. Consequently, we investigated forest structure, and the presence and abundance of snags in six southern mistbelt forests in the Eastern Cape, South Africa. These forests have had varying levels of timber extraction over the past 150 years or more. We found snags were relatively rare in all six forests (<4.3% of trees sampled). Mean diameter at breast height (dbh) of snags ranged from 52 to 82 cm across the forests, with smaller snags in Kologha Forest and larger snags in Tyume Forest. A bimodal distribution of snag successional stages was found, with frequencies peaking at early and late stages, and few in the intermediate stages. Tree species diversity in the forests was relatively low (twelve–nineteen species across forests; only 28 species in total). There was no significant difference in dbh of trees between forests, with most occurring in the 20–29‐cm dbh size class. Future studies are required to identify trees that most likely support suitable cavities for tree cavity‐nesting bird species, and to determine cavity‐nester assemblage requirements in southern African forests.     

Does forest restoration using taungya foster tree species diversity? The case of Afram Headwaters Forest Reserve in Ghana

The taungya agro‐forestry system is an under‐researched means of forest restoration that may result in high tree diversity. Within a forest reserve in Ghana, the forest core and its surrounding Teak‐ and Cedrela‐taungya on logged, cropped and burned land were mapped with ALOS satellite imagery. Native trees, seedlings and saplings were enumerated in 70 random, nested plots, equally divided between forest and taungya. The native tree regeneration was assessed by species richness (SR), Shannon‐Wiener Index (SWI), Shannon Evenness Index (SEI) and species density (SeD) for seedlings, saplings and trees separately and combined and subsequently correlated with canopy covers (CC) in taungya. As anticipated, the taungya diversity was lower than the forest diversity but higher than reported from nontaungya exotic plantations. In the forest, the diversity of native trees increased from seedlings through saplings to trees. The reverse was found in the taungya. Taungya seedling diversity was not significantly different from the forest, while the sapling and tree diversity were significantly lower. Weak correlations of CC with SR, SWI, SEI and SeD were found. Our results suggest the need for treatment to maintain the tree diversity beyond the seedling stage in the taungya.     

Shrub facilitation drives tree establishment in a semiarid fog‐dependent ecosystem

Questions

The exceptional occurrence of tall rain forest patches on foggy coastal mountaintops, surrounded by extensive xerophytic shrublands, suggests an important role of plant–plant interactions in the origin and persistence of these patches in semi‐arid Chile. We asked whether facilitation by shrubs can explain the growth and survival of rain forest tree species, and whether shrub effects depend on the identity of the shrub species itself, the drought tolerance of the tree species and the position of shrubs in regard to wind direction.

Location

Open area–shrubland–forest matrix, Fray Jorge Forest National Park, Chile.

Methods

We recorded survival after 12 years of a ~3600 tree saplings plantation (originally ~30‐cm tall individuals) of Aextoxicon punctatum, Myrceugenia correifolia and Drimys winteri placed outside forests, beneath the shrub Baccharis vernalis, and in open (shrub‐free) areas. We assessed the effects of neighbouring shrubs and soil humidity on survival and growth along a gradient related to the direction of fog movement.

Results

B. vernalis had a clear facilitative effect on tree establishment and survival since, after ~12 years, saplings only survived beneath the shrub canopy. Long‐term survival strongly depended on tree species identity, drought tolerance and position along the soil moisture gradient, with higher survival of A. punctatum (>35%) and M. correifolia (>14%) at sites on wind‐ and fog‐exposed shrubland areas. Sites occupied by the shrub Aristeguietia salvia were unsuitable for trees, presumably due to drier conditions than under B. vernalis.

Conclusions

Interactions between shrubs and fog‐dependent tree species in dry areas revealed a strong, long‐lasting facilitation effect on planted tree's survival and growth. Shrubs acted as benefactors, providing sites suitable for tree growth. Sapling mortality in the shrubland interior was caused by lower soil moisture, the consequence of lower fog loads in the air and thus insufficient facilitation. While B. vernalis was a key ecosystem engineer (nurse) and intercepted fog water that dripped to trees planted underneath, drier sites with A. salvia were unsuitable for trees. Consequently, nurse effects related to water input are strongly site and species specific, with facilitation by shrubs providing a plausible explanation for the initiation of forest patches in this semi‐arid landscape.     

Asian Tapirs Are No Elephants When It Comes To Seed Dispersal

The elimination of the largest herbivores (elephants and rhinoceroses) from many forests in tropical East Asia may have severe consequences for plant species that depend on them for seed dispersal. We assessed the capacity of Malayan tapirs Tapirus indicus—the next largest nonruminant herbivore in the region—as a substitute for the lost megafauna in this role by studying their ability to disperse the seeds of nine fleshy‐fruited plants with seeds 5–97 mm in length. We combined information from feeding trials, germination tests, and field telemetry to assess the effect of tapir consumption on seed viability and to estimate how far the seeds would be dispersed. The tapirs (N=8) ingested few seeds. Seed survival through gut passage was moderately high for small‐seeded plants (e.g., 36.9% for Dillenia indica) but very low for medium‐ (e.g., 7.6% for Tamarindus indica) and large‐seeded (e.g., 2.8% for Artocarpus integer) plants. Mean seed gut passage times were long (63–236 h) and only the smallest seeds germinated afterwards. Using movement data from four wild tapirs in Peninsular Malaysia we estimated mean dispersal distances of 917–1287 m (range=22–3289 m) for small‐seeded plants. Malayan tapirs effectively dispersed small‐seeded plants but acted as seed predators for the large‐seeded plants included in our study, suggesting that they cannot replace larger herbivores in seed dispersal. With the absence of elephants and rhinos many megafaunal‐syndrome plants in tropical East Asia are expected to face severe dispersal limitation problems.     

Rapid recovery of tropical forest diversity and structure after shifting cultivation in the Philippines uplands

Shifting cultivation is a widespread land‐use in the tropics that is considered a major threat to rainforest diversity and structure. In the Philippines, a country with rich biodiversity and high rates of species endemism, shifting cultivation, locally termed as kaingin, is a major land‐use and has been for centuries. Despite the potential impact of shifting cultivation on forests and its importance to many people, it is not clear how biodiversity and forest structure recover after kaingin abandonment in the country, and how well these post‐kaingin secondary forests can complement the old‐growth forests. We investigated parameters of forest diversity and structure along a fallow age gradient in secondary forests regenerating after kaingin abandonment in Leyte Island, the Philippines (elevation range: 445–650 m asl). We first measured the tree diversity and forest structure indices in regenerating secondary forests and old‐growth forest. We then measured the recovery of tree diversity and forest structure parameters in relation to the old‐growth forest. Finally, using linear mixed effect models (LMM), we assessed the effect of different environmental variables on the recovery of forest diversity and structure. We found significantly higher species density in the oldest fallow sites, while Shannon’s index, species evenness, stem number, basal area, and leaf area index were higher in the old‐growth forest. A homogeneous species composition was found across the sites of older fallow age. Multivariate analysis revealed patch size as a strong predictor of tree diversity and forest structure recovery after shifting cultivation. Our study suggests that, secondary forests regenerating after shifting cultivation abandonment can recover rapidly. Although recovery of forest structure was not as rapid as the tree diversity, our older fallow sites contained a similar number of species as the old‐growth forest. Many of these species are also endemic to the Philippines. Novel and emerging ecosystems like tropical secondary forests are of high conservation importance and can act as a refuge for dwindling tropical forest biodiversity.     

Lowland tapirs facilitate seed dispersal in degraded Amazonian forests

The forests of southeastern Amazonia are highly threatened by disturbances such as fragmentation, understory fires, and extreme climatic events. Large‐bodied frugivores such as the lowland tapir (Tapirus terrestris) have the potential to offset this process, supporting natural forest regeneration by dispersing a variety of seeds over long distances to disturbed forests. However, we know little about their effectiveness as seed dispersers in degraded forest landscapes. Here, we investigate the seed dispersal function of lowland tapirs in Amazonian forests subject to a range of human (fire and fragmentation) and natural (extreme droughts and windstorms) disturbances, using a combination of field observations, camera traps, and light detection and ranging (LiDAR) data. Tapirs travel and defecate more often in degraded forests, dispersing much more seeds in these areas [9,822 seeds per ha/year (CI_95% = 9,106; 11,838)] than in undisturbed forests [2,950 seeds per ha/year (CI_95% = 2,961; 3,771)]. By effectively dispersing seeds across disturbed forests, tapirs may contribute to natural forest regeneration—the cheapest and usually the most feasible way to achieve large‐scale restoration of tropical forests. Through the dispersal of large‐seeded species that eventually become large trees, such frugivores also contribute indirectly to maintaining forest carbon stocks. These functions may be critical in helping tropical countries to achieve their goals to maintain and restore biodiversity and its ecosystem services. Ultimately, preserving these animals along with their habitats may help in the process of natural recovery of degraded forests throughout the tropics. Abstract in Portuguese is available with online material.     

The middle Miocene palynoflora and palaeoenvironments of Eskihisar (Yatağan basin,south‐western Anatolia): a combined LM and SEM investigation

We investigated a palynological section from middle Miocene sediments at Eskihisar (south‐western Anatolia) to establish biogeographic links of the palynoflora and to infer the palaeoenvironment. Four algal palynomorphs, nine spore taxa, eight gymnosperms, three monocots and 67 dicot pollen types were encountered and investigated using the ‘single grain method’ that combines light microscopy and scanning electron microscopy. Two pollen zones reflect different phases of basin development. Zonal vegetation remained fairly stable across the section and reflects heterogeneous environments including broad‐leaved deciduous forest, subtropical forest and sclerophyllous and semi‐evergreen oak forest. Conifers were accessory elements in the broad‐leaved deciduous forest communities and replaced these at higher elevations. Some herbaceous taxa (Plumbaginaceae) indicate scattered occurrences of sandy and/or rocky soils. Biogeographic affinities are general Northern Hemisphere, North American and East Asian, as also suggested by the macrofossil record. Only two taxa provide potential biogeographic links with the African flora. This suggests that biome shifts of plant taxa between African subtropical/tropical biomes and Anatolian (western Eurasian) temperate forests and shrublands may have been rare in the middle Miocene.     

Relationships between the density of two potential restoration tree species and plant species abundance and richness in a degraded Afromontane forest of Kenya

In recent years, there have been considerable efforts to restore degraded tropical montane forests through active restoration using indigenous tree species. However, little is known about how these species used for restoration influence other species. In this study, two potential restoration species, Albizia gummifera and Neoboutonia macrocalyx, are investigated with regard to the relationship between their density and the abundance and richness of other plant species. The study was conducted in a degraded forest consisting of disturbed transition zones and secondary forest. Our results show positive relationships between the density of A. gummifera and the abundance of tree seedling and sapling richness in the transition zones and in the secondary forest. Shrub richness was negatively related to the density of A. gummifera. Abundance and richness of tree saplings and shrubs were positively related to N. macrocalyx density both in the transition zones and in the secondary forest. Herb species richness declined with N. macrocalyx density in the transition zones but increased with N. macrocalyx density in the secondary forest. The positive relationships between the density of the two tree species and species richness of other woody species suggest that both A. gummifera and N. macrocalyx can be suitable for active restoration of degraded mountain forests within their natural range.     

Molecular phylogenetics of slit‐faced bats (Chiroptera: Nycteridae) reveal deeply divergent African lineages

The bat family Nycteridae contains only the genus Nycteris, which comprises 13 currently recognized species from Africa and the Arabian Peninsula, one species from Madagascar, and two species restricted to Malaysia and Indonesia in South‐East Asia. We investigated genetic variation, clade membership, and phylogenetic relationships in Nycteridae with broad sampling across Africa for most clades. We sequenced mitochondrial cytochrome b (cytb) and four independent nuclear introns (2,166 bp) from 253 individuals. Although our samples did not include all recognized species, we recovered at least 16 deeply divergent monophyletic lineages using independent mitochondrial and multilocus nuclear datasets in both gene tree and species tree analyses. Mean pairwise uncorrected genetic distances among species‐ranked Nycteris clades (17% for cytb and 4% for concatenated introns) suggest high levels of phylogenetic diversity in Nycteridae. We found a large number of designated clades whose members are distributed wholly or partly in East Africa (10 of 16 clades), indicating that Nycteris diversity has been historically underestimated and raising the possibility that additional unsampled and/or undescribed Nycteris species occur in more poorly sampled Central and West Africa. Well‐resolved mitochondrial, concatenated nuclear, and species trees strongly supported African ancestry for SE Asian species. Species tree analyses strongly support two deeply diverged subclades that have not previously been recognized, and these clades may warrant recognition as subgenera. Our analyses also strongly support four traditionally recognized species groups of Nycteris. Mitonuclear discordance regarding geographic population structure in Nycteris thebaica appears to result from male‐biased dispersal in this species. Our analyses, almost wholly based on museum voucher specimens, serve to identify species‐rank clades that can be tested with independent datasets, such as morphology, vocalizations, distributions, and ectoparasites. Our analyses highlight the need for a comprehensive revision of Nycteridae.     

What shapes cerambycid beetle communities in a tropical forest mosaic? Assessing the effects of host tree identity,forest structure,and vertical stratification

Due to anthropogenic activities, tropical rain forests face many challenges in sustaining biodiversity and maintaining global climates. This study explores how forest successional stage, tree composition, and stratum affect communities of saproxylic cerambycid beetles—concealed feeders that play important roles in forest nutrient cycling. Forty trees in five families (Fabaceae, Lecythidaceae, Malvaceae, Moraceae, and Sapotaceae) were sampled in a mosaic of old‐growth and secondary forest on the Osa Peninsula, Costa Rica. Bait branches yielded 3549 cerambycid individuals in 49 species. Species richness was almost identical in old‐growth and secondary forest, and both yielded specialists, but abundance was higher in old‐growth forest. Overall community structure was most strongly influenced by host plant species; within most plant families it was also impacted by forest successional status. Moraceae was the exception, presumably because the focal tree species was abundant in both old‐growth and secondary forest. Several host and old‐growth specialist species reached high densities within patches of old‐growth forest, but seldom colonized apparently suitable trees within secondary forest. This suggests that even small areas of old‐growth forest can act as refuges, but that secondary forest may act as a barrier to dispersal. The vulnerability of specialized saproxylic insects to land use change will be linked to the ability of their preferred hosts to disperse to and persist in successional habitats; rearing studies may provide the most accurate method to monitor community changes over time.     

Sap‐feeding insects on forest trees along latitudinal gradients in northern Europe: a climate‐driven patterns

Knowledge of the latitudinal patterns in biotic interactions, and especially in herbivory, is crucial for understanding the mechanisms that govern ecosystem functioning and for predicting their responses to climate change. We used sap‐feeding insects as a model group to test the hypotheses that the strength of plant–herbivore interactions in boreal forests decreases with latitude and that this latitudinal pattern is driven primarily by midsummer temperatures. We used a replicated sampling design and quantitatively collected and identified all sap‐feeding insects from four species of forest trees along five latitudinal gradients (750–1300 km in length, ten sites in each gradient) in northern Europe (59 to 70°N and 10 to 60°E) during 2008–2011. Similar decreases in diversity of sap‐feeding insects with latitude were observed in all gradients during all study years. The sap‐feeder load (i.e. insect biomass per unit of foliar biomass) decreased with latitude in typical summers, but increased in an exceptionally hot summer and was independent of latitude during a warm summer. Analysis of combined data from all sites and years revealed dome‐shaped relationships between the loads of sap‐feeders and midsummer temperatures, peaking at 17 °C in Picea abies, at 19.5 °C in Pinus sylvestris and Betula pubescens and at 22 °C in B. pendula. From these relationships, we predict that the losses of forest trees to sap‐feeders will increase by 0–45% of the current level in southern boreal forests and by 65–210% in subarctic forests with a 1 °C increase in summer temperatures. The observed relationships between temperatures and the loads of sap‐feeders differ between the coniferous and deciduous tree species. We conclude that climate warming will not only increase plant losses to sap‐feeding insects, especially in subarctic forests, but can also alter plant‐plant interactions, thereby affecting both the productivity and the structure of future forest ecosystems.     

Contrasting Demographic Structure of Short‐ and Long‐lived Pioneer Tree Species on Amazonian Forest Edges

Although tropical forests have been rapidly converted into human‐modified landscapes, tree species response to forest edges remains poorly examined. In this study, we addressed four pioneer tree species to document demographic shifts experienced by this key ecological group and make inferences about pioneer response to forest edges. All individuals with dbh ≥ 1 cm of two short‐lived (Bellucia grossularioides and Cecropia sciadophylla) and two long‐lived species (Goupia glabra and Laetia procera) were sampled in 20 1‐ha forest edge plots and 20 1‐ha forest interior plots in Oiapoque and Manaus, Northeast and Central Amazon, respectively. As expected, pioneer stem density with dbh ≥ 1 cm increased by around 10–17‐fold along forest edges regardless of species, lifespan, and study site. Edge populations of long‐lived pioneers presented 84–94 percent of their individuals in sapling/subadult size classes, whereas edge populations of short‐lived pioneers showed 56–97 percent of their individuals in adult size classes. These demographic biases were associated with negative and positive net adult recruitment of long‐ and short‐lived pioneers, respectively. Our population‐level analyses support three general statements: (1) native pioneer tree species proliferate along forest edges (i.e., increased density), at least in terms of non‐reproductive individuals; (2) pioneer response to edge establishment is not homogeneous as species differ in terms of demographic structure and net adult recruitment; and (3) some pioneer species, particularly long‐lived ones, may experience population decline due to adult sensitivity to edge‐affected habitats.     

The role of remnant trees in carbon sequestration,vegetation structure and tree diversity of early succession regrowing fallows in eastern Sierra Leone

Remnant tree presence affects forest recovery after slash‐and‐burn agriculture. However, little is known about its effect on above‐ground carbon stocks, especially in Africa. We focused our study on Sierra Leone, part of the Upper Guinean forests, an important centre of endemism threatened by encroachment and forest degradation. We studied 99 (20‐m‐radius) plots aged 2–10 years with and without remnant trees and compared their above‐ground carbon stocks, vegetation structure (stem density, basal area) and tree diversity. Above‐ground carbon stocks, stem density, basal area, species richness and tree diversity increased significantly with fallow age. Remnant tree presence affected significantly tree diversity, species dominance and above‐ground carbon stocks, but not vegetation structure (stem density, basal area). Number of remnant trees and number of species of remnant trees were also important explanatory variables. Although other factors should be considered in future studies, such as the size and dispersal modes of remnant trees, our results highlight that more strategic inclusion of remnant trees is likely to favour carbon stock and forest recovery in old fallows. To our knowledge, this is the first study on early succession regrowing fallows in West Africa.     

Large herbivores regulate the spatial recruitment of a hyperdominant Neotropical palm

Large mammalian herbivores play an important role in shaping the diversity of tropical forests by affecting the survival of seedlings and saplings beneath parent plants. The white‐lipped peccary (Tayassu pecari) accounts for the largest herbivore biomass that controls seed and seedling survival in Neotropical ecosystems. However, hunting and habitat loss has driven peccaries to local extinction for most of their original distribution, so it is likely that their absence will affect plant recruitment dynamics. We tested the effects of peccary local extinction on the density and spatial distribution of the hyperdominant palm Euterpe edulis by performing a fine‐scale characterization of its spatial recruitment in six forest sites in the Brazilian Atlantic forest. We compared the age structure and the spatial patterns of seedlings, saplings, and adults as well as the relationship between them. We found that while under the presence of peccaries there was a decrease in recruitment rates under adults, the local extinction of these large mammals led to a more clumped process of spatial recruitment. Despite such contrasting spatial patterns of recruitment dynamics, neither age structure nor the random spatial distribution of adults was affected by the presence or absence of peccaries, indicating that their early effects on these palm populations are mitigated as recruitment advances. Our findings highlight the role of large‐bodied forest‐dwelling herbivores in regulating the fine‐scale spatial recruitment of plants and advance our understanding on the effects of defaunation in tropical forests. Abstract in Portuguese is available with online material.     

Changes in Elephant Abundance Affect Forest Composition or Regeneration?

While overall numbers of African elephant have declined dramatically in recent times, some populations are now confined to protected areas and are locally overabundant—an undesirable situation for both biodiversity conservation and elephants. In forested protected areas, options to manage elephants are limited because it is difficult to safely approach animals, yet it is vital that these populations are managed because browsing by elephants can dramatically alter forest ecosystems. Using data collected over 50 yr in Kibale National Park, Uganda, we examine the prediction that increasing elephant numbers and associated changes in their foraging behavior have caused a shift in tree community composition. Although the relative abundance of elephants increased significantly between 1996 and 2010, the population structure of their preferred tree food species did not change, nor did tree community composition change in favor of species able to re‐sprout after elephant damage. Furthermore, over the last 50 yr Kibale elephants have not become more selective foragers, as would be expected if more nutritious tree species were declining. However, elephants are more abundant in disturbed areas dominated by shrubs and grasses and appear to have arrested forest succession in these areas. At their current abundance, elephants have not selectively altered the composition of intact old growth forest, but they do inhibit the regeneration of disturbed areas.     

Functional community structure of African monodominant Gilbertiodendron dewevrei forest influenced by local environmental filtering

Monodominant patches of forest dominated by Gilbertiodendron dewevrei are commonly found in central African tropical forests, alongside forests with high species diversity. Although these forests are generally found sparsely distributed along rivers, their occurrence is not thought to be (clearly) driven by edaphic conditions but rather by trait combinations of G. dewevrei that aid in achieving monodominance. Functional community structure between these monodominant and mixed forests has, however, not yet been compared. Additionally, little is known about nondominant species in the monodominant forest community. These two topics are addressed in this study. We investigate the functional community structure of 10 one‐hectare plots of monodominant and mixed forests in a central region of the Congo basin, in DR Congo. Thirteen leaf and wood traits are measured, covering 95% (basal area weighted) of all species present in the plots, including leaf nutrient contents, leaf isotopic compositions, specific leaf area, wood density, and vessel anatomy. The trait‐based assessment of G. dewevrei shows an ensemble of traits related to water use and transport that could be favorable for its location near forest rivers. Moreover, indications have been found for N and P limitations in the monodominant forest, possibly related to ectomycorrhizal associations formed with G. dewevrei. Reduced leaf N and P contents are found at the community level for the monodominant forest and for different nondominant groups, as compared to those in the mixed forest. In summary, this work shows that environmental filtering does prevail in the monodominant G. dewevrei forest, leading to lower functional diversity in this forest type, with the dominant species showing beneficial traits related to its common riverine locations and with reduced soil N and P availability found in this environment, both coregulating the tree community assembly.