Non-native plantation forests as alternative habitat for native forest beetles in a heavily modified landscape

The once extensive native forests of New Zealand’s central North Island are heavily fragmented, and the scattered remnants are now surrounded by a matrix of exotic pastoral grasslands and Pinus radiata plantation forests. The importance of these exotic habitats for native biodiversity is poorly understood. This study examines the utilisation of exotic plantation forests by native beetles in a heavily modified landscape. The diversity of selected beetle taxa was compared at multiple distances across edge gradients between each of the six possible combinations of adjacent pastoral, plantation, clearfell and native forest land-use types. Estimated species richness (Michaelis–Menten) was greater in production habitats than native forest; however this was largely due to the absence of exotic species in native forest. Beetle relative abundance was highest in clearfell-harvested areas, mainly due to colonisation by open-habitat, disturbance-adapted species. More importantly, though, of all the non-native habitats sampled, beetle species composition in mature P. radiata was most similar to native forest. Understanding the influence of key environmental factors and stand level management is important for enhancing biodiversity values within the landscape. Native habitat proximity was the most significant environmental correlate of beetle community composition, highlighting the importance of retaining native remnants within plantation landscapes. The proportion of exotic beetles was consistently low in mature plantation stands, however it increased in pasture sites at increasing distances from native forest. These results suggest that exotic plantation forests may provide important alternative habitat for native forest beetles in landscapes with a low proportion of native forest cover.     

Agricultural intensification alters bat assemblage composition and abundance in a dynamic Neotropical landscape

The recent trend of agricultural intensification in tropical landscapes poses a new threat to biodiversity conservation. Conversion of previously heterogeneous agricultural landscapes to intensive plantation agriculture simplifies and homogenizes the landscape, reducing availability, and connectivity of natural habitat for native species. To assess the impact of agricultural intensification on bats, we characterized the bat assemblage in the Sarapiquí region of Costa Rica, where heterogeneous land uses are being converted to intensive, large‐scale pineapple plantations. In 2012 and 2013, we sampled bats in 20 remnant forest patches surrounded by varying proportions of pasture, mature forest, and pineapple and captured 1821 individual bats representing 39 species. We used ordination analyses to evaluate changes in species composition, where pineapple is the main component of the agricultural matrix. We identified landscape metrics specifically correlated with pineapple and used multiple linear regression to test their effects on bat species richness, diversity, and guild‐specific relative abundance. Results suggest pineapple expansion is driving changes in assemblage composition in remnant forest patches, resulting in new assemblages with higher proportions of frugivorous bats and lower proportions of insectivorous bats than in continuous mature forests. In addition, while pineapple does not diminish total bat species richness and diversity, the reduced forest cover and increased distance between forest patches in pineapple plantations has a significant negative impact on the relative abundance of insectivores. We also identify a potential threshold effect whereby patches surrounded by more than 50 percent forest can retain assemblage composition similar to that found in continuous mature forest.     

Diversity and composition of tropical butterflies along an Afromontane agricultural gradient in the Jimma Highlands,Ethiopia

Afromontane landscapes are typically characterized by a mosaic of smallholder farms and the biodiversity impacts of these practices will vary in accordance to local management and landscape context. Here, we assess how tropical butterfly diversity is maintained across an agricultural landscape in the Jimma Highlands of Ethiopia. We used transect surveys to sample understory butterfly communities within degraded natural forest, semi‐managed coffee forest (SMCF), exotic timber plantations, open woodland, croplands and pasture. Surveys were conducted in 29 one‐hectare plots and repeated five times between January and June 2013. We found that natural forest supports higher butterfly diversity than all agricultural plots (measured with Hill's numbers). SMCF and timber plantations retain relatively high abundance and diversity, but these metrics drop off sharply in open woodland, cropland and pasture. SMCF and timber plantations share the majority of their species with natural forest and support an equivalent abundance of forest‐dependent species, with no increase in widespread species. There was some incongruence in the responses of families and sub‐families, notably that Lycaenidae are strongly associated with open woodland and pasture. Adult butterflies clearly utilize forested agricultural practices such as SMCF and timber plantations, but species diversity declines steeply with distance from natural forest suggesting that earlier life‐stages may depend on host plants and/or microclimatic conditions that are lost under agricultural management. From a management perspective, the protection of natural forest remains a priority for tropical butterfly conservation, but understanding functioning of the wider landscape mosaic is important as SMCF and timber plantations may act as habitat corridors that facilitate movement between forest fragments.     

Adjacent woodlands rather than habitat connectivity influence grassland plant,carabid and bird assemblages in farmland landscapes

One response to biodiversity decline is the definition of ecological networks that extend beyond protected areas and promote connectivity in human-dominated landscapes. In farmland, landscape ecological research has focused more on wooded than open habitat networks. In our study, we assessed the influence of permanent grassland connectivity, described by grassland amount and spatial configuration, on grassland biodiversity. We selected permanent grasslands in livestock farming areas of north-western France, which were sampled for plants, carabids and birds. At two spatial scales we tested the effects of amount and configuration of grasslands, wooded habitats and crops on richness and abundance of total assemblages and species ecological groups. Grassland connectivity had no significant effects on total richness or abundance of any taxonomic group, regardless of habitat affinity or dispersal ability. The amount of wooded habitat and length of wooded edges at the 200 m scale positively influenced forest and generalist animal groups as well as grassland plant species, in particular animal-dispersed species. However, for animal groups such as open habitat carabids or farmland bird specialists, the same wooded habitats negatively influenced richness and abundance at the 500 m scale. The scale and direction of biodiversity responses to landscape context were therefore similar among taxonomic groups, but opposite for habitat affinity groups. We conclude that while grassland connectivity is unlikely to contribute positively to biodiversity, increasing or maintaining wooded elements near grasslands would be a worthwhile conservation goal. However, the requirements of open farmland animal species groups must be considered, for which such action may be deleterious.     

Leaf-litter herpetofaunal richness, abundance, and community assembly in mono-dominant plantations and primary forest of northeastern Costa Rica

Given current deforestation and land-use change in species-rich tropical forests, a pressing need in conservation biology is to understand how converted, human-modified landscapes support biodiversity. Here, we measured the species richness, abundance, and community composition of amphibians and reptiles in reference primary forest and mono-dominant plantations of three native tree species (Pentaclethra macroloba, Virola koschnyi, Vochysia guatemalensis) at La Selva Biological Station in the Caribbean lowlands of northern Costa Rica. Because these plantation species generate markedly different forest-floor habitats, we hypothesized that tree species would support different assemblages of leaf-litter herpetofauna. Primary forest, Virola, and Vochysia supported greater richness of frogs than Pentaclethra. Frog densities were significantly lower in Pentaclethra and Vochysia than in nearby primary forest. Using non-metric multidimensional scaling and permutational multivariate analysis of variance, we found Pentaclethra to support significantly different assemblages of frogs and lizards than primary forest reference sites, while Vochysia supported a unique assemblage of frogs. Our results suggest that some tree species plantations can support herpetofaunal assemblages comparable to primary forest in richness, community assembly, and abundance. While herpetofaunal community ecology varies among plantation species, our study provides a compelling example of how plantation landscapes can facilitate the restoration of native fauna on degraded landscapes.     

Bird communities of natural and modified habitats in Panama

Only a small proportion of land can realistically be protected as nature reserves and thus conservation efforts also must focus on the ecological value of agroecosystems and developed areas surrounding nature reserves. In this study, avian communities were surveyed in 11 habitat types in central Panama, across a gradient from extensive forest to intensive agricultural land uses, to examine patterns of species richness and abundance and community composition. Wooded habitats, including extensive and fragmented forests, shade coffee plantations, and residential areas supported the most species and individuals. Nearctic-Neotropical migratory species were most numerous in lowland forest fragments, shade coffee, and residential areas. Introduced Pinus caribbea and sugar cane plantations supported the fewest species compared to all other habitats. Cattle pastures left fallow for less than two years supported more than twice as many total species as actively grazed pastures, such that species richness in fallow pastures was similar to that found in wooded habitats. Community similarities were relatively low among all habitat types (none exceeding the observed 65% similarity between extensive and fragmented lowland forests), but communities in shade coffee and residential areas were 43% and 54′% similar to lowland forest fragments, respectively. Fallow pastures and residential areas shared 60% of their species. Bird communities in shade coffee and residential areas were characterized by higher proportions of frugivorous and nectarivorous species than in native forests. These same guilds also were better represented in fallow than in grazed pastures. Raptors and piscivorous species were most prevalent in cattle pastures and rice fields. These results, though based upon only species richness and abundance, demonstrate that many human-altered habitats have potential ecological value for birds, and conservation efforts in tropical areas should focus greater attention on enhancement of agricultural and developed lands as wildlife habitat. To understand the true conservation value of these modified lands will require examination not only of numbers but also of the types of species supported by these habitats, their reproductive output and survival rates.     

The effects of land-use change on arthropod richness and abundance on Santa Maria Island (Azores): unmanaged plantations favour endemic beetles

We study how endemic, native and introduced arthropod species richness, abundance, diversity and community composition vary between four different habitat types (native forest, exotic forest of Cryptomeria japonica, semi-natural pasture and intensive pasture) and how arthropod richness and abundance change with increasing distance from the native forest in adjacent habitat types in Santa Maria Island, the Azores. Arthropods were sampled in four 150 m long transects in each habitat type. Arthropods were identified to species level and classified as Azorean endemic, single-island endemic (SIE), native, or introduced. The native forest had the highest values for species richness of Azorean endemics, SIEs and natives; and also had highest values of Azorean endemic diversity (Fisher’s alpha). In contrast, the intensive pasture had the lowest values for endemic and native species richness and diversity, but the highest values of total arthropod abundance and introduced species richness and diversity. Arthropod community composition was significantly different between the four habitat types. In the semi-natural pasture, the number of SIE species decreased with increasing distance from the native forest, and in the exotic forest the abundance of both Azorean endemics and SIEs decreased with increasing distance from the native forest. There is a gradient of decreasing arthropod richness and abundance from the native forest to the intensive pasture. Although this study demonstrates the important role of the native forest in arthropod conservation in the Azores, it also shows that unmanaged exotic forests have provided alternative habitat suitable for some native species of forest specialist arthropods, particularly saproxylic beetles.     

Synergistic effects of habitat configuration and land-use intensity shape the structure of bird assemblages in human-modified landscapes across three major neotropical biomes

Maximizing biodiversity persistence in heterogeneous human-modified landscapes is hindered by the complex interactions between habitat quality and configuration of native and non-native habitats. Here we examined these complex interactions considering avian diversity across 26 sampling sites, each of which comprised of three sampling points located across a gradient of disturbance: core native habitat fragment, fragment edge, and non-native adjacent matrix. The 78 sampling points were further nested within three neotropical biomes—Amazonia, Cerrado and Pantanal—in central-western Brazil. Matrix type consisted of cattle pastures in the Amazon and teak plantations in the Pantanal and Cerrado. We considered the interactive effects of (1) disturbance-context: fragment core, edge and adjacent matrix, (2) matrix type: tree plantation or cattle pastures, both subject to varying land-use intensity, and (3) native habitat configuration (fragment size, shape and isolation) on bird species richness, abundance and composition. Based on point-count surveys, we recorded 210 bird species. Bird species richness and abundance declined across the disturbance gradient, while genus composition only differed within the adjacent matrix, particularly cattle-pastures. The effect of native habitat area was positive but only detected at fragment edges. Overall bird diversity increased at sites characterized by higher availability of either relict trees within pasture landscapes or old-growth trees within teak plantation landscapes. The core of native fragments played a primary role in ensuring the persistence of bird diversity, regardless of fragment size. In contrast to pastures, tree plantations likely harbour a higher proportion of forest-dependent species while bird diversity can be further enhanced by reduced management intensity in both matrix types. Strategies to maximize avian persistence should not only include retaining native habitats, but also maximizing the size of core native habitats. Likewise, more structurally complex matrix types should be encouraged while maintaining low levels of land-use intensity.

     

Does plantation forestry restore biodiversity or create green deserts? A synthesis of the effects of land-use transitions on plant species richness

Plantations are established for a variety of reasons including wood production, soil and water conservation, and more recently, carbon sequestration. The effect of this growing land-use change on biodiversity, however, is poorly understood and considerable debate exists as to whether plantations are ‘green deserts’ or valuable habitat for indigenous flora and fauna. This paper synthesizes peer-reviewed articles that provide quantitative data on plant species richness in plantations and paired land uses, most often representative of pre-plantation land cover. The results of this synthesis suggest that the value of plantations for biodiversity varies considerably depending on whether the original land cover is grassland, shrubland, primary forest, secondary forest, or degraded or exotic pasture, and whether native or exotic tree species are planted. The results of this study suggest that plantations are most likely to contribute to biodiversity when established on degraded lands rather than replacing natural ecosystems, such as forests, grasslands, and shrublands, and when indigenous tree species are used rather than exotic species. These findings can help guide afforestation and reforestation programs, including those aimed at increasing terrestrial carbon sequestration.     

Effects of habitat transitions on rainforest bird communities across an anthropogenic landscape mosaic

We compared bird community responses to the habitat transitions of rainforest‐to‐pasture conversion, consequent habitat fragmentation, and post‐agricultural regeneration, across a landscape mosaic of about 600 km² in the eastern Australian subtropics. Birds were surveyed in seven habitats: continuous mature rainforest; two size classes of mature rainforest fragment (4–21 ha and 1–3 ha); regrowth forest patches dominated by a non‐native tree (2–20 ha, 30–50 years old); two types of isolated mature trees in pasture; and treeless pasture, with six sites per habitat. We compared the avifauna among habitats and among sites, at the levels of species, functional guilds, and community‐wide. Community‐wide species richness and abundance of birds in pasture sites were about one‐fifth and one‐third, respectively, of their values in mature rainforest (irrespective of patch size). Many measured attributes changed progressively across a gradient of increased habitat simplification. Rainforest specialists became less common and less diverse with decreased habitat patch size and vegetation maturity. However, even rainforest fragments of 1–3 ha supported about half of these species. Forest generalist species were largely insensitive to patch size and successional stage. Few species reached their greatest abundance in either small rainforest fragments or regrowth. All pastures were dominated by bird species whose typical native habitats were grassland, wetland, and open eucalypt forest, while pasture trees modestly enhanced local bird communities. Overall, even small scattered patches of mature and regrowth forest contributed substantial bird diversity to local landscapes. Therefore, maximizing the aggregate rainforest area is a useful regional conservation strategy.     

Ferns,frogs, lizards,birds and bats in forest fragments and shade cacao plantations in two contrasting landscapes in the Atlantic forest,Brazil

The traditional shade cacao plantations (cabrucas) of southern Bahia, Brazil, are biologically rich habitats, encompassing many forest-dwelling species. However, a critical question for the conservation management of this specific region, and the highly fragmented Atlantic forest in general, is to what extent the conservation value of cabrucas relies on the presence of primary forest habitat in the landscape. We investigated the relative importance of cabrucas and forests for the conservation of five diverse biological groups (ferns, frogs, lizards, birds and bats) in two contrasting landscapes in southern Bahia, one dominated by forest with some interspersed cabrucas, and one dominated by cabrucas with interspersed forest fragments. The community structure (richness, abundance and diversity) of all biological groups differed between cabrucas and forests, although these differences varied among groups. A high number of forest species was found in the cabrucas. However, there were pronounced differences between the two landscapes with regard to the ability of cabrucas to maintain species richness. Irrespective of the biological group considered, cabrucas located in the landscape with few and small forest fragments supported impoverished assemblages compared to cabrucas located in the landscape with high forest cover. This suggests that a greater extent of native forest in the landscape positively influences the species richness of cabrucas. In the landscape with few small forest fragments interspersed into extensive areas of shade cacao plantations, the beta diversity of birds was higher than in the more forested landscape, suggesting that forest specialist species that rarely ventured into cabrucas were randomly lost from the fragments. These results stress both the importance and the vulnerability of the small forest patches remaining in landscapes dominated by shade plantations. They also point to the need to preserve sufficient areas of primary habitat even in landscapes where land use practices are generally favorable to the conservation of biodiversity.     

Conservation value of degraded habitats for forest birds in southern Peninsular Malaysia

Clearance of tropical forest for agricultural purposes is generally assumed to seriously threaten the survival of forest species. In this study, we quantified the conservation value, for forest bird species, of three degraded habitat types in Peninsular Malaysia, namely rubber tree plantations, oil palm plantations, and open areas. We surveyed these degraded habitats using point counts to estimate their forest bird species richness and abundance. We assessed whether richness, abundance, and activities of different avian dietary groups (i.e. insectivores and frugivores) varied among the habitats. We identified the critical habitat elements that accounted for the distribution of forest avifauna in these degraded habitats. Our results showed that these habitats harboured a moderate fraction of forest avifauna (approximately 46–76 species) and their functions were complementary (i.e. rubber tree plantations for moving; open habitats for perching; shrubs in oil palm plantations for foraging). In terms of species richness and abundance, rubber tree plantations were more important than oil palm plantations and open habitats. The relatively high species richness of this agricultural landscape was partly due to the contiguity of our study areas with extensive forest areas. Forecasts of forest-species presence under various canopy cover scenarios suggest that leaving isolated trees among non-arboreal crops could greatly attract relatively tolerant species that require tree canopy. The conservation value of degraded habitats in agricultural landscapes seems to depend on factors such as the type of crops planted and distance to primary forest remnants.     

Width of riparian buffer and structure of adjacent plantations influence occupancy of conservation priority birds

Conservation of biodiversity on forest landscapes dominated by plantations has become an increasingly important topic, and opportunities to maintain or enhance biodiversity within these forests need to be recognized and applied. Riparian buffers of mature forest retained along streams in managed forest landscapes offer an opportunity to enhance biodiversity across these landscapes. However, influence of buffer width and structure of adjacent plantations on habitat use by birds is not well understood. We modeled probability of occupancy, while accounting for variable detection probabilities, for 16 bird species of regional conservation importance in the Ouachita Mountains of Arkansas, USA. We examined occurrence of breeding birds in streamside management zone (SMZ) buffers embedded in three structural classes of pine plantation: young open-canopy, closed-canopy, and older thinned plantations. Our occupancy models included a positive association with SMZ width for nine bird species associated with mature forests. Models for three early successional species (prairie warbler [Dendroica discolor], white-eyed vireo [Vireo griseus], and northern bobwhite [Colinus virginianus]) included a negative association with SMZ width. Occupancy models for Acadian flycatcher (Empidonax virescens), summer tanager (Piranga rubra), pine warbler (Dendroica pinus), prairie warbler, and northern bobwhite also included structural condition of adjacent plantations, but most species did not appear affected by condition of surrounding plantations. We found diverse responses among species to width of retained SMZs and structure of adjacent plantations; some species apparently benefitted from SMZs >100 m wide, while others benefitted from narrow buffers. Furthermore, most species traditionally associated with mature forests were common in narrow SMZs, regardless of width. Thus, optimal width of SMZs relative to avian conservation depends on the species of greatest conservation interest.     

Understory Colonization of Eucalyptus Plantations in Hawaii in Relation to Light and Nutrient Levels

Exotic tree plantations may serve as catalysts for native forest regeneration in agriculturally degraded landscapes. In 2001, we evaluated plant species regeneration in the understory of a 7‐year‐old experimental Eucalyptus saligna forest in Hawaii approximately 1 year after the cessation of 5 years of herbicide. These forests were organized in a 2 × 2–factorial design of planting density (1 × 1– or 3 × 3–m spacing) and fertilization (unfertilized control and regular fertilization), which resulted in varying resource availabilities. We found that understory biomass was highest under high light conditions, regardless of fertilization treatment, whereas species richness was lowest under fertilized 1 × 1–m plots. The understory was dominated by species exotic to Hawaii. The most common tree species, the noxious weed Citharexylum caudatum, was particularly successful because high light–saturated photosynthesis rates and a low light compensation point allowed for high growth and survival under both light conditions. To assess longer‐term recruitment patterns, we resurveyed a portion of this site in 2006 and also surveyed five Eucalyptus plantations in this region of Hawaii that differed in age (5–23 years), species (E. saligna, E. grandis, E. cloeziana, E. microcorys), and management (experimental, industrial, nonindustrial stewardship); all were established on previous agricultural sites within approximately 3 km of native‐dominated forest. Again, very few native species were present in any of the stands, indicating that within certain landscapes and for native species with certain life history traits, exotic plantations may be ineffective nursery ecosystems for the regeneration of native species.     

Effects of abandoned Eucalyptus plantations on lizard communities in the Brazilian Cerrado

The rapid expansion of human altered landscapes affects biodiversity on every continent. A fundamental goal of conservation biologists is to understand why certain species are at risk of extinction while others are able to persist in human altered landscapes. Afforestation, the conversion of unforested lands to planted forest, is rapidly altering many natural landscapes worldwide. In the Cerrado (Brazilian savanna), a global biodiversity hotspot, a shortage of government incentives has the landscape riddled with abandoned plantation forests that are not subject to active restoration projects. Studies investigating the impacts of abandoned plantations on biodiversity are strikingly limited. We examine the effects of abandoned Eucalyptus plantations on the structure of Cerrado lizard communities. We assessed changes in lizard capture, richness and equitability along cerrado sensu stricto—Eucalyptus transects. Our results indicate abandoned Eucalyptus plantations have subsets of Cerrado species persisting with a great loss of endemic species. The cerrado sensu stricto—Eucalyptus linear transect analysis demonstrated distance from native habitat is positively correlated with loss of biodiversity. We performed correspondence analyses to summarize the variation in species captures across different sites, habitats and pitfall array positions. These analyses depicted strong species associations between habitats and their pitfall array positions. This study is the first to show the negative impacts of abandoned Eucalyptus plantations on Cerrado lizard communities, serving as a cautionary tale of Cerrado biodiversity non-resilience in abandoned Eucalyptus plantations. Mitigation requires that abandoned Eucalyptus plantations are made more suitable to Cerrado lizards by implementing targeted habitat heterogeneity restoration.     

Predicting effects of large‐scale reforestation on native and exotic birds

Aim

Ecological restoration is critical for recovering biodiversity and ecosystem services, yet designing interventions to achieve particular outcomes remains fraught with challenges. In the extensive regions where non‐native species are firmly established, it is unlikely that historical conditions can be fully reinstated. To what degree, and how rapidly, can human‐dominated areas be shifted via restoration into regimes that benefit target species, communities or processes?

Location

We explore this question in a >20‐year‐old reforestation effort underway at Hakalau Forest National Wildlife Refuge in montane Hawaii. This large‐scale planting of Acacia koa trees is designed to secure populations of globally threatened bird species by transitioning the site rapidly from pasture to native forest.

Methods

We surveyed all forest birds in multiple corridors of young planted trees, remnant corridors of mature trees along gulches and at sites within mature forest. Using a Bayesian hierarchical approach, we identified which factors (distance from forest, habitat type and surrounding tree cover) had the most important influence on native and exotic bird abundance in the reforestation area.

Results

We found that 90% of native and exotic bird species responded quickly, occupying corridors of native trees approximately a decade after planting. However, native and exotic forest birds responded to markedly different characteristics of the reforested area. Native bird abundance was strongly predicted by proximity to mature forest and remnant corridors; conversely, exotic bird abundance was best predicted by overall tree cover throughout the area reforested.

Main conclusions

Our results demonstrate that large‐scale tree planting in corridors adjacent to mature forest can catalyse rapid recovery (both increased abundance and expanded distribution) of forest birds and that it is possible to design reforestation to benefit native species in novel ecosystems.

     

The role of native forest plantations in the conservation of Neotropical birds: the case of the Andean alder

The gradual increase in reforested areas worldwide, as a strategy for mitigating native forest loss, has stressed the need of assessing their real value as habitat for native species. Forest plantations, particularly those based on native species, could be valuable for conservation purposes, especially in heavily fragmented and disturbed ecosystems. We evaluated the value of a monoculture of a native tree species, the Andean alder (Alnus acuminata), for the conservation of avifauna in the Central Andes region, which is considered a bird species diversity hotspot but also suffers from high anthropogenic disturbance levels. Our results suggest that alder plantations are valuable for conservation from three points of view: (1) they have similar or greater bird species richness and abundance than secondary native forests; (2) low community similarities are found between this type of forest compared to secondary forest stands (with 27 species exclusive to alder plantations); and (3) three near threatened species (Odontophorus hyperythrus, Eriocnemis derbyi, and Cyanolyca viridicyanus). Further, 27 out of the 85 species found at the alder plantations were of least concern but showing decreasing population trends. While forest plantations do not replace native forests, they offer habitat for many bird species, some of them being of conservation concern (i.e., included in an IUCN threat category) or with decreasing populations. Hence establishing native species plantations among native forest remnants – especially in heavily fragmented landscapes – could have a positive effect in the conservation of threatened avifauna.     

Diversity and composition of arboreal beetle assemblages in tropical pasture afforestations: effects of planting schemes and tree species identity

Timber tree plantations are considered for rehabilitating forest biodiversity in the tropics, but knowledge on determinants of faunal diversity patterns in such human-modified forest landscapes is scarce. We quantified the composition of beetle assemblages on three native timber species (Anacardium excelsum, Cedrela odorata and Tabebuia rosea) planted on former pasture to assess effects of tree species identity, tree species diversity, and insecticide treatment on a speciose group of animals in tropical plantations. The beetle assemblage parameters ‘abundance’, ‘species richness’, ‘Chao1 estimated species richness’ and ‘Shannon diversity’ were significantly reduced by insecticide treatment for each tree species. Shannon diversity increased with stand diversification for T. rosea but not for A. excelsum and C. odorata. Species similarity was highest (lowest species turnover) between beetle assemblages on T. rosea, and it was lowest (highest species turnover) for assemblages on insecticide-treated trees of all timber species. Considering trophic guilds, herbivorous beetles dominated on all tree species and in all planting schemes. Herbivores were significantly more dominant on T. rosea and C. odorata than on A. excelsum, suggesting that tree species identity affects beetle guild structure on plantation trees. Insecticide-treated stands harbored less herbivores than untreated stands, but exhibited a high abundance of predator beetle species. Our study revealed that even young pasture-afforestations can host diverse beetle assemblages and thus contribute to biodiversity conservation in the tropics. The magnitude of this contribution, however, may strongly depend on management measures and on the selected tree species.     

Impact of landscape and corridor design on primates in a large-scale industrial tropical plantation landscape

Tropical plantations are rapidly expanding as a source of industrial wood. In Indonesia, such large-scale industrial plantations are generally made of large mono-specific blocks interspersed with natural forest remnants. The extent and biodiversity value of these remnants vary as laws and regulations on their design and management are either unclear, without solid scientific basis or left to the interpretation of private companies responsible for the plantations. Our study area comprises of three Acacia mangium plantations, which have on average 18% of their total area set aside from production and conserved as natural forests. These remnant natural forests may, if appropriately designed and managed, be used to mitigate the negative impact of plantations on biodiversity by providing some degree of connectivity with and between remaining natural forest patches (such as the Tesso Nilo conservation area). We sampled natural vegetation in one and primate diversity in all three plantation sector and examined patterns of primate species richness and abundance with relation to spatial arrangement and dimensions of conservation area, which has been set aside from plantation production. We demonstrate unambiguously the critical importance of a well-connected network of natural forest corridors in the plantation landscape to maintain primates and discuss the potential biodiversity value of natural forest remnants in broad-scale industrial landscapes.     

Do riparian reserves support dung beetle biodiversity and ecosystem services in oil palm-dominated tropical landscapes?

Agricultural expansion and intensification are major threats to global biodiversity, ecological functions, and ecosystem services. The rapid expansion of oil palm in forested tropical landscapes is of particular concern given their high biodiversity. Identifying management approaches that maintain native species and associated ecological processes within oil palm plantations is therefore a priority. Riparian reserves are strips of forest retained alongside rivers in cultivated areas, primarily for their positive hydrological impact. However, they can also support a range of forest‐dependent species or ecosystem services. We surveyed communities of dung beetles and measured dung removal activity in an oil palm‐dominated landscape in Sabah, Malaysian Borneo. The species richness, diversity, and functional group richness of dung beetles in riparian reserves were significantly higher than in oil palm, but lower than in adjacent logged forests. The community composition of the riparian reserves was more similar to logged forest than oil palm. Despite the pronounced differences in biodiversity, we did not find significant differences in dung removal rates among land uses. We also found no evidence that riparian reserves enhance dung removal rates within surrounding oil palm. These results contrast previous studies showing positive relationships between dung beetle species richness and dung removal in tropical forests. We found weak but significant positive relationships between riparian reserve width and dung beetle diversity, and between reserve vegetation complexity and dung beetle abundance, suggesting that these features may increase the conservation value of riparian reserves. Synthesis and applications: The similarity between riparian reserves and logged forest demonstrates that retaining riparian reserves increases biodiversity within oil palm landscapes. However, the lack of correlation between dung beetle community characteristics and dung removal highlights the need for further research into spatial variation in biodiversity–ecosystem function relationships and how the results of such studies are affected by methodological choices.