Tree Flora Research Articles

Consistent patterns of elevational change in tree taxonomic and phylogenetic diversity across Malesian mountain forests

AbstractAimIn order to investigate the relative importance of ecological (habitat specialization) and biogeographical (speciation, geographical dispersal limitation) processes as causes of non‐random spatial distribution of tree species in the mountain forests of Malesia, we analysed the elevational change in the taxonomic and phylogenetic diversity of tree assemblages in different biogeographical subregions.LocationMalesia (Borneo, Java, Sulawesi and the Philippines).MethodsTree inventory data of 12 old‐growth forests from a wide elevational range (650–3080 m a.s.l.) were taxonomically harmonized and standardized (50 random draws of 245 individuals each per plot), and the phylogeny of 204 genera was resolved and scaled to its evolutionary origin. The taxonomic and phylogenetic diversities were calculated using effective generic measures, and the diversity patterns analysed by regression, ordination and classification.ResultsThe primary factor determining the diversity patterns of the tree assemblages was elevation, whereas the influence of region was surprisingly low. This results in common elevational patterns in taxonomic and phylogenetic community structure across western and central Malesia. The major clades of the contemporary mountain forest trees must therefore have evolved before the formation of the Malay Archipelago in its present form (sympatric speciation). Taxonomic richness and phylogenetic diversity exhibited opposite trends with elevation. Generic richness decreased linearly with elevation; the phylogenetic structure of high‐elevation forests revealed overdispersion, indicating convergent trait evolution towards higher elevations, whereas the submontane and colline assemblages showed clustering with a considerable number of confamilials. The upper montane forests of Borneo and Sulawesi were characterized by the dominance of Southern Hemisphere conifers, which differentiated them from lower‐elevation communities.Main conclusionsOur results indicate that ecological, evolutionary and biogeographical processes (environmental filtering, sympatry and long‐distance dispersal) have shaped the contemporary community structure of Malesian mountain forests. Wallace's Line may represent a significant barrier between the lowland tree floras of Borneo and Sulawesi, but this is not true for those at higher elevations. The uniqueness of high‐elevation forests in terms of their high phylogenetic diversity and of their unusual structure calls for a high priority in conservation programmes.

Drivers for colonization and sustainable management of tree-dominated stonewall ecosystems

Cities provide diverse natural, ruderal and artificial habitats for plants to enrich urban biodiversity. Stone retaining walls (SRW) in urban Hong Kong offer unique analog artificial-cliff habitats for spontaneous colonization mainly by native strangler-fig trees of genus Ficus, to create a special stonewall ecosystem. Field survey of 289 SRW in the old urban core found 793 stonewall trees from 28 species, 21 of which were rare to solitary. Tree seedlings, hacked trees and coverage of shrubs, herbs and non-vascular plants were also assessed. Old SRW with irregular stone size and shape and open unmortared joints were conducive to seed lodging by frugivorous birds and seedling establishment. Spread of aerial roots on wall face followed by penetration of joints to reach the soil retained behind the wall (aft-soil) denoted the critical tipping point in tree establishment. Regression analysis identified explanatory variables for presence and quantities of wall vegetation. Open joints, ledges and cracks provided enabling micro-niches to raise tree frequencies or diversities. Volcanic masonry blocks with more nutrient release upon weathering were more amenable to tree colonization than granite. Aggressive government wall maintenance regularly removed tree seedlings. Similarly unsympathetic maintenance by private land-owners also led to tree hacking. Low-elevation location with intensive urban development demanded more vigorous wall-vegetation clearance. Similarity in species composition of tree seedlings, hacked trees and established trees signified persistence of initial tree flora in the course of stonewall ecosystem succession. Abiotic components also experienced little changes. Wall and tree should be co-managed as an integrated unit to foster unimpeded tree growth and regeneration. Harmful maintenance operations could be revamped to preserve or restore pertinent conditions for trees. Key research findings were translated into specific measures for sustainable ecosystem management of the valuable natural and cultural heritage.

Seed Dispersal in the Dark: Shedding Light on the Role of Fruit Bats in Africa

AbstractIn spite of their recognized importance as seed dispersers in other parts of the tropics, seed dispersal by fruit bats has received scant research attention in Africa. To evaluate the role of African fruit bats in seed dispersal, we studied fruits and seeds below 480 bat feeding roosts in the East Usambara Mountains of Tanzania. We compared these findings to those reported in other African localities to place our results in a broader context. We found 49 plant species dispersed by bats: 28 species, 18 genera, and one family are novel reports of bat dispersal in Africa. Approximately 20 percent of the submontane tree flora of the East Usambaras is bat‐dispersed, including both widespread and endemic trees. African fruit bats are important seed dispersers at our study site because they move seeds of dozens of species tens or hundreds of meters, even seeds that are too large to ingest (greater than 5 mm in length). Fruit bats are likely important seed dispersers in other Afrotropical forests, as bats elsewhere in Africa are known to consume 20 genera and 16 species of plants reported here. Insights from studying remains under bat feeding roosts offer a simple method to further document and substantially increase our understanding of the role of African fruit bats in seed dispersal.

Biodiversità nella dendroflora italiana

In the vascular flora native to Italy,which consists of about 7,000 species, trees include few units. that, between Gymnosperms and Angiosperms, are not more than 188 species and infraspecific taxa.Indeed the Italian tree flora is diversified and enriched by woody polistemmed or shrubby species that, growing old and in special conditions, could reach a tree-likesize. Genetic expressions of classic tree-like species, variously treated from the taxonomical point of view, are also to be added. The tree like flora here taken into account amounts to 53 genera (7 Gymnosperms and 46 Angiosperms) on the whole consisting of 188 specific and infraspecific taxa (21 Gymnosperms and 167 Angiosperms). Several genera (Pinus,Quercus, Salix, Pyrus, Tamarix) are highly diversified. The Rosaceae family, including Crataegus, Malus, Pyrus, Prunus and Sorbus is the richest in genera. In the Fagaceae family, consisting of Castanea, Fagus, and Quercus, the first two genera are monospecific while Quercus is highly diversified from the taxonomical point of view. In the Salicaceae family, the genus Salix alone is taxonomically diversified almost as the whole genus Quercus. Under the the phyto-geographycal aspect, the Italian tree flora is mainly correlated to the European characteristics, rather than the Mediterranean ones; endemism is more remarkable as far as infraspecific taxa are concerned;nevertheless there are also several noteworthy endemic species belonging to the genera Abies, Betula,Malus and Pyrus.

Evolution of gliding in Southeast Asian geckos and other vertebrates is temporally congruent with dipterocarp forest development

Gliding morphologies occur in diverse vertebrate lineages in Southeast Asian rainforests, including three gecko genera, plus frogs, snakes, agamid lizards and squirrels. It has been hypothesized that repeated evolution of gliding is related to the dominance of Asian rainforest tree floras by dipterocarps. For dipterocarps to have influenced the evolution of gliding in Southeast Asian vertebrates, gliding lineages must have Eocene or later origins. However, divergence times are not known for most lineages. To investigate the temporal pattern of Asian gliding vertebrate evolution, we performed phylogenetic and molecular clock analyses. New sequence data for geckos incorporate exemplars of each gliding genus (Cosymbotus, Luperosaurus and Ptychozoon), whereas analyses of other vertebrate lineages use existing sequence data. Stem ages of most gliding vertebrates, including all geckos, cluster in the time period when dipterocarps came to dominate Asian tropical forests. These results demonstrate that a gliding/dipterocarp correlation is temporally viable, and caution against the assumption of early origins for apomorphic taxa.

Bacterial community structure of contrasting soils underlying Bornean rain forests: Inferences from microarray and next-generation sequencing methods

Soil microbial diversity is vast, and we lack even basic understanding of how this diversity is distributed ecologically. Using pyrosequencing and microarray methods, we quantified the structure of bacterial communities in two contrasting soils underlying Bornean rain forest (clay and sandy loam) that differ markedly in soil properties, aboveground tree flora, and leaf litter decomposition rates. We found significant soil-related taxonomic and phylogenetic differences between communities that, due to their proximity, are independent of climate. Bacterial communities showed distinct compositional and taxon-abundance distributions that were significantly correlated with the structure of the overlying tree community. Richness of bacteria was greater in the more resource-rich clay soil. Phylogenetic community analyses suggested that environmental filtering may be an important mechanism of community assembly in clay, compared to niche-competition in sandy loam. The Acidobacteria were the most abundant group in clay, but the Proteobacteria dominated in sandy loam. Of the ten most abundant classes, the Actinobacteria, Betaproteobacteria, Clostridia, Bacilli, and Gammaproteobacteria were more abundant in sandy loam than clay. Our study, which is the first to quantify edaphic variation in bacterial communities using high-throughput methods in soils underlying one of the most tree species rich forests on Earth, indicates an important role of plant–soil feedbacks linking the community structure of the trees and the underlying soil microbiome. We suggest the biochemical composition of carbon and nutrient resources in plant litter and soil pH and oxygen availability as important determinants of the distribution of bacterial diversity.

The status of conservation of urban forests in eastern Amazonia

This study aims to identify the remnant tree flora in six forest fragments in the metropolitan area of Belém and to analyze these fragments in terms of biological conservation, species richness and diversity in the local urban landscape. The fragments and their respective sampling areas were as follows: Amafrutas reserve (15 ha), Trambioca Is. reserve (2 ha), Bosque Rodrigues Alves city park (15 ha), Combu Is. reserve (10 ha), Gunma Park reserve (10 ha) and Mocambo reserve (5 ha). Inventories were built from lineal plots of 250 m² and included trees with DBH equal to or greater than 10 cm at a height of 1.3 m above ground. Sixty-nine families and 759 species, of which eight were officially listed as endangered (Brazilian National Flora: Ministry of Environment, Normative Instruction of September, 2008; Pará State Flora: Decree Nº. 802 of February 2008) were recorded. These endangered species are: Aspidosperma desmanthum Benth. ex Müll. Arg. (Apocynaceae), Cedrela odorata L. (Meliaceae), Eschweilera piresii S.A Mori (Lecythidaceae), Euxylophora paraensis Huber (Rutaceae), Hymenolobium excelsum Ducke (Leguminosae), Manilkara huberi (Ducke) Chevalier (Sapotaceae), Tabebuia impetiginosa (Mart. ex DC.) Standl. (Bignoniaceae), Mezilaurus itauba (Meisn.) Taub. ex Mez (Lauraceae) and Qualea coerulea Aubl. (Vochysiaceae). Emergency actions such as implementing management plans for already existing Conservation Units, the creation of new such units in areas of primary forest fragments (as in the case of the Amafrutas reserve), as well as the intensification of actions of surveillance and monitoring, should be undertaken by Federal, State, and Municipal environmental agencies so as to ensure the conservation of these last primary forest remnants in the metropolitan area of Belém.

REGENERATION DYNAMICS O F SILVICULTURALLY ASSISTED DRY ZONE SCRUB VEGETATION AT DAMBULLA ARBORETUM

Regeneration dynamics of silviculturally assisted scrub vegetation is described for a three year period between 1993 and 1995 in Dambulla Arboretum. The tree flora based on an enumeration of all trees above 3.1 cm girth at breast height (1cm dbh) in a plot of 1352 m2 were tabulated and analyzed. The diversity recorded in 1995 was 45 species, 42 genera and 19 families. The most diverse families were Euphorbiaceae (Relative Diversity [RD]-8.9 ) and Sapindaceae (RD-8.9) in 1993; and Euphorbiaceae (RD-13.3), Rubiaceae (RD-13.3) and Rutaceae (RD-11,1) in 1995. The most abundant families in all size classes were Euphorbiaceae (Relative Frequency [RF] -12.9) and Mimosaceae (RD-13.9) in 1993, whilst those in 1995 were 10.6 and 6.5 respectively. The most abundant species, Phyllanthus polyphyllus (Euphorbiaceae) accounted for 57.4% of the total number of trees in 1993, and 37.6% in 1995. The common species of canopy and emergent trees in the Dry Zone primary forest are not common at this stage. Six emergents (2 from root suckers), six pioneers, eight main canopy species and 25 understorey species were recorded in 1995. On this floristic evidence, it is too early to predict which species will prevail on the study plot in the regeneration process in future. Long-term studies should provide further information.

Phytogeography of the trees of the Osa Peninsula, Costa Rica

A phytogeographic analysis of the distributions of 454 species of trees native to the Osa Peninsula in 22 families revealed that 4.8% of the species are endemic to the Osa Peninsula and the adjacent mainland of Costa Rica. However, nearly one-fourth of the species might be regionally endemic to Central-South Mesoamerica (Costa Rica, Nicaragua, and Panama). Our sample suggests that 53.6% of the species occur in some part of Mesoamerica and sometimes range into northwestern South America, and that 44.5% of the species have wide distributions throughout tropical America. There is a strong affinity with the flora of northwestern South America, with 46.2% of the species on the Osa also found there. In addition, 50.6% of the tree species on the Osa occur on both the Atlantic and Pacific slopes of Central America or, if they reach South America, are sometimes found on both sides of the Andes. Major contributions to the tree flora of the Osa have been made by species arriving in the Osa by 1) dispersal from South and North America to islands in proto Central America before the formation of a dry-land connection between the two continents, and 2) migration from South America and North America after the closure of the Panamanian isthmus was made. This analysis demonstrates the importance of the Osa as a regional refuge for protecting species with distributions limited to the Osa and parts of Panama, Costa Rica, or Nicaragua. The Osa is also important because it harbors the last expanse of tropical wet forest on the Pacific slope of Central America large enough to ensure the survival of the Central American populations of widely distributed plants and animals.

A Remarkable New Species of <I>Jarandersonia</I> (Malvaceae-Brownlowioideae) from Central Kalimantan, Borneo

A new species, Jarandersonia pentaceoides (Malvaceae-Brownlowioideae), endemic to central Kalimantan, Borneo is described and illustrated. Salient morphological features of the new species that can be used to distinguish it from previously known species of the genus (i.e. J. clemensiae, J. parvifolia, J. purseglovei, J. rinoreoides and J. spinulosa) are tabulated. These include: the densely stellate-lepidote and dentate-lepidote edges of tertiary veins and honeycomb-like quaternary veins on the lower leaf surface, the kneed petiole that is swollen at both ends, and the sparsely stellate-lepidote and tufted-hairy seed coat. A key to the species of Jarandersonia is provided, as is a map of its distribution. Keywords—Borneo, endemic, flora, Jarandersonia, Malvaceae-Brownlowioideae, taxonomy. Jarandersonia Kosterm. (Malvaceae-Brownlowioideae) was established as a monotypic genus by Kostermans (1960) based on Jarandersonia paludosa Kosterm. (currently a synonym of Jarandersonia purseglovei (Kosterm.) Kosterm.), an endemic species that occurs in Sarawak, Borneo. Kostermans (1960, 1970) recognized the genus based on the distinctness of its fruit covered with slender spines bearing setose hairs. It com- prises five species distributed in Borneo (Kostermans 1970). Jarandersonia purseglovei and J. spinulosa Kosterm. are endemic to Sarawak, J. rinoreoides Kosterm. is endemic to Sabah, while the other two species J. clemensiae (Burret) Kosterm. is known from Sarawak and Kalimantan, and J. parvifolia Kosterm. occurs in Sarawak, Brunei and Kalimantan. Recent phylogenetic analy- sis of plastid atpB, rbcL and ndhF DNA sequences support the placement of Jarandersonia, together with Brownlowia Roxb., Diplodiscus Turcz. and Pentace Hassk. in the Brownlowioideae clade of Malvaceae s. l. (Judd and Manchester 1997; Alverson et al. 1999; Bayer et al. 1999; Nyffeler and Baum 2000). The author's recent revision of the genus for the Tree Flora of Sabah and Sarawak Project recognized six species of Jarandersonia from Borneo. Of these, J. pentaceoides, endemic to central Kalimantan, is new to science and is here described for the first time as a precursory paper to the publication of the revi- sion for the genus.

Further Analysis of the Forest Vegetation of Central Indian Mountains of Madhya Pradesh

From the academic point of view even today the forests of Central India possess highly valuable tree wealth in spite of the fact that a lot of Teak and Sal plantations have been cut down after Independence. The present studies on the forests were therefore under-taken for two more years in continuation of our early work**. The thick forests occupy even today the ground growth of fuelwood plants and young timber trees of different species constituting highly thick ground vegetation. Abundant amount of water sources are available through the hilly streams which are helpful in the growth of dense forests. Presently, the explored forests consists of Dry Deciduous and Moist Deciduous types categorized mainly under the tropical forests whereas mountain subtropical forests flourish at lower altitudes. Dry Teak (Tectona grandis) and Sal Forests (Shorea robusta) are of common occurrence. Timber trees of Central Indian mountains number more than several dozens and are of high value for future use. Detailed information is provided about the forest tree flora as well as about the ferns, the liverworts and shrubby flowering plants.

Identity and relationships of the Arboreal Caatinga among other floristic units of seasonally dry tropical forests (SDTFs) of north‐eastern and Central Brazil

The tree species composition of seasonally dry tropical forests (SDTF) in north-eastern and central Brazil is analyzed to address the following hypotheses: (1) variations in species composition are related to both environment (climate and substrate) and spatial proximity; (2) SDTF floristic units may be recognized based on peculiar composition and environment; and (3) the Arboreal Caatinga, a deciduous forest occurring along the hinterland borders of the Caatinga Domain, is one of these units and its flora is more strongly related to the caatinga vegetation than to outlying forests. The study region is framed by the Brazilian coastline, 50th meridian west and 21st parallel south, including the Caatinga Domain and extensions into the Atlantic Forest and Cerrado Domains. Multivariate and geostatistic analyses were performed on a database containing 16,226 occurrence records of 1332 tree species in 187 georeferenced SDTF areas and respective environmental variables. Tree species composition varied significantly with both environmental variables and spatial proximity. Eight SDTF floristic units were recognized in the region, including the Arboreal Caatinga. In terms of species composition, its tree flora showed a stronger link with that of the Cerrado Dry Forest Enclaves. On the other hand, in terms of species frequency across sample areas, the links were stronger with two other units: Rock Outcrops Caatinga and Agreste and Brejo Dry Forests. There is a role for niche-based control of tree species composition across the SDTFs of the region determined primarily by the availability of ground water across time and secondarily by the amount of soil mineral nutrients. Spatial proximity also contributes significantly to the floristic cohesion of SDTF units suggesting a highly dispersal-limited tree flora. These units should be given the status of eco-regions to help driving the conservation policy regarding the protection of their biodiversity.

Patterns of plant species richness of temperate and tropical grassland in South Africa

Grasslands are so called based on the structural facet of this vegetation type. Grasslands are dominated by species of the Poaceae, are mostly one-layered in structure with few trees and shrubs, and are climatically controlled (Mucina & Rutherford 2006). Grasslands occur in both temperate and tropical regions of the world. In southern Africa, Mucina & Rutherford (2006) consider grasslands to be either sub-tropical or temperate. The differentiation between these two grassland types is based on the factors responsible for the maintenance thereof. Tropical grasslands are often regarded as secondary (e.g. fire maintained) or edaphic (e.g. shallow water table) (Matthews et al. 1999). Temperate grasslands are thought to be naturally maintained by subzero temperatures and dry winters, in combination with fire, which prevent colonisation of grasslands by the tropically-derived tree flora of southern Africa (Bredenkamp et al. 2002). South African grasslands are characterised by plant species with special modified underground organs which enable them to escape fire (e.g. geoxylic suffrutices; White 1977) or become dormant in winter (e.g. geophytes; Tainton & Mentis 1984) when growing conditions become unfavourable. Such adaptations are thought to be major mechanisms whereby grassland plants survive severely cold, dry winters and subsequent fires in temperate southern African grasslands (Bredenkamp et al. 2002). Grassland species, especially perennial forbs, are usually quick in responding to the effects of fire and such plants are characterised by profuse flowering and mass seed production (Retief & Van Wyk 2002).

Composição, estrutura e similaridade florística da Floresta Atlântica, na Serra Negra, Rio Preto - MG

Resumo A Serra Negra, no município de Rio Preto (MG), estende-se por uma região com fisionomias florestais serranas da Mantiqueira e campos altimontanos, entre as elevações do maciço do Itatiaia (RJ, SP e MG) e da Serra do Ibitipoca (MG). Com o objetivo de investigar o comportamento das variáveis comunitárias da flora arbórea em condições diferentes de altitude e alagamento, determinou-se a composição florística, estrutura e similaridade entre três fragmentos de floresta (aluvial, montana e nebular) e a suas relações florísticas com estudos da região. Foram amostrados 2.572 indivíduos, identificados em 194 espécies, distribuídas em 59 famílias e 118 gêneros. As famílias com maior riqueza foram Myrtaceae (30 espécies), Lauraceae (20), Melastomataceae (17) e Fabaceae (13). Os três tipos de vegetação estudados, associados a diferentes condições ambientais, diferem entre si em sua composição e estrutura. A floresta aluvial revelou-se com reduzida diversidade, baixa estatura e alta dominância ecológica. A floresta nebular destacou-se por apresentar elementos típicos de altitude em detrimento de espécies freqüentes na região abaixo da escarpa da serra, onde a diversidade foi maior. A flora arbórea da Serra Negra, formada pelo conjunto das áreas estudadas, apresenta um conjunto considerável de elementos com distribuição característica de ambientes montanhosos do Sudeste do Brasil.

Phylogenetic beta diversity reveals historical effects in the assemblage of the tree floras of the Ryukyu Archipelago

Quantifying the roles of historical versus contemporary constraints in determining species diversity is a central issue in island biogeography, and the phylogenetic beta diversity between islands is an essential measure specifying the influence of historical barriers on insular assemblages. In this study, using phylogenetic information for 513 tree species on 26 islands in the subtropical Ryukyu Archipelago, phylogenetic beta diversity between islands was calculated, and effects of historical factors (gaps as surrogate measures of historical barriers) and current ones (distance, area and elevation) on the phylogenetic structure of tree assemblages were examined. The pattern of phylogenetic beta diversity demonstrated that the Tokara Gap and geographical distance were consistently important for characterizing tree assemblages in the Ryukyus relative to other historical and current factors, which suggests that the Tokara Gap and distance-limited dispersal from the two adjacent source islands have left a deep imprint on the phylogenetic structure of the current tree flora of the islands.

Flammable biomes dominated by eucalypts originated at the Cretaceous–Palaeogene boundary

Fire is a major modifier of communities, but the evolutionary origins of its prevalent role in shaping current biomes are uncertain. Australia is among the most fire-prone continents, with most of the landmass occupied by the fire-dependent sclerophyll and savanna biomes. In contrast to biomes with similar climates in other continents, Australia has a tree flora dominated by a single genus, Eucalyptus, and related Myrtaceae. A unique mechanism in Myrtaceae for enduring and recovering from fire damage likely resulted in this dominance. Here, we find a conserved phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution, dating from 60 to 62 Ma, in the earliest Palaeogene. Thus, fire-dependent communities likely existed 50 million years earlier than previously thought. We predict that epicormic resprouting could make eucalypt forests and woodlands an excellent long-term carbon bank for reducing atmospheric CO(2) compared with biomes with similar fire regimes in other continents.

Niche expansion after competitor extinction? A comparative assessment of habitat generalists and specialists in the tree floras of south-eastern North America and south-eastern Europe

Aim The aim of this study was to test R.H. MacArthur’s hypothesis that realized niche breadth is constrained by species pool size – the greater the number of species in a region, the more competition restricts the distribution of each species with respect to environmental tolerances and habitat characteristics. Location The northern Balkan region in south-eastern Europe (Illyrian Floristic Province) and the southern Appalachian region of the USA. Methods We compared co-occurrence-based distributions of habitat specialization of tree species in two geographic regions that are ecologically similar but differ in species pool size. We applied two methods. First, we used a rank-ordering of species along a gradient of estimated niche breadth that is based solely on species co-occurrence information derived from vegetation databases from each region. To compare niche-breadth distributions of different datasets we developed a procedure that standardizes expected values of species co-occurrences independently of the size of the species pool. Second, we calculated species turnover along an elevational gradient for both regions, estimated as the rate of decay of compositional similarity with elevation distance. Results Despite a twofold larger species pool, and in contrast to our hypothesis, there was no greater specialization trend in the tree species of the southern Appalachian region, regardless of phylogenetic subgroupings or whether rare species were included. After correcting for differences in species pools, the similarity decay with elevation distance was marginally stronger in the southern Appalachian region. Main conclusions MacArthur’s hypothesis was not supported by our analysis. While the compositional distance decay with elevation revealed only a slight trend towards narrower realized niches in the tree flora of the southern Appalachian region, the co-occurrence approach suggested the opposite. Our results indicate that species distributions are largely constrained by environmental tolerances, and that biotic pressure in the form of competition from ecologically similar species plays a relatively minor role in the ability of species to establish mature individuals in different habitat types.

Forest fragmentation drives Atlantic forest of northeastern Brazil to biotic homogenization

AbstractAim To examine whether the tree flora of the Atlantic forest of northeastern Brazil has experienced detectable taxonomic homogenization via the proliferation of native pioneer species in response to habitat loss and fragmentation.Location Biotic homogenization (BH) was examined across the Atlantic forest of northeast Brazil, i.e. a 56,000 km2 piece of tropical forest and a distinct centre of species endemism in South America.Methods We assessed a dataset consisting of 5122 tree records and compared the similarity of tree floras from 12 semi‐natural sub‐regions of the Atlantic forest between two time periods: pre‐1980 (plant records between 1902 and 1980), and post‐1980 (between 1981 and 2006). To understand the mechanisms leading to BH (1) tree floras were ordered (via non‐metric multidimensional scaling – NMDS) by date (pre/post 1980) based on species occurrence and frequency, (2) NMDS axes were regressed against the proportion of those species that increased their occurrence post‐1980 (i.e. the winner species), and (3) patterns of geographic distribution and frequency of particular life‐history traits were examined across winner species and a control group.Results Tree floras across the Atlantic forest became c. 20–40% more similar to each other post‐1980, but patterns of species similarity were also influenced by between‐plot geographical distance. NMDS ordination clearly segregated pre‐ and post‐1980 floras with a clear signal of floristic convergence. Furthermore, winner tree species were largely composed of short‐lived and small‐seeded pioneer species that exhibit wide geographic distributions.Main conclusions Our results suggest that tropical forest biotas are susceptible to taxonomic homogenization (i.e. increasing levels of similarity) in the context of severe human‐disturbance via the proliferation of particular groups of native species comprised mainly by ecologically‐plastic, generalist species. We are thus extending the concept of homogenization to address and highlight a pervasive biological shift in the structure of tropical forest communities currently taking place across hyper‐fragmented landscapes.

Pl@ntwood: A Computer-Assisted Identification Tool for 110 species of amazon trees based on wood Anatomical Features

Sustainable management and conservation of tropical trees and forests require accurate identification of tree species. Reliable, user-friendly identification tools based on macroscopic morphological features have already been developed for various tree floras. Wood anatomical features provide also a considerable amount of information that can be used for timber traceability, certification and trade control. Yet, this information is still poorly used, and only a handful of experts are able to use it for plant species identification. Here, we present an interactive, user-friendly tool based on vector graphics, illustrating 99 states of 27 wood characters from 110 Amazonian tree species belonging to 34 families. Pl@ntWood is a graphical identification tool based on the IDAO system, a multimedia approach to plant identification. Wood anatomical characters were selected from the IAWA list of microscopic features for hardwood identification, which will enable us to easily extend this work to a larger number of species. A stand-alone application has been developed and an on-line version will be delivered in the near future. Besides allowing non-specialists to identify plants in a user-friendly interface, this system can be used with different purposes such as teaching, conservation, management, and selftraining in the wood anatomy of tropical species.

Composição florística do componente arbóreo e afinidade fitogeográfica de uma floresta semidecídua em Nova Lima, MG

The Nova Lima city (metropolitan area of Belo Horizonte, Minas Gerais State, Brazil) is located in an ecotone between Cerrado (Brazilian Savanna) and Atlantic Forest, wich are two of the world's biodiversity hotspots. A floristic survey was carried out in a semideciduous forest (20°00' S and 43°55' W) in order to establish its relations with other forests (rain forest and semideciduous) from both hotspots, as well as to assess their phytogeographical insertion. The region is under high pressure due to urban expansion. The floristic survey of the semideciduous forest was based on specimens of woody plants collected both in and outside of 44 plots of 20 × 5 meters. The studied forest was compared with other 72 forests of Minas Gerais, Sao Paulo, Espirito Santo, Rio de Janeiro and Goias States and the Federal District using multivariate analyses. At semideciduous forest 205 species of 49 botanical families were found. The record of species with restricted distribution to Atlantic Forest was 15 times greater than in the Cerrado. The tree flora of the semideciduous forest studied is a subset of that of rainforests, with species that are more efficient in coping with a longer dry season. Thus, the forest may be considered an Atlantic Forest.