Tree Taxa Research Articles

Information retrieval in physical geography

Information retrieval (IR) methods seek to locate meaningful documents in large collections of textual and other data. Few studies apply these techniques to discover descriptions in historical documents for physical geography applications. This absence is noteworthy given the use of qualitative historical descriptions in physical geography and the amount of historical documentation online. This study, therefore, introduces an IR approach for finding meaningful and geographically resolved historical descriptions in large digital collections of historical documents. Presenting a biogeography application, it develops a ‘search engine’ using a boosted regression trees (BRT) model to assist in finding forest compositional descriptions (FCDs) based on textual features in a collection of county histories. The study then investigates whether FCDs corroborate existing estimates of relative abundances and spatial distributions of tree taxa from presettlement land survey records (PLSRs) and existing range maps. The BRT model is trained using portions of text from 458 US county histories. Evaluating the model’s performance upon a spatially independent test dataset, the model helps discover 97.5% of FCDs while reducing the amount of text to search through to 0.3% of total. The prevalence rank of taxa in FCDs (i.e. the number of times a taxon is mentioned at least once in an FCD, divided by the total number of FCDs, then ranked) is strongly related to the abundance rank in PLSRs. Patterns in species mentions from FCDs generally match relative abundance patterns from PLSRs. However, analyses suggest that FCDs contain biases towards large and economically valuable tree taxa and against smaller taxa. In the end, the study demonstrates the potential of IR approaches for developing novel datasets over large geographic areas, corroborating existing historical datasets, and providing spatial coverage of historic phenomena.

Paleobotany and Global Change: Important Lessons for Species to Biomes from Vegetation Responses to Past Global Change.

Human carbon use during the next century will lead to atmospheric carbon dioxide concentrations (pCO2) that have been unprecedented for the past 50-100+ million years according to fossil plant-based CO2 estimates. The paleobotanical record of plants offers key insights into vegetation responses to past global change, including suitable analogs for Earth's climatic future. Past global warming events have resulted in transient poleward migration at rates that are equivalent to the lowest climate velocities required for current taxa to keep pace with climate change. Paleobiome reconstructions suggest that the current tundra biome is the biome most threatened by global warming. The common occurrence of paleoforests at high polar latitudes when pCO2 was above 500 ppm suggests that the advance of woody shrub and tree taxa into tundra environments may be inevitable. Fossil pollen studies demonstrate the resilience of wet tropical forests to global change up to 700 ppm CO2, contrary to modeled predictions of the future. The paleobotanical record also demonstrates a high capacity for functional trait evolution as an additional strategy to migration and maintenance of a species' climate envelope in response to global change.

Conservation of three historic forest landscapes in the New York metropolitan area

Conservation of historic forest landscapes at national historic sites involves maintaining and replacing the historic trees as well as removing modern trees. Tree stem inventories in 1995 and 2013 are compared to assess conservation efforts for the historic forest landscapes of three U.S. National Historic Sites located in the New York metropolitan area: Glenmont of Thomas Edison; Sagamore Hill; and Vanderbilt Mansion. The terms alien tree taxa and native tree taxa are defined in regard to the eastern United States. Among the three historic forest landscapes there are 77 alien tree taxa, but only Abies nordmanniana, Acer palmatum, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica, and Magnolia × soulangeana are present in Glenmont, Sagamore Hill, and Vanderbilt Mansion. Of the 56 native tree taxa, there are 15 species common to the three historic forest landscapes. Paired t-tests (P ≤ 0.05) of taxa stem counts from the 1995 and 2013 inventories reveal the alien and native tree stems for historic and modern trees declined significantly at Sagamore Hill. Both alien and native historic tree stems decreased significantly at Glenmont. Only alien historic tree stems were significantly smaller at Vanderbilt Mansion. Differences in forest landscape management efforts among the national historic sites provide explanations for the significant decreases in alien and native trees at Glenmont, Sagamore Hill, and Vanderbilt Mansion.

The potential of paleoecology for functional forest restoration planning: lessons from Late Holocene Italian pollen records

We describe forest landscape transformations during the last two millennia in the Italian peninsula by analyzing local (Rieti basin – Lago Lungo) and regional (RF93-30 Adriatic Sea) sediment cores. We identify a dynamic forest ecosystem through paleoecologic reconstruction and consider potential interventions for effective restoration of the most ancient, least disturbed forest ecosystem. The most degraded ecosystems in consequence of human activities were hygrophilous (wet) and mesic forests. In the Rieti Basin, degraded forest ecosystems on mountain slopes are undergoing some degree of forest succession and have less need of restoration. However, management plans for biodiversity, ecosystem services and resources conservation are needed to achieve more sustainable development. In Rieti, the paleoecological investigation revealed a dramatic decrease of deciduous wet and mesic tree taxa through time due to human landscape transformation. The starting point for restoration of a Mediterranean forest ecosystem that preserves natural biodiversity and associated ecosystem services requires recreating some portion of the floodplain wetland ecological niche. Once floodplain forest ecological niche has been recreated, the original ecosystem composed of Alnus, Fraxinus excelsior, Tilia spp., Carpinus betulus and Acer spp., all species which today are rare, should be planted on the basis of microsite characteristics and tree autoecology.

Under pressure? Epicormic shoots and traumatic growth zones in high-latitude Triassic trees from East Antarctica.

Investigating the biology of trees that were growing at high latitudes during warmer geological periods is key to understanding the functioning of both past and future forest ecosystems. The aim of this study is to report the first co-occurrence of epicormic shoots and traumatic growth zones in fossil trees from the Triassic of Antarctica and to discuss their biological and environmental implications. Permineralized woods bearing scars of epicormic shoots were collected from the Triassic Fremouw Formation in Gordon Valley, Central Transantarctic Mountains, Antarctica in 2010. Samples from different portions of three specimens were prepared using standard thin section and hydrofluoric (HF) acid peel techniques, and anatomical details were studied in transmitted light. The fossil woods represent the outer part of trunks, with at least 40 growth rings that are 0.2-4.8 mm in width. Anatomical comparisons suggest that they represent a new tree taxon for the Triassic of Antarctica. Numerous small epicormic shoots can be seen crossing the wood almost horizontally and are locally branched. Each specimen also contains several occurrences of traumatic growth zones located in the early wood, in the cells produced either at the very start of the growing season or slightly later. This is the first report of epicormic shoots and traumatic growth zones in the wood of a Triassic tree from Antarctica. Their co-occurrence indicates that these trees from Gordon Valley were subjected to environmental stresses not seen in Triassic trees previously described from this region. This suggests that they had a different biology and/or were growing in a different habitat, which offers a new glimpse into the diversity of high-latitude trees in the Triassic greenhouse climate.

Новые таксоны деревьев и кустарников в коллекции Ботанического сада Петра Великого

Новые таксоны деревьев и кустарников в коллекции Ботанического сада Петра Великого

Phylogenetic Relatedness of Several Agarwood-Producing Taxa (Thymelaeaceae) from Indonesia.

Indonesia is home to several tree taxa that are harvested for agarwood. This highly valuable oleoresin ironically was the cause for some species to become vulnerable due to gluttonous human activity. However, information on the genetic diversity of these endangered trees is limited. In this study, 28 specimens representing eight species from two genera, Aquilaria and Gyrinops, were collected from ex-situ and in-situ populations in Indonesia. Phylogenetic analysis conducted on DNA sequences of the nuclear ribosomal internal transcribed spacer (ITS) and the trnL-trnF intergenic spacer regions, revealed that Aquilaria and Gyrinops are paraphyletic when Aquilaria cumingiana is excluded. The phylogenetic analysis for ITS and trnL-trnF showed capability to categorise agarwood-producing species based on their regions: East Indonesia and West Indonesia, using Wallace’s Line as the divider. In addition, we discuss challenges in species identification and taxonomy of agarwood-producing genera, and their conservation efforts in Indonesia.

The allergenic pollen in the atmosphere of El-Hadjar city (Annaba, Algeria)

The aeropalynogical study of the atmosphere of El-Hadjar town was carried out during one year, from June 1, 2012 to May 31, 2013. The collected pollen during the sampling period yielded 2729 pollen grains/cm2 belonging to 50 taxa, distributed on 20 families (Apiaceae, Arecaceae, Asteraceae, Boraginaceae, Brassicaceae, Caryophyllaceae, Chenopodiaceae/Amaranthaceae, Cupressaceae, Cyperaceae, Ericaceae, Fabaceae, Lamiaceae, Mimosaceae, Pinaceae, Poaceae, Rosaceae, Scrophulariaceae, Ulmaceae, Urticaceae and Vitaceae.); 24 genera (Alnus, Artemisia, Betula, Borago, Carya, Casuarina, Echium, Ephedra, Eucalyptus, Fraxinus, Juglans, Juncus, Ligustrum, Mercurialis, Melia, Pistacia, Plantago, Platanus, Populus, Quercus, Rumex, Salix, Tilia and Trifolium.) and, 6 species (Castanea sativa, Corylus avellana, Olea europaea, Quercus ilex, Ricinus communis and Typha angustifolia). The pollen peak concentration was recorded in April with 715 GP/cm2 and the minimum value in October with 36.08 GP/cm2. The pollen spectrum has a percentage of 52.31% of pollen tree. The Cupressaceae family contributed with 12.84%, Olea europaea with 6.95%, Eucalyptus and Casuarina with 5.85 and 5.71%. The highest percentage of this type of pollen occurs in November with 90.51%, dominated by Casuarina pollen with 86.31%. The highest concentrations of tree taxa are: Eucalyptus (35.03%) and Ligustrum (16.21%) in June. Fraxinus with 64.64% in December, Ericaceae 17.42% in March; Olea europaea and Quercus in April with 18.86% and 6.79% respectively. The pollens of the herbs present 44.89%. They are characterized by the major presence of Poaceae and Mercurialis pollen with the following percentages: 21.49% and 11.75%. It seems that the months of July (86.33%) and August (80.14%) mark the highest percentages of non-tree pollen

Differentiation of herb layer vascular flora in reclaimed areas depends on the species composition of forest stands

Abstract Spoil heaps, resulting from open-pit mining, are deprived of soil cover. A common method of reclamation for such sites is afforestation aimed at creating whole forest ecosystems. Forest stands planted on soilless areas make it possible to determine the effects of different tree taxa on the species composition of flora. The study focused on the vascular species of herb layers in young forest stands formed by Alnus glutinosa, Betula pendula, Pinus sylvestris, Quercus petraea and Robinia pseudoacacia, and mixed stands dominated by Acer pseudoplatanus or Betula pendula. The study included 227 randomly selected plots across the afforested Belchatow Brown Coal Mine spoil heap. Species composition of the herb layer was composed mainly of synanthropic species (over 70%), and was clearly related to the overstory tree species composition of forest stands. TWINSPAN divided sample plots into two groups that developed under the canopy of stands formed by: (1) Betula pendula, Pinus sylvestris or Quercus petraea, or mixed stands with Betula pendula, or (2) Alnus glutinosa or Robinia pseudoacacia, or mixed stands dominated by Acer pseudoplatanus. The first group was dominated by meadow species (25.8%), while the second had higher richness of ruderal (18.6%) and forest-edge species (14.1%). Plant species associated with fertile and moist forest habitats were more frequent in the second group (Alnus-Robinia), whereas species of acidic and dry forests occurred only in the first group (Betula-Pinus). Non-parametric tests on Ellenberg’s indicator values showed that forest stands of Betula-Pinus group created habitat conditions for light-demanding species with low fertility requirements, whereas forest stands of Alnus-Robinia group created habitat conditions for nitrophilous and shade-tolerant plant species. Our data revealed that tree species composition of forest stands is a key factor shaping herb layer conditions and – as a consequence – herb layer species composition despite of initial habitat variability on the spoil heap. These results highlight a key role of forest stand composition in the development of herb layer richness on post-industrial habitats.

Late Holocene palynology of a saline lake in the Pantanal of Nhecolândia, Brazil

ABSTRACTThis work presents the first description of a palynological assemblage preserved in sediments deposited in a saline lake (salina) in the Nhecolândia area of the Brazilian Pantanal. Pollen studies from salinas have been underappreciated due to inferred taphonomic issues related to elevated alkalinity. We have found a well-preserved assemblage that allowed the reconstruction of the history of local vegetation. Radiocarbon dating revealed a constant deposition since ∼3760 calibrated years before present (cal yrs BP), and pollen analyses suggested two main phases of vegetation and environmental development. From 3760 to 1510 cal yrs BP, the site was a swamp to shallow lake dominated by cattails (Typha domingensis) and Poaceae. From 1510 cal yrs BP to the present the herbaceous community is enriched with Cyperaceae and Bromeliaceae, and with tree taxa such as the Arecaceae (palm trees), evidencing the local development of a fringe vegetation. These two phases were interpreted as a change from drier to wetter settings, largely in agreement with regional lake and speleothem records, as well as pollen and carbon isotope studies from other locations in central South America during the latest Holocene. Given that salinas are non-floodable and pollen was found to be well preserved, we highlight the potential of palaeopalynology in these environments as a source of palaeoecological information for the Pantanal Basin.

Culm Age and Rhizome Affects Night-Time Water Recharge in the Bamboo Phyllostachys pubescens.

Bamboo species—the only herbaceous trees—have unique structural and physiological characteristics that differ from those of other tree taxa. However, the role of night-time water use in bamboo is poorly understood and has rarely been investigated. We studied the day- and night-time sap flow response to culm age and rhizome structure in three age levels (juvenile, mature, and senescent) of Phyllostachys pubescens growing in the Nankun Mountain Natural Reserve, South China. We found that sap flow density and whole-tree hydraulic conductance decreased with culm age. After cutting of rhizome, the day-time sap flow and night-time water recharge decreased obviously. In addition, night-time water recharge accounted for the largest proportion (up to 30%) of total daily transpiration in normal senescent bamboos. Therefore, our study indicates that the connected rhizome system and night-time water recharge played a significant role in water compensation during the day and at night in bamboos. Night-time water recharge is especially critical to senescent bamboos, given their weaker transpiration due to the lower whole-tree hydraulic conductance, and consequently, they are more dependent on night-time water recharge for fulfilling their whole-day water consumption needs.

Vegetation dynamics during last 35,000 years at a cold desert locale: preferential loss of forbs with increased aridity

AbstractPaleoecological records are an important source of data to better understand ecological responses to climate. To help understand vegetation–climate relationships in the Great Basin cold desert of North America, we analyzed 154 plant taxa from 52 fossil woodrat middens that spanned both an 800‐m elevation gradient and the last 35,000 yr (35 ka) within a single study area. Vegetation was analyzed by community assemblage (CA), by plant functional type, and by individual species. Concordant with a predominant trend of increased aridity since glacial maximum, CA change was largely unidirectional despite centennial‐scale cycles of climate variation. Richness of forb and other herbaceous plant functional types peaked from 15 to 26 ka during glacial maximum and then gradually decreased from ~15 ka to present. Analysis of individual taxa indicates that once a herbaceous species was lost from the study area, that species did not re‐occur. In contrast, woody (shrubs and trees) species richness peaked from 8 to 15 ka during and following the Bolling‐Allerod rapid warming. However, most tree taxa that established during this period of warming were subsequently lost as climate became more arid after the beginning of Mid‐Holocene Temperature Maximum warming ~8 ka. These shifts in plant functional types decreased relative richness of forbs compared to shrubs (i.e., decreased forb/shrub ratio), and these shifts continue to the present despite intervening cycles of climate cooling and warming. We conclude that the relative importance of herbaceous species in current CAs of the Great Basin cold desert has been decreasing for the last 15 ka. We also speculate that decreased richness of herbaceous species has, in part, provided opportunities for exotic species to establish and proliferate in the Great Basin during the last 100 yr. Thus, observations of past vegetation change suggest that increased aridity with future climate warming will continue to favor woody vegetation over herbaceous species at our cold desert locale, at least until invasive species displace native shrub species.

Effects of Retention Time in Nursery Containers and Root Pruning at Planting on Landscape Establishment and Anchorage of Three Tree Taxa

Tree lodging in landscapes during storms has been attributed to root architecture in nurseries. Objectives of this study were to evaluate influence of retention time in three progressively larger nursery containers, and root pruning at landscape planting, on establishment, anchorage, and root architecture in the first four post-planting years. All trees were retained in three progressively larger containers (11, 57, and 170 L) for a total of 32 months, with varying retention times in each. Retention time had little influence on post-planting xylem water potential for Acer rubrum and Ulmus parvifolia. There were few differences in aboveground growth among retention times. Except for Acer, retention time had a negligible influence on anchorage. Root pruning by shaving 170 L root ball periphery when planting had no impact on growth except for one post-planting year. However, root pruning invoked a dramatic reduction in circling and descending roots four years after planting caused by root deflection in the final nursery container. Although root pruning had no influence on bending stress required to winch Magnolia trunks to any degree of trunk tilt, approximately 10% more bending stress was required to winch Acer trunks up to five degrees tilt when root balls were shaved at planting.

Spectroscopic and chromatographic exploration of different phytochemical and mineral contents from Syzygium alternifolim (Wt.) Walp. an endemic, endangered medicinal tree taxon.

The present study is aimed to explore different phytochemical and mineral contents in endemic medicinal plant- Syzygium alternifolium. Different spectroscopic (UV-Vis, FT-IR, ICP-OES) and chromatographic techniques (GC-MS) are used to identify versatile phytochemical and mineral contents in different parts of S. alternifolium by qualitative and quantitative means. For qualitative phytochemical screening a total of 16 types of different primary and secondary metabolites are extracted in 07 different solvents, among them 15 types of metabolites out of 16 are identified in methanol extract. In quantitative analysis higher quantities of sugar i.e., 45.2 mg/g among primary metabolites of fruit and 451.20 mg/g of phenols among secondary metabolites from stem bark are quantified. FT-IR and GC-MS analysis of methanol extracts of plant reveals different functional groups and phytochemical compounds. In addition to these, mineral analysis through ICP-OES shows higher quantities of Potassium (43.60 mg/L) in fruit, Iron (2.186 mg/L) in stem bark among macro and micro elements respectively. The results of the present study reveal, S. alternifolium is potential source towards number of phytochemicals and different types of mineral contents. Hence, it becomes a treasure house for pharmaceutical as well as nutraceutical companies for preparation novel products.

Interpreting modern and fossil pollen data along a steep environmental gradient in northern Patagonia

Vegetation reconstructions rest on modern vegetation–pollen rain relationships and deductive reasoning. Establishing this relationship is a nontrivial task because differences among pollen assemblages are not necessarily proportional to differences in vegetation. This task is particularly challenging in Patagonia, where some tree taxa have indistinguishable pollen, and pollen grains can be transported long distances. In this study, we describe the modern pollen of 48 lake and wetland samples from northern Patagonia (40.5–44°S) to better discriminate the major vegetation zones of the region through pollen analysis. Specifically, we focus on the performance of three methodological approaches, namely, pollen indicators, classification trees, and optimal thresholds of dissimilarity. As a proof of concept, we use the modern pollen–vegetation relationships to reconstruct the vegetation history at Laguna el Trébol (41.07°S; 71.5°W). Our results revealed that (1) pollen sums exceeding 260 grains ensured replicable vegetation reconstructions, (2) modern vegetation zones could not be separated solely by visual inspection of their pollen spectra, (3) the classification tree and optimal thresholds of dissimilarity permitted discrimination of most vegetation zones, (4) detection of nonanalog communities required use of pollen indicators or optimal thresholds of dissimilarity, and (5) vegetation at L. el Trébol was likely dominated by late glacial shrubland with no modern analogs in the study area (15,000–12,180 cal. yr BP), modern shrubland (12,180–6500 cal. yr BP) and mixed forest (6500 cal. yr BP–present). This study allows a more realistic understanding of the pollen–vegetation relationship and provides new tools for interpreting past vegetation in northern Patagonia.

Why do trees die? Characterizing the drivers of background tree mortality.

The drivers of background tree mortality rates-the typical low rates of tree mortality found in forests in the absence of acute stresses like drought-are central to our understanding of forest dynamics, the effects of ongoing environmental changes on forests, and the causes and consequences of geographical gradients in the nature and strength of biotic interactions. To shed light on factors contributing to background tree mortality, we analyzed detailed pathological data from 200,668 tree-years of observation and 3,729 individual tree deaths, recorded over a 13-yr period in a network of old-growth forest plots in California's Sierra Nevada mountain range. We found that: (1) Biotic mortality factors (mostly insects and pathogens) dominated (58%), particularly in larger trees (86%). Bark beetles were the most prevalent (40%), even though there were no outbreaks during the study period; in contrast, the contribution of defoliators was negligible. (2) Relative occurrences of broad classes of mortality factors (biotic, 58%; suppression, 51%; and mechanical, 25%) are similar among tree taxa, but may vary with tree size and growth rate. (3) We found little evidence of distinct groups of mortality factors that predictably occur together on trees. Our results have at least three sets of implications. First, rather than being driven by abiotic factors such as lightning or windstorms, the "ambient" or "random" background mortality that many forest models presume to be independent of tree growth rate is instead dominated by biotic agents of tree mortality, with potentially critical implications for forecasting future mortality. Mechanistic models of background mortality, even for healthy, rapidly growing trees, must therefore include the insects and pathogens that kill trees. Second, the biotic agents of tree mortality, instead of occurring in a few predictable combinations, may generally act opportunistically and with a relatively large degree of independence from one another. Finally, beyond the current emphasis on folivory and leaf defenses, studies of broad-scale gradients in the nature and strength of biotic interactions should also include biotic attacks on, and defenses of, tree stems and roots.

Modern pollen assemblages from surface lake sediments and their environmental implications on the southwestern Tibetan Plateau

The relationships amongst modern pollen assemblages, vegetation, climate and human activity are the basis for reconstructing palaeoenvironmental changes using pollen records. It is important to determine these relationships at regional scales due to the development of vegetation under different climatic conditions and human activities. In this paper, we report on an analysis of modern pollen assemblages of 31 surface lake samples from 31 lakes (one sample per lake) on the southwestern Tibetan Plateau where the knowledge of modern pollen and their relationships with vegetation, climate and human activities is insufficient. The region includes five vegetation zones: sub‐alpine shrub steppe, alpine steppe, alpine meadow and steppe ecotone, mountain desert and alpine desert. The lakes span a wide range of mean annual precipitation (50–500 mm) and mean annual temperature (−8 to 6 °C). Modern pollen assemblages from our samples mainly consist of herb taxa (Artemisia, Cyperaceae, Poaceae, Chenopodiaceae, etc.) and some tree taxa (Pinus, Fagaceae, Alnus, etc.). The results indicate that modern pollen assemblages are able to reflect the main vegetation distribution. Redundancy analysis for the main pollen types and environmental variables shows that precipitation is the leading factor that influences the pollen distribution in the study area with the first axis capturing 13.7% of the variance in the pollen data set. The Artemisia/Chenopodiaceae ratio is valid for separating the desert component (<2) from the steppe and other vegetation zones (>2) but is unable to distinguish moisture variations. The Artemisia/Cyperaceae ratio is able to identify meadows (<1) and steppes (>1) and can be used as a moisture index on the southwestern Tibetan Plateau. Our results show that an appropriate range is needed for a modern pollen data set in order to perform pollen‐based quantitative climate reconstructions in one region. It is essential to perform modern studies before using pollen ratios to reconstruct palaeovegetation and palaeoclimate at a regional scale.

Ancestral range reconstruction of Galliformes: the effects of topology and taxon sampling

AbstractAimWe examined divergence times and biogeography of the avian order Galliformes (which, despite a nearly world‐wide distribution, includes many weak fliers), to test whether current distributions reflect vicariance or long‐distance dispersal. We also tested the impact of taxon sampling and tree topology on our estimates of historical biogeography.LocationWorld‐wide.MethodsWe generated timetrees for all major galliform lineages using several fossil calibrations and a combination of mitochondrial and nuclear data. We compared divergence times and reconstructed ancestral ranges using this timetree and the galliforms from a recent synthetic tree for all birds. Thus, we explored the sensitivity of our conclusions to differences in topology and taxon sampling.ResultsThe results suggest late Cretaceous origins for Megapodiidae and possibly for Cracidae, the earliest diverging families. The other families diversified in the Eocene after the break‐up of Gondwana, contrary to previous suggestions. Both topology and taxon sampling affected the ancestral area estimates, although many nodes were consistent among the approaches.Main conclusionsDivergences of Numididae, Odontophoridae and Phasianidae occurred in Africa, with subsequent dispersal to other continents. Reconstructed ranges for ancestors of the earliest diverging families, Megapodiidae and Cracidae, are less conclusive, but may have involved a South American origin, then dispersal to other continents. Thus, long‐distance dispersal is likely to have been important in galliforms, possibly reflecting more vagile ancestors and repeated range expansions and contractions. There appears to be a trade‐off between the use of trees with rich taxon sampling but limited data, where key taxa can be misplaced, and more robust trees with missing taxa. When biogeographically important taxa are included, complete taxon sampling does not appear necessary for accurate ancestral area reconstruction. Robust trees that include taxa targeted based on their distribution may be the best way to improve our understanding of historical biogeography.

Pollen-based characterization of montane forest types in north-eastern Brazil

Surface soil samples were collected in three mountainous massifs in north-eastern Brazil to characterize the different vegetation types according to their respective pollen assemblages. Complementary approach between pollen and vegetation data shows that the pollen rain accurately reflects the following three main forest types: i) a dense ombrophilous forest (or tropical moist broadleaf forest) characterized by Myrtaceae associated with high percentages of Miconia, Guapira, Ilex, Moraceae-Urticaceae undif. or Byrsonima, ii) a seasonal semi-deciduous montane forest characterized by an increase of Arecaceae associated with Fabaceae-Mimosideae, Myrtaceae, Piper, Cecropia, Urera and Mitracarpus, and iii) a seasonal deciduous forest dominated by Fabaceae-Mimosideae and Arecaceae tree taxa associated with Alternanthera, Cyperaceae and Mitracarpus. Using of botanical data from several plots of ombrophilous forest, in which several surface soil samples have been collected, allows to roughly estimate the over- and underrepresentation of pollen taxa relative to their floristic abundance. Furthermore, distribution of surface soil samples at different altitude and mountain sides also allows to characterize vegetation variation according to several environmental parameters. The precipitation increase with altitude is confirmed as the main environmental factor controlling vegetation distribution. However, the forests located close to the crest with a proportion increase of pollen taxa characteristic of heliophilous and pioneer trees (Alchornea, Miconia, Clusia), are also influenced by changes of edaphic conditions. In addition to provide useful information in understanding of fossil pollen records, this approach improves our understanding of the ecosystem functioning in mountainous massifs in north-eastern Brazil. A useful knowledge for conservation or restoration purposes.

The discovery of the Amazonian tree flora with an updated checklist of all known tree taxa.

Amazonia is the most biodiverse rainforest on Earth, and the debate over how many tree species grow there remains contentious. Here we provide a checklist of all tree species collected to date, and describe spatial and temporal trends in data accumulation. We report 530,025 unique collections of trees in Amazonia, dating between 1707 and 2015, for a total of 11,676 species in 1225 genera and 140 families. These figures support recent estimates of 16,000 total Amazonian tree species based on ecological plot data from the Amazonian Tree Diversity Network. Botanical collection in Amazonia is characterized by three major peaks, centred around 1840, 1920, and 1980, which are associated with flora projects and the establishment of inventory plots. Most collections were made in the 20th century. The number of collections has increased exponentially, but shows a slowdown in the last two decades. We find that a species’ range size is a better predictor of the number of times it has been collected than the species’ estimated basin-wide population size. Finding, describing, and documenting the distribution of the remaining species will require coordinated efforts at under-collected sites.