Terra Firme Rainforest Research Articles

Tadpoles of Central Amazonia (Amphibia: Anura).

Amazonian lowland rainforests epitomize, as few other biomes, the terrestrial and freshwater biological diversity of our planet. We provide here a comprehensive description of the larval anurans of Central Amazonia, and their natural history. We base our analyses on fieldwork conducted in six terra-firme rainforest and two várzea floodplain sites during ~60 months between 1990 and 2013, complemented with an examination of museum specimens and a review of published literature. Ninety-nine species of anurans are known to occur in Central Amazonia. Of these, 84 species (85%) have a free-swimming exotrophic larva, six species (6%) have a terrestrial endotrophic larva, one species has a terrestrial exotrophic larva (1%) and another seven species (7%) have direct development of eggs into froglets. The life cycle of one species (1%) remains unknown. We formally describe and illustrate the larval stage of 68 species (i.e., 75% of the species with a known larval stage), five of them previously unkown and nineteen never described for Central Amazonia. We compile, review and update information on species natural history including reproductive modes, habitat use, phenology, and species interactions including diet, predators, competitors and parasites. Finally, we assessed the ecomorphological diversity in the region by the application of a system inspired in Altig & Johnston (1989), later updated by Altig & McDiarmid (1999), which recognizes tadpole guilds based on a combination of morphological and natural history data. Basic scientific information presented in this monograph provide the essential background for further studies on the ecological and evolutionary forces shaping anuran Amazonian assemblages, and their conservation.

Late Holocene peatland palm swamp (aguajal) development, carbon deposition and environment changes in the Madre de Dios region, southeastern Peru

Tropical peatlands are an important carbon reservoir; however, they are vulnerable to climate change, fire events, and human disturbances, and may become a significant carbon source if degraded. In this paper, we investigated the late Holocene record of vegetation change, peatland evolution, and C accumulation based on analysis of a sediment core through a Mauritia-flexuosa palm dominated swamp (locally called “ aguajal ”) in the Madre de Dios region in southern Peru to better understand tropical peatland dynamics. Sedimentation commenced within shallow water, ponded on an impervious substrate, perhaps within an abandoned river channel or oxbow lake (1380–820 cal yr BP) located adjacent to a steep escarpment with terra firme (upland) rainforest above and lateral to floodplain forests. This was followed by the development of marsh (820–640 cal yr BP). A closed-canopy Mauritia flexuosa -dominated palm swamp was subsequently established (640300calyr BP) which later changed into an open canopy and mixed Mauritia - Hedyosmum palm swamp (300 cal yr BP to present). Two major changes in peat and C accumulation rates were observed: (1) onset of peat and C accumulation at 820 cal yr BP and (2) decrease of peat and C accumulation after 520 cal yr BP. Comparisons of our results with palaeoecological records from aguajales in northern Peru suggest that the dynamics were different in this region. The peat and C accumulation rates in our study core in southern Peru were ca. 4 mm yr −1 and ca. 200 g m −2 yr −1 faster, similar to a few sites in northern Peru. Aguajales in Madre de Dios region in southern Peru are an important carbon sink. Analyzing the dynamics of aguajales which are a kind of typical peatlands in Amazonia and comparing among different sites allows exploration and prediction of regional peatlands' development under the potential future impact of natural changes. • First study of a palm peatland ( aguajal ) development in Madre de Dios region, southern Peru • This study includes late Holocene vegetation dynamics, peat and C accumulation of the aguajal • Controlling factors in the dynamics are fluvial changes and climate • Comparisons with northern Peru suggest different vegetation succession • Peat and C accumulation rates in Madre de Dios were faster, similar to a few sites in northern Peru

Soil phosphorus fractions and their relation to leaf litterfall in a central Amazonian terra firme rainforest

ABSTRACT Phosphorus (P) cycling is an important yet poorly studied aspect of the macronutrient balance in tropical rainforest ecosystems. As soil P occurs in different organic and inorganic forms (fractions) with varying degrees of lability, we hypothesized that these fractions will vary between soil types, and temporally within soil types. Additionally, we hypothesized a direct influence of leaf litterfall P input on soil total P and soil P fractions. We collected soil and leaf litter samples from three soil types in a central Amazonian lowland rainforest in Brazil over five months, and used a modified Hedleys fractionation method to determine six organic and inorganic soil P fractions, and also total, labile and residual P. Leaf litterfall P concentrations were determined colorimetrically. Soil inorganic and organic P fractions varied between soil types and across months, but soil type and month interactions were mostly non-significant. Some inorganic P fractions (Pi-NaOH) peaked while the organic fractions (Po-NaOH) fell and vice versa. Leaf litterfall production and leaf litterfall P input peaked around two months following the wettest month. Leaf litterfall P input was a significant predictor of Po-NaHCO3, a bioavailable P fraction. Future studies on P cycling in terrestrial ecosystems should examine the roles played by individual soil P fractions as they cycle asynchronistically and differently across soil types.

Avian ecological succession in the Amazon: A long-term case study following experimental deforestation.

Approximately 20% of the Brazilian Amazon has now been deforested, and the Amazon is currently experiencing the highest rates of deforestation in a decade, leading to large‐scale land‐use changes. Roads have consistently been implicated as drivers of ongoing Amazon deforestation and may act as corridors to facilitate species invasions. Long‐term data, however, are necessary to determine how ecological succession alters avian communities following deforestation and whether established roads lead to a constant influx of new species.We used data across nearly 40 years from a large‐scale deforestation experiment in the central Amazon to examine the avian colonization process in a spatial and temporal framework, considering the role that roads may play in facilitating colonization.Since 1979, 139 species that are not part of the original forest avifauna have been recorded, including more secondary forest species than expected based on the regional species pool. Among the 35 species considered to have colonized and become established, a disproportionate number were secondary forest birds (63%), almost all of which first appeared during the 1980s. These new residents comprise about 13% of the current community of permanent residents.Widespread generalists associated with secondary forest colonized quickly following deforestation, with few new species added after the first decade, despite a stable road connection. Few species associated with riverine forest or specialized habitats colonized, despite road connection to their preferred source habitat. Colonizing species remained restricted to anthropogenic habitats and did not infiltrate old‐growth forests nor displace forest birds.Deforestation and expansion of road networks into terra firme rainforest will continue to create degraded anthropogenic habitat. Even so, the initial pulse of colonization by nonprimary forest bird species was not the beginning of a protracted series of invasions in this study, and the process appears to be reversible by forest succession.

Biological traits, rather than environment, shape detection curves of large vertebrates in neotropical rainforests.

Line transect surveys are widely used in Neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as encounter rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species' biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests that represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species' vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon, or localized species for which few data are available to fit the detection function.

Impact of pre-Columbian “geoglyph” builders on Amazonian forests

Over 450 pre-Columbian (pre-AD 1492) geometric ditched enclosures ("geoglyphs") occupy ∼13,000 km2 of Acre state, Brazil, representing a key discovery of Amazonian archaeology. These huge earthworks were concealed for centuries under terra firme (upland interfluvial) rainforest, directly challenging the "pristine" status of this ecosystem and its perceived vulnerability to human impacts. We reconstruct the environmental context of geoglyph construction and the nature, extent, and legacy of associated human impacts. We show that bamboo forest dominated the region for ≥6,000 y and that only small, temporary clearings were made to build the geoglyphs; however, construction occurred within anthropogenic forest that had been actively managed for millennia. In the absence of widespread deforestation, exploitation of forest products shaped a largely forested landscape that survived intact until the late 20th century.

Run, hide, or fight: anti-predation strategies in endangered red-nosed cuxiú (Chiropotes albinasus, Pitheciidae) in southeastern Amazonia.

Although primate predation is rarely observed, a series of primate anti-predation strategies have been described. Energetic costs of such strategies can vary from high-cost mobbing, via less costly alarm calling, to low-cost furtive concealment. Here we report the anti-predation strategies of red-nosed cuxiú, Chiropotes albinasus, based on direct observations from four study sites in southeastern Brazilian Amazonia. Over a collective period of 1255 fieldwork hours, we observed nine direct interactions between raptors (all potential predators) and red-nosed cuxiús. Of these, one (11%) resulted in predation. Raptors involved were: Harpia harpyja (four events), Leucopternis sp. (two events), Spizaëtus tyrannus (one event), and unidentified large raptors (two events). Predation attempts occurred in flooded-forest and terra firme rainforest, were directed at both adult and non-adult cuxiús, and involved both adult and juvenile raptors. Anti-predation strategies adopted by the cuxiús included: (1) group defence and mobbing behaviour (two occasions), (2) dropping into dense sub-canopy (seven occasions), (3) alarm calling (eight occasions), and (4) fleeing to, and hiding in, dense vegetation (eight occasions). During each encounter at least two of these behaviours were recorded. These are the first published records of predation, predation attempts, and anti-predator behaviour involving red-nosed cuxiú.

Effect of sampling grain on patterns of species richness and turnover in Amazonian forests

Grain (size of sampling units) affects the spatial resolution at which ecological patterns can be observed and analysed, and potentially has an important effect on the results of broad‐scale studies on diversity gradients. Here we examine the effect of grain on patterns of species richness and turnover in lowland rainforests of western Amazonia (Peru and Colombia). We inventoried pteridophytes (ferns and lycophytes), melastomes (Melastomataceae) and palms (Arecaceae) in four line transects of 22–29 km length. Different grains were obtained by aggregating original 100‐m‐long sampling units into larger segments up to 19.2 km long. With any given grain and plant group, local species richness varied considerably both within and among transects, and a transect segment that was species‐rich with one grain could be relatively species‐poor with another. Which transect had the highest vs lowest mean species richness per sampling unit (α richness) differed among plant groups. It also varied to some degree with grain, as transects differed in how rapidly local species richness increased with increasing grain. Patterns of species turnover were more consistently correlated among plant groups than patterns of species richness were, and NMDS ordinations were rather similar with all grains and plant groups. Floristic heterogeneity within the Amazonian terra firme rainforest seems to contain a general compositional pattern that is sufficiently robust to be detectable with various sampling schemes, but patterns of species richness appear more case‐specific. Therefore, using one plant group as an indicator for patterns in other plant groups can be expected to work better for species turnover than for species richness.

Tree growth, wood and bark water content of 28 Amazonian tree species in response to variations in rainfall and wood density

Abstract: Pole diameter and wood density are variables commonly used in allometric equations to estimate tree biomass and carbon stocks in tropical forests. The effect of variations in tree water content on pole diameters is often disregarded in allometric equations. This study aimed to determine the effect of rainfall seasonality on tree growth, stem wood and bark water content and to assess the relationship between water content and wood density (dry mass to fresh mass volume ratio) in 120 trees from 28 species in a terra-firme rain forest in the central Amazon. In 2006, stem wood and bark water content were gravimetrically determined in the dry season (August-September) and rainy season (April-May). In the same year, growth in diameter was measured at monthly intervals in the 120 trees (DBH ≥ 10 cm) with dendrometric bands previously adapted to the tree. Mean wood water content was lower in the dry season than the rainy season. On the contrary, bark water content was higher in the dry season than in the rainy season. Wood densities higher than 0.75 g cm-3 were found in 64.3% of the trees. Trees with denser woods grew slower and had lower stem water content. Monthly rainfall did not affect tree growth in diameter, which was contrary to our initial expectation on the effect of rainfall seasonality on tree growth in central Amazonia. This finding supports the hypothesis that in central Amazonia, the mild dry season is not long enough to deplete soil water beyond the reach of the root system, which allows the trees to grow at quite constant rates over the year.

Results from two sampling techniques for carabid beetles (Coleoptera: Carabidae) in temporarily flooded and terra firme rainforest of western Amazonia

ABSTRACTCarabidae beetles (Coleoptera) were sampled by flight intercept traps (FITs) and hand sampling in the understory of a lowland rainforest in eastern Ecuador. Sampling occurred in June and July of 2011 and 2012 at 24 sites within temporarily flooded forest (FP) and non-flooded terra firme (TF) forest. A total of 674 Carabidae (excluding Cicindelinae) individuals, representing 18 tribes, 50 genera and 133 morphospecies, were collected. Significantly more individuals were collected by hand compared to FITs, particularly by hand in FP forests. After correction through sample-based rarefaction there are no significant differences in species richness between sampling methods and forest types. Ordination and dissimilarity analysis show FITs and hand sampling target different portions of the Carabidae community. Understanding sampling biases for various sampling methods and how it may be affected by forest type will result in more accurate and efficient surveys in tropical forests.

Spatial cluster detection using nearest neighbor distance

Motivated by the analysis of the impact of ecological processes on spatial distribution of tree species, we introduce in this paper a novel approach to detect spatial cluster of points. Our procedure is based on an iterative transformation of the distance between points into a measure of closeness. Our measure has the advantage of being independent of an arbitrary cluster shape and allowing adjustment for covariates. The comparison of the observed measure of closeness to a reference point process leads to a hierarchical clustering of spatial points. The selection of the optimal number of clusters is performed using the Gap statistic. Our procedure is illustrated on a spatial distribution of the Dicorynia guianensis species in the French Guiana terra firme rainforest.

Origin and alteration of organic matter in termite mounds from different feeding guilds of the Amazon rainforests.

The impact of termites on nutrient cycling and tropical soil formation depends on their feeding habits and related material transformation. The identification of food sources, however, is difficult, because they are variable and changed by termite activity and nest construction. Here, we related the sources and alteration of organic matter in nests from seven different termite genera and feeding habits in the Terra Firme rainforests to the properties of potential food sources soil, wood, and microepiphytes. Chemical analyses comprised isotopic composition of C and N, cellulosic (CPS), non-cellulosic (NCPS), and N-containing saccharides, and molecular composition screening using pyrolysis-field ionization mass spectrometry (Py-FIMS). The isotopic analysis revealed higher soil δ13C (-27.4‰) and δ15N (6.6‰) values in nests of wood feeding Nasutitermes and Cornitermes than in wood samples (δ13C = -29.1‰, δ15N = 3.4‰), reflecting stable-isotope enrichment with organic matter alterations during or after nest construction. This result was confirmed by elevated NCPS:CPS ratios, indicating a preferential cellulose decomposition in the nests. High portions of muramic acid (MurAc) pointed to the participation of bacteria in the transformation processes. Non-metric multidimensional scaling (NMDS) revealed increasing geophagy in the sequence Termes < Embiratermes < Anoplotermes and increasing xylophagy for Cornitermes < Nasutitermes, and that the nest material of Constrictotermes was similar to the microepiphytes sample, confirming the report that Constrictotermes belongs to the microepiphyte-feeders. We therewith document that nest chemistry of rainforest termites shows variations and evidence of modification by microbial processes, but nevertheless it primarily reflects the trophic niches of the constructors.

Juvenile tree growth correlates with photosynthesis and leaf phosphorus content in central Amazonia

Light and soil water availability may limit carbon uptake of trees in tropical rainforests. The objective of this work was to determine how photosynthetic traits of juvenile trees respond to variations in rainfall seasonality, leaf nutrient content, and opening of the forest canopy. The correlation between leaf nutrient content and annual growth rate of saplings was also assessed. In a terra firme rainforest of the central Amazon, leaf nutrient content and gas exchange parameters were measured in five sapling tree species in the dry and rainy season of 2008. Sapling growth was measured in 2008 and 2009. Rainfall seasonality led to variations in soil water content, but it did not affect leaf gas exchange parameters. Subtle changes in the canopy opening affected CO2 saturated photosynthesis (A pot, p = 0.04). Although A pot was affected by leaf nutrient content (as follows: P &gt; Mg &gt; Ca &gt; N &gt; K), the relative growth rate of saplings correlated solely with leaf P content (r = 0.52, p = 0.003). At present, reduction in soil water content during the dry season does not seem to be strong enough to cause any effect on photosynthesis of saplings in central Amazonia. This study shows that leaf P content is positively correlated with sapling growth in the central Amazon. Therefore, the positive effect of atmospheric CO2 fertilization on long-term tree growth will depend on the ability of trees to absorb additional amount of P

Soil CO2 exchange in seven pristine Amazonian rain forest sites in relation to soil temperature

We analysed soil respiration measurements made in seven distinctly different pristine rain forests in Central Amazon, ranging from stunted heath forest (Campina) to tall terra-firme rain forest. The differences in soil respiration fluxes between sites and their causes were investigated, as well as diurnal patterns and their dependency on temperature. Ensemble averages of hourly fluxes were calculated for both wet and dry seasons (as far as these were sampled). These values were processed using an analytical model estimating soil surface temperature from the temperature measured at two depths. The soil CO2 efflux can be viewed as a proxy for forest productivity. The low productive Campina stunted heath forest site (on leached sandy soils and covered by scleromorphic vegetation) has the lowest respiration (<1.5μmolCO2m−2s−1, dry period). Respiration increased in local patches of taller heath forest on finer textured soil to about 4μmolCO2m−2s−1. In the Cuieiras lowland rain forest respiration changed along a toposequence. The lowest value of 2.5μmolCO2m−2s−1 was observed on the plateau (terra-firme rain forest), whereas a maximum of 6.0μmolCO2m−2s−1 was observed in the valley (Campinarana forest). Soil respiration decreased to about 4μmolCO2m−2s−1 close to the river (riparian forest) where soils remained close to saturation. To find the optimum correlation between soil temperature and respiration flux, relationships were derived between the amplitudes and phases of respiration and soil temperatures measured at different depths. Compared to the use of soil temperatures measured at 5cm and 10cm depth, the use of (modelled) soil surface temperatures strongly reduced the hysteresis between respiration and temperature, and improved the coefficient of determination (R2) for the Cuieiras forest sites, whereas the Campina sites still showed time lags of several hours between respiration and soil temperature diurnal patterns. With respect to the surface temperature, Q10 ranged from 1.7 (bare soil, dry season) to 2.0–2.5 (Cuieiras slope and plateau sites, dry season) and 3.3–5.2 (ibidem, wet season) to 5.5–7.7 (Cuieiras Campinarana and valley forests, dry/wet season).

Large trees as key elements of carbon storage and dynamics after selective logging in the Eastern Amazon

The long term effect of Reduced-Impact Logging (RIL) on above-ground live biomass (AGB) dynamics was investigated in 18 1-ha logged over permanent sample plots set up in a terra firme rain forest in the Eastern Amazon (Brazil, Paragominas). Both tree survival and growth were investigated among three Diameter at Breath Height (DBH) classes (20–40, 40–60, ⩾60cm) to assess the contribution of each DBH class to the post-logging AGB recovery. Before logging, mean tree density and AGB per plot (dbh⩾20cm) were 187±14 trees ha−1 and 377.6±62.8Mgha−1 respectively. Although big trees (dbh⩾60cm) only represented 9.3% of the total tree density, they gathered almost half of total AGB. During the post-logging period (8years), the mortality of large trees was found to drive the annual net changes and largely overcame the AGB gain in the smaller DBH classes. Indeed, plots with high post-logging mortality of large trees showed negative carbon balance t over the study period (8years). The over mortality of large trees injured by logging contributed significantly to the annual AGB losses (up to 40%) in the first years after logging. Due to the overwhelming importance of this size class in carbon stocks and dynamic, reducing logging damages and intensity might have great impact in the post-logging biomass dynamics. We estimated that reducing logging intensity from 6 to 3 stems ha−1 would save 27.7Mg C ha−1 for a 35years rotation cycle. To compensate this loss of profits, compensatory payments of avoided CO2 emission should worth US $ 6.5/Mg of CO2. This price falls into the range of prices of the international carbon market. Sustainable forest management aiming at enhancing carbon stocks could therefore promote the preservation of the large trees. At our study site, we recommend the adoption of a maximum diameter cutting limit of 110cm.

Lophostoma carrikeri (Allen, 1910) (Chiroptera: Phyllostomidae): first confirmed records in Ecuador

Herein we confirm the occurrence of Lophostoma carrikeri in Ecuador. One adult female was collected in Orellana province on 17 September 2012 at Boanamo, Waorani Ethnic Reserve, and another on 5 May 2013 at Yasuni Research Station, Yasuni National Park. These records extend the distributional range of the species about 570 km northwest of the nearest previously known record in Jenaro Herrera, Loreto, Peru. Both Ecuadorian localities are characterized by well-conserved primary Terra Firme rainforest. Morphological characters of the specimens presented here broaden the known intraspecific variation in this taxon, including uniformly dark ears without white margins, undeveloped sagittal crests, and smaller forearm size than previously reported. In addition, information on ectoparasites for this species in Ecuador is provided.

Superfamilia Scarabaeoidea (Insecta: Coleoptera) como elemento bioindicador de perturbación antropogénica en un parque nacional amazónico

Abstract: Scarabaeoidea superfamily (Insecta: Coleoptera) as a bioindicator element of anthropogenic disturbance in an amazon national park. Insects have been recognized to be important indicators of the quality elements of ecosystems, among others, because of their rapid response to environmental variability and ease cost-effective capture. In this work we evaluated whether beetles of the Scarabaeoidea superfamily may be used as bioindicators of anthropogenic disturbance of Amazonian terra firme rain forests, in order to provide guidelines for monitoring strategies of the Amacayacu National Park. We considered three different levels of anthropogenic disturbance (i.e. low, medium, high) in 12 transects (four in each intervention level), and caught all beetle species of this superfamily. Three interception traps, two light traps, three pitfalls and four bottle fruit traps were used per transect, as well as manual catch. In total, 593 individuals belonging to 92 species, 44 genera and seven families were collected. Scarabaeidae (n = 232, 27 spp.) and Dynastidae (n = 161, 26 spp.) were the families with the highest number of individuals and species, while Aphodiidae, Cetoniidae and Geotrupidae exhibited the lowest. The most abundant species per family were Ateuchus sp. (33.2%) from Scarabaeidae, Cyclocephala verticalis (55.9%) from Dynastidae, Astaena sp. (75.8%) from Melolonthidae, Ceratocanthus amazonicus (66.7%) from Ceratocanthidae y Chaetodus asuai (96.8%) from Hybosoridae. Results showed that the number of species and individuals increased with the anthropogenic disturbance. The Margalef and Shannon indexes also revealed that the highest richness and equity occurred in the high-disturbed site, respectively. Dynastidae exhibited the highest number of exclusive species per gradient, while Scarabaeidae shared most of its species. Ten species were recorded in the three disturbance levels, 26 species in two and 56 species were exclusive to one level. The most abundant species Chaetodus asuai (Hybosoridae) presented a significant decrease in the number of individuals as disturbance increased, while an inverse relationship occurred for C verticalis (Dynastidae). For Astaena sp. (Melolonthidae) and Ligyrus gyas (Dynastidae) a high number of individuals was recorded and were exclusive for one forest site (low and high disturbed forest, respectively). The complete superfamily cannot be used like a single bioindicator element because it displays, in a specific level, very different behaviors in each disturbance condition. We discuss the use of richness and diversity as indicators of disturbance, while we highlight abundance of particular taxa as a better metric for disturbance.

A new species of the Dendropsophus parviceps group from the western Amazon Basin (Amphibia: Anura: Hylidae)

We describe Dendropsophus frosti sp. nov. from lowland terra firme rainforests of the headwaters of the Amazon RiverBasin in Colombia and Peru. The new species is known from only two localities, the type locality near Leticia (Departa-mento Amazonas, Colombia, 04° 06' 24.2" S, 69° 56' 57.4" W; 103 m.a.s.l.), and the paratopotypic locality, Piedras in thePutumayo basin (Departamento Loreto, Peru, 02.79278° S, 72.91750° W; 90–170 m.a.s.l.). Maximum likelihood and par-simony analyses of 2436 aligned base pairs of the 12S and 16S rRNA genes recovered the new species as a member of D.parviceps group and sister to D. brevifrons. The new species is most closely related to D. parviceps, D. brevifrons, and D.koechlini, and it can be readily distinguished from these and all other members of the D. parviceps group by, among othercharacters, its plain dorsal light brown coloration, copper iris, plain immaculate pale yellow to white venter coloration, lack of flash marks on groin and axillae, and absence of white spots on lips.

Species Diversity and Growth Forms in Tropical American Palm Communities

To advance our understanding of the processes that govern the assembly of palm communities and the local coexistence of numerous palm species, we here synthesize available information in the literature on species diversity and growth-form composition in palm communities across the Americas. American palm communities surveyed had 4–48 (median 16) species in study plots covering 0.09–7.2 ha. Climate, soils, hydrology, and topography are the main factors determining palm community species richness. Tropical lowland terra firme rain forests are the most species-rich whereas forests that are inundated or grow on sandy soils or in areas with seasonal climate have much fewer species. Palm communities in the central-western Amazon and in Central America are significantly richer than the average region and those in the Caribbean significantly poorer in species. As for branching, the 789 species of tropical American palms belong to Corner’s model (solitary, 268 species, 33%), Tomlinsons model (cespitose, 521 species, 66%) and Schoute’s model (dichotomous branching, three species, <1%). We assigned the species to eight different growth forms: (i) Large tall-stemmed Palms (102 spp), (ii) Large-leaved medium–short-stemmed Palms (31 spp), (iii) Medium-sized Palms (95 spp), (iv) Medium/Small Palms with Stout Stem (42 spp), (v) Small Palms (423 spp), (vi) Large acaulescent Palms (28 spp), (vii) Small acaulescent Palms (56 spp), and (viii) Climbing Palms (12 spp). The eight growth forms are differently represented in the palm communities, and the categories Small Palms and Large tall-stemmed Palms dominate the communities both in terms of species richness and in number of individuals.

Influence of drainage status on soil and water chemistry, litter decomposition and soil respiration in central Amazonian forests on sandy soils

Central Amazonian rainforest landscape supports a mosaic of tall terra firme rainforest and ecotone campinarana, riparian and campina forests, reflecting topography-induced variations in soil, nutrient and drainage conditions. Spatial and temporal variations in litter decomposition, soil and groundwater chemistry and soil CO2 respiration were studied in forests on sandy soils, whereas drought sensitivity of poorly-drained valley soils was investigated in an artificial drainage experiment. Slightly changes in litter decomposition or water chemistry were observed as a consequence of artificial drainage. Riparian plots did experience higher litter decomposition rates than campina forest. In response to a permanent lowering of the groundwater level from 0.1 m to 0.3 m depth in the drainage plot, topsoil carbon and nitrogen contents decreased substantially. Soil CO2 respiration decreased from 3.7±0.6 µmol m -2 s -1 before drainage to 2.5±0.2 and 0.8±0.1 µmol m -2 s -1 eight and 11 months after drainage, respectively. Soil respiration in the control plot remained constant at 3.7±0.6 µmol m -2 s -1 . The above suggests that more frequent droughts may affect topsoil carbon and nitrogen content and soil respiration rates in the riparian ecosystem, and may induce a transition to less diverse campinarana or short-statured campina forest that covers areas with strongly-leached sandy soil.