Wood growth of Tabebuia barbata (E. Mey.) Sandwith (Bignoniaceae) and Vatairea guianensis Aubl. (Fabaceae) in Central Amazonian black-water (igapó) and white-water (várzea) floodplain forests

Tree growth is a fundamental indicator for conservation plans of Amazonian floodplain forests. In this study we use dendrochronology to analyze wood growth patterns of Tabebuia barbata and Vatairea guianensis, two tree species occurring in nutrient-rich white-water (várzea, Mamirauá Sustainable Development Reserve, MSDR) and nutrient-poor black-water (igapó, Amanã Sustainable Development Reserve, ASDR) floodplain forests of Central Amazonia. From 20 trees per species and floodplain system (total of 80 trees) growing under a similar flooding regime with a mean inundation height of about 4 m we measured diameter at breast height (dbh). We sampled two cores per tree with an increment corer at the height of dbh to determine wood density (WD), tree age and mean radial increment (MRI) rates. The wood samples were macroscopically analyzed. Both tree species show distinct annual tree rings characterized by marginal parenchyma tissues. MRI was measured by a digital measuring device and WD was determined by the ratio dry mass/fresh volume. MRI of both tree species was significantly higher in the várzea than in the igapó, which can be traced back to the contrasting nutrient status. WD showed no difference comparing both floodplain forest types. Tree ages of a species for the same diameter are more than twofold higher in the igapó than in the várzea. To insure a sustainable harvest, felling cycles in these forests should be adjusted according to rates of growth.     

Primate assemblage structure in Amazonian flooded and unflooded forests

There is considerable variation in primate species richness across neotropical forest sites, and the richest assemblages are found in western Amazonia. Forest type is an important determinant of the patterns of platyrrhine primate diversity, abundance, and biomass. Here we present data on the assemblage structure of primates in adjacent unflooded (terra firme) and seasonally inundated (várzea and igapó) forests in the lower Purús region of central-western Brazilian Amazonia. A line-transect census of 2,026 km in terra firme, 2,309 km in várzea, and 277 km in igapó was conducted. Twelve primate species were recorded from 2,059 primate group sightings. Although terra firme was found to be consistently more species-rich than várzea, the aggregate primate density in terra firme forest was considerably lower than that in the species-poor várzea. Consequently, the total biomass estimate was much higher in várzea compared to either terra firme or igapó forest. Brown capuchin monkeys (Cebus apella) were the most abundant species in terra firme, but were outnumbered by squirrel monkeys (Saimiri cf. ustus) in the várzea. The results suggest that floodplain forest is a crucial complement to terra firme in terms of primate conservation in Amazonian forests.     

Tree species composition and diversity gradients in white-water forests across the Amazon Basin

Aim Attention has increasingly been focused on the floristic variation within forests of the Amazon Basin. Variations in species composition and diversity are poorly understood, especially in Amazonian floodplain forests. We investigated tree species composition, richness and α diversity in the Amazonian white‐water (várzea) forest, looking particularly at: (1) the flood‐level gradient, (2) the successional stage (stand age), and (3) the geographical location of the forests. Location Eastern Amazonia, central Amazonia, equatorial western Amazonia and the southern part of western Amazonia. Methods The data originate from 16 permanent várzea forest plots in the central and western Brazilian Amazon and in the northern Bolivian Amazon. In addition, revised species lists of 28 várzea forest inventories from across the Amazon Basin were used. Most important families and species were determined using importance values. Floristic similarity between plots was calculated to detect similarity variations between forest types and over geographical distances. To check for spatial diversity gradients, α diversity (Fisher) of the plots was correlated with stand age, longitudinal and latitudinal plot location, and flood‐level gradient. Results More than 900 flood‐tolerant tree species were recorded, which indicates that Amazonian várzea forests are the most species‐rich floodplain forests worldwide. The most important plant families recorded also dominate most Neotropical upland forests, and c. 31% of the tree species listed also occur in the uplands. Species distribution and diversity varied: (1) on the flood‐level gradient, with a distinct separation between low‐várzea forests and high‐várzea forests, (2) in relation to natural forest succession, with species‐poor forests in early stages of succession and species‐rich forests in later stages, and (3) as a function of geographical distance between sites, indicating an increasing α diversity from eastern to western Amazonia, and simultaneously from the southern part of western Amazonia to equatorial western Amazonia. Main conclusions The east‐to‐west gradient of increasing species diversity in várzea forests reflects the diversity patterns also described for Amazonian terra firme. Despite the fine‐scale geomorphological heterogeneity of the floodplains, and despite high disturbance of the different forest types by sedimentation and erosion, várzea forests are dominated by a high proportion of generalistic, widely distributed tree species. In contrast to high‐várzea forests, where floristic dissimilarity increases significantly with increasing distance between the sites, low‐várzea forests can exhibit high floristic similarity over large geographical distances. The high várzea may be an important transitional zone for lateral immigration of terra firme species to the floodplains, thus contributing to comparatively high species richness. However, long‐distance dispersal of many low‐várzea trees contributes to comparatively low species richness in highly flooded low várzea.     

Seasonal patterns of spatial variation in understory bird assemblages across a mosaic of flooded and unflooded Amazonian forests

We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale.     

Tree Phenology in Adjacent Amazonian Flooded and Unflooded Forests1

Most phenological studies to date have taken place in upland forest above the maximum flood level of nearby streams and rivers. In this paper, we examine the phenological patterns of tree assemblages in a large Amazonian forest landscape, including both upland (terra firme) and seasonally flooded (várzea and igapó) forest. The abundance of vegetative and reproductive phenophases was very seasonal in all forests types. Both types of flooded forest were more deciduous than terra firme, shedding most of their leaves during the inundation period. Pulses of new leaves occurred mainly during the dry season in terra firme, whereas those in the two floodplain forests were largely restricted to the end of the inundation period. Flowering was concentrated in the dry season in all forest types and was strongly correlated with the decrease in rainfall. The two floodplain forests concentrated their fruiting peaks during the inundation period, whereas trees in terra firme tended to bear fruits at the onset of the wet season. The results suggest that the phenological patterns of all forest types are largely predictable and that the regular and prolonged seasonal flood pulse is a major determinant of phenological patterns in várzea and igapó, whereas rainfall and solar irradiance appear to be important in terra firme. The three forest types provide a mosaic of food resources that has important implications for the conservation and maintenance of wide‐ranging frugivore populations in Amazonian forests.     

Vertebrate responses to fruit production in Amazonian flooded and unflooded forests

We document patterns of fruit and vertebrate abundance within an extensive, virtually undisturbed mosaic of seasonally flooded (várzea and igapó) and unflooded (terra firme) forests of central Amazonia. Using phenological surveys and a standardised series of line-transect censuses we investigate the spatial and temporal patterns of immature and mature fruit availability and how this may affect patterns of habitat use by vertebrates in the landscape. All habitats showed marked peaks in fruiting activity, and vertebrate detection rates varied over time for most species both within and between forest types. Many arboreal and terrestrial vertebrates used both types of flooded forest on a seasonal basis, and fluctuations in the abundance of terrestrial species in várzea forest were correlated with fruit availability. Similarly, the abundance of arboreal seed predators such as buffy saki monkeys (Pithecia albicans) and macaws (Ara spp.) were closely linked with immature fruit availability in terra firme forest. We conclude that highly heterogeneous landscapes consisting of terra firme, várzea and igapó forest appear to play an important role in the dynamics of many vertebrate species in lowland Amazonia, but the extent to which different forest types are used is highly variable in both space and time.     

Seasonal flooding decreases fruit-feeding butterfly species dominance and increases spatial turnover in floodplain forests of central Amazonia

The seasonal flood pulse in Amazonia can be considered a primary driver of community structure in floodplain environments. Although this natural periodic disturbance is part of the landscape dynamics, the seasonal inundation presents a considerable challenge to organisms that inhabit floodplain forests. The present study investigated the effect of seasonal flooding on fruit-feeding butterfly assemblages in different forest types and strata in central Amazonia. We sampled fruit-feeding butterflies in the canopy and the understory using baited traps in adjacent upland (unflooded forests—terra firme), white and blackwater floodplain forests (várzea and igapó, respectively) during the low- and high-water seasons. Butterfly abundance decreased in the high-water season, especially of dominant species in várzea, but the number of species was similar between seasons in the three forest types. Species composition differed between strata in all forest types. However, the flood pulse only affected butterfly assemblages in várzea forest. The β-diversity components also differed only in várzea. Species replacement (turnover) dominated the spatial β-diversity in igapó and terra firme in both seasons and várzea in the high-water season. Nonetheless, nestedness was relatively higher in várzea forests during the low-water season, mainly due to the effect of dominant species. These results emphasize the importance of seasonal flooding to structure butterfly assemblages in floodplain forests and reveal the idiosyncrasy of butterfly community responses to flooding in different forest types. Our results also suggest that any major and rapid changes to the hydrological regime could severely affect floodplain communities adapted to this natural seasonal hydrological cycle, threatening the existence of these unique environments.     

Notes on the vegetation of amazonia III. The terminology of amazonian forest types subject to inundation

The types of Amazonian forests subject to inundation can be organized into seven categories which are herewith named and described. This classification is intended to set in order the confusion of terminology used in the past. The types are: (1)seasonal várzea—forest flooded by regular annual cycles of white-water rivers; (2)seasonal igapó—forest flooded by regular annual cycles of black- and clear-water rivers; (3) mangrove—forests flooded twice daily by salt-water tides; (4)tidal várzea—forest flooded twice daily by fresh water backed up from tides; (5)floodplain forest—on low lying ground flooded by irregular rainfall, generally in upper reaches of rivers; (6)permanent white- water swamp forest; (7)permanent igapó—black-water forest. The first five types are periodically inundated and the last two are permanently waterlogged. This terminology is closer to that used by lim nologists by restricting the use ofigapó to forest inundated by black and clear water.     

Sapling communities in Amazonian white-water forests

Aim Structure and floristic composition of forest regeneration (trees between 1 and 10 cm diameter at breast height (d.b.h), ≥ 1 m growth height) was described in three forest types of Amazonian white‐water forests (várzea), in order to analyse whether floristic composition of saplings is related to the successional stage of the forests, whether it differs in comparision with the mature flora, and if there exists a zonation of sapling species along the gradients of flooding and irradiation. Location Mamirauá Sustainable Development Reserve, Western Brazilian Amazon. Methods The investigated forests were of the low and the high várzea type, on an annual average flooded around 4 and 1 months, respectively. The two low‐várzea forests belonged to the secondary and to the late‐successional stage, the high‐várzea forest also to the late‐successional stage. A total of 24 circular sample plots covering 1885 m² were installed. They were nested within three rectangular 1 ha permanent sample plots where individuals ≥ 10 cm d.b.h. were formerly inventoried. Average inundation and radiation [relative photosynthetically active radiation (rPAR)] at the forest floor was recorded in all inventoried plots. The Mean spatial Distribution Center (MDC; Ebdon, 1998 ) for all sapling species was calculated. Sapling species were grouped into associations with respect to their light‐demand and their location along the flood‐level gradient. Results Average flood height and average rPAR at the forest floor was highest in the secondary stage of the low várzea and lowest in the high‐várzea forest. Overall average density and basal area of the saplings averaged 2250 individuals and 2.3 m² ha^?1 in the secondary stage, 2330 individuals and 2.6 m² ha^?1 in the late‐successional stage of the low várzea and 5000 individuals and 4.8 m² ha^?1 in the high várzea. In all forest types, species richness of saplings was lower than species richness of trees ≥ 10 cm d.b.h., and amounted to 25 species in the secondary stage, to 35 species in the late‐successional stage of the low várzea and to 88 species in the high‐várzea forest. The amount of ‘immigrants’ ( Bazzaz, 1991 ) at the sapling level increased with proceeding forest succession and amounted to 24 and 29% in the low várzea and to 31% in the high várzea. Sapling species distribution, species richness and individual density was linked to both, the gradient of flooding and the gradient of irradiation. Species richness and individual density was highest in the high várzea and decreased with increasing influence of flooding. The high várzea was predominated by pronounced shade‐tolerant sapling species, whereas in the low várzea occured both, light demanding and shade‐tolerant species groups. Main conclusions Influence of flooding seems to be the main factor triggering species composition and structure of sapling communities in várzea forests. Proceeding forest succession reduces the impact of flooding because of the biogenical induced silting up of the forested sites. However, forest succession also alters forest architecture of the overstory and such the light conditions at the sapling level. Therefore, radiation is an important factor influencing species composition of sapling communities in várzea forests.     

Germinative behaviour of ten tree species in white-water floodplain forests in central Amazonia

Amazonian floodplain forests (known as várzea) are classified into high or low várzea depending on the spatial position on the plains. This topographic feature exposes the terrain over different time periods of inundation, causing a major limiting factor for tree seedling establishment. We hypothesize that, strategically, most of the seeds produced by trees in low várzea forests germinate faster and in synchrony (temporally concentrated germination), and that their seedlings tend to have cotyledons without reserve or foliaceous cotyledons (PEF). By contrast, seeds produced by high-várzea specialist trees exhibit slower and temporally scattered germination, and their seedlings tend to have reserve storage cotyledons (CHR). Generalist species may show no clear pattern or may be related to high-várzea species. To test this hypothesis, diaspores of 10 tree species were collected: five of low-várzea specialist trees, three of high-várzea specialist trees and two of generalist species. Seedling emergence and morphology were monitored daily in a nursery for a period of 150 days of being subjected to non-flooded (sown directly in várzea soil) and flooded conditions (15 days in water before sowing in the same soil). The seedling emergence of low-várzea species showed an increase of 37% in germinability whereas high-várzea and generalist species exhibited a decrease of 38% and 35% of germinability, respectively. Foliaceous cotyledons were preferentially found in seedlings of low-várzea species, and storage cotyledons were more common in those of high-várzea species, indicating how cotyledon morphology may determine the amount and use of resources available to a seedling during the first stages of establishment and growth. Conservation plans aiming for the maintenance of ecosystem services must consider these strategies.     

Floristic variation across 600 km of inundation forests (Igapó) along the Negro River,Central Amazonia

We inventoried 10 ha of late-successional and seasonally inundated black-water floodplain (igapó) forest along four river sections of the Negro River, Central Amazonia, Brazil. The aim of the study was to test if tree species composition and diversity changes along the river course, and whether these changes reflect the different geological formations of the Negro River. On a continental-wide scale, we assessed alpha-diversity patterns of black-water flooded forests across the Amazon and Orinoco basins. Phytosociological analyses include family and species importance, species similarity, and Fisher’s alpha-diversity, as well as Detrended Correspondence Analysis. A total of 6.126 individuals were recorded, belonging to 243 tree species. Only few tree species occurred in more than one river section, and floristic composition changed abruptly from one section to the other. Tree species richness ranged from 57 to 79 species ha^?1, and alpha-diversity was highest (27.24) in the lower river section upon sediments of Pliocene–Pleistocene origin. We found a gradual decrease in species diversity with increasing age of the geological formations. The igapó forest is relatively species-poor, which we interpret to be the result of general low nutrient availability in alluvial substrates of the Negro River.     

Tree community structure reflects niche segregation of three parapatric squirrel monkey species (<Emphasis Type="Italic">Saimiri</Emphasis> spp.)

Integration between ecology and biogeography provides insights into how niche specialization affects the geographical distribution of species. Given that rivers are not effective barriers to dispersal in three parapatric species of squirrel monkeys (Saimiri vanzolinii, S. cassiquiarensis and S. macrodon) inhabiting floodplain forests of Central Amazonia, we tested whether forest structure and tree diversity may explain species differences in niche specialization and spatial segregation. We sampled 6617 trees of 326 species in three habitats (high várzea, low várzea and chavascal) used by three Saimiri species, and estimated tree species richness in each of them. For each tree, we measured variables known to influence habitat use in primates, such as crown area and presence of lianas, epiphytes and hemi-epiphytes. We used ANOVA to compare these variables and performed multivariate analyses (NMDS, ANOSIM and SIMPER) to evaluate dissimilarities in forest structure among each habitat inhabited by the three Saimiri species. We identified differences in the tree species richness, crown area and presence of lianas, epiphytes and hemi-epiphytes between the three habitats for all Saimiri species. NMDS demonstrated that areas of high and low várzeas occupied by S. vanzolinii were clearly separated from the other species. We also found that different plant species contributed to dissimilarity among Saimiri ranges. Our findings support the hypothesis that tree community structure may promote niche specialization and spatial segregation among primates. We discuss how these patterns could have been favored by historical changes in forest flood patterns, the evolutionary history of Saimiri spp., and past competition.     

Central Amazonian floodplain forests: Tree adaptations in a pulsing system

Amazonian floodplain forests are characterized by an annual flood pulse with changes of the water table that exceed 10 meters. Seedlings and adult trees are waterlogged or submerged for continuous periods lasting up to seven months per year. The monomodal flood pulse of the rivers causes drastic changes in the bioavailability of nutrients, oxygen levels, and concentrations of phytotoxins. The aquatic phase occurs during a period in which temperature and light conditions are optimal for plant growth and development, implying the need for adaptations. Not only do trees persist in a dormant state, they grow vigorously during most of the year, including the aquatic period. The regularity of flooding may have enhanced the evolution of specific traits, which partially are well known from floodplain trees in other tropical and in temperate regions. Different kinds of adaptations are found at the level of structural, physiological, and phenological traits. Combinations of adaptations regarding seed germination, seedling development, and traits of roots, shoots, and leaves result in a variety of growth strategies among trees. These lead to specific species distributions and zonations along the flooding gradient and within Amazonian floodplain systems (nutrient-rich white-water várzea and nutrient-poor black-water igapó).     

Habitat specifity,endemism and the neotropical distribution of Amazonian white‐water floodplain trees

.The Amazon basin is covered by the most species‐rich forests in the world and is considered to house many endemic tree species. Yet, most Amazonian ecosystems lack reliable estimates of their degree of endemism, and causes of tree diversity and endemism are intense matters of debate. We reviewed the spatial distribution of 658 of the most important flood‐tolerant Amazonian white‐water (várzea) tree species across the entire Neotropics by using data from herbaria, floras, inventories and checklists. Our results show that 90% of the várzea tree species are partially or widely distributed across neotropical macro‐regions and biomes. Chi‐square analyses indicated that várzea species richness in non‐várzea macro‐regions was dependent on the flooding gradient and the longitudinal position. Cluster analysis combined with association tests indicated four significant patterns of várzea species distributions depending on species flood‐tolerance (low vs high) and spatial distribution (restricted vs widespread). We predict that the predominance of Andean substrates is the most important factor that determines the distribution of várzea tree species within and beyond the Amazon basin and explains the high floristic similarity to the Orinoco floodplains. Distribution patterns in other extra‐Amazonian macro‐regions are more likely linked to climatic factors, with rainforest climates housing more várzea species than savanna climates. 130 tree species were restricted to South‐American freshwater floodplains, and 68 (> 10%) were endemic to Amazonian várzea. We detected two centers of endemism, one in the western Amazon characterized by low and brief floods, and one in the central Amazon, characterized by high and prolonged floods. Differences in taxonomic composition of endemic centers in the western and central Amazon are the result of different abiotic factors (i.e. flood regimes), as well as the regional species pools from where the species are recruited from. We hypothesize that numerous morphological, physiological and biochemical adaptations permit survival of trees in flooded environments. Furthermore, these adaptations are independently derived across many taxa and result in a highly specialized flora. We attribute higher than expected levels of endemism to the great spatial extent and age of floodplain ecosystems in the Amazon basin, and highlight the role of Amazonian várzea as an potential driver in speciation and diversification processes.     

Interspecific primate associations in Amazonian flooded and unflooded forests

Stable associations between two or more primate species are a prominent feature of neotropical forest vertebrate communities and many studies have addressed their prevalence, and their costs and benefits. However, little is known about the influence of different habitat types on the frequency, seasonality, and composition of mixed-species groups in Amazonian forest primates. Here we examine the features of interspecific primate groups in a large mosaic of flooded (várzea and igapó) and unflooded (terra firme) forest in central Amazonia. In total, 12 primate species occurred in the study area, nine of which were observed in mixed-species associations. Primates were more than twice as likely to form associations in várzea forest than in terra firme forest. Squirrel monkeys were most frequently found in mixed-species groups in all forest types, most commonly in association with brown capuchins. Another frequent member of interspecific associations was the buffy saki, which often formed mixed-species groups with tamarins or brown capuchins. There was no seasonality in the frequency of associations in terra firme forest whereas associations in várzea forest were twice as frequent during the late-dry and early-wet seasons than in the late-wet and early-dry seasons. Interspecific primate associations were common in all forest types, but the degrees to which different species associate varied between these environments. We suggest that the temporal variation of várzea forest associations is connected with seasonal changes in habitat structure and resource abundance. However, more work is needed to pinpoint the underlying causes of mixed-species associations in all forest types and their strong seasonality in várzea forest.     

A comparison of the phytosociology and dynamics of three floodplain (Várzea) forests of known ages, Rio Jurua, western Brazilian Amazon

CAMPBELL, D. G., STONE, J. L. & ROSAS Jr, A., 1992. A comparison of the phytosociology and dynamics of three floodplain (Várzea) forests of known ages, Rio Juruá, western Brazilian Amazon. An unusual historic accident has resulted in three adjacent inundated (vórzea) forests of known ages (50 years old, 14–50 years old, and 14 years old), on the margin of the Rio Juruá, near the village of Rodrigues Alves in western Acre, Brazilian Amazon. One-hectare quantitative inventories (500 × 20 m) were conducted on each of the three forests. Physical characteristics of the plots, including soil particle size, soil cation levels, level of inundation and rate of soil deposition were measured. Plot 1, steeply sloping and ecotonal between várzea and terra firme, was infrequently flooded, with a mean high water mark of 0.0. Plot 2, on slightly undulating terrain, had a mean high water mark of 1.16 m. Plot 3 was level and deeply-flooded, with a mean high water mark of 4.00 m. All trees ≥ 10 cm diameter at breast height (dbh) were mapped, measured and identified to species. Plots 1, 2 and 3 contained 523, 420 and 777 trees, 106, 73 and 20 species, Shannon diversity indices of 3.60, 3.51 and 1.82, and stand basal areas of 25.46 m², 27.01 m² and 25.72 m², respectively. Alchomea triplinervia was the superior competitor on species-rich plot 1; Annona sp. strongly dominated in the limiting conditions of plot 3. On plot 2, no single species was able to achieve dominance. For the 25 species with N≥ 10, habitat specialization as a function of the level of annual inundation was demonstrated, and for five of these species that occurred on plot 1, further refinement of niche as a function of gradient was demonstrated. One-year mortality in plots 1, 2 and 3, was 1.99%, 1.56% and 1.70%, respectively. In Plot 3, 77% of the mortalities were trees that had died standing, vs 40% and 43% in plots 1 and 2.     

Species richness,composition, and spatial distribution of vascular epiphytes in Amazonian black-water floodplain forests

This study examines the occurrence of vascular epiphytic species in Central Amazonian black-water floodplain forests (igapó) and considers whether their horizontal and vertical distribution is influenced by the flood pulse, as is the case with tree species (phorophytes). Research was conducted in sixteen forest plots the Jaú National Park. In these, epiphytes on all phorophytes with DBH ≥ 10 cm were identified. We measured flood height using the watermark left by the last high-water period, then estimated the height relative to the ground of every epiphytic individual. We recorded 653 individuals in 37 species, distributed on 109 phorophytes. Igapó floodplain forests have much lower richness and abundance of vascular epiphyte species than do other Amazonian forests. This may reflect the limitation of available sites for colonization (only 24.9% of studied trees were occupied by epiphytes). Holoepiphytes predominated, and the combined presence of a flood-pulse, linked to the nutrient-poor soil poor seems to limit the occurrence of nomadic vines. Horizontal distribution of epiphytes followed the distribution of phorophytes, which in turn followed the flood-level gradient. Also flooding interacted strongly with vertical zonation to determine species richness. As already well-reported for trees, and unlike reports of epiphytes in other floodplains, flooding strongly influenced richness and distribution of vascular epiphytes in the studied igapó forests.     

On the dynamics,floristic subdivision and geographical distribution of várzea forests in Central Amazonia

Abstract. Within different stands of the white-water inundation forest (várzea forest) in the Central Amazon region, composition, abundance, frequency and basal area of tree species were recorded. Determinations of age and radial growth rates were conducted using dendrochronological methods. Results show significant differences in age, history and species composition between stands as well as different growth strategies among dominant species. Assignment of tree species to growth strategies by means of anatomical and morphological features together with quantitative aspects of vegetational analysis permit the further differentiation of successional stages of várzea forests. General features of successional stages were quantitatively described and compared with forest types from outside the várzea. Many tree species of the várzea forests are widespread in South America, and not limited to floodplains. Their occurrence on sites with distinct dry seasons suggests that they are not specifically adapted to flooding but are tolerant to seasonality in general.     

Spatial, Temporal, and Economic Constraints to the Commercial Extraction of a Non–timber Forest Product: Copaíba (Copaifera spp.) Oleoresin in Amazonian Reserves

Spatial, Temporal, and Economic Constraints to the Commercial Extraction of a Non?CTimber Forest Product: Copaíba (Copaifera spp.) Oleoresin in Amazonian Reserves. The increasing prevalence of government?C and NGO?Csponsored programs to encourage commercial non?Ctimber forest product (NTFP) extractivism in the humid tropics has highlighted the need for ecological and socioeconomic appraisal of the viability of extractive industries. We adopted a novel integrative approach to examine NTFP resource potential and produced credible landscape?Cscale estimates of the projected value of an economically important Amazonian NTFP, the medicinal oleoresin of Copaifera trees, within two large contiguous extractive reserves in Brazilian Amazonia. We integrated results derived from previous spatial ecology and harvesting studies with socioeconomic and market data, and mapped the distribution of communities within the reserves. We created anisotropic accessibility models that determined the spatial and temporal access to Copaifera trees in permanently unflooded (terra firme) and seasonally flooded (várzea) forests. Just 64.9?% of the total reserve area was accessible, emphasizing the distinction between the actual resource stock and that which is available to extractors. The density of productive tree species was higher in the várzea forests, but per?Ctree productivity was greater in the terra firme forests, resulting in similar estimates of oleoresin yield per unit area (64?C67?ml?ha^?C1) in both forest types. A greater area of the várzea forests was accessible within shorter travel times of ??250 minutes; longer travel times allowed access to increasingly greater volumes of oleoresin from the terra firme forests. The estimated total volume of oleoresin accessible within the two reserves was 38,635 liters for an initial harvest, with projected offtake for a subsequent harvest falling to 8,274 liters. A household that extracted just 2 liters of oleoresin per month could generate 5?% of its mean income; market data suggested that certification could increase the value of the resource fivefold. Our approach is valuable in that it incorporates a range of methodologies and quantitatively accounts for the numerous constraints to the commercial viability of NTFP extraction.     

Distribution and population structure of four Central Amazonian high-várzea timber species

Amazonian white-water (várzea) floodplains harbor many commercially important timber species which in Brazil are harvested following regulations of the Federal Environmental Agency (IBAMA). Although it is well-known that tree physiology, growth, and species distribution of Amazonian floodplain trees is linked to the heights and durations of the periodical inundations, information about timber stocks and population dynamics is lacking for most tree species. We investigated timber stocks and the population structure of four intensely logged tree species in a western Brazilian várzea forest on an area totaling 7.5 ha. Spatial distribution was investigated in all trees as a function of inundation height and duration and the distance to the river channel, and additionally for saplings (trees <10 cm diameter at breast height––DBH) as a function of the relative photosynthetically active radiation (rPAR). The diameter-class distribution in Hura crepitans and Ocotea cymbarum indicated that populations are subject to density variations that possibly are traced to small-scale flood variability. In all species, saplings concentrated at higher topographic elevations than the mature tree populations, which suggest that the physical ‘escape’ from a flooded environment is an important acclimation to flooding. While Ocotea cymbarum and Guarea guidonia were high-density wood species characterized by random dispersion and a pronounced shade-tolerance, Hura crepitans and Sterculia apetala presented lower wood density, aggregated dispersion, and were more light-demanding. All species presented exploitable stems according to the current harvest regulations, with elevated abundances in comparison to other Amazonian forest types. However, stem densities are below the harvest rates indicating that the harvest regulations are not sustainable. We recommend that the forest management in várzea forests should include specific establishment rates of timber species in dependence of the peculiar site conditions to achieve sustainability.