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.     

Pressurized gas transport in Amazonian floodplain trees

Trees of Central Amazonian whitewater floodplain forests are subjected to extended flood periods lasting several months. They must therefore be highly adapted to long-term flooding and to oxygen shortage in the soil and roots which is expected to be the main stress factor in this environment. The improvement of oxygen transport to the roots by pressurized gas transport, known for some tree species of the temperate zone, is one specific adaptation to flooding. To evaluate its significance, gas transport measurements were carried out under experimental conditions with saplings of five Amazonian tree species. Internal aeration of the roots was improved under conditions of pressurized gas transport as shown by polarographical measurements of oxygen exchange between root and rhizosphere. Tracer gas measurements using sulphur hexafluoride (SF₆) showed gas permeability of transport pathways between stem base and roots. Based on the data, we suppose that pressurized gas transport significantly contributes to internal aeration of roots in Amazonian floodplain saplings growing on the higher levels in the flooding gradient, with low water columns, and is an important adaptation for establishment in these temporarily inundated habitats also in the weeks of rising and lowering water levels.     

Hardwood floodplain forests in Slovakia: syntaxonomical revision

Hardwood floodplain forests in Slovakia have been traditionally classified within the class Querco-Fagetea, order Fagetalia, alliance Alnion incanae, suballiance Ulmenion. Five main syntaxonomical studies on this topic come from the years 1958–1972 and were published by several authors from different regions. Each author described several new geographically delimited subassociations which were considered to be confined to single lowland region. This resulted in unclear classification scheme of hardwood floodplain forests in Slovakia with numerous floristically poorly differentiated units, especially at the subassociation level. We used 404 relevés ordered to the suballiance Ulmenion in the Slovak national database (http://ibot.sav.sk/cdf/) and analysed the dataset by cluster analysis and detrended correspondence analysis. We distinguished four groups of relevés which represents four subassociations within one association Fraxino pannonicae-Ulmetum: Fraxino pannonicae-Ulmetum caricetosum acutiformis Soó in Aszód 1936 corr. Soó 1964, Fraxino pannonicae-Ulmetum populetosum Jurko 1958 (D?atko 1972), Fraxino pannonicae-Ulmetum carpinetosum (Simon 1957) D?atko 1972 and Fraxino pannonicae-Ulmetum convallarietosum Jurko 1958. Associations Querco pedunculiflorae-Populetum tremuli ?om?ák et Háberová 1979, Arunco-Salicetum capreae Hada? et al. 1969 and Filipendulo-Salicetum capreae Hada? et al. 1969 we propose to exclude from the suballiance Ulmenion.     

Phytoplankton composition and abundance of a central Amazonian floodplain lake

The phytoplankton community of Lake Camaleão, a smallfloodplainlake influenced by a large whitewater river, the Solimões, was monthlyinvestigated for the composition and abundance of itsphytoplankton. The seasonal influence of the floodregime on biomass, species richness and diversity, andits relation with physical and chemical factors(temperature, pH, dissolved oxygen, electricalconductivity, total seston and inorganic nutrients)was analyzed and subjected to principal componentanalysis. Diversity was variable along the seasonalcycle: relatively high values were observed at the endof the dry season supported by high nutrientconcentrations. The phytoplankton was comprised of 262 taxa,with strong dominanceof euglenoids (81%). The three sample stations did not differamong each other, except in the dry season, due todata cluster in relation to theprincipal axis (1 and 2), explaining 63% of thevariation. Biomass accumulation as a function of lakearea reduction contributed to theseresults, indicating that the phytoplankton dynamicswere hydrology-driven.     

Tree and stand level variables influencing diversity of lichens on temperate broad-leaved trees in boreo-nemoral floodplain forests

Tree and stand level variables affecting the species richness, cover and composition of epiphytic lichens on temperate broad-leaved trees (Fraxinus excelsior, Quercus robur, Tilia cordata, Ulmus glabra, and U. laevis) were analysed in floodplain forest stands in Estonia. The effect of tree species, substrate characteristics, and stand and regional variables were tested by partial canonical correspondence analysis (pCCA) and by general linear mixed models (GLMM). The most pronounced factors affecting the species richness, cover and composition of epiphytic lichens are acidity of tree bark, bryophyte cover and circumference of tree stems. Stand level characteristics have less effects on the species richness of epiphytic lichens, however, lichen cover and composition was influenced by stand age and light availability. The boreo-nemoral floodplain forests represent valuable habitats for epiphytic lichens. As substrate-related factors influence the species diversity of lichens on temperate broad-leaved trees differently, it is important to consider the effect of each tree species in biodiversity and conservation studies of lichens. Nomenclature Randlane et al. (2007) for lichens; Leht (2007) for vascular plants.     

Impact of a drier Early-Mid-Holocene climate upon Amazonian forests

This paper uses a palaeoecological approach to examine the impact of drier climatic conditions of the Early-Mid-Holocene (ca 8000-4000 years ago) upon Amazonia's forests and their fire regimes. Palaeovegetation (pollen data) and palaeofire (charcoal) records are synthesized from 20 sites within the present tropical forest biome, and the underlying causes of any emergent patterns or changes are explored by reference to independent palaeoclimate data and present-day patterns of precipitation, forest cover and fire activity across Amazonia. During the Early-Mid-Holocene, Andean cloud forest taxa were replaced by lowland tree taxa as the cloud base rose while lowland ecotonal areas, which are presently covered by evergreen rainforest, were instead dominated by savannahs and/or semi-deciduous dry forests. Elsewhere in the Amazon Basin there is considerable spatial and temporal variation in patterns of vegetation disturbance and fire, which probably reflects the complex heterogeneous patterns in precipitation and seasonality across the basin, and the interactions between climate change, drought- and fire susceptibility of the forests, and Palaeo-Indian land use. Our analysis shows that the forest biome in most parts of Amazonia appears to have been remarkably resilient to climatic conditions significantly drier than those of today, despite widespread evidence of forest burning. Only in ecotonal areas is there evidence of biome replacement in the Holocene. From this palaeoecological perspective, we argue against the Amazon forest 'dieback' scenario simulated for the future.     

Dietary–morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain

Morphological correlates of diet were examined in 48 species of freshwater fishes from floodplain lakes in the central part of the Mamoré River (Bolivian Amazon). The species were classified, according to the percentage occurrence of seven food items, into eight broad trophic categories: mud feeders, algivores, herbivores, terrestrial invertivores and omnivores, carnivores, zooplanktivores, aquatic invertivores and piscivores. There were significant relationships between the diet and morphology of the fishes even when the effect of taxonomical relatedness between species was eliminated. Relative gut length was the main morphological variable used to order species on a carnivore to mud feeder gradient. Standard length and head and mouth size were the morphological variables most closely associated with prey size. Mud feeder, algivore and piscivore species appeared as the most dietary and morphologically specialized. These results support both the hypotheses that species morphology influences the diet and that morphological similarity is conserved even in comparison with taxonomically unrelated species.     

Adaptations of fish species to oxygen depletion in a central Amazonian floodplain lake

Pronounced seasonal and daily oxygen concentration changes are characteristic for Amazonian floodplain lakes. Studies on the fish fauna of the Lago Camaleão, Solimões River, Amazonas, Brazil, showed several fish species which are able to survive prolonged periods of heavy hypoxia. Twenty species belonging to eight families were observed in the laboratory in order to determine their respiratory adaptations to hypoxic conditions and oxygen concentrations at which the fish present respiratory adaptations. Finally, the fish species were distributed throughout the habitats of Lake Camaleão according to their adaptation responses. Ten fish species used the surface water for aquatic surface respiration, four species used atmospheric oxygen for aerial respiration, four species used oxygen supplied by the exudation of the roots of floating macrophytes and two exhibited a high tolerance to hypoxic conditions, and well-developed physiological biochemical mechanisms. The fish fauna is well adapted to low oxygen concentrations. The large variety of morpho-anatomical adaptations associated with biochemical and physiological mechanisms to tolerate hypoxic and anoxic conditions enable the 20 fish species to exploit several habitats of Lago Camaleão, such as floating aquatic macrophyte meadows, open water and near the shoreline.     

High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats

Seed dispersal is a critical stage in the life history of plants. It determines the initial pattern of juvenile distribution, and can influence community dynamics and the evolutionary trajectories of individual species. Vertebrate frugivores are the primary vector of seed dispersal in tropical forests; however, most studies of seed dispersal focus on birds, bats and monkeys. Nevertheless, South America harbors at least 200 species of frugivorous fishes, which move into temporarily flooded habitats during lengthy flood seasons and consume fruits that fall into the water; and yet, we know remarkably little about the quality of seed dispersal they effect. We investigated the seed dispersal activities of two species of large-bodied, commercially important fishes (Colossoma macropomum and Piaractus brachypomus, Characidae) over 3 years in Pacaya-Samiria National Reserve (Peru). We assessed the diet of these fishes during the flood season, conducted germination trials with seeds collected from digestive tracts, and quantified fruit availability. In the laboratory, we fed fruits to captive Colossoma, quantified the proportion of seeds defecated by adult and juvenile fish, and used these seeds in additional germination experiments. Our results indicate that Colossoma and Piaractus disperse large quantities of seeds from up to 35% of the trees and lianas that fruit during the flood season. Additionally, these seeds can germinate after floodwaters recede. Overexploitation has reduced the abundance of our focal fish species, as well as changed the age structure of populations. Moreover, older fish are more effective seed dispersers than smaller, juvenile fish. Overfishing, therefore, likely selects for the poorest seed dispersers, thus disrupting an ancient interaction between seeds and their dispersal agents. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The role of fungi in periodically inundated Amazonian forests

In a comparative survey the terms (terra-firme) flood plain, igapó, várzea with and without black water influence are reviewed and the importance of ectotrophic mycorrhiza for their definition emphasized. Várzea alta with fluvisol base is briefly characterized and a first list of Basidiomycetes collected in it is provided. These are all non-mycorrhizal litter fungi.     

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.     

Sedimentation and pedogenesis in a Central Amazonian Black water basin

Sedimentation rates were estimated in a Central Amazonian Black-water inundation forest. Sediment deposition on the forest ground, remote from the river bed, during an annual flood period, is of the order of 1 to 10 tons per hectare, depending on water depth and duration of flooding. The sediments consisted of fine organic matter, kaolinite, quartz sands and biogenic particles of silica. Their genesis and deposition depend on the interplay between pedogenic, limnological and biological processes. Sediments derive primarily from the materials leached from the soils. Clay soils are the main source of dissolved silica, and the sandy soils are the main sources of organic coumpounds and mineral particles. The physical sedimentation of particles as quartz sand grains only occurs in the upper reaches of the studied river. In the flood plain, the sedimentation is due to the coagulation and deposition of combined mineral particles and humic substances, and to the biological precipitation of the silica leached from the soil by sponges.     

Photochemical capacity after submersion in darkness: How Amazonian floodplain trees cope with extreme flooding

We used maximum quantum yield of photosystem II (PSII) to study the functional state of Amazonian floodplain tree species after prolonged submergence. Saplings of four common tree evergreen species which maintain their leaves when submerged were analysed. The responses showed that (1) maximum quantum yield of PSII in all submerged mature leaves remained in the range of healthy non-flooded leaves with maximum quantum yield of photosystem II F_v/F_m never dropping below 0.66 in the four species, indicating an intact photosynthetic apparatus. (2) In young mature leaves (2-7 mo) F_v/F_m is higher, ranging from 0.76 to 0.82, than in old mature leaves aged >10 mo where F_v/F_m ranges from 0.73 to 0.78. (3) F_v/F_m values of saplings are significantly lower (0.3-0.6) shortly after being taken out of darkness and out of the water than before submersion (0.66-0.78). Leaves suffered from photoinhibition when taken out of the darkness from below water, with decreases of 70% in F_v/F_m, but they recovered full photosynthetic activity within approximately one week after the end of submersion indicating that all leaves retained the potential to be photosynthetically active in spite of six months of submersion in darkness. A recovery period of F_v/F_m of over several days, as described for Pouteria glomerata, Tabernaemontana juruana, Gustavia augusta and Nectandra amazonum after long-lasting submergence, has not been reported so far.     

Forest structure and carbon dynamics in Amazonian tropical rain forests

Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha^–1 respectively), less biodiversity (Shannon–Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha^–1) than the Manaus site (626 trees ha^–1, 180.1 Mg C ha^–1), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41–45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha^–1 year^–1. At all sites, trees in the 10–30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha^–1 year^–1 in Manaus (40% of annual mean) and 0.9 Mg C ha^–1 year^–1 (33% of annual mean) in Santarém, though this variability showed no significant relation with precipitation among years. Initial estimates of the C balance of live wood including recruitment and mortality as well as growth suggests that live wood biomass is at near steady-state in Manaus, but accumulating at about 1.5 Mg C ha^–1 at the other two sites. The causes of C imbalance in living wood pools in Santarém and Rio Branco sites are unknown, but may be related to previous disturbance at these sites. Based on size distribution and growth rate differences in the three sites, we predict that trees in the Manaus forest have greater mean age (~240 years) than those of the other two forests (~140 years).     

Ungulate biomass in relation to feeding strategy within Amazonian forests

Summary The relationship between diet and biomass was examined in the Amazonian ungulates (red brocket deer, grey brocket deer, collared peccary, white-lipped peccary, and lowland tapir) of Northeastern Peru. Tropical forest ungulates have lower biomasses than savanna or grassland ungulates, because in tropical forests the majority of primary production occurs in the canopy, well out of reach from terrestrial herbivores. Within the Amazonian ungulates, species that supplement their diet with animal material, namely the peccaries, obtain a greater crude and metabolic biomass, and higher reproductive rates than the purely herbivorous species. Omnivory appears to help terrestrial herbivores inhabiting closed canopy forests overcome some effects of food limitation.     

Tree diversity and phytogeographical patterns of tropical high mountain rain forests in Central Sulawesi,Indonesia

Tropical high mountain forests in Lore Lindu National Park, Sulawesi, Indonesia, were described by their floristic composition and the importance of tree families (Family importance values, FIV), based on tree inventories conducted on 4 plots (each 0.24 ha) in old-growth forest stands at c. 1800 and 2400 m a.s.l. (mid- and upper montane elevations). To identify general patterns and regional peculiarities of the forests in the SE Asian and SW Pacific context, the biogeography of the tree species was analysed using distribution records. Out of the total of 87 tree species, only 18 species were found at both elevational zones. The discovery of new species and new distribution records (28% of the data set) highlights the deficiencies in the taxonomic and distribution data for Sulawesi. Sulawesi endemism rate was 20%. In the mid-montane Fagaceae–Myrtaceae forests, Lithocarpus spp. (Fagaceae) were overall important (4 spp. occupying around half of the total basal area) and the Myrtaceae the most species rich (8 spp.), thus showing typical features of Malesian montane forests. The upper montane conifer-Myrtaceae forest contained several high mountain tree taxa and showed affinity to the forests of New Guinea. The mountain flora comprised both eastern and western Malesian elements, with the nearest neighbouring islands Borneo and Maluku both sharing species with Sulawesi, reflecting the complex palaeogeography of the island. A separate analysis showed the mid-montane forest to possess greatest biogeographical affinity to Borneo/western Malesia, and the upper montane forest had a number of typical elements of Papuasia/eastern Malesia and the Phillipines, which may be a result of historical patterns in land connection and the emergence of mountain ranges.     

Submerged in darkness: adaptations to prolonged submergence by woody species of the Amazonian floodplains

Background

In Amazonian floodplain forests, >1000 tree species grow in an environment subject to extended annual submergence which can last up to 9 months each year. Water depth can reach 10 m, fully submerging young and also adult trees, most of which reproduce during the flood season. Complete submergence occurs regularly at the seedling or sapling stage for many species that colonize low-lying positions in the flooding gradient. Here hypoxic conditions prevail close to the water surface in moving water, while anaerobic conditions are common in stagnant pools. Light intensities in the floodwater are very low.

Questions and Aims

Despite a lack of both oxygen and light imposed by submergence for several months, most leafed seedlings survive. Furthermore, underwater growth has also been observed in several species in the field and under experimental conditions. The present article assesses how these remarkable plants react to submergence and discusses physiological mechanisms and anatomical adaptations that may explain their success.Key words: Adaptation, Amazonian floodplains, darkness, environmental stress, flooding, hypoxia, submergence tolerance, trees, underwater photosynthesis, woody species     

Mobile piscivores and the nature of top-down forcing in Upper Amazonian floodplain lakes

Shallow lakes can change states in response to manipulations of top predators. In most reported experiments, the top piscivore has been a fish. However, low-latitude lakes typically support non-piscine piscivores, including mammals, birds, and reptiles. The roles of these groups have been little investigated, and whether they are more important as piscivores than fish remains unknown. We report both a longitudinal (2001–2018) and a cross-sectional (2012) study of the bird, caiman, and giant otter populations of floodplain lakes in Perú’s Manu National Park. We compare the three groups, after removing the effects of taxonomic status and body mass, using allometric equations to estimate the field metabolic rate (FMR) for each group in each lake. Giant otters emerge as the dominant piscivore in lakes that support a resident family, with an energy requirement more than twice that of piscivorous birds and more than seven times that of caiman. However, giant otters were resident in only eight of 27 surveyed lakes. Indirect evidence suggests that these eight lakes are more productive than lakes not occupied by otters. The fact that lakes occupied by otters are dominated by phytoplankton suggests an underlying five-tiered trophic structure in keeping with the prominence of alternating levels in the structure of food webs.