Floristic composition and topographic variation in a tidal floodplain forest in the Amazon Estuary

Slight topographic variations appear to exert dramatic effects on the structure of forests subject to inundation. In a late successional tidal floodplain forest near the Amazon port of Belém, Brazil, we examined these effects by studying floristic composition along a topographic gradient. We predicted that, relative to high sites, low sites would be characterized by high representation of life forms and taxa characteristic of inundated sites. We found striking variations in floristic composition along a slight topographic gradient. In comparison with topographically high sites, low sites were characterized by a high representation of Palm trees (Arecaceae), low diversity of trees and lianas, and high plant density. These variations appear to reflect edaphic limitations imposed by periodic flooding. The high spatial variation in floristic composition found in this ecosystem suggest caution in implementing intensive forms of agriculture.

Phenology, litterfall, growth, and root biomass in a tidal floodplain forest in the Amazon estuary

The dynamics of forests subject to inundation appears to be strongly influenced by the frequency and intensity of natural disturbances such as flooding. In a late successional tidal floodplain forest near the Amazon port of Belém, Brazil, we tested this prediction by measuring seasonal patterns of phenology and litterfall in relation to two key variables: rainfall and tide levels. In addition, we estimated the root biomass and the annual growth of the forest community by measuring stem increments over time. Our results showed high correlations between phenological events (flowering and fruiting) and rainfall and tide levels, while correlations between litterfall and these variations were generally weaker. Contrary to our prediction, root biomass to 1 m depth showed no significant differences along the topographic gradient, and the root biomass at all topographic levels was low to intermediate compared with other neotropical forests. Both litterfall and total stem increment were high compared to other tropical forest, indicating the high productivity of this ecosystem.

Atmosphere and hydrological controls of the evapotranspiration over a floodplain forest in the Bananal Island region, Amazonia

This article discusses seasonal and interannual variations of the evapotranspiration (ET) rates in Bananal Island floodplain, Brazil. Measurements included ET and sensible heat flux using the eddy covariance method, atmospheric forcings (net radiation, Rn, vapor pressure deficit, VPD, wind speed and air temperature), soil moisture profiles, groundwater level and flood height, taken from November 2003 to December 2006. For the hydrological years (October-September) of 2003/2004, 2004/2005 and 2005/2006, the accumulated precipitation was 1692, 1471, 1914 mm and the accumulated ET was 1361, 1318 and 1317 mm, respectively. Seasonal analyses indicated that ET decreased in the dry season (average 3.7 mm day(-1)), despite the simultaneous increase in Rn, air temperature and VPD. The increase of ET in the wet season and particularly in the flood period (average 4.1 mm day(-1)) showed that the free water surface evaporation strongly influenced the energy exchange. Soil moisture, which was substantially depleted during the dry season, and adaptative vegetation mechanisms such as leaf senescence contributed to limit the dry season ET. Strong drainage within permeable sandy soils helped to explain the soil moisture depletion. These results suggest that the Bananal flooding area shows a different pattern in relation to the upland Amazon forests, being more similar to the savanna strictu senso areas in central Brazil. For example, seasonal ET variation was not in phase with Rn; the wet season ET was higher than the dry season ET; and the system stored only a tiny memory of the flooding period, being sensitive to extended drought periods.

Predator-prey interactions: jaguar predation on caiman in a floodplain forest

Advances in the understanding of ecological factors determining predatorprey interactions have provided a strong theoretical background on diet preferences of predators. We examined patterns of jaguar predation on caiman in southern Pantanal, Brazil. We investigated factors affecting predation rates and vulnerability of caiman to predation by jaguars. We recorded 114 caiman mortality incidents. Predation accounted for 62.3% (n = 71) of all caiman found dead, while other causes of mortality (nonpredation) accounted for 37.7% (n = 43). We found that jaguars prey on a broad size range of caiman body and caiman predation was influenced by distance to forests. During dry seasons, 70% (n = 49) of deaths were due to predation, while 30% (n = 21) were due to nonpredation causes. However, we found no significant relationship between annual and monthly killings of caiman and rainfall totals by year and month (r = 0.130, r = -0.316). The annual flooding regime may be a more important factor influencing prey selection by jaguars. Although neotropical crocodilians are relatively well studied, their interactions with jaguars have been mostly ignored and should be prioritized in future studies.

Wood density of trees in black water floodplains of Rio Jaú National Park, Amazonia, Brazil

The Jaú National Park is the largest protected forested area in the world. The Vitória Amazônica Foundation is working towards understanding its ecosystem, to which this paper contributes. Wood density was analysed in 27 common tree species growing in the blackwater flood-plains of the Rio Jaú, an affluent of the Rio Negro (Amazonia, Brazil). Wood was sampled with an increment borer. Mean wood density of the analysed species ranged from 0.35 to 0.87 g cm-3. The mean of all sampled species was 0.67 g cm-3 (st. dev. 0.13). Lowest density was found for Hevea spruceana with 0.32 g cm-3 and highest for Crudia amazonica with 0.9 g cm-3.

Nutritional preferences of wood-feeding termites inhabiting floodplain forests of the Amazon River, Brazil

The alimentary preferences of five species of wood-feeding termites of the genus Nasutitermes that coexist in the inundated forests of the floodplains of the Amazon river várzea for species of fresh wood and for wood in different stages of decomposition was evaluated in laboratory tests. Wood of low density was generally preferred; the decay stages were preferred over fresh wood. The five termite species differ in the amplitude of their choices, indicating a strong differentiation in food choice among them. Differences in feeding preferences may be a niche-separating factor for these five Nasutitermes species of the floodplains.

Reconstructing historical forest cover change in the Lower Amazon floodplains using the LandTrendr algorithm

ABSTRACTThe Amazon várzeas are an important component of the Amazon biome, but anthropic and climatic impacts have been leading to forest loss and interruption of essential ecosystem functions and services. The objectives of this study were to evaluate the capability of the Landsat-based Detection of Trends in Disturbance and Recovery (LandTrendr) algorithm to characterize changes in várzeaforest cover in the Lower Amazon, and to analyze the potential of spectral and temporal attributes to classify forest loss as either natural or anthropogenic. We used a time series of 37 Landsat TM and ETM+ images acquired between 1984 and 2009. We used the LandTrendr algorithm to detect forest cover change and the attributes of "start year", "magnitude", and "duration" of the changes, as well as "NDVI at the end of series". Detection was restricted to areas identified as having forest cover at the start and/or end of the time series. We used the Support Vector Machine (SVM) algorithm to classify the extracted attributes, differentiating between anthropogenic and natural forest loss. Detection reliability was consistently high for change events along the Amazon River channel, but variable for changes within the floodplain. Spectral-temporal trajectories faithfully represented the nature of changes in floodplain forest cover, corroborating field observations. We estimated anthropogenic forest losses to be larger (1.071 ha) than natural losses (884 ha), with a global classification accuracy of 94%. We conclude that the LandTrendr algorithm is a reliable tool for studies of forest dynamics throughout the floodplain.

The igapó of the Negro River in central Amazonia: Linking late-successional inundation forest with fluvial geomorphology

Despite important progress on Amazonian floodplain research, the flooded forest of the Negro River igapó has been little investigated. In particular, no study has previously focused the linkage between fluvial geomorphology and the floristic variation across the course of the river. In this paper we describe and interpret relations between igapó forest, fluvial geomorphology and the spatial evolution of the igapó forest through the Holocene. Therefore, we investigate the effect of geomorphological units of the floodplain and channel patterns on tree diversity, composition and structural parameters of the late-successional igapó forest. Our results show that sites sharing almost identical flooding regime, exhibit variable tree assemblages, species richness and structural parameters such as basal area, tree density and tree heights, indicating a trend in which the geomorphologic styles seem to partially control the organization of igapó's tree communities. This can be also explained by the high variability of well-developed geomorphologic units in short distances and concentrated in small areas. In this dynamic the inputs from the species pool of tributary rivers play a crucial role, but also the depositional and erosional processes associated with the evolution of the floodplain during the Holocene may control floristic and structural components of the igapó forests. These results suggest that a comprehensive approach integrating floristic and geomorphologic methods is needed to understand the distribution of the complex vegetation patterns in complex floodplains such as the igapó of the Negro River. This combination of approaches may introduce a better comprehension of the temporal and spatial evolutionary analysis and a logic rationale to understand the vegetation distribution and variability in function of major landforms, soil distributions and hydrology. Thus, by integrating the past into macroecological analyses will sharpen our understanding of the underlying forces for contemporary floristic patterns along the inundation forests of the Negro River. © 2013 Elsevier Ltd.

Floristic, edaphic and structural characteristics of flooded and unflooded forests in the lower Rio Purús region of central Amazonia, Brazil

Despite a natural history interest in the early 1900s, relatively little ecological research has been carried out in the Rio Purús basin of central Amazonia, Brazil. Here we describe a new study area in the region of Lago Uauaçú with an emphasis on the climate, forest structure and composition, and soil characteristics between adjacent unflooded (terra firme) and seasonally inundated forests; situated within both the white-water (várzea) and black-water (igapó) drainage systems that dominate the landscape. The climate was found to be typical of that of the central Amazon. Várzea forest soils had high concentrations of nutrients, while terra firme and igapó soils were comparatively nutrient-poor. Terra firme forests were the most floristically diverse forest type, whereas várzea was intermediate, and igapó the most species-poor. The Lecythidaceae was the most important family in terra firme while the Euphorbiaceae was the most important in both várzea and igapó. There were significant differences between forest types in terms of number of saplings, canopy cover and understorey density. In contrasting our results with other published information, we conclude that the Lago Uauaçú region consists of a typical central Amazonian forest macro-mosaic, but is a unique area with high conservation value due to the intimate juxtaposition of terra firme, várzea and igapó forests.

Vegetational changes during the last millennium inferred from a palynological record from the Bananal Island, Tocantins, Brazil

The Bananal Island is regarded the largest fluvial island in the world, bounded by Araguaia and Javaés rivers, being located in southwest of Tocantins. The objectives of this work were to provide information about the vegetational changes that occurred at the Bananal Island, in order to contribute to the understanding the dynamics of past and current savanna and areas of ecotones with forests. Thus, a sedimentary core collected from a small lake at the Bananal Island plain was submitted to pollen and radiocarbon dating analyses. The results showed that the last millennium was dominated by forest reflecting a wet climate. At the beginning of the record (920-770 yr cal BP) the wet climate and high rainfall produced flooding during long rainy seasons that maintained the Javaés River connected to the studied lake, and hence, this environment was marked by the presence of a homogenous forest rich in Moraceae/Urticaceae, due to flooded soils occurrence. During the following period (770-304 yr cal BP) the reduced rainfall and shortening of the rainy seasons isolated the lake from the Javaés River for long periods, which caused a diversification of the forest and gave rise to the appearance of the components of floodplain forest and marsh vegetation adapted to waterlogged soils. Since 304 years cal BP to the present day this environment remained dominated by this diverse forest and the lacustrine conditions were also similar to previous phase, with a slight increase of moisture in the last 84 years that caused the increase of Piranhea.

Floristic composition of two wetland forests in Araguaian Plain, State of Tocantins, Brazil, and comparison with other areas

Seasonally inundated native forest fragments ("ipucas") located in natural landform depression swales of the Araguaian Plain are currently under land use pressure. Their composition needs to be better understood to guarantee their protection. This comparative study of fragments under different land use conditions was carried out at Lago Verde Farm, Lagoa da Confusão,Tocantins, Brazil. The location coordinates are UTM 643586 and 644060 East and 8792795 and 8799167 North. This study aimed to first analyze and compare the floristic composition of two seasonally inundated forest fragments of approximately one hectare each. The first is located in an intact (without human intervention) Gramineous-Woody Savanna region and the second in a rice cultivation region. The floristic composition of both fragments was then compared to that of other wetland forests located in the Northern, Central Western and Southeastern regions of Brazil.All the floristic compositions are affected by seasonal flooding and soil water saturation. The floristic inventory used a census method that sampled all trees and shrubs with perimeter at 1.30 m from soil (PAP) = 15cm; 665 individuals, 33 families and 49 species were recorded for the intact region and 807 individuals, 35 families and 70 species for the altered region fragment. The values of H' = 0.806 (Shannon-Weaver) and J = 3.44 nats /individual (equability) for the fragment in the region affected by rice cultivation are considered high compared to the intact region fragment values (H' = 0.761 and J = 2.97). Families contributing to floristic richness in the altered region fragment were Fabaceae (9 species), Vochysiaceae (6) and Annonaceae (4). In the intact region fragment, Fabaceae also presented the largest number of species (8) followed by Arecaceae, Chrysobalanaceae and Vochysiaceae (3 each). When comparing the forests from various regions in Brazil, floristic similarity was found to be small. Greater similarity was found when indices for the two Lagoa da Confusão fragments were compared to riparian forests located in the Federal District of Brasilia.

Spechte als ökologische Indikatoren in Natur- und Wirtschaftswäldern im Bialowiera-Wald (Ostpolen)

Die vorliegende Untersuchung analysiert die Eignung der "Spechtgemeinschaft" als ökologische Indikatorengruppe und formuliert vor dem Hintergrund der Ergebnisse Forderungen und Empfehlungen für einen "spechtgerechten" Umgang mit Wäldern. Die Habitatnutzung von sieben Spechtarten beim Nahrungserwerb wurde über einen Zeitraum von zwei Jahren in urwaldartigen und forstlich genutzten Beständen verschiedener Waldgesellschaften systematisch beobachtet. Das Untersuchungsgebiet ist der Bialowieza-Wald im äußersten Osten Polens, wo in enger räumlicher Nachbarschaft Natur- und Wirtschaftswaldflächen bearbeitet werden konnten. Die Beobachtungen erfolgten zwischen Anfang März 1999 und Ende Februar 2001 und wurden zu allen Jahreszeiten durchgeführt. Vier der insgesamt sechs Probeflächen repräsentieren die wichtigste Laubwaldgesellschaft des Gebietes, das Tilio-Carpinetum, die übrigen zwei die wichtigste Nadelwaldgesellschaft, das Peucedano-Pinetum. Die Hälfte der zwischen 42 und 54 ha großen Probeflächen lag im streng geschützten Urwaldreservat des Bialowieza-Nationalparkes, die übrigen in forstlich genutzten Waldbeständen. Zusätzlich wurde ein 2,5 km langes Transekt durch bewirtschafteten Erlen-Eschen-Auenwald und sehr naturnahen Erlenbruch bearbeitet. Die Probeflächen wurden in ein Raster aus 50x50m großen Quadranten unterteilt. Zur Beobachtung der Spechte beim Nahrungserwerb erfolgten 21 Begehungen je Probefläche bzw. Transekt. Die Probeflächen wurden dazu auf parallelen Linien mit Abständen von je 100m begangen, Startpunkt und Startrichtung wurden variiert. Zur Charakterisierung der Vegetation und Bestandesstruktur erfolgten Erhebungen zur Baumartenzusammensetzung, Größenklassenverteilung der Bäume, Totholzanteil und Krautvegetation. 1332 Beobachtungen von Spechten beim Nahrungserwerb konnten ausgewertet werden. Der Buntspecht wurde in allen Flächen am häufigsten gesehen. Mittel-, Weißrücken- und Kleinspecht wurden überwiegend in den Tilio-Carpineten beobachtet, in den Naturwäldern häufiger als in den bewirtschafteten Beständen. Der Dreizehenspecht wurde im Nadelwald und stärker mit Fichten durchmischtem Laubwald angetroffen. Bei Schwarz- und Grauspecht konnte keine klare Vorliebe für bestimmte Waldgesellschaften ermittelt werden. Der Buntspecht ernährte sich vor allem im Herbst und Winter überwiegend von fetthaltigen Samen und wurde dann meist beim Bearbeiten von Fichten- oder Kiefernzapfen in Schmieden beobachtet. Der Mittelspecht suchte als "Sammelspecht" seine Nahrung vor allem an den Oberflächen der Stämme und Äste. Klein-, Weißrücken-, Dreizehen- und Schwarzspecht traten als Hackspechte in Erscheinung. Die wenigen Daten zum Grauspecht reichen nicht zur Ermittlung der bevorzugten Nahrungserwerbstechnik aus. Bei Bunt-, Mittel- und Weißrückenspecht konnte eine deutliche Vorliebe für die Stieleiche als Nahrungsbaum nachgewiesen werden. Der Dreizehenspecht ist jedoch die einzige der beobachteten Arten mit einer weitgehenden Spezialisierung auf eine bestimmte Baumart, er nutzte in allen Waldgesellschaften meist die Fichte. Insgesamt bevorzugten die Spechte Bäume mit großen Stammdurchmessern, beim Kleinspecht ist diese Vorliebe allerdings nur schwach ausgeprägt. Totholz wurde von Weißrücken-, Dreizehen- und Kleinspecht bei der Nahrungssuche bevorzugt, vom Mittelspecht jedoch nur gelegentlich genutzt. Beim Buntspecht zeigte der Totholz-Nutzungsanteil erhebliche Unterschiede zwischen verschiedenen Baumarten. Liegendes Totholz spielte in den Tilio-Carpineten im Vergleich zu stehendem Totholz und toten Teilen lebender Bäume nur eine geringe Rolle für Nahrung suchende Spechte.

Proposta conceitual de colhedoras autopropelidas de açaí (Euterpe oleracea Mart.) para a região amazônica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Bird species of black water inundation forests in the Jau National Park (Amazonas state, Brazil): their contribution to regional species richness

We compared the relative contribution of blackwater inundation forest (igapo) and unflooded (terra firme) forest for regional bird species diversity in the lower Rio Negro region. For analyses of habitat preference we used mist-net samples and an unpublished bird species check-list. The igapo forest had lower bird species diversity than the terra firme forest. However, some 14% of the forest bird species in the region are restricted to igapo forest. Species composition was found to be distinct between the understories of the two forest types. Common forest bird guilds in the Neotropics such as ant-following birds avoid igapo forest. The differential habitat selection among birds in the inundated and unflooded forest is likely to result from vegetation structure and biological interactions such as aggressive behaviour. Since the inundated forest has a typical biota, conservation efforts needs to be directed to protect these habitats. Unfortunately, inundation forests are threatened by several human actions, especially dam construction. The extent of protected areas in the Brazilian Amazon is insufficient for the adequate protection of the inundated habitats, because it includes only 3% of the total area.

Uso da fitossociologia na avaliação da efetividade da restauração florestal em uma várzea degradada do rio Mogi Cuaçu, SP

This study objective was to evaluate the effective revegetation in a Mogi Guaçu River degraded floodplain area, located at Luiz Antonio municipality (21° 31' S e 47° 55' W), São Paulo State, Brazil. Two native riparian forest remnants (RIP1 and RIP2) and three 10-year-old reforested areas, planted of native species (R1, R2 and R3), were analyzed by using phytosociological describers of the arboreal stratum (trees with DBH ≥ 5 cm) as indicators. The arboreal stratum inventory was accomplished by 180 plots (10 × 10 m each), 60 representing every native forest and 20 for every reforested area. A total of 60 arboreal species was recorded, only six species (Cecropia hololeuca, Crotón urucurana, Genipa americana, Inga striata, Nectandra megapotamica e Peltophorum dubium) occurring in all the five studied areas. Seventeen species were common to both native forests, and nine species were recorded in all the reforested areas. Sebastlania commersonlana and Guarea macrophyllawere recorded in the native forests (RlP1 and RIP2), and Cecropia hololeuca, Croton urucurana and Inga striata occurring in all the reforested areas, were the species that best characterize the physiognomy of local diversity and were the most important among the studied species. The results showed that the rehabilitation of the areas made by the reforestation created conditions to implant forests with similar structures of the adjacent natural remainders. The reforestation with native species performed in the degraded floodplain of Mogi Guaçu River, initially with the predomination of invasive grasses, has been effective at the first stage of the ecological restoration process. The reforestation is making possible the natural regeneration of species from the adjacent remnants, what indicates that the similarity between planted forests and the native ones are rising through the time. The phytosociology, accomplished ten years after the planting date, is adequate to evaluate the effectiveness of the reforestation during the restoration process of degradated areas in the Mogi Guaçu floodplain.