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The Many-colored Rush Tyrant (Tachuris rubrigastra) and Wren-like Rushbird (Phleocryptes melanops) are birds that inhabit the subtropical salt marshes of Brazil, a newly recognized ecosystem of tidal marshes. We studied the habitat selection of these species in the subtropical salt marshes, characterizing the vegetation types where the species did and did not occur in the same habitats. The species occurred in a total of four very simplified vegetation types, characterized by the dominance of one or two plant species, including Schoenoplectus californicus, Crinum americanum, Cladium jamaicense, and Typha domingensis. We found that the habitats selected by the birds have very specific phytophysiognomic characteristics related to vegetation height and density. Moreover, the lower altitudes of certain areas of occurrence implies longer and higher flooding during periods of high tides; thus, the greater height of the vegetation maintains an above-water-level foraging and protective area for the birds. The fact that subtropical salt marshes are a transitional ecosystem suggests the possibility of rapid changes in plant succession or an intensification of the tropicalization process with mangrove expansion, which could eliminate habitat characteristics that are crucial to the survival of these two bird species in the subtropical salt marshes of Brazil. [ABSTRACT FROM AUTHOR]

This study aimed to estimate the nutrient absorption rate in soybean plants cultivated in succession to cover crops and under soil management systems. We performed two experiments with soybean grown on the remaining straw of Crotalaria spectabilis and Pennisetum glaucum (millet), under no-tillage (NT) and minimum tillage (MT), over the cropping years 2016/2017 and 2017/2018, in the Cerrado of Piauí state. The experimental design was a randomized blocks, arranged in split-plots. Plots corresponded to soil management systems and subplots to days after emergence (DAE) of soybean, with 3 replications. Nutrients contents were evaluated at 31, 38, 45, 52, 59, 66, 73, 80, 87, 94, 101, 108 and 115 DAE. Higher soybean dry matter (DM) production occurred in MT compared to no tillage. Crotalaria spectabilis enhanced accumulation of DM and N until stage R2. Accumulation of nutrients and DM in soybean cultivated on the straw of millet and C. spectabilis were similar across soil management systems. The phase of highest accumulation of nutrients and DM in soybean occurs between stages R5 and R7. All the nutrients, except Ca and Mn, are allocated to the grains during physiological maturity, in proportions higher than 50% of the total amount accumulated in soybean plants. [ABSTRACT FROM AUTHOR]

The southern Brazilian coastal area harbors one of the largest wetland systems of South America, important for its plant and animal biodiversity and ecosystems services provided for human populations. As an attempt to understand the development of those wetlands, samples from a diatom ooze and indurated diatomites found in the coastal plain of the state of Rio Grande do Sul were analyzed. The fragmented state of the frustules found in the samples allowed identification of most diatoms only to the genus level, nevertheless the assemblages are represented by 16 genera reported today in freshwater bodies in the studied region. The identified taxa include the planktonic Aulacoseira and Cyclotella and several benthic genera, mostly Eunotia , Pinnularia and Rhopalodia. The diatomites consist mostly of corroded irregular-shaped silica grains from frustules dissolved by alkaline water, but five diatom genera were identified. These diatomites accumulated in ephemeral ponds developed on loess sediments in dry environments and seasonal climate between the latest Pleistocene and Middle Holocene. The diatom ooze and associated organic-rich silty sediments accumulated in shallow lakes with abundant catchment vegetation and considerable dissolved organic carbon, and contain fragmented but slightly dissolved frustules as a result of hydrodynamics and low pH, and also megascleres of Porifera, cysts of Chrysophyceae, and abundant phytoliths of Poaceae. The sediment underlying the diatom ooze was dated as of 4.6–4.4 cal 14C ka BP and contains a diatom assemblage dominated by benthic epiphytic and acidophilous forms such as Eunotia , Pinnularia , and Gomphonema. The ooze and sediment overlying it contain an assemblage dominated by the planktonic Aulacoseira and Cyclotella , indicating ≥1 m-deep water column subject to moderate wind-driven hydrodynamics and variable water table. This succession shows that the development of the modern wetlands during the Middle Holocene, accompanied by the expansion of vegetation, resulted from a combination of high sea-level and increased rainfall and productivity driven by the wetter and warmer climate of the Holocene Hypsithermal, although the dense accumulation of frustules in the diatom ooze suggests a drier episode around ~4 ka BP. The results show that diatom assemblges preserved as diatomites can be used to understand the origins and response of the southern Brazilian wetlands to environmental changes, which may help address the extent of anthropogenic influence and response to future climate change, thereby contributing for the conservation and management of the coastal ecosystems. [ABSTRACT FROM AUTHOR]

For the first time in the extreme southern Brazilian coastal plain, we analyzed palynomorphs in a continuous sequence, using an outcrop profile of relict muds in Hermenegildo Beach (33°42′12″S, 53°18′57″W), Santa Vitória do Palmar, Rio Grande do Sul state. Five radiocarbon dates were obtained. The results revealed the plant succession in an ancient water reservoir near the coastal line. 7500–4000 BP: Marine organisms and freshwater taxa, with herbaceous marsh at the margins. Marine taxa were markedly present from 6000 to 5000 BP, the time of the maximum transgression. Regionally, the vegetation was dominated by grasslands and forest groupings. 4000–2000 BP: Regressive marine phase, with an increased record of freshwater organisms due to increased rainfall. A large increase in herbaceous marsh components resulted in a gradual filling-in of the water reservoir and the development of regional vegetation. 2000–1760 BP: With the end of the marine regression, progressive desalinization promoted the local herbaceous marsh development. Regionally, grassland and forest also developed, indicative of climate amelioration. Local plant succession ceased during this phase of herbaceous marsh ca. 1760 BP, when beach sands covered the sedimentary sequence. This study reveals the phases of a hydrosere in a coastal water reservoir, influenced by marine oscillations, with gradual desalinization and filling-in that culminated in an herbaceous marsh deposit. These results provide a basis for understanding many other similar relict muds spread throughout the coastal plain in the extreme south of Brazil. [ABSTRACT FROM AUTHOR]

The sunflower is a oilseed crop kind of prominence before the cultures used in succession in the Brazil. However, little information concerning the effects of residual activity of herbicides on the crop in this region are known. The aim of this study was to evaluate the residual activity of herbicides in weed management in pre and post-emergence soybean and evaluate its effects on sunflower crop in succession. In field experiments we adopted the randomized block design with four replications, being appointed nine treatments (kg of i.a. ha-1): imazaquin (0.161), diclosulan (0.035), sulfentrazone (0.600) and flumioxazin (0.050) in pre emergence applications, and chlorimuron-ethyl (0.015), imazethapyr (0.060), imazethapyr (0.100) and fomesafen (0.250) applied post emergence soybean and a control without herbicide. One bioassay was differentiated by the treatments contained in each treatment and soil samples collected at six different times (0, 35, 70, 105, 140 and 200 days after application); evaluated the dry matter accumulation of sunflower plants as a function of time of sample collection. The results showed that: imazethapyr (0.1kg ha-1) and diclosulan (0.035kg ha-1) caused a reduction in sunflower yield. Sensitivity to diclosulan continued throughout the interval evaluation of the range of bioassay. [ABSTRACT FROM AUTHOR]

This paper aims to characterize the floristic composition of the arboreal stratum in a spring area and to classify the species into their respective ecological groups. The study was developed in the surrounding of the spring of Córrego do Campo, located in Engenho Buranhém, belonging to Usina Trapiche S/A, in Sirinhaém, PE, Brazil. The floristic survey was carried out between September 2008 and November 2009. For its development, 10 plots with 10x25m placed in radius in the target area and distributed in a systematic form in 5 lines (2 plots per line), separated by an angle of 45°, were used. Regarding the ecological groups, the species were classified as pioneers, initial secondary, late secondary and without characterization. 309 individuals, belonging to 27 botanical families, 46 genders and 58 species were sampled. From these species, six were identified only at gender level, three at family level and one was not identified. In relation to the successional classification, the species in the beginning of the succession showed a larger number of individuals, presenting characteristics of a forest in an initial state in the successional development. The diameter distribution follows a negative exponential function with greater individuals frequency in smaller diameter classes, demonstrating characteristics of a initial regeneration state. [ABSTRACT FROM AUTHOR]

We investigated changes in species composition and structure of tree and liana communities along a successional gradient in a seasonally dry tropical forest. There was a progressive increase in tree richness and all tree structural traits from early to late stages, as well as marked changes in tree species composition and dominance. This pattern is probably related to pasture management practices such as ploughing, which remove tree roots and preclude regeneration by resprouting. On the other hand, liana density decreased from intermediate to late stages, showing a negative correlation with tree density. The higher liana abundance in intermediate stage is probably due to a balanced availability of support and light availability, since these variables may show opposite trends during forest growth. Predicted succession models may represent extremes in a continuum of possible successional pathways strongly influenced by land use history, climate, soil type, and by the outcomes of tree–liana interactions. [ABSTRACT FROM AUTHOR]

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The all-weather capability, signal independence to the solar illumination angle, and response to 3D vegetation structures are the highlights of active radar systems for natural vegetation mapping and monitoring. However, they may present significant soil background effects. This study addresses a comparative analysis of the performance of L-band synthetic aperture radar (SAR) data and optical vegetation indices (VIs) for discriminating the Brazilian cerrado physiognomies. The study area was the Brasilia National Park, Brazil, one of the test sites of the Large-Scale Biosphere-Atmosphere (LBA) experiment in Amazonia. Seasonal Japanese Earth Resources Satellite-1 (JERS-1) SAR backscatter coefficients (σ°) were compared with two vegetation indices [normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI)] over the five most dominant cerrados' physiognomies plus gallery forest. In contrast to the VIs, σ° from dry and wet seasons did not change significantly, indicating primary response to vegetation structures. Discriminant analysis and analysis of variance (ANOVA) showed an overall higher performance of radar data. However, when both SAR and VIs are combined, the discrimination capability increased significantly, indicating that the fusion of the optical and radar backscatter observations provides overall improved classifications of the cerrado types. In addition, VIs showed good performance for monitoring the cerrado dynamics. [ABSTRACT FROM AUTHOR]

(1) Changes in vegetation structure, species composition, and species dominance were studied over the first twenty-two months of succession after the cutting and burning of several mature tierra firme (i.e. non-flooded) forest sites in south Venezuela in the upper Rio Negro region of the Amazon Basin. To explain the observed succession, additional field investigations were undertaken. (2) Four months after burning the density of plants was less than 1 m[sup -2]. The density of successional woody plants, forbs, and grasses increased rapidly from the fourth to the tenth month of succession. There was little change in plant density between the tenth and twenty-second month, but a large change in vegetation height occurred during this time By the twenty-second month a loose canopy of Cecropta spp was present at 5 m height. (3) Many of the forest tree species sprouted from the stump when cut but burning killed sprouts and significantly reduced the size of the seed bank. Nevertheless the first successional woody colonizers established from seed which survived the burn The first forb and grass colonizers established from seeds dispersed onto the site after the burn. (4) The common successional woody species had bat- or bird-dispersed seeds Many forbs and grasses had wind-dispersed seeds. (5) Population densities were low during the first months of succession because of the low density of propagules and because the low rainfall during this time was not favourable for seedling germination or establishment. The rapid increase in plant density after about the fourth month occurred because the early colonizers had then begun to produce and disperse locally, large numbers of seeds. (6) There were six distinct microhabitat types present on the sites after burning Most species tested showed distinct microhabitat preferences. [ABSTRACT FROM AUTHOR]

The diversity of hoverflies in five different habitats of the Parque Estadual de Vila Velha, Ponta Grossa, Paraná, Brazil, from September 1999 to August 2002 was studied. These five areas had been exposed to various types of anthropogenic disturbance at different times, which resulted in different stages of plant succession. In total, 2,841 specimens of 151 species of Syrphidae were collected using malaise traps. The highest species richness and abundance were found at the edge of the forest (Forest Edge), whereas the lowest was found in the most conserved areas. Evenness values increased along the succession gradient. The accumulation curve of new occurrences of syrphid species nearly approached an asymptote starting on the third month of the third year. Estimates of syrphid species richness using different methods indicated that between 155 and 288 species are found in the study area, according the Michaelis-Menten and the Chao2 estimators, respectively. The richness and abundance of representatives of the subfamily Syrphinae were higher in more open areas, where herbaceous plants predominate. Nineteen hoverfly species can be considered as environmental indicators, as they were collected exclusively or mainly in one of the defined habitat types. The degree of opening of the vegetation seems to be the factor determining the distribution of Syrphidae species, a conclusion based on the finding that grassy clearings in Araucaria Forests had more species. Hence, we conclude that, to become established, Syrphidae communities need conserved mosaic landscapes., (© The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.)