Embrapa Roraima

Boa Vista, Brazil

Embrapa Roraima

Boa Vista, Brazil
Time filter
Source Type

Barbosa R.I.,National Institute of Amazonian Research | de Castilho C.V.,Embrapa Roraima | de Oliveira Perdiz R.,National Institute of Amazonian Research | Damasco G.,University of California at Berkeley | And 2 more authors.
Forest Ecology and Management | Year: 2017

Estimates of carbon-stock changes in forest ecosystems require information on dead wood decomposition rates. In the Amazon, the lack of data is dramatic due to the small number of studies and the large range of forest types. The aim of this study was to estimate the decomposition rate of coarse woody debris (CWD) in two oligotrophic undisturbed forest formations of the northern Brazilian Amazon: seasonally flooded and unflooded. We analyzed 20 arboreal individuals (11 tree species and 3 palm species) with distinct wood-density categories. The mean annual decomposition rate of all samples independent of forest formation ranged from 0.044 to 0.963 yr−1, considering two observation periods (12 and 24 months). The highest rate (0.732 ± 0.206 [SD] yr−1) was observed for the lowest wood-density class of palms, whereas the lowest rate (0.119 ± 0.101 yr−1) was determined for trees with high wood density. In terms of forest formation, the rates values differ when weighted by the wood-density classes, indicating that unflooded forest (0.181 ± 0.083 [SE] yr−1; mean decay time 11–30 years) has a decomposition rate ∼19% higher than the seasonally flooded formations (0.152 ± 0.072 yr−1; 13–37 years). This result reflects the dominance of species with high wood density in seasonally flooded formations. In both formations 95% of the dead wood is expected to disappear within 30–40 years. Based on our results, we conclude that the CWD decomposition in the studied area is slower in forests on nutrient-poor seasonally flooded soils, where structure and species composition result in ∼40% of the aboveground biomass being in tree species with high wood density. Thus, it is estimated that CWD in seasonally flooded forest formations has longer residence time and slower carbon release by decomposition (respiration) than in unflooded forests. These results improve our ability to model stocks and fluxes of carbon derived from decomposition of dead wood in undisturbed oligotrophic forests in the Rio Negro-Rio Branco Basin, northern Brazilian Amazon. © 2017 The Authors

Moreno S.C.,Federal University of Lavras | Carvalho G.A.,Federal University of Lavras | Picanco M.C.,Federal University of Viçosa | Morais E.G.,Embrapa Roraima | Pereira R.M.,Federal University of Viçosa
Pest Management Science | Year: 2012

Background: Tropical plants are recognised sources of bioactive compounds that can be used for pest control. The objective of this study was to evaluate the biological activity of compounds present in Acmella oleracea (Asteracea) against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), which is the main pest of tomato crops in Latin America. The selectivity of these compounds to the predator Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) and to the pollinator Tetragonisca angustula (Latr.) (Hymenoptera: Apidae: Meliponinae) was also of interest. Results: A bioassay screening with hexane and ethanol extracts from 23 plants was performed. The hexane extract of A. oleraceae was the most active of the extracts and was selected for further study. The following three alkamides were isolated from a hexane extract of the aerial parts of A. oleracea: spilanthol, (E)-N-isobutylundeca-2-en-8,10-diynamide and (R, E)-N-(2-methylbutyl)undeca-2-en-8,10-diynamide. All of the isolated compounds showed insecticidal activity, with spilanthol being the most active (LD 50 = 0.13 μg mg -1) against T. absoluta. The alkamides were selective to both beneficial species studied. Conclusion: The crude hexane extract of A. oleraceae showed high insecticidal activity and can be used to control T. absoluta in organic or conventional crops. Quantification of LD 50 values of isolated compounds against T. absoluta showed that alkamides could serve as potent insecticides for T. absoluta control programmes. Spilanthol was the main alkamide active isolated. This alkamide is the most promising as it has the highest insecticidal activity and is selective to non-target organisms. © 2011 Society of Chemical Industry.

Ivar do Sul J.A.,Grande Rio University | Santos I.R.,Southern Cross University of Australia | Friedrich A.C.,Southern Cross University of Australia | Matthiensen A.,Embrapa Roraima | Fillmann G.,Grande Rio University
Estuaries and Coasts | Year: 2011

Sea turtles are highly susceptible to plastic ingestion and entanglement. Beach debris were surveyed along the most important sea turtle nesting beaches in Brazil (Costa dos Coqueiros, Bahia State). No significant differences among developed and undeveloped beaches were observed in terms of total number of items. Local sources (tourism activities) represented 70% of debris on developed beaches, where cigarette butts, straws, paper fragments, soft plastic fragments, and food packaging were the most abundant items. Non-local sources (domestic and fishing activities) accounted for about 70% of debris on undeveloped beaches, where the most abundant items were rigid plastic fragments, ropes, soft plastic fragments, caps, and polystyrene. The projected surface area of beach debris did not vary among developed and undeveloped beaches. Overseas containers accounted for about 25% of regional plastic pollution, implying that international pollution prevention agreements are not being respected off the Brazilian coast. © 2011 Coastal and Estuarine Research Federation.

Costa N.D.L.,Federal University of Paraná | Gianluppi V.,Embrapa Roraima | De Moraes A.,Federal University of Paraná
Ciencia Animal Brasileira | Year: 2012

The effects of plant regrowth age (21, 28, 35, 42, 49, 56, 63 and 70 days) on dry matter (DM) yield, and morphogenetic and structural characteristics of Trachypogon vestitus, submitted to burning, during dry season, were evaluated under natural field conditions. The experimental design was completely randomized, with three replications. Evaluations were carried out during the period from December 2009 to February 2010. DM yields, absolute growth rate, number of tillers/plant (NTP), number of leafs/plant (NLP), leaf area, leaf senescence and elongation rates and blade length (BL) increased consistently with growth stage (P<.05). The relations among DM yield, forage production rate, NTP, NLP and BL with plants regrowth age were described by the quadratic regression model and the maximum values were estimated at 64.8; 42.3; 59.6; 61,8 and 59.4 days of regrowth, respectively. The crop growth and relative growth rates, tiller and leaf appearance rates were inversely proportional to plant age.KEYWORDS: dry matter; leaves; morphogenesis; plant age; tillering.

Zilli J.E.,Embrapa Roraima | Campo R.J.,Rua Prefeito Hugo Cabral | Hungria M.,Embrapa Soja
Pesquisa Agropecuaria Brasileira | Year: 2010

The objective of this work was to evaluate the effect of Bradyrhizobium inoculation on soybean pre-sowing and the effect of the treatments of seeds using fungicides on nodulation. Control treatments consisted of two non-inoculated treatments, with or without N-fertilizer supply (200 kg ha-1 of N). Inoculation at pre-sowing had a performance similar to the standard inoculation at sowing regarding soybean nodulation, dry matter production, grain yield and N accumulation in tissues and grains. However, when seeds were treated with fungicides, nodulation and grain yield decreased.

Smiderle O.J.,Embrapa Roraima | Schwengber L.A.M.,Federal University of Roraima
Revista Brasileira de Sementes | Year: 2011

Dormancy is a phenomenon in which seeds of a species do not germinate, even when they are viable and environmental conditions are suitable. The objective of this study was to assess the effects on seeds of different periods of immersion in boiling water, with or without posterior immersion in sodium hypochlorite, on the alleviation of paricarana (Bowdichia virgilioides Kunth.) seed dormancy. Seeds were previously homogenized and separated according to size and color, with red-colored seeds being used. The treatments applied were: T1 = immersion in water at 100 °C for one second; T2 = immersion in water at 100 °C for 10 seconds; T3 = T2 + posterior immersion in 2.5% sodium hypochlorite for 1 minute; T4 = immersion in water at 100 °C for 20 seconds; T5 = T4 + immersion in 2.5% sodium hypochlorite for 1 minute. Each treatment consisted of four replicates of 50 seeds. The highest emergence scores were obtained with seed immersion in water at 100 °C for 10 seconds, with or without the posterior use of sodium hypochlorite. This is the recommended procedure for breaking the seed tegument dormancy of paricarana (B. virgilioides). Immersion of paricarana seeds in sodium hypochlorite for one minute, after seed immersion in water, facilitates imbibition and reduces seed deterioration.

The objective of this study was to evaluate the physiological quality of pepper seeds as a function of maturity, presence of seeds in fruits and storage. Pepper seeds used for the study were collected in July 2009, from plants grown in greenhouse belonging to Embrapa Roraima sector of technology transfer. The experimental design was entirely randomized under a (3 × 2 × 2) factorial scheme. At harvest, immature, intermediate and ripe fruits were collected, totalizing 90 fruits. Extraction of seeds was immediate in part of fruits, and therest of fruits were left for 10 days at room temperature at 25 °C. Seed physiological quality was evaluated concerning germination, germination speed. The tests were repeated three months after harvest to assess storage aspects. According to results, the maturation stages that showed better physiological quality were the seeds originated from green orange color fruits (intermediate class) as compared to those obtained from ripe (intense red color) fruits and immature (green) fruits. Seed permanence within fruits for ten days improved its physiological quality among early harvested fruits (intermediate). Seeds extracted from fruits ten days after harvest showed better physiological at three months of storage, when compared to seeds extracted immediately after harvest.

Smiderle O.J.,Embrapa Roraima | Das Gracas Souza A.,Federal University of Pelotas
Revista Brasileirade Ciencias Agrarias | Year: 2016

Brazil imports great amounts of C. zeylanicum from different countries, both barks and essential oil, given the absence of commercial cultivation of this spice in the country. Hence, due to the need of studying and indicating adequate mineral fertilizers in the production of C. zeylanicum seedlings, this work intended to investigate the effect of adding different concentrations of the complete nutrient solution in the production of high-quality seedlings with potential for commercial purposes. The experimental design used was completely randomized in the split-plot scheme and ten evaluations. In the plots, we evaluated the effect of the concentrations (T1 - 0%, T2 - 25%; T3 - 50%; T4 - 75%; T5 - 100%) of the nutrient solution during the growth period and in the subplots, the evaluation periods was evaluated monthly. Both growth characteristics (height, stem diameter and dry matter of shoots and roots) and quality parameters of the seedlings (Dickson index) was assessed. The nutrient solution at the concentration of 75% provides height and stem diameter growth and increased indices of Dickson quality, shoot dry matter, root dry matter and total dry matter, being suitable for the production of C. zeylanicum seedlings. C. zeylanicum seedlings have low nutrient requirements; thus, the concentration of 100% of the nutrient solution characterizes luxury consumption.

Amaro G.,Embrapa Roraima | de Morais E.G.F.,Embrapa Roraima
Experimental and Applied Acarology | Year: 2013

Among pests that have recently been introduced into the Americas, the red palm mite, Raoiella indica Hirst (Prostigmata: Tenuipalpidae), is the most invasive. This mite has spread rapidly to several Caribbean countries, United States of America, Mexico, Venezuela, Colombia and Brazil. The potential dispersion of R. indica to other regions of South America could seriously impact the cultivation of coconuts, bananas, exotic and native palms and tropical flowers such as the Heliconiaceae. To facilitate the development of efficacious R. indica management techniques such as the adoption of phytosanitary measures to prevent or delay the dispersion of this pest, the objective of this paper was to estimate the potential geographical distribution of R. indica in South America using a maximum entropy model. The R. indica occurrence data used in this model were obtained from extant literature, online databases and field sampling data. The model predicted potential suitable areas for R. indica in northern Colombia, central and northern Venezuela, Guyana, Suriname, east French Guiana and many parts of Brazil, including Roraima, the eastern Amazonas, northern Pará, Amapá and the coastal zones, from Pará to north of Rio de Janeiro. These results indicate the potential for significant R. indica related economic and social impacts in all of these countries, particularly in Brazil, because the suitable habitat regions overlap with agricultural areas for R. indica host plants such as coconuts and bananas. © 2012 Springer Science+Business Media Dordrecht.

This work was carried out in order to study the phenological pattern of brasil-nut trees in natural forest located in the south of Roraima state, in order to relate the frequency of occurrence of phenophases with rainfall. For the phenological survey 20 adult trees (DBH > 50 cm) were selected in a permanent sample plot of 9 ha. The phenological observations occurred fortnightly from February 2006 to February 2009, when data were collected on the presence or absence of events of flowering, fruiting, leaf flushing and leaf fall for each tree. The Index of population synchrony was used for estimating the synchrony of phenological events. The flowering of brasil-nut proved to be regular, annual, long and synchronous and was correlated with the reduction of rainfall. The fruiting was regular and synchronous, and dispersal was correlated with rainfall reduction. The phenological pattern of leaf flushing tended to vary yearly, being around the continual one in 2007 and bimodal in 2006 and 2008. It was noticed a higher proportion of trees falling leaves between August and October which characterizes a period of transition between the dry and the rainy time with sensitive reduction of rainfall.

Loading Embrapa Roraima collaborators
Loading Embrapa Roraima collaborators