Levantamento preliminar da entomofauna associada às plantas daninhas em cultivos de soja.

O manejo e o controle de ácaros, insetos e plantas daninhas fazem parte do sistema de produção de qualquer cultivo agrícola, sendo fundamental conhecer suas práticas e ferramentas para alcançar produtividades satisfatórias, sem agredir o ambiente. O trabalho teve como objetivo identificar os artrópodes presentes nas plantas daninhas que ocorrem em cultivos de soja.Autoria: QUERINO, [i.e. SILVA], R. B. Q. da. RANYSE BARBOSA QUERINO DA SILVA

Caracterização da comunidade de plantas daninhas em áreas de plantio de feijão-caupi, Teresina, Piauí.

O conhecimento de plantas daninhas em cultivos é essencial para o seu manejo adequado, sendo que a sua presença pode acarretar grandes problemas para a produção agrícola. O trabalho objetivou realizar o levantamento florístico sistemático de plantas daninhas em áreas experimentais de cultivo de feijão-caupi, no município de Teresina-PI (Embrapa Meio-Norte) durante o ano de 2011.Autoria: QUERINO [i.e. SILVA], R. B. Q. da. RANYSE BARBOSA QUERINO DA SILVA

Methane flux, vertical gradient and mixing ratio measurements in a tropical forest

Measurements of CH<sub>4</sub> mixing ratio, vertical gradients and turbulent fluxes were carried out in a tropical forest (Reserva Biológica Cuieiras), about 60 km north of Manaus, Brazil. The methane mixing ratio and flux measurements were performed at a height of 53 m (canopy height 35 m). In addition, vertical CH<sub>4</sub> gradients were measured within the canopy using custom made air samplers at levels of 2, 16 and 36 m above ground. The methane gradients within the canopy reveal that there is a continuous methane source at the surface. No clear evidence for aerobic methane emission from the canopy was found. The methane fluxes above the canopy are small but consistently upwards with a maximum early in the morning. The measured fluxes are in agreement with the observed CH<sub>4</sub> gradient in the canopy. In the morning hours, a strong canopy venting peak is observed for both CH<sub>4</sub> and CO<sub>2</sub>, but for CO<sub>2</sub> this peak is then superimposed by photosynthetic uptake, whereas the peak lasts longer for CH<sub>4</sub>. Monthly averaged diurnal cycles of the CH<sub>4</sub> mixing ratio show a decrease during daytime and increase during nighttime. The magnitude of the difference in CH<sub>4</sub> mixing ratio between day and night gradually increases throughout the wet season. The fluxes required to explain the nighttime increase are in agreement with the nighttime fluxes measured above the canopy, which implies that the CH<sub>4</sub> increase in the nighttime boundary layer originates from local sources

Methane exchange in a boreal forest estimated by gradient method

Forests are generally considered to be net sinks of atmospheric methane (CH4) because of oxidation by methanotrophic bacteria in well-aerated forests soils. However, emissions from wet forest soils, and sometimes canopy fluxes, are often neglected when quantifying the CH4 budget of a forest. We used a modified Bowen ratio method and combined eddy covariance and gradient methods to estimate net CH4 exchange at a boreal forest site in central Sweden. Results indicate that the site is a net source of CH4. This is in contrast to soil, branch and leaf chamber measurements of uptake of CH4. Wetter soils within the footprint of the canopy are thought to be responsible for the discrepancy. We found no evidence for canopy emissions per se. However, the diel pattern of the CH4 exchange with minimum emissions at daytime correlated well with gross primary production, which supports an uptake in the canopy. More distant source areas could also contribute to the diel pattern; their contribution might be greater at night during stable boundary layer conditions

Can the understory affect the Hymenoptera parasitoids in a Eucalyptus plantation?

The understory in forest plantations can increase richness and diversity of natural enemies due to greater plant species richness. The objective of this study was to test the hypothesis that the presence of the understory and climatic season in the region (wet or dry) can increase the richness and abundance of Hymenoptera parasitoids in Eucalyptus plantations, in the municipality of Belo Oriente, Minas Gerais State, Brazil. In each eucalyptus cultivation (five areas of cultivation) ten Malaise traps were installed, five with the understory and five without it. A total of 9,639 individuals from 30 families of the Hymenoptera parasitoids were collected, with Mymaridae, Scelionidae, Encyrtidae and Braconidae being the most collected ones with 4,934, 1,212, 619 and 612 individuals, respectively. The eucalyptus stands with and without the understory showed percentage of individuals 45.65% and 54.35% collected, respectively. The understory did not represent a positive effect on the overall abundance of the individuals Hymenoptera in the E. grandis stands, but rather exerted a positive effect on the specific families of the parasitoids of this order