ABSTRACT Swamps have high biological diversity and are the largest producers of biomass. However, such ecosystems are threatened by human activities. This study analyzes the plant community structure of two swamp sites, with and without grazing. A total of 200 sample units with 0.25 m2 were distributed every 13 m to determine diversity, the Importance Value Index (IVI), and coverage. Fifty species and 18 families were recorded. Luziola peruviana Juss. ex. JF Gmel had the highest IVI, accounting for 62.57% of the relative coverage in cattle-influenced sites. In the portions without cattle, Commelina diffusa Burm.f. had the highest IVI (24.33). The Shannon and Pielou indexes were 2.18 nats.ind.–1 and 0.56, respectively, decreasing to 1.62 nats.ind.–1 and 0.47 in grazing sites. There was less richness in the cattle grazing area, with a single species accounting for a high percentage of coverage, indicating the possible role of grazing on the plant community structure.

We tested the functional response of the phytoseiid predator Phytoseiulus macropilis (Banks, 1904) to different population densities of Tetranychus urticae Koch, 1836 (the two-spotted spider mite - TSSM) in the laboratory. We evaluated the curve that best fits the data obtained, based on the reduced X². The predators were obtained from leaves of Oso Grande strawberries at the municipality of Bom Princípio, state of Rio Grande do Sul, Brazil. Fifteen seemingly healthy females of P. macropilis were randomly chosen and individualized in each of the arenas with different TSSM densities. The following prey densities were tested: 1, 2, 3, 5, 10, 20, 30, 35, 45, 55, 70 and 125 females. The tests were performed in a germination chamber with photoperiod of 12 hours at 28 ± 1ºC per day and 22 ± 1ºC at night and 80 ± 5% relative humidity. In all tests with up to three prey items, P. macropilis showed low functional response, whereas higher rates were observed when more prey items were offered. There was a strong positive correlation between increased prey numbers and daily prey consumption (r = 0.84 and p = 0.0006). A significant correlation was found between prey consumption and total oviposition (r = 0.70, p = 0.01). The daily oviposition rate was lower when few prey items were offered, increasing significantly with increased prey availability. The results showed a positive correlation between the number of prey items offered to the predator and its oviposition rate (r = 0.66, p = 0.01). Nevertheless, a strong correlation was observed between the daily consumption of prey and eggs/female/day (r = 0.92, p < 0.0001). A shorter oviposition period was reported when up to three prey items were offered. The oviposition period and the increase in prey numbers were positively correlated (r = 0.30, p = 0.34), but the difference was not statistically significant. Nevertheless, the longer the egg-laying period, the greater the oviposition rate (r = 0.90, p < 0.0001). The curve that best fits the data obtained in each case was also calculated, based on the least square method.

Neste trabalho foi realizado o estudo da degradação fotoquímica do corante vermelho bordeaux. O estudo objetivou a avaliação de tratamentos alternativos com vistas à aplicação de tecnologias limpas. Os experimentos de fotodegradação foram realizados através da incidência de radiação UV em um compartimento contendo o corante (solução). O tratamento fotoquímico reduziu em 99% a coloração e a concentração da solução contendo o corante vermelho bordeaux.

This paper studied the photochemical degradation of food dye (red dye). The investigation aimed at the assessment of alternative treatments, focusing the use of clean technologies. The photochemical degradation experiments were performed in a compartment with UV radiation (mercury lamp - 250W). The photochemical treatment showed a 99% color and concentration reduction in the dye solution.