No abstract

Com a nova legislação ambiental brasileira vislumbra-se a possibilidade do uso de sistemas agroflorestais diversificados para recompor áreas de preservação permanente e reserva legal, principalmente em pequenas propriedades rurais. Uma pergunta que surge, diz respeito a capacidade desses sistemas em reduzir custos na restauração florestal e ao mesmo tempo apresentar eficiência ecológica similar aos plantios em que se faz uso exclusivo de espécies nativas do bioma em questão. Buscando a resposta avaliou-se nesse estudo um sistema agroflorestal implantado em 2005, em Seropédica, RJ, que tinha o objetivo de interligar dois fragmentos florestais ali existentes. Desde então foram feitas uma série de avaliações sobre a eficácia ecológica desse “corredor agroflorestal” na interligação desses fragmentos. Os resultados indicaram que a quantidade e a qualidade da fauna do solo e fungos micorrízicos foram favorecidos pelo sistema agroflorestal em comparação à matriz de pastagem, mas ainda se encontram em níveis inferiores aos fragmentos florestais interligados. A pastagem próxima ao sistema agroflorestal vem se beneficiando da melhoria ambiental ali existente, criando um “efeito de borda positivo”, situação bem distinta da pastagem que se encontrava mais distante da área de influência do corredor agroflorestal. Para os indicadores utilizados, o sistema agroflorestal foi eficiente.

RESUMOSistemas em aléias podem consistir numa solução para o uso da terra em regiões do Trópico Úmido. A relação dessa forma de manejo com a dinâmica dos fungos micorrízicos arbusculares (FMA) Arbuscular mycorrhizal fungi in an alley cropping system in the state of Maranhão, Brazil ABSTRACTAlley cropping systems may be a solution for land use in tropical regions. How land use is connected to mycorrhizal arbuscular fungi (AMF) is poorly understood, especially in the tropics. The aim of this study was to evaluate the influence of leguminous trees in an alley cropping system in regard to the infectivity and diversity of native AMF species in São Luís, Maranhão, Brazil. Soil samples were collected in an experimental area of the Universidade Estadual do Maranhão (UEMA) -São Luís, in two seasons (July/2006 and April/2007), two distances (0 m and 0.5 m) from the trunk of three leguminous trees (Leucaena leucocephala, Clitoria fairchildiana e Acacia mangium), and in a control area 0-20 cm deep. Soil samples were used to evaluate the infectivity of AMF, density and diversity of glomerospores. The alley cropping systems increased the infectivity of AMF which varied according to the leguminous tree species, raining season and distance from trees. Sixteen AMF species of five genera were identified in the area, and Scutellospora was the most representative genus.

In order to obtain an arbuscular mycorrhizal fungi (AMF) native inoculum from Sierra de Moa and determine the most appropriate conditions for its big scale production, four light and temperature combinations were tested in three plant species (Calophyllum antillanum, Talipariti elatum and Paspalum notatum). Growth and development parameters, as well as the mycorrhizal functioning of the seedlings were evaluated. The natural light treatment under high temperatures (L-H) was the most suitable for the growth and development of the three plant species, showing the highest total biomass values, mainly of root, and a positive root-shoot ratio balance. This treatment also promoted higher values of root mycorrhizal colonization, external mycelium and AMF spore density. A total of 38 AMF species were identified among the plants and environmental conditions tested. Archaeospora sp.1, Glomus sp.5, Glomus brohultii and G. glomerulatum were observed in all the treatments. The L-H condition can be recommended for native inoculum production, as it promotes a better expression of the AM symbiosis and an elevated production of mycorrhizal propagules.

Babassu, Attalea speciosa (Arecaceae) is a ruderal palm native to Amazonia, which turned dominant in frequently burned lands throughout the ‘arc of deforestation’ and other degraded lands, in extreme cases attaining complete dominance. This study investigated arbuscular mycorrhizal fungi (AMF) as one possible explanation for the outstanding ecological success of this exceptional palm. We explored the relationships between the babassu palm and native arbuscular mycorrhizal fungi and babassu effects on the AMF richness and mycorrhizal inoculum potential (MIP) in the eastern periphery of Amazonia. For this purpose, we sampled topsoil (0-20 cm) at the onset of the rainy season from a 5-year-old secondary forest regrowth (SEC) area with three levels of babassu dominance (sites with 10, 50 and 70% babassu biomass shares), and at three distances (0, 2.5 and 4 m) from isolated babassu patches within a degraded pasture (PAS), both with five replications per treatment. Glomerospore density varied from 100 to 302 per gram of soil, 56% higher in SEC than PAS. We identified a total of 16 AMF species, with dominance of Acaulospora (six species) followed by Glomus (three species). AMF richness increased with babassu dominance in SEC sites, and reduced with distance from babassu patches within the PAS. The colonization rate of babassu roots was higher in SEC than in PAS, whereas MIP was similar in both areas and without treatment differences. Our study points to strong mycorrhizal association of the babassu palm as a potential mechanism for its outstanding ecological success in degraded lands.

At the Brazilian Amazon forest, studies were carried out to estimate the community of arbuscular mycorrhizal fungi (AMF), from this it was used a bioassay of dilutions of samples collected from preserved and regenerated areas after bauxite extraction. To regenerate areas, tree species were introduced and samples were taken after 2, 6, 12, and 16 years, the spores obtained were compared to those obtained by direct extraction and the number of species recovered from the bioassay was significantly higher. Therefore, the species founded after different periods regeneration was similar to the ones from the native forest. Since the early years of revegetation, the number of rare species was high with strong dominance of G. macrocarpum. Among older communities this high dominance decreased while at the same time, there was an increase in the number of individuals from other AMF species, concluding that the number of species did not change with the age of the revegetation.

In this study, we evaluated the growth of the liverwort Lunularia cruciata, inoculated or not with the arbuscular mycorrhizal fungi (AMF) Glomus proliferum (15 spores per Petri dish), in Strullu-Romand Variant (SRV) medium modified and enriched with humic acid (HA) at different concentrations (0, 20, 40 and 80 mg C L −1 ), as well as the sporulation of the AMF. We assessed the absolute growth rate (AGR) and relative growth rate (RGR) at inoculation, as well as at 7, 14, 21, 28, 43, 52 and 60 days after inoculation (DAI), whereas we assessed sporulation at 25, 43, 60 and 70 DAI. The main determinant of L. cruciata growth was the presence of AMF. With and without G. proliferum inoculation, respectively, the AGR peaked at 39 and 42 DAI, and the RGR was 0.0474 and 0.0387 cm 2 cm −2 d −1 . Doses of 20 and 80 mg C L −1 of HA had a positive influence on the growth of L. cruciata. With and without HA, respectively, the AGR peaked at 38 and 39 DAI, and the RGR was 0.0484 and 0.0422 cm 2 cm −2 d −1 . The sporulation of G. proliferum, which was as high as 199 spores plate −1 , was influenced by HA, especially at 20 and 80 mg C L −1 .

The use of beneficial microorganisms such as arbuscular mycorrhizal fungi (AMF) may favor both the growth phase and the stabilization of the seedlings after transplantation. The aim of this study was to evaluate the effect of inoculation of different AMF species on the development of Barbados cherry seedlings from herbaceous and semi-hardwood cuttings. Softwood and semi-hardwood cuttings, previously rooted, were planted in 500 ml tubes filled with Plantmax® substrate and inoculated with three species of mycorrhizal fungi (Gigaspora margarita -Gimarg, Claroideoglomus etunicatum -Claetun and Glomus clarum -Glclar) isolated and combined (Gimarg + Claetun, Gimarg + Glclar, Claetun + Glclar and Gimarg + Claetun + Glclar). The statistical design was completely randomized in factorial scheme 2 x 8 (two types of cuttings and eight types of inoculation, including control without AMF inoculation) with ten replications. The seedlings were kept in a greenhouse for 100 days and height was measured every 15 days to determine the absolute and relative growth rate (AGR and RGR). At the end of the experiment the seedlings were sacrificed and determined height, fresh and dry shoot mass and root and mycorrhizal colonization rate. The results indicate potential for production of Malpighia emarginata D.C. seedlings inoculated with AMF with tendency to reduce the time for transplanting. The Gimarg + Claetun combination promoted higher rates of absolute growth and height of seedlings from herbaceous cuttings. The species Glomus clarum, isolated or associated with C. etunicatum, promoted higher colonization rates in herbaceous and semi-hardwood seedlings, respectively.