Resumo -O objetivo deste trabalho foi avaliar a composição e a diversidade de fungos micorrízicos arbusculares (FMA) em áreas em processo de revegetação na região de Porto Trombetas, PA. Coletaram-se amostras compostas de solo em revegetação com 2, 4, 6, 12 e 16 anos, em subsolo exposto sem vegetação e em floresta primária, nos meses de agosto de 1998 (estação seca) e abril de 1999 (estação chuvosa). Os esporos de FMA foram extraídos e identificados taxonomicamente. Analisou-se a densidade relativa, a freqüência de cada espécie e os índices de Shannon-Wiener e de Simpson. Os resultados indicaram que a densidade de esporos de FMA não diferiu significativamente em razão da estação do ano. O número de espécies foi maior no período seco, na floresta primária e na área revegetada aos 2 anos de idade. Entre as espécies de FMA recuperadas, Glomus macrocarpum e Acaulospora mellea foram as que apresentaram maior ocorrência. A diversidade de espécies de FMA foi mais alta e a dominância de espécies foi mais baixa na área revegetada com 2 anos de idade. O retorno do horizonte superficial orgânico com o plantio de mudas micorrizadas é uma prática eficiente para a produção de esporos em subsolo resultante da mineração de bauxita.Termos para indexação: micorriza vesicular-arbuscular, esporo, revegetação, recuperação ambiental. Arbuscular mycorrhizal fungi occurrence in revegetated areas after bauxite mining at Porto Trombetas, Pará State, BrazilAbstract -The objective of this study was to evaluate the structure and diversity of arbuscular mycorrhizal fungi (AMF) in revegetated areas at Porto Trombetas, Pará, Brazil. Composite samples were collected in August (dry season) and April (wet season) in areas with top soil after 2, 4, 6, 12 and 16 years of revegetation, in area without the top soil or vegetation, and in a pristine forest. The AMF spores were extracted, and the species identified. The relative density and frequency of occurrence of each species, the Shannon-Wiener and Simpson indexes were calculated. The results indicated that the density of AMF spores did not differ significantly with season. However, the number of AMF species was significantly higher in the dry season at the pristine forest and in the area two years after revegetation. Among the AMF species, Glomus macrocarpum and Acaulospora mellea were represented in higher numbers. After two years of planting, the diversity was highest and the dominance of AMF species was lowest. The addition of top soil with the planting of mycorrhizal seedlings were efficient to colonize areas with AMF after open cast bauxite mining.Index terms: vesicular arbuscular mycorrhizae, spores, revegetation, environmental recovery.(1) Aceito para publicação em 27 de outubro de 2003. IntroduçãoA mineração de bauxita no Estado do Pará destacase economicamente, apesar de causar grande impacto ambiental decorrente da remoção da cobertura vegetal e das camadas superficiais do solo. Uma das estratégi-as de recuperação dessas áreas é a reposição do horizonte superficial orgânico sobre o subs...

ResumoApesar de obras rodoviárias serem importante fonte de degradação de solos e paisagens, existem poucos estudos de restauração destes ambientes. Processos erosivos causados por estas ações acabam por comprometer a regeneração natural e a capacidade do solo em armazenar carbono e água, bem como sua resiliência frente a precipitações intensas. O impacto sobre a segurança de comunidades urbanas e sobre o ecoturismo é significativo. Além disso, a falta de conhecimento básico sobre solos e a qualidade de sua cobertura acaba por tornar limitante a qualidade de processos de recuperação. Este trabalho teve como objetivo a comparação das características físico-químicas dos solos das áreas degradadas pelas obras de implantação da rodovia MG-010 com os solos da vegetação preservada no entorno. Esta rodovia corta áreas de campo rupestre na Área de Proteção Ambiental Morro da Pedreira, adjacente ao Parque Nacional Serra do Cipó. Foram feitas análises físico-químicas em amostras de solo coletadas em seis áreas degradadas e suas respectivas áreas adjacentes preservadas. Os solos nas áreas degradadas diferiram significativamente das áreas adjacentes em quase todos os atributos químicos e físicos avaliados. Com exceção do pH e do teor de alumínio, as áreas degradadas mostraram-se significativamente menos férteis que as áreas adjacentes de campo rupestre. Não foi observado nenhum tipo de regeneração substancial da vegetação local mesmo após décadas de retirada do solo superficial, sugerindo que a qualidade física e química destes solos tenha sido o principal fator que impediu sua regeneração. Tal fato indica que os campos rupestres sejam ambientes extremamente frágeis e de baixa resiliência, demandando estratégias de restauração ecológica condizentes com suas peculiaridades bióticas e abióticas. Palavras-chave:Cadeia do Espinhaço, conservação, fertilidade do solo, obras rodoviárias. AbstractWhile road works are an important source of soil and landscape degradation, there are few studies on restoration of these environments. Erosive processes caused by these actions end up compromising the natural regeneration, the ability to store carbon and water in soil, decreasing its resilience in the face of intense rainfall. The impact on the safety of urban communities and ecotourism is significant. Furthermore, the lack of basic knowledge about soils and the quality of the land cover eventually become a limiting factor for land reclamation. This study aimed to compare the physical and chemical properties of degraded soils with the soils of preserved adjacent areas, along the MG-010 highway. This highway cuts through areas of rupestrian fields in the Environmental Pro-

This study evaluates the interaction effects on corn (Zea mays L.) growth between intact humic substances (HS) extracted in an alkaline medium from three different origins (an Organosol [HS-Org], an Andisol [HS-And], and vermicompost [HS-Vc]) and the arbuscular mycorrhizal fungus (AMF) Dentiscutata heterogama. The HS were characterized by spectroscopic techniques, and different biochemical, morphological, nutritional, and AMF colonization parameters were evaluated in corn plants. The experiment was conducted in a greenhouse, and low-fertility soils sterilized after solarization were used as the substrate. Hybrid corn BR-3025 was planted, and the HS concentrations used were 5, 10, and 20 mg carbon L −1 for HS-And, HS-Vc, and HS-Org, respectively, applied 15, 25, and 45 d after emergence close to the roots. The results show that HS application and D. heterogama inoculation significantly stimulated the biomass in relation to the treatments without AMF. Carbohydrate and protein content were stimulated by HS-AMF interaction. A higher leaf content of nutrients was observed in the AMF-and HS-inoculated plants. The HS-Vc application and AMF inoculation resulted in intense stimulation, which was confirmed with a high mycorrhizal efficiency. The spore density and glomalin content were also stimulated by the three different HS applications independently of their source. The HS-Vc has intermediate structural chemical characteristics in terms of polarity and aromaticity compared with HS-Org and HS-And. The HS-Vc more strongly stimulated the plant physiological parameters when combined with the AMF inoculation. These results may indicate that the HS formed in soil and characterized by structures that are more balanced may function more effectively.

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Sandy soils in tropical climates with low organic matter (OM) content result in degradation and fertility loss. It is important to note that humified OM accumulation and stabilization increases soil fertility. This study aimed to characterize humic acids (HAs) in sandy soils on an agroecological farm operating for more than 20 years. The structures of the HA of two Planosols under a grazing (G) and crop rotation (R) management system and of an Acrisol under an agroforestry management system (AFS) were characterized using HA extracted from a local Organosol under cassava monoculture (M) as a structural reference. Lower C HA /C FA ratio in sandy soil reveals a slightly humified OM and higher E 4 /E 6 ratio value in HA confirming lower aromatic structure condensation. The HA in Planosols (R and G) and Acrisols (AFS) are predominantly formed by C Alq-O,N -, C Alq-O -, and C Alq-di-O structures closely related to the soil physical properties and preserved by interaction with the mineral fraction confirmed by νO-H, νSi-O stretching of kaolinite and hematite bands in FTIR spectroscopy. Management and vegetal carbon type (−20.65‰ AFS -C 3 ) or (−15.55‰ (G) and −17.82‰ (R) -C 4 ) had no effect on HA formation. Evolution of structural change in HA modeled by chemometric analyses showed that more recalcitrant structure characteristic in HA can enhance OM preservation in these sandy soils. This study elucidated the OM stabilization mechanisms of sandy soil HA, their relationship with soil properties and models structural changes for humified OM recovery and preservation, which contribute to increased fertility and agricultural production.

Resumo -O objetivo deste trabalho foi avaliar a capacidade infectiva das espécies de fungos micorrízicos arbusculares (FMA) e relacioná-la com o número mais provável (NMP) de propágulos infectivos e número de esporos extraídos diretamente do campo. Amostras de solo foram coletadas em áreas degradadas pela mineração de bauxita com cobertura de 2, 6, 12 e 16 anos após revegetação e em uma área de floresta primária, em Porto Trombetas, PA. Os esporos de FMA foram extraídos e identificados taxonomicamente por suas características morfológicas. A maioria das espécies apresentou comportamento diferente nas áreas em estudo. Glomus macrocarpum foi a que apresentou infectividade mais rápida e alto potencial infectivo, nos solos das cinco áreas estudadas. Esta espécie também apresentou alto NMP de propágulos e alto número de esporos em todas as áreas estudadas. A capacidade infectiva das espécies não está relacionada com a densidade de propágulos. As espécies de FMA possuem diferentes graus de tolerância às condições de solo e se comportaram de maneira diferente de acordo com a idade da revegetação.Termos para indexação: propágulo, esporo, densidade, Amazônia. Infective capacity of arbuscular mycorrhizal fungi in reforested areas after bauxite mining in the Pará State, BrazilAbstract -The objective of this work was to evaluate the infective capacity of arbuscular mycorrhizal fungi (AMF) species and relate it to the most probable number (MPN) of infective propagules and number of spores extracted directly from the field. Soil samples were taken from areas degraded by bauxite mining, 2, 6, 12 and 16 years after reforestation and from an area of primary forest. The spores were extracted and morphologically identified. Most of the species had different behavior for the areas of study. Glomus macrocarpum showed fast infectivity in soils with high infective potential, independently of the soil origin. This species also showed high MPN values of infective propagules and high number of spores in all areas. The infective capacity of the species did not relate to the density of infective propagules. AMF species have different degrees of tolerance to the soil conditions and they behaved in different ways, according to the age of the revegetation.

Environmental filtering and niche differentiation are often invoked to explain species coexistence at local scales. The ironstone campo rupestre of Brazil provides a biodiverse natural experiment in which edaphic gradients represent filters to test the hypothesis that plant community functional composition, despite converging on extreme stress tolerance, exhibits a co-structure with environmental parameters. At the Serra do Rola-Moça State Park, soil physico-chemical parameters were characterized alongside community-weighted mean plant functional traits and Grime’s competitor, stress-tolerator and ruderal strategies for species at each sampling site. In general, species exhibited a high degree of stress tolerance (between 72.6% and 100%), while ruderalism was 0% for all species. Soil nutrients related to plant metabolism (e.g. P, Ca, Mg) were associated with the stress-tolerant strategy and with traits involved in the leaf economics and size spectra. Despite a major edaphic filter selecting stress tolerance, fine-scale microhabitat variability represented by soil parameters related to fertility (i.e. P, Ca, Mg) and water retention capacity (i.e. clay content) was associated with subtle variation in ecological strategies and functional traits of species in the ironstone campo rupestre.

Dark septate endophytes (DSEs) constitute a polyphyletic group within the Ascomycota, with global distribution and a wide range of host plant species. The present study evaluated the diversity of DSE in sugarcane roots of the varieties RB867515, RB966928, and RB92579, and four varieties of not commercialized energy cane. A total of 16 DSE strains were isolated, mostly from the varieties RB966928 and RB867515, with six and five isolates, respectively. Just one of the four energy cane varieties had fungi with DSE appearance. The analyses of the DNA sequences from the internal transcribed spacer (ITS) and the large subunit (LSU), in association with the micromorphology of the isolates, allowed the differentiation of the 16 isolates in at least five species, within the families Periconiaceae, Pleosporaceae, Lentitheciaceae, Vibrisseaceae, and Apiosporaceae and the orders Pleosporales, Helotiales, and Xylariales. The order Pleosporales represented 80% of the isolates, and the species Periconia macrospinosa, with six isolates, accounted for the highest isolation frequency. The results confirm the natural occurrence of the DSE symbiosis in sugarcane varieties and the generalist character of these fungi as some of the detected species have already been reported associated with other host plants, ecosystems, and regions of the world.