The diversity of arbuscular mycorrhizal fungi (AMF) was studied in the Atlantic Forest in Serra do Mar Park (SE Brazil), based on seven host plants in relationship to their soil environment, altitude and seasonality. The studied plots along an elevation gradient are located at 80, 600, and 1,000 m. Soil samples (0-20 cm) were collected in four seasons from SE Brazilian winter 2012 to autumn 2013. AMF spores in rhizosperic soils were morphologically classified and chemical, physical and microbiological soil caracteristics were determined. AMF diversity in roots was evaluated using the NS31/AM1 primer pair, with subsequent cloning and sequencing. In the rhizosphere, 58 AMF species were identified. The genera Acaulospora and Glomus were predominant. However, in the roots, only 14 AMF sequencing groups were found and all had high similarity to Glomeraceae. AMF species identities varied between altitudes and seasons. There were species that contributed the most to this variation. Some soil characteristics (pH, organic matter, microbial activity and microbial biomass carbon) showed a strong relationship with the occurrence of certain species. The highest AMF species diversity, based on Shannon's diversity index, was found for the highest altitude. Seasonality did not affect the diversity. Our results show a high AMF diversity, higher than commonly found in the Atlantic Forest. The AMF detected in roots were not identical to those detected in rhizosperic soil and differences in AMF communities were found in different altitudes even in geographically close-lying sites.
Arbuscular mycorrhizal fungi (AMF) are very important to plant nutrition, mostly in terms of acquisition of P and micronutrients. While Acacia mangium is closely associated with AMF throughout the whole cycle, Eucalyptus grandis presents this symbiosis primarily at the seedling stage. The aim of this study was to evaluate the dynamics of AMF in these two tree species in both pure and mixed plantations during the first 20 months after planting. We evaluated the abundance, richness and diversity of AMF spores, the rate of AMF mycorrhizal root colonization, enzymatic activity and soil and litter C, N and P. There was an increase in AMF root colonization of E. grandis when intercropped with A. mangium as well as an increase in the activity of acid and alkaline phosphatase in the presence of leguminous trees. AMF colonization and phosphatase activities were both involved in improvements in P cycling and P nutrition in soil. In addition, P cycling was favored in the intercropped plantation, which showed negative correlation with litter C/N and C/P ratios and positive correlation with soil acid phosphatase activity and soil N and P concentrations. Intercropping A. mangium and E. grandis maximized AMF root colonization of E. grandis and phosphatase activity in the soil, both of which accelerate P cycling and forest performance.
RESUMOO trabalho foi realizado em cafeeiros cultivados a pleno sol e consorciado com grevíleas em Vitória da Conquista (BA), em duas estações: seca e chuvosa, com objetivo de verificar a influência da arborização dos cafezais e da disponibilidade hídrica sobre a densidade de Fungos Micorrízicos Arbusculares (FMA) e ainda relacionar tais fatores com aspectos fisiológicos do cafeeiro. O experimento foi realizado em campos de observação com dois tratamentos e seis repetições, sendo as médias comparadas pelo teste t (p<0,05), relacionando os sistemas e as estações. Verificou-se maior número de esporos em época seca. A taxa de colonização radicular de FMA foi maior no cultivo consorciado, não diferindo em função da estação. O manejo dos cafeeiros sob sombra e a época seca contribuíram para maior teor de clorofila nas folhas. Maior valor absoluto do potencial hídrico foliar foi verificado quando avaliado na época chuvosa.
Palavras-chave:Grevillea robusta A. Cunn., Coffea arabica L., micorrizas
ABSTRACT
ARBUSCULAR MYCORRHIZAL FUNGI AND PHYSIOLOGICAL ASPECTS OF COFFEE CONDUCTED IN AGROFLORESTAL SYSTEM AND AT FULL SUNThe work was performed aiming to check the influence of the agroforestry system and water availability on the density of Arbuscular Mycorrhizal Fungi (AMF), and to correlate these factors with physiological aspects of coffee. This study was conducted in a full sun coffee field, where coffee plants were associated with grevilea during dry and rainy seasons. The experiment had two treatments and six replicates, and the resulting averages were compared by a t test at 5% of probability, comparing the systems and seasons. There was a rise in spore number in the dry season. Also the rate of root colonization of AMF was higher in intercropped cultivation but it did not differ between seasons. The shading of coffee plants in dry season promoted a raise of leaf Spad index. In the rainy season the leaf water potential had higher absolute value.
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