Sandra Maria Gomes-da-Costa

Arbuscular mycorrhizal fungi associated with Araucaria angustifolia (Bert.) O. Ktze

Specimens of Araucaria angustifolia from a native forest reserve and a reforested area in the State Park of Campos do Jordão were studied to determine the number and diversity of spore populations of arbuscular mycorrhizal fungi (AMF) and root colonization. Six randomly chosen plots (planted with 8- to 12-year-old plants) were delimited, four in the native forest and two in the reforested area. Rhizosphere and root samples were collected during two periods of the year corresponding to the rainy and dry seasons. A greenhouse experiment was set up for multiplication of field propagules (from the native forest and reforested area) for two consecutive generations. Araucaria leaves from the experimental plots were collected during the first sampling for nutrient analysis. Twenty-four AMF taxa were found and percent AM colonization was determined in all plots. Not all AMF species observed in the field were re-isolated through the recovery pot cultures, even after a second cultivation cycle. The foliar nutrient analysis showed higher nutrient levels in plants from the native forest than the reforested area. Generally, spore richness and diversity were highest during the warmer and more humid period and in the native forest plants.

Biodiversity and distribution of arbuscular mycorrhizal fungi in Araucaria angustifolia forest

Araucaria angustifolia (Bert.) O. Ktze. is an endangered Brazilian coniferous tree that has been almost exterminated in the native areas because of uncontrolled wood exploitation. This tree has been shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) and, therefore, AMF may be essential for forest sustainability and biological diversity. Root colonization, density and diversity of AMF spores were assessed in two Araucaria forest stands at the State Park of Alto Ribeira (PETAR), at two sampling dates: May and October. A comparison was made between a mature native stand composed of Araucaria trees mixed into a variety of tropical trees and shrubs, without any sign of anthropogenic interference (FN) and an Araucaria stand planted in 1987 (R), which has been used as a pasture. Assessments included percent root colonization, AMF spore numbers and species richness, Simpsons dominance index (Is), and Shannons diversity index (H). Mycorrhizal root colonization did not differ between ecosystems in May. In October, however, the native stand (FN) presented a higher colonization than the planted forest (R), and the root colonization was more intense than in May. When considering both sampling periods and forests, 27 species of AM fungi, with higher numbers of spores in FN than in R were found. Canonical discriminant analysis (CDA) indicated Shannons diversity index as the ecological attribute that contributed the most to distinguish between forest ecosystems, with higher value of H in FN in relation to R. CDA showed to be a useful tool for the study of ecological attributes.

Comparação entre as técnicas de amostragem direta em campo e cultura-armadilha para mensuração da diversidade de espécies de fungos micorrízicos arbusculares

O conhecimento das comunidades de fungos micorrizicos arbusculares (FMA) depende dos esporos, que podem ou nao ser recolhidos na coleta. Este trabalho teve como objetivo determinar a diversidade de especies de FMA a partir do exame de amostras do campo e de culturas-armadilha. Foram coletadas cinco amostras de solo em tres areas, a fim de isolar os esporos e realizar a multiplicacao dos FMA em vasos. Os esporos foram extraidos do solo via peneiramento umido e centrifugacao em sacarose, montados em lâminas e identificados. As comunidades de FMA foram avaliadas por meio de indices descritores de alfa e beta diversidade. Nas areas I, II e III verificaram-se respectivamente 12, 17 e 15 especies. Nos vasos foram isoladas seis especies na area I, 12 na area II e 10 na area III. Constatou-se que o levantamento da diversidade de FMA e mais eficiente quando as duas tecnicas sao associadas.

Environmental degradation impact on native communities of arbuscular mycorrhizal fungi in an urban fragment of semideciduous plateau forest

No municipio de Maringa (PR) existem tres parques abertos a visitacao, todos com areas degradadas. O impacto causado pelo corte de arvores, trafego de automoveis e visitacao sobre o estabelecimento de fungos micorrizicos arbusculares (FMA) foi avaliado em duas areas do Horto Florestal Dr. Luis Teixeira Mendes, remanescente de floresta estacional semidecidua. Amostras de solo foram retiradas de tres pontos em cada area. Os esporos foram isolados do solo via peneiramento umido e centrifugacao em sacarose, e montados em lâminas permanentes. Sob microscopio foram quantificados e identifi cados morfologicamente. Com os dados de abundância, calcularam-se os indices: diversidade, dominância, equitabilidade e similaridade. A area degradada apresentou maior numero de esporos e comunidades com valores menores de riqueza, diversidade e equitabilidade. No entanto, convem esclarecer que a maior densidade de esporos foi ocasionada pela presenca frequente de esporocarpos de G. sinuosum. Na area preservada foram verificadas 10 a 12 especies por ponto de coleta, enquanto na area degradada, esse numero variou de 6 a 12. Na area degradada, o ponto II, localizado na regiao mais protegida do fragmento, apresentou comunidades bem diversificadas e equilibradas, a semelhanca dos pontos da area preservada. Os resultados sugerem que a degradacao ambiental teve reflexos negativos no estabelecimento e na diversidade dos FMA.