Resumo
Thirty-eight taxa of Zygomycetes distributed in 15 genera were recorded from tapir (Tapirus terrestris), camel (Camelus bactrianus), horse (Equus caballus), deer (Cervus elaphus), agouti (Dasyprocta aguti), donkey (Equus asinus), llama (Llama glama) and waterbuck (Kobus ellipsiprymnus) dung collected at the Reserva Ecológica de Dois Irmãos located in Recife, State of Pernambuco, Northeast Brazil. The samples were collected on a monthly basis from June 2005 to May 2006, taken to the laboratory and incubated in moist chambers. Higher number of taxa was observed in the excrements of tapir, followed by deer and donkey. The highest number of species was detected for Mucor, followed by Pilobolus. Statistical analyses showed significant differences in richness of Zygomycetes taxa between the herbivore dung types. Differences of species composition, however, were weak. Seasonality influenced the Zygomycetes species composition but not its richness. Variations in taxa composition between ruminants and non-ruminants dung were non significant.
Resumo
A large number of propagules and a broad spectrum of species are two important components of ecosystem (including agroecosystem) sustainability. Previous studies carried out in temperate areas showed that repeated monoculture leads to a decrease in the species abundance of arbuscular mycorrhizal fungi (AMF). This study evaluated the influence of maize monoculture and its agricultural practices on AMF during three consecutive cropping years in a Brazilian field. At the end of each cycle, soil and root samples were evaluated for species composition, spore populations and root colonization by AMF. The AMF community present during this period was scored according to the Spearman rank correlation and Principal Components Analysis. The mean percent root colonization values for the three cultivation periods were: 66.9, 60.7 and 70.5, respectively. Seven species were detected in the first year, Scutellospora persica being the most abundant (24.1% of spores) and Glomus macrocarpum the most observed (100% of samples). In the second year, Glomus etunicatum was the species with the greatest number of spores (24.7%) and, like G. macrocarpum, the most frequently observed (90%) in a community of thirteen. In the third year, twenty-three AMF species were identified, Scutellospora sp. 1 being the most abundant (17.4%), and Gigaspora decipiens and Glomus claroideum the most frequent (both with a relative frequency of 70%). The main soil factors influencing root colonization and sporulation by AMF were pH (and related properties), phosphorus and organic matter contents.
Elevado número de propágulos e de espécies são componentes importantes para manter a sustentabilidade dos ecossistemas, incluindo agrossistemas. Estudos desenvolvidos em áreas temperadas indicaram que monocultivo prolongado conduziu ao decréscimo na abundância de esporos e de espécies de fungos micorrízicos arbusculares (FMA). O presente estudo avaliou a influência da monocultura de milho e de suas práticas culturais sobre o desenvolvimento de FMA durante três anos sucessivos de cultivo em campo. Ao final de cada ciclo, amostras de solo e raízes foram avaliadas quanto à composição de espécies, populações de esporos e colonização radical por FMA. As mudanças da composição das comunidades de FMA estabelecidas durante estes anos foram avaliadas a partir da correlação de Spearman e da Análise dos Componentes Principais. As percentagens médias de colonização radical foram: 66,9, 60,7 e 70,5, respectivamente. No primeiro ano, sete espécies foram detectadas, sendo Scutellospora persica a mais abundante (24,1% dos esporos) e Glomus macrocarpum a espécie mais frequente (100% das amostras). No segundo ano, Glomus etunicatum foi a espécie com maior número de esporos (24,7%) e, juntamente com G. macrocarpum, foi a mais frequentemente observada (90%) numa comunidade de treze espécies. No terceiro ano, vinte e três espécies de FMA foram identificadas, sendo Scutellospora sp. 1 a mais abundante (17,4%), e Gigaspora decipiens e Glomus claroideum as espécies mais frequentes (ambas em 70% das amostras). As principais causas de variação que puderam ser identificadas foram pH e concentrações de fósforo e matéria orgânica no solo.