Resumo

CARDONA, Gladys I.; ARCOS, Adriana L.  e  MURCIA, Uriel G.. Actinomycetes and Arbuscular mycorrhyzal fungi abundance in fragment landscape from Colombian Amazon region*. Agron. colomb. [online]. 2005, vol.23, n.2, pp.317-326. ISSN 0120-9965.

The abundance of actinomycetes and Arbuscular mycorrhizal (AM) fungi was evaluated in soils covered by forest and pasture, having 3 types of anthropogenic intervention, near San José del Guaviare in Colombia’s northern Amazon region. Landscape fragmentation was spatially stratified using a 1997 Spot satellite image. Geographic information system (GIS) information was used for obtaining a vegetal coverage map of the area and a 48,000 hectare area was thereby selected for study. The abundance of actinomycetes was determined by counting and diluting in plates and AM percentage by clearing with KOH and dyeing with trypan blue. Spores were extracted by wet sieving and centrifuged (Sieverding, 1983). The soil in fragments having high human intervention displayed significant differences between types of coverage, smaller values for actinomycete abundance and AM being registered in pasture, which is explained by high soil compaction. There were no significant differences in fragments having less intervention. Nine morphotypes were identified as being for actinomycetes and ten for AM, Streptomyces sp. and Glomus sp. being the most representative ones. The soils did not display significant differences in their physical-chemical characteristics. It was inferred that these groups could be possible indicators of landscape alteration in areas undergoing high human intervention.

Palavras-chave : edafic microbiota; intervention; fragmentation; forest; pastures.

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