A Estrutura da Vegetação e os Fungos Ectomicorrízicos em uma Campinarana na Amazônia

Abstract

White-sand forests known as Campinaranas are oligotrophic soil ecosystems, generally insular, ranging from open grasslands to forests. They are characterized by low diversity and dominance of some tree species which are not the same throughout the Amazon. The abundance and dominance of plants in Campinaranas may be associated with several factors, and one of them is the association with ectomycorrhizal fungi. Therefore, the objectives of this work are: 1) Describe the variation in the floristic and structural composition of an "island" of Campinarana located in the Madeira-Tapajós interfluve (Manicoré, Amazonas), 2) Know the composition of ectomycorrhizal macrofungi and, 3) Verify the presence or absence of ectomycorrhizal association in the most abundant and dominant plants in this “island” of Campinarana. For this, a vegetation inventory was carried out using the Quadrant Points method, and in addition, a mycological inventory. The presence or absence of ectomycorrhizal association was investigated in five abundant and dominant plant species in the study area. According to phytosociological parameters, Pagamea coriacea (Rubiaceae), Neea obovata (Nyctaginaceae), Eperua oleifera (Fabaceae), Caraipa savannarum (Calophyllaceae), Ormosia macropylla (Fabaceae), Lacmella gracilis (Apocynaceae), Remijia amazonica (Rubiaceae), Myrcia eximia (Myrtaceae), and Sacoglottis amazonica (Humiriaceae) were the most abundant, dominant, frequent species with the highest importance value index. These species are different from the abundant and dominant species in other Campinaranas of the Rio Negro Basin. In relation to the macrofungi inventory, we recorded 18 families, 29 genera and 62 species. Among the species collected, seven species are ectomycorrhizal: Cantharellus guyanensis (Hydnaceae), Coltricia cinnamomea, Coltricia sp.1, Coltriciella sp.1 (Hymenochaetaceae), Fistulinella campinarae var. scrobiculata (Boletaceae), Inocybe sp.1 (Inocybaceae), and Scleroderma (Sclerodermataceae). Furthermore, based on potentially ectomycorrhizal lineages recorded in the literature, in this study we also recorded 11 species from the Entolomataceae family and one species from the Hymenochaetaceae family. The species selected to investigate the presence or absence of ectomycorrhizal symbiosis were Pagamea coriacea, Neea obovata, Ormosia macrophylla, Eperua oleifera and Coccoloba paraensis. This last one is a species of lianescent shrub apparently abundant in the study area. Among these species, we found an ectomycorrhizal association in Neea obovata, Eperua oleifera and Coccoloba paraensis. While Ormosia macrophylla presented rhizobial nodules and Pagamea coriacea has the ability to sprout and propagate vegetatively. These factors also promote the abundance and dominance of plants in the Amazon. Furthermore, we recorded the interaction network between Eperua oleifeira and Coltricia sp.1, and Neea obovata with two types of mycobionts simultaneously, one of them, a Coltricia sp. or Coltriciella sp., and another unidentified mycorrhizal fungus with a white mantle. In general, the present work opens paths that are expected to help further studies on ectomycorrhizal symbiosis in the Campinaranas of the Amazon.