Spore density and root colonization by arbuscular mycorrhizal fungi in preserved or disturbed Araucaria angustifolia (Bert.) O. Ktze. ecosystems

Abstract

Araucaria angustifolia (Bert.) O. Ktze., a native forest tree from Brazil, is under extinction risk. This tree depends on arbuscular mycorrhizal fungi for growth and development, especially in tropical low-P soils but, despite being a conifer, Araucaria does not form ectomycorrhiza, but only the arbuscular endomycorrhiza. This study aimed at surveying data on the spore density and root colonization (CR) by arbuscular mycorrhizal fungi (AMF) in Araucaria angustifolia forest ecosystems, in order to discriminate natural, implemented, and anthropic action-impacted ecosystems, by means of Canonical Discriminant Analysis (CDA). Three ecosystems representative of the Campos do Jordão (SP, Brazil) region were selected: 1. a native forest (FN); 2. a replanted Araucaria forest (R); and 3. a replanted Araucaria forest, submitted to accidental fire (RF). Rhizosphere soil and roots were sampled in May and October, 2002, for root colonization, AMF identification, and spores counts. Root percent colonization rates at first collection date were relatively low and did not differ amongst ecosystems. At the second period, FN presented higher colonization than the other two areas, with much higher figures than during the first period, for all areas. Spore density was lower in FN than in the other areas. A total of 26 AMF species were identified. The percent root colonization and spore numbers were inversely related to each other in all ecosystems. CDA indicated that there is spatial distinction among the three ecosystems in regard to the evaluated parameters. Key words: Brazil pine, biodiversity, species richness, reforestation DENSIDADE DE ESPOROS E COLONIZAÇÃO RADICULAR POR FUNGOS MICORRÍZICOS ARBUSCULARES EM ECOSSISTEMAS DE Araucaria angustifolia (Bert.) O. Ktze. PRESERVADOS E IMPACTADOSRESUMO: A Araucaria angustifolia (Bert.) O. Ktze. é uma espécie florestal nativa do Brasil e encontrase ameaçada de extinção. É altamente dependente de fungos micorrízicos arbusculares para seu desenvolvimento, principalmente em solos com baixos teores de fósforo. Embora sendo uma conífera, esta árvore não forma ectomicorriza, mas sim a endomicorriza arbuscular. O presente estudo teve como objetivo levantar dados sobre a densidade de esporos e a colonização radicular de fungos micorrízicos arbusculares (FMAs) em ecossistemas florestais de Araucaria angustifolia, visando discriminar os ecossistemas natural, implantado e impactado pela ação antrópica, através da Análise Canônica Discriminante (ACD). Foram selecionados três ecossistemas representativos da região de Campos do Jordão (SP): 1. floresta nativa (FN); 2. floresta replantada de araucária (R); e 3. floresta replantada de araucária, submetida a uma queima acidental (RF

Species richness of arbuscular mycorrhizal fungi in forests with Araucaria in Southern Brazil

“…Although these data might be overestimated, due to the possible inclusion of non-infective and dead spores in the count, the comparison among sites is still valid. In contrast to Moreira-Souza et al (2003) and Moreira et al (2007a), but in agreement with Moreira et al (2006), we found greater spore abundance in the Araucaria reforestation than in the native forest. These contrasting observations are probably related to historical and structural differences between the examined forests.…”

“…The slow growth rate of Araucaria angustifolia, its common association with AMF (e.g., Oliveira & Ventura 1952, Muchovej et al 1992, Breuninger et al 2000, Moreira-Souza et al 2003, Moreira et al 2006, and its strong growth response to inoculation with AM fungi (Moreira-Souza & Cardoso 2002, Zandavalli et al 2004 suggest that the success of any plantation effort, aiming either the conservation or the sustainable use of the species, might greatly depend on ensuring that the young plants are colonized by the fungal partners.…”

Arbuscular mycorrhizal fungal symbiosis with Sorbus torminalis does not vary with soil nutrients and enzyme activities across different sites

“…Our result showed that despite differences in soil properties in the studied sites, no significant differences in SD and root length colonization were observed. In a similar study on Araucaria angustifolia, Moreira et al (2006) showed similar rates of root colonization in spring. A reasonable colonization rate is usually about 40% (Thonar et al 2011).…”

Impacto do controle de plantas espontâneas sobre propágulos de fmas e micorrização de cafeeiro

“…Apesar de alguns autores relatarem alta esporulação em solos cultivados quando comparados à vegetação natural (MoREIRA et al, 2006), as amostras de solo dos tratamentos com roçadora e controle químico apresentaram valores de densidade de esporos abaixo dos encontrados em dunas antropizadas (de 28,8 a 31,8 esporos 100 ml -1 ), conforme Stürmer, Stürmer e Pasqualini (2013).Apesar dos resultados controversos obtidos por Silveira et al (2015), os herbicidas podem afetar diretamente ou indiretamente a eficiência e a densidade dos FMAs (Tabela 3). na análise multivariada dos atributos microbiológicos, químicos, físicos e de produtividade do cafeeiro, apresentada na Figura 1, podem ser observados dois componentes principais (CP), por acumularem 81,78% da variância total dos dados, sendo 55,98 % no CP1 e 25,80 % no CP2.…”