Shifts in the bacterial community composition along deep soil profiles in monospecific and mixed stands of Eucalyptus grandis and Acacia mangium

Abstract

Our knowledge of the rhizosphere bacterial communities in deep soils and the role of Eucalyptus and Acacia on the structure of these communities remains very limited. In this study, we targeted the bacterial community along a depth profile (0 to 800 cm) and compared community structure in monospecific or mixed plantations of Acacia mangium and Eucalyptus grandis. We applied quantitative PCR (qPCR) and sequence the V6 region of the 16S rRNA gene to characterize composition of bacterial communities. We identified a decrease in bacterial abundance with soil depth, and differences in community patterns between monospecific and mixed cultivations. Sequence analysis indicated a prevalent effect of soil depth on bacterial communities in the mixed plant cultivation system, and a remarkable differentiation of bacterial communities in areas solely cultivated with Eucalyptus. The groups most influenced by soil depth were Proteobacteria and Acidobacteria (more frequent in samples between 0 and 300 cm). The predominant bacterial groups differentially displayed in the monospecific stands of Eucalyptus were Firmicutes and Proteobacteria. Our results suggest that the addition of an N2-fixing tree in a monospecific cultivation system modulates bacterial community composition even at a great depth. We conclude that co-cultivation systems may represent a key strategy to improve soil resources and to establish more sustainable cultivation of Eucalyptus in Brazil.

Acacia mangium Willd: benefits and threats associated with its increasing use around the world

“…mangium, one of the Australian acacias that is widely planted in many parts of the world, has clear benefits in agricultural, agroforestry and forestry ecosystems (Bernhard-Reversat 1993;Franco et al 1994;Parrotta and Knowles, 1999;Richardson et al 2004;Kull et al 2011;Epron et al 2013). Key reasons for the widespread planting of A. mangium, in commercial monoculture plantations or in mixed plantings with other tree species or crops in areas with infertile soils, are its capacity to improve soil fertility (Wang et al 2010;Forrester et al 2013;Koutika et al 2014;Machado et al 2017;Tchichelle et al 2017), change the soil faunal, microbial and bacterial communities (Bernhard-Reversat 1993;Bini et al 2012Bini et al , 2013Huang et al 2014;Pereira et al 2017), and to stimulate crop or tree growth and forest productivity Epron et al 2013;Paula et al 2015). The species is considered useful for these purposes due to the enhanced nutrient cycling, higher nutrient availability and microbial activities that accrue from its presence (Khanna 1998;Bini et al 2012;Rachid et al 2013;Santos et al, 2017a, b).…”

Análise da comunidade de fungos em áreas de monoculturas e consórcio de <em>Eucalyptus grandis</em> e <em>Acacia mangium</em>

“…O grupo tem obtido resultados interessantes sobre a composição e estrutura da comunidade microbiana, tanto em superfície quanto em profundidade do solo e suas interações com os cultivos (BINI, 2012;BINI et al, 2013BINI et al, , 2013aPEREIRA, 2014;SANTANA et al, 2016;PEREIRA et al, 2017).…”

“…Dessa forma, para manter altos níveis de produtividade, é necessário suprir a demanda de nutrientes das plantas, aplicando fertilizantes minerais no solo (BALIEIRO et al, 2008), o que pode gerar problemas ambientais e econômicos. Assim, a busca por manejos alternativos tem crescido e, dentre as opções, destaca-se a integração do Eucalyptus com árvores leguminosas, em sistemas de plantios consorciados (BOUILLET et al, 2008, BINI et al, 2013, PEREIRA et al, 2017.…”

“…Recentemente, pesquisas envolvendo a microbiota do solo em plantios de E. grandis e A. mangium foram desenvolvidas (BINI 2012;BINI et al, 2013a;RACHID, 2013;PEREIRA 2014;SANTANA et al 2016;PEREIRA et al, 2017), indicando que há influência dos sistemas de consórcio sobre a comunidade microbiana do solo. Nesse sentido, as plantas de A. mangium parecem ser importantes na modificação dessas comunidades, principalmente pelo estímulo à ciclagem da matéria orgânica e presença de grupos microbianos associados ao ciclo do N no solo, como as Proteobacterias (FONSECA et al, 2017;PEREIRA et al, 2017).…”

“…Nesse sentido, as plantas de A. mangium parecem ser importantes na modificação dessas comunidades, principalmente pelo estímulo à ciclagem da matéria orgânica e presença de grupos microbianos associados ao ciclo do N no solo, como as Proteobacterias (FONSECA et al, 2017;PEREIRA et al, 2017).…”