Microbial biomass and activity in litter during the initial development of pure and mixed plantations of Eucalyptus grandis and Acacia mangium

Abstract

SUMMARYStudies on microbial activity and biomass in forestry plantations often overlook the role of litter, typically focusing instead on soil nutrient contents to explain plant and microorganism development. However, since the litter is a significant source of recycled nutrients that affect nutrient dynamics in the soil, litter composition may be more strongly correlated with forest growth and development than soil nutrient contents. This study aimed to test this hypothesis by examining correlations between soil C, N, and P; litter C, N, P, lignin content, and polyphenol content; and microbial biomass and activity in pure and mixed second-rotation plantations of Eucalyptus grandis and Acacia mangium before and after senescent leaf drop. The numbers of cultivable fungi and bacteria were also estimated. All properties were correlated with litter C, N, P, lignin and polyphenols, and with soil C and N. We found higher microbial activity (CO 2 evolution) in litter than in soil. In the E. grandis monoculture before senescent leaf drop, microbial biomass C was 46 % higher in litter than in soil. After leaf drop, this difference decreased to 16 %. In A. mangium plantations, however, microbial biomass C was lower in litter than in soil both before and after leaf drop. Microbial biomass N of litter was approximately 94 % greater than that of the soil in summer and winter in all plantations. The number of cultivable fungi and bacteria increased after leaf drop, especially so in the litter. Fungi were also more abundant in the E. grandis litter. In general, the A. mangium monoculture was associated with higher levels of litter lignin and N, especially after leaf drop. In contrast, the polyphenol and C levels in E. grandis monoculture litter were higher after leaf drop. These properties were negatively correlated with total soil C and N. Litter in the mixed stands had lower C:N and C:P ratios and higher N, P, and C levels in the microbial biomass. This suggests more effective nutrient cycling in mixed plantations in the long term, greater stimulation of microbial activity in litter and soil, and a more sustainable system in general.Index terms: microorganism, litterfall, bioindicators, forestry, legumes, basal respiration. Daniel Bini et al. RESUMO: BIOMASSA E ATIVIDADE MICROBIANA DA SERAPILHEIRA DURANTE O DESENVOLVIMENTO INICIAL DE PLANTIOS PUROS E MISTOS DE Eucalyptus grandis E Acacia mangium A serapilheira é, muitas vezes, um compartimento negligenciado para avaliação e melhor entendimento do comportamento da atividade e biomassa microbiana em plantios florestais. Quase sempre, em estudos dessa natureza, os autores tentam encontrar explicações para o padrão de desenvolvimento de plantas e microrganismos, por meio da avaliação dos nutrientes minerais no solo. Entretanto, considerando-se a dinâmica de disponibilização desses nutrientes, a hipótese é que provavelmente ocorra maior relação entre o crescimento de plantas florestais e da atividade microbiana com os nutrientes presentes na serapilheira. Este estudo teve como ob...

Influência da profundidade do solo e do manejo de Eucalyptus grandis e Acacia mangium na estrutura das comunidades microbianas do solo

“…Keywords: Microbial ecology; Consortium; DGGE; qPCR; Legumes (GONÇALVES et al, 2004;LACLAU et al, 2005;LI, 2010;BINI et al, 2013a). Desta forma, para manter constantes os índices de produção, é necessário fornecer ao solo grande quantidade de fertilizantes minerais, principalmente N e P, os quais são considerados insumos bastante onerosos para a silvicultura brasileira e que podem contribuir para a poluição ambiental.…”

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

“…Accrual in nutrients as soil N, P and C in A. mangium monocultures or in A. mangium mixed with non-Nfixing species is due to more effective and higher nutrient cycling and availability (Santos et al 2017a) and greater stimulation of microbial activity and dynamics in the litter (Bini et al 2012;Pereira et al 2018, Table 2). Distinct microbial communities have been reported in mixed A. mangium/E.…”

“…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).…”

Influência do sistema de plantio sobre atributos dendrométricos e fauna edáfica, em área degradada pela extração de argila

“…No entanto, informações sobre o efeito de plantios consorciados de eucalipto e leguminosas sobre a dinâmica de organismos do solo ainda são escassas (Batista et al, 2008;Silva et al, 2012;Bini et al, 2013), principalmente no que se refere à fauna edáfica.…”

“…Além de influenciar as propriedades do solo, os sistemas de plantio consorciados podem interferir no desenvolvimento das espécies arbóreas (Balieiro et al, 2002;Bauhus et al, 2004;Forrester et al, 2004Forrester et al, , 2005Forrester et al, , 2010Laclau et al, 2008;Silva et al, 2012;Bini et al, 2013). Diversos estudos têm evidenciado que as interações (competição, redução competitiva e facilitação) (Forrester et al, 2005(Forrester et al, , 2006b) existentes entre as espécies nesse tipo de plantio permitem que essas apresentem resultados positivos ou negativos em seu desenvolvimento.…”