Tropical terrestrial model ecosystems for evaluation of soil fauna and leaf litter quality effects on litter consumption, soil microbial biomass and plant growth

Abstract

-The aim of this work was to evaluate whether terrestrial model ecosystems (TMEs) are a useful tool for the study of the effects of litter quality, soil invertebrates and mineral fertilizer on litter decomposition and plant growth under controlled conditions in the tropics. Forty-eight intact soil cores (17.5-cm diameter, 30-cm length) were taken out from an abandoned rubber plantation on Ferralsol soil (Latossolo Amarelo) in Central Amazonia, Brazil, and kept at 28°C in the laboratory during four months. Leaf litter of either Hevea paucifl ora (rubber tree), Flemingia macrophylla (a shrubby legume) or Brachiaria decumbens (a pasture grass) was put on top of each TME. Five specimens of either Pontoscolex corethrurus or Eisenia fetida (earthworms), Porcellionides pruinosus or Circoniscus ornatus (woodlice), and Trigoniulus corallinus (millipedes) were then added to the TMEs. Leaf litter type signifi cantly affected litter consumption, soil microbial biomass and nitrate concentration in the leachate of all TMEs, but had no measurable effect on the shoot biomass of rice seedlings planted in top soil taken from the TMEs. Feeding rates measured with bait lamina were signifi cantly higher in TMEs with the earthworm P. corethrurus and the woodlouse C. ornatus. TMEs are an appropriate tool to assess trophic interactions in tropical soil ecossistems under controlled laboratory conditions. Index terms: Brachiaria decumbens, Flemingia macrophylla, Hevea paucifl ora, diplopods, earthworms, isopods. Efeitos de fauna de solo e qualidade de liteira sobre o consumo, biomassa microbiana e crescimento de plantas em modelo de ecossistemas terrestres tropicaisResumo -O objetivo deste trabalho foi avaliar o modelo de ecossistema terrestre (TME) como ferramenta para o estudo dos efeitos da qualidade da liteira, de invertebrados do solo e da fertilização mineral na decomposição da liteira e no crescimento das plantas em condições controladas. Foram coletados quarenta e oito cilindros de solo intacto (Latossolo Amarelo) de17,5 cm de diâmetro e 30 cm de comprimento em um seringal abandonado na Amazônia Central brasileira e mantidos a 28°C em laboratório, por quatro meses. Folhas da liteira de Hevea paucifl ora (seringueira), ou de Flemingia macrophylla (leguminosa arbustiva) ou de Brachiaria decumbens (gramínea) foram colocadas na superfície do solo em cada TME. Em seguida, foram adicionados aos TMEs, cinco espécies de minhocas: Pontoscolex corethrurus ou Eisenia fetida; isópodes: Porcellionides pruinosus ou Circoniscus ornatus, e o diplópode Trigoniulus corallinus. O tipo de liteira afetou de forma signifi cativa o consumo, a biomassa microbiana e a concentração de nitrato no líquido percolado de todos os TMEs, mas não apresentou efeito mensurável sobre a biomassa da parte aérea de mudas de arroz, plantadas em solo retirado da superfície dos TMEs. As taxas de alimentação da fauna edáfi ca, medidas por meio de lâminas-isca, foram signifi tivamente mais altas nos TMEs com a minhoca P. corethrurus e com o isópode C. ornatus. O mé...

Avaliação agronômica da rebrota, dinâmica de decomposição e liberação de nutrientes de flemingia (Flemingia macrophylla (Willd.) Kuntze ex Merr.)

“…Ao final deste estudo, portanto, aos 150 dias, folhas apresentavam 36% de nitrogênio remanescente; caules, Tabela 3. Concentração inicial de nutrientes na folha, caule e caule + folha da parte aérea de flemingia inserida nas bolsas "litter bags" Förster et al, (2009) encontraram aumento na biomassa microbiana e nos teores de nitrato, em solos com biomassa de flemingia.…”

Environmental risk assessment of pesticides in tropical terrestrial ecosystems: Test procedures, current status and future perspectives

“…Regarding semi-field studies, Förster et al (2006Förster et al ( , 2009 reported that they conducted the first terrestrial model ecosystem (TME) studies ever under tropical conditions. From a technical point of view, the TME test method could be applied without problems and without any relevant methodological modifications from the method developed under temperate conditions (Förster et al, 2006).…”

“…While in temperate ecosystems earthworms are often the most important organisms governing OM breakdown, in the tropics not only earthworms but also microarthropods such as millipedes and woodlice seem to be the main driving force for the decomposition process (Förster et al, 2009 and references therein; Geissen and Guzman, 2006). Wiktelius et al (1999) also indicated that other groups of organisms are involved in various processes in tropical countries than those known from the temperate region, e.g.…”

A simple experimental set‐up to disentangle the effects of altered temperature and moisture regimes on soil organisms

“…; Foerster et al . ). For these TMEs, intact soil cores including living vegetation are excavated from the field, placed in mesocosms and incubated in the field or laboratory.…”

“…As an alternative to using climate-controlled artificial systems that contain a standardized soil and/or a specific (group of) model soil organisms, the use of terrestrial model ecosystems (TME) has been proposed (Morgan & Knacker 1994;Knacker et al 2004;Foerster et al 2009). For these TMEs, intact soil cores including living vegetation are excavated from the field, placed in mesocosms and incubated in the field or laboratory.…”