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 28ºC in the laboratory during four months. Leaf litter of either Hevea pauciflora (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 significantly 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 significantly 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.
Highlights
Terrestrial model ecosystems (TME) are used to study processes in the soil by selectively maintaining part of the natural spatial, temporal and genetic heterogeneity (Edwards & Bohlen, 1996), while controlling selected variables and observing the input and output of the system
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
Each TME test unit consisted of an intact soil core encased by a high-density polyethylene tube and placed on a Büchner funnel with a thin layer of inert gauze to fit between the drilled holes of the funnel and the bottom of the soil core (Knacker et al, 2004)
Summary
Terrestrial model ecosystems (TME) are used to study processes in the soil by selectively maintaining part of the natural spatial, temporal and genetic heterogeneity (Edwards & Bohlen, 1996), while controlling selected variables and observing the input and output of the system. The intact-soil-core approach has been successfully used in an wide experiment to assess its applicability to test potentially harmful substances at the ecosystem level (Förster et al, 2004; Knacker et al, 2004; Römbke et al, 2005b). The restoration of abandoned plantations in Central Amazonia is a main goal to achieve sustainable land use and to prevent the ongoing transformation of native forest into arable land The soils of these abandoned plantations are characterized by severe nutrient limitations, especially with regard to phosphorus (Lehmann et al, 2001). To improve soil properties, such as organic matter content, and to increase soil fertility, plant litter management strategies that focus on litter quality and soil fauna abundance have been proposed (Martius et al, 2001) Such ecological (non-technological) approaches contradict the increasing use of mineral fertilizers and plant protection products, which may negatively affect soil organisms and litter decomposition. The environmental risk assessment schemes applied in the registration of pesticides are usually based on temperate conditions and do not take into consideration the different physical-chemical (e.g. high temperature, low pH) and biological (soil organism species) conditions in the tropics (Römbke et al, 2005a)
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