Termites, ants and earthworms are considered as soil engineers because of their effects on soil properties and their influence on the availability of resources for other organisms, including microorganisms and plants. However, the links... more
Termites, ants and earthworms are considered as soil engineers because of their effects on soil properties and their influence on the availability of resources for other organisms, including microorganisms and plants. However, the links between their impacts on the soil environment and the resulting modification of natural selection pressures on engineer as well as on other organisms have received little attention. We suggest that the strategy evolved by species, or functional groups to control their environment can explain the difference between extended phenotype and accidental engineers. Extended phenotype engineers concentrate their activities on the building of biogenic structures in order to maintain optimal conditions for their growth. Conversely, accidental engineers expend energy in moving through the soil to be as close as possible to their optimal environment. We discuss in this paper why termites and ants are best viewed as extended phenotype engineers, and particularly how their impacts on ecosystem functioning can be considered as results of their requirements and how their activities could induce feedback loops affecting themselves. We also focus on the engineering activities of earthworms and discuss why some species can be considered as extended phenotype while others are more accidental engineers. Finally, we discuss links between the strategies developed by engineers and ecosystem functioning. Although both types of engineer create ''hot-spots'' in soil, we argue that extended phenotype engineers have a greater effect on the maintenance of ecosystem heterogeneity since they concentrate their activities at a few points, as compared to accidental engineers which may move through the soil and thus contribute to homogenisation of nutrient distribution throughout the whole ecosystem.
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Compost, vermicompost and biochar amendments are thought to improve soil quality and plant yield. However, little is known about their long-term impact on crop yield and the environment in tropical agro-ecosystems. In this study we... more
Compost, vermicompost and biochar amendments are thought to improve soil quality and plant yield. However, little is known about their long-term impact on crop yield and the environment in tropical agro-ecosystems. In this study we investigated the effect of organic amendments (buffalo manure, compost and vermicompost) and biochar (applied alone or with vermicompost) on plant yield, soil fertility, soil erosion and water dynamics in a degraded Acrisol in Vietnam. Maize growth and yield, as well as weed growth, were examined for three years in terrestrial mesocosms under natural rainfall. Maize yield and growth showed high inter-annual variability depending on the organic amendment. Vermicompost improved maize growth and yield but its effect was rather small and was only significant when water availability was limited (year 2). This suggests that vermicompost could be a promising substrate for improving the resistance of agrosystems to water stress. When the vermicompost-biochar mixt...
Research Interests: Soil, Biomass, Fertility, Agriculture, Vietnam, and 9 moreCharcoal, Animals, Plants, Oligochaeta, Zea mays, Ecosystem, Fertilizers, Manure, and Geological Processes
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While considered as sustainable and low-cost agricultural amendments, the impacts of organic fertilizers on downstream aquatic microbial communities remain poorly documented. We investigated the quantity and quality of the dissolved... more
While considered as sustainable and low-cost agricultural amendments, the impacts of organic fertilizers on downstream aquatic microbial communities remain poorly documented. We investigated the quantity and quality of the dissolved organic matter leaching from agricultural soil amended with compost, vermicompost or biochar and assessed their effects on lake microbial communities, in terms of viral and bacterial abundances, community structure and metabolic potential. The addition of compost and vermicompost significantly increased the amount of dissolved organic carbon in the leachate compared with soil alone. Leachates from these additions, either with or without biochar, were highly bioavailable to aquatic microbial communities, although reducing the metabolic potential of the community and harbouring more specific communities. Although not affecting bacterial richness or taxonomic distributions, the specific addition of biochar affected the original lake bacterial communities, r...