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Titre du document / Document title

Population- and ecosystem-level effects of predation on microbial-feeding nematodes

Auteur(s) / Author(s)

LAAKSO J. (1) ; SETÄLÄ H. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) University of Jyväskylä, Department of Biological and Environmental Science, PO Box 35, 40351, Jyväskylä, FINLANDE

Résumé / Abstract

We studied the role of nematode predation in the functioning of detrital food webs assembled in microcosms. The microcosms contained defaunated humus and litter materials, a diverse microbial community with bacteria, fungi and protozoa, and a birch (Betula pendula) seedling infected with mycorrhizal fungi. Different levels of top-down control upon microbivorous nematodes were set up by assembling food webs either without predators, or in combinations with a specialist and a non-specialist predatory mite (Mesostigmata). The nematode community was composed of either (1) three species of bacterivorous, or (2) three species of fungivorous nematodes or (3) both groups together. After two growing periods for the birch (38 weeks), the microcosms were destructively sampled for animal and microbial biomasses, concentration of mineral N in the soil, plant biomass and plant N concentration. The specialist predator reduced biomasses of both bacterial-and fungal-feeding nematodes by more than 50%, whereas the non-specialist predator weakly increased the biomass of fungivorous nematodes. Thus, under high predation pressure, the biomass of microbivores changed as predicted by trophic dynamic models assuming strong top-down control and uniformly behaving trophic levels. Despite this, microbial biomass was unaffected by the predators. However, microbial respiration increased slightly in the presence of predators. Assuming that microbial respiration correlates with microbial productivity, the increase in microbial respiration indicates a cascading productivity regulation. The composition of the microbivore community had only a minor effect on the outcome of the top-down control on microbes. The > 50% reduction in nematode biomass and respiration coincided with <16% increase in microbial respiration and did not affect microbial biomass. Presence of the specialist predator slightly reduced soil NH4+ concentration in communities with fungivore nematodes but plant growth and N uptake remained unchanged. Thus, the structure of the community only weakly controlled nutrient mineralisation.

Revue / Journal Title

Oecologia    ISSN  0029-8549   CODEN OECOBX 

Source / Source

1999, vol. 120, no2, pp. 279-286 (45 ref.)

Langue / Language

Anglais

Editeur / Publisher

Springer, Berlin, ALLEMAGNE  (1968) (Revue)

Mots-clés anglais / English Keywords

Food web

;

Bacterivorous

;

Mycophagous

;

Ecosystem

;

Predation

;

Microbial community

;

Biogeochemical cycle

;

Nutrient

;

Trophic relation

;

Bacteria

;

Forest soil

;

Microcosm

;

Nematoda

;

Fungi

;

Protozoa

;

Nemathelminthia

;

Helmintha

;

Invertebrata

;

Thallophyta

;

Mots-clés français / French Keywords

Réseau trophique

;

Bactérivore

;

Mycophage

;

Ecosystème

;

Prédation

;

Communauté microbienne

;

Cycle biogéochimique

;

Nutriment

;

Relation trophique

;

Bactérie

;

Sol forestier

;

Microcosme

;

Nematoda

;

Fungi

;

Protozoa

;

Nemathelminthia

;

Helmintha

;

Invertebrata

;

Thallophyta

;

Mots-clés espagnols / Spanish Keywords

Red trófica

;

Bacterívoro

;

Micófago

;

Ecosistema

;

Rapiña

;

Comunidad microbiana

;

Ciclo biogeoquímico

;

Nutriente

;

Relación trófica

;

Bacteria

;

Suelo forestal

;

Microcosmos

;

Nematoda

;

Fungi

;

Protozoa

;

Nemathelminthia

;

Helmintha

;

Invertebrata

;

Thallophyta

;

Localisation / Location

INIST-CNRS, Cote INIST : 3568 B, 35400008617210.0140

Nº notice refdoc (ud4) : 1209140



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