Effects of soil decomposer invertebrates (protozoa and earthworms) on an above-ground phytophagous insect (cereal aphid) mediated through changes in the host plant

• Published in: Oikos Vol. 95; no. 3; pp. 441 - 450
• Main Authors: Bonkowski, Michael, Geoghegan, Irene E., Birch, A. Nicholas E., Griffiths, Bryan S.
• Format: Journal Article
• Language: English
• Published: Copenhagen Munksgaard International Publishers 01.12.2001; Munksgaard International Publishers, Ltd; Blackwell
• Subjects: Agricultural soils; AMOEBA; Animal and plant ecology; Animal, plant and microbial ecology; Aphididae; APORRECTODEA CALIGINOSA; AZOTE; Barley; Biological and medical sciences; BIOMASA; BIOMASS; BIOMASSE; CILIOPHORA; DEGRADACION; DEGRADATION; Earthworms; ECOSSE; ESCOCIA; Fundamental and applied biological sciences. Psychology; Hordeum; MASTIGOPHORA; NITROGEN; NITROGENO; OLIGOCHAETA; Plant roots; Plants; Protozoa; SCOTLAND; SITOBION AVENAE; SOIL; Soil biochemistry; Soil fauna; SOL; SUELO; Synecology; Terrestrial ecosystems; TRITICUM AESTIVUM; United Kingdom; Scotland; Great Britain; Europe; Monocotyledones; Growth; Insecta; Environmental factor; Oligochaeta; Cereal crop; Soil fauna; Plant; Pest; Phytophagous; Homoptera; Gramineae; Angiospermae; Aporrectodea caliginosa; Aphididae; Protozoa; Aphidoidea; Microcosm; Biogeochemical cycle; Experimental study; Annelida; Carbon nitrogen ratio; Animal plant relation; Arthropoda; Nutrient; Above ground plant part; Spermatophyta; Invertebrata; Soil plant relation; Sitobion avenae; Triticum aestivum; Interspecific relation
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1034/j.1600-0706.2001.950309.x

We investigated if the activity of soil invertebrates (protozoa and earthworms) affected the performance of barley and if effects propagated higher up the above-ground food chain into herbivores (cereal aphid, Sitobion avenae). Barley plants were grown individually in microcosms containing defaunated soil and grass residues. Plants were grown in soil containing: a) no added fauna, b) protozoa, c) earthworms, or d) protozoa and earthworms. After 7 weeks growth at 20°C three adult cereal aphids were added to each plant on separate leaves. The aphids were allowed to grow and reproduce for another 2 weeks before the experiment was destructively sampled. Amounts of mineral N in the soil and leached from the microcosms were significantly reduced by the presence of soil animals. Correspondingly plant biomass and total plant N content were increased significantly by soil animals, protozoa in particular. The different mechanisms responsible for changes in nutrient turnover in presence of protozoa and earthworms are discussed. Aphid performance was strongly influenced by the presence of protozoa, but not by earthworms. In the presence of protozoa the numbers and biomass of adult and juvenile aphids were significantly increased. These effects are likely due to an increased N content in barley plants and consequently increased nitrogen availability to aphids. The results underline that the detritivore and herbivore systems are intimately linked.