INDIRECT EFFECTS OF ROOT HERBIVORY BY INSECT LARVAE ON THE STRUCTURE OF THE SOIL FOOD WEB

Authors: TREONIS, AMY - DEPT BIOL, UNIV. RICHMOND; Zasada, Inga

Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2005
Publication Date: 9/1/2005
Citation: Treonis, A., Zasada, I.A. 2005. Indirect effects of root herbivory by insect larvae on the structure of the soil food web. Journal of Nematology 37: 400.

Interpretive Summary:

Technical Abstract: Below-ground insect herbivores have negative impacts on plant productivity, but less is understood about the indirect effects of these organisms on the detrital-based soil food web (e.g., the soil microbial biomass and microbial grazers). We used a corn (Zea mays) and corn rootworm (Diabrotica virgifera) model system to study the effects of increasing root herbivore density on soil food web structure. Pots (11-cm diameter) of soil were established in the greenhouse containing rootworm eggs (0, 100, 500, or 1000 eggs/pot) and a single corn plant. The experiment was destructively harvested 22 d after planting and soil microbial biomass and activity, protozoan density, and nematode abundance and community structure were analyzed. Plant root and shoot biomass declined with increasing rootworm density. Soil nematode abundance increased with rootworm abundance, averaging 8,098 kg-1 soil at the highest density of rootworms and 3,878 kg-1 in the control pots. Soil protozoa (ciliates, flagellates, naked amoebae) responded similarly, with 27,232 cells g-1 in pots with the highest density of rootworms and 3,990 cells g-1 in the control. Soil microbial biomass and respiration were unaffected by rootworm herbivory. Rootworm larvae convert living plant material into dead tissue and feces and likely enhance rhizodeposition. The response of microbial grazers in this study suggests that the soil food web is very sensitive to these inputs.