Effects of resource availability and quality on the structure of the micro-food web of an arable soil across depth

• Published in: Soil biology & biochemistry 2012-07, Vol.50, p.1-11
• Main Authors: Scharroba, Anika, Dibbern, Dörte, Hünninghaus, Maike, Kramer, Susanne, Moll, Julia, Butenschoen, Olaf, Bonkowski, Michael, Buscot, Francois, Kandeler, Ellen, Koller, Robert, Krüger, Dirk, Lueders, Tillmann, Scheu, Stefan, Ruess, Liliane
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amoeba; arable soils; bacteria; Biochemistry and biology; Biological and medical sciences; carbon; Chemical, physicochemical, biochemical and biological properties; community structure; corn; Depth transect; field crops; Fundamental and applied biological sciences. Psychology; fungi; Litter; microbial biomass; Microorganisms; Nematoda; Nematodes; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant residues; plows; Protozoa; roots; soil depth; soil food webs; soil profiles; Soil science; species diversity; summer; Triticum aestivum; Trophic interactions; vegetation; wheat; Zea mays
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2012.03.002

Soil food webs are important determinants for the carbon flow through terrestrial systems, with the trophic networks between microbes and microfaunal grazers forming the basis for processing plant resources. At an agricultural field site cropped with maize or wheat, plant carbon input to soil was experimentally manipulated by amendment with maize litter. The community structure of dominant micro-food web components, the bacteria, fungi, protozoa and nematodes, was investigated across a depth gradient comprising plough layer, rooted soil below plough horizon, and deeper root free soil. The community composition and diversity within micro-food webs, and the response to resource supply, were assessed in summer, the vegetation period with highest root exudation. In the plough layer amendment with plant residues increased microbial biomass as well as density of fan shaped amoeba morphotypes and of bacterial- and fungal-feeding nematodes. Diversity of food web assemblages was assessed by operational taxonomic units (OTU) for bacteria and fungi, protozoa morphotypes and nematode families. Changes in diversity were either not apparent (fungi, protozoa), negatively related to litter (bacteria) or positively linked to the presence of a specific crop plant (bacteria, nematodes). Based on nematode functional guilds and the related enrichment and structure index, general food web conditions were assigned as nutrient enriched, with a high degree of disturbance, and a dominance of the bacterial energy channel. In sum, litter amendment fostered the abundance but not the diversity of organisms as food webs remained bottom heavy with only small amounts of carbon conserved at higher trophic levels. Food web structure was more affected by the abiotic (soil profile) and biotic (crop plant) environment than by the supply with litter resources. ► Litter amendment trigged bottom-up effects in nematode guilds that feed on microbes. ► Enhanced resource supply did not sustain large biomass at higher trophic levels. ► Dominant groups of the food web, even with similar function, exploit different niches. ► Abiotic and biotic environment shaped food web structure more than resource amendment.