How does litter quality and site heterogeneity interact on decomposer food webs of a semi-natural forest?

• Published in: Soil biology & biochemistry Vol. 37; no. 2; pp. 203 - 213
• Main Authors: Bjørnlund, Lisa, Christensen, Søren
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2005; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; biodegradation; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; deciduous forests; Decomposers; Fagus sylvatica; food webs; forest litter; forest soils; Fraxinus excelsior; functional diversity; Fundamental and applied biological sciences. Psychology; Litter quality; Natural forest; Nematoda; Nematodes; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plectus; population density; Rhabditidae; Site heterogeneity; soil microorganisms; soil nematodes; soil quality; soil respiration; Soil science; Denmark; Nematodes; Decomposers; Natural forest; Site heterogeneity; Litter quality; Forests; Litter; Decomposer; Trophic chain; Heterogeneity; Food web; Helmintha; Nemathelminthia; Soil science; Invertebrata; Nematoda
• DOI: 10.1016/j.soilbio.2004.07.030
• ISSN: 0038-0717

The relative importance of litter quality and site heterogeneity on population dynamics of decomposer food webs was investigated in a semi-natural mixed deciduous forest in Denmark. Litterbags containing beech or ash leaves were placed in four plots. Plots were located within gaps and under closed canopies at two topographically different sites, above and below a slope, respectively, to cover variable environmental conditions. Litter was collected after 2, 4 and 9 months of decomposition. Extensive decay prevented analysis of ash after 9 months. Density of bacteria (CFU), active fungal mycelium (FDA), protozoa (MPN) and nematodes were 4–15-fold higher in ash leaves than in beech leaves in accordance with the higher resource quality of ash. Similar effects of site on density of decomposers were evident in both litter types: with some exceptions, decomposers were higher at the low site and stimulated in gaps. Taxonomic diversity of nematodes increased during decomposition and functional diversity of nematodes followed a pattern often encountered, i.e. opportunistic bacterial-feeders were gradually replaced by fungal-feeders and slower growing bacterial-feeders while predators and omnivors peaked at the end of the study period. At the first sampling, where bacterial activity prevailed, the relative abundance of the two dominant bacterial-feeders, Rhabditidae (fast growing) and Plectus spp. (slower growing), depended more on site than litter type. At the second sampling where fungal activity became more important, the proportions of bacterial and fungal-feeding nematodes also depended more on site than on litter type. At the third sampling individual nematode taxa responded differently to site. In summary, we conclude that although litter quality had a major influence on the density of organisms in the decomposer food web, site effects were also detected and nematode functional groups responded more to site than to litter quality early on in the decomposition process.