Protozoan Community Structure in a Fractal Soil Environment

• Published in: Protist 2001-09, Vol.152 (3), p.203-218
• Main Authors: Finlay, Bland J., Fenchel, T.o.m.
• Format: Article
• Language: English
• Subjects: Animals; Environment; Eukaryota - classification; Eukaryota - isolation & purification; Population Density; Soil - parasitology
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1078/1434-4610-00060

Protozoan abundance was quantified, and 365 protozoan species were recorded, in 150 soil samples from an upland grassland in Scotland. Across the entire size range (2—200 m) protozoan species richness varied by a factor of two, whereas abundance increased by a factor of 20 with decreasing body size. As the soil had fractal structure, the relatively flat species curve can be explained if spatial heterogeneity determines species number — for in a fractal environment, heterogeneity will be the same at all spatial scales. Community structure appeared to approach a temporary steady-state about six days after re-hydration of dried soil. A simple model based on combining the fractal character of increasing habitat area at smaller spatial scales, with the weight-specific energy requirements of protozoa, provided theoretical curves of abundance and biovolume on body size which provide a reasonable fit to real data. We suggest two possibilities — that the apparent competence of the theoretical model is fortuitous and the product of poorly understood dynamic elements of the trophic structure in the community; or that key elements of protozoan community structure in a fractal soil environment may be largely explained in terms of habitat space and energy requirements.