Seasonal population changes of myxomycetes and associated organisms in five non-woodland soils, and correlations between their numbers and soil characteristics

Abstract

Microbial populations and other characteristics of five non-woodland soils from sites in the West of England were studied quantitatively over the course of a year, and special attention was paid to the changing abundance of myxomycetes. The latter, expressed as numbers of plasmodium-forming units (PFUs), were on average more abundant than in three representative woodland soils. During the year, instances were recorded in which rapidly increasing populations of bacteria were accompanied by increasing numbers of phagotrophic microorganisms, including myxomycetes, and others in which rapidly increasingly populations of phagotrophs were accompanied by falls in the numbers of bacteria. Oscillating predator-prey relationships were suggested. Myxomycetes were generally a significant component of the phagotrophic populations, even exceeding 50% of the total soil naked amoebae. Data on the biological and abiotic characteristics of woodland [3] and non-woodland soils were combined and statistically analysed for correlations. Myxomycete abundance was positively correlated with numbers of soil amoebae, ciliates, total bacteria, myxobacteria and nematodes, but inversely correlated with numbers of dictyostelid cellular slime moulds. It was positively correlated with soil pH and level of potassium, and negatively correlated with moisture content, organic matter content, and nitrogen/phosphorus ratio. Calculations suggest that the biomass of myxomycetes in temperate soils is commonly 6.4–64 mg dry weight · m −2.