The analysis of communities of saprophytic microfungi with special reference to soil fungi

Abstract

The distinction between microfungi and macrofungi reflects ecological differences. Microfungi are usually cosmopolitan and have an enormous potential for dispersal. An efficient enzyme equipment and competitive saprophytic ability characterize the saprophytic mode of life. The present review is mainly concerned with saprophytic soil fungi.

The techniques used for soil-fungal analyses are briefly reviewed. The choice depends on the purposes of the study, such as the microbiological characterization of vegetation and soil types, studies of decomposition processes, etc. This paper is mainly confined to synecological studies of the fungal community; methods of soil sampling, direct observation and isolation techniques are assessed. Parameters for quantification and statistical analysis are subsequently reviewed.

The soil mycoflora comprises species of all major categories of fungi. Besides a nutritional grouping of the individual components, the potential of obligocarbotrophic growth deserves much attention. Specialist groups of thermophilic, heat-resistant, osmophilic, xerophilic and nematophagous fungi are considered. The possibility of chemical elimination of certain functional groups opens an important tool in ecological studies. In a discussion of growth patterns and strategies, r-strategists with short-lived mycelia and abundant sporulation and K-strategists with a slower growing, more persistent mycelium are confronted. Grimes’ concept that stress, disturbance and competition also determine the strategies has some impact on soil fungal ecology.

Fungal successions are partly determined by individual capacities to decompose resistant plant cell wall substances, but also by different speed of fructification. A view that K-strategists appear mainly after r-strategists must be considered with caution.

Besides soil fungi, the components of the leaf-surface microflora and the microfloras developing in various kinds of litter are mentioned. Factors that affect fungal colonization patterns include soil depth, microhabitats determined by roots and the rhizosphere, moisture and soil atmosphere, temperature, crop plants, seasonal effects, and anthropogenic disturbance and stress. The latter comprise i.a. acidification and ploughing of agricultural soils. Effects of the soil fauna on fungal colonization are increasingly appreciated. Antagonistic effects of other micro-organisms are recognized in many autecological studies.

The question whether there are associations of microfungi in soils comparable to those of plants is critically considered. The quantitatively dominant species have high communality values in the comparison of different biotopes, the infrequent ones show a large amount of unique variation. Few species are known to have an indicator role for particular ecological factors. Only in rare cases mycologists advance beyond the compiling of species lists in the study of successions.