Soil Microorganisms and Activities in Relation to Season, Soil Factors and Fire

Abstract

Microorganisms play major roles in cycling carbon, nitrogen and other elements in nature, in particular in the mineralization of organic compounds and transformations of inorganic nutrients (Alexander 1977). Fire can be expected to affect the nutrient status of the soil (Viro 1974; Christensen and Muller 1975; Dunn and DeBano 1977; DeBano and Conrad 1978; DeBano et al. 1979a,b; Wells et al. 1979; Gray and Schlesinger 1981; DeBano and Dunn 1982; Rundel 1983; Brown and Mitchell 1986; Mitchell and Brown 1986; Stock and Lewis 1986a; Mitchell 1987) and soil microbial populations (Ahlgren 1974; Christensen and Muller 1975; Dunn and DeBano 1977; Dunn et al. 1979, 1985; Wells et al. 1979; Warcup 1981; Arianoutsou-Faraggitaki and Margaris 1982). The nutrient budget of the Swartboskloof catchment in relation to fire (Chap. 13) does not indicate the roles of microorganisms nor the effects of fire on microbial determinants. Microorganisms through their mineralization activity might contribute to the seasonal increase in the outflow of nutrients in water from the catchment, while their nitrogen-fixing abilities might replenish losses of nitrogen.

Table 14.1 Physical and chemical properties of three soil forms in Swartboskloof. Data from Fry (1987) for soil to depth 250mm (Glenrosa, Clovelly forms) or 200 mm (Fernwood form)

catchment in relation to fire (Chap. 13) does not indicate the roles of microorganisms nor the effects of fire on microbial determinants. Micro-organisms through their mineralization activity might contribute to the seasonal increase in the outflow of nutrients in water from the catchment, while their nitrogen-fixing abilities might replenish losses of nitrogen.