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Nutrient cycling

Soil structure

Microflora

Catabolize organic matter Mineralize and immobilize nutrients

Produce organic compounds that bind aggregates Hyphae entangle particles onto aggregates

Microfauna

Regulate bacterial and fungal populations Alter nutrient turnover

May affect aggregate structure through interactions with microflora

Mesofauna

Regulate fungal and micro-

faunal populations Alter nutrient turnover Fragment plant residues

Produce fecal pellets Create biopores Promote humification

Macrofauna

Fragment plant residues Stimulate microbial activity

Mix organic and mineral particles Redistribute organic matter and microorganisms Create biopores Promote humification Produce fecal pellets

From Hendrix et al., 1990.

From Hendrix et al., 1990.

large fauna capable of breaking through physical barriers of soil) (Heal and Dighton, 1985).

Further concerns about fauna as indicators of soil quality led Linden et al. (1994) to erect a hierarchical array of three categories in which fauna and soil quality interact, namely: (1) organisms and populations, relating to behavior, physiology, and numbers; (2) communities, with concerns about functional groups (i.e., guilds of burrowers and nonbur-rowers, trophic groups, and biodiversity); and (3) biological processes, relating to the several processes and properties listed in Table 4.13 (Linden et al., 1994). These processes are considered in greater detail in later chapters on decomposition and nutrient cycling processes.

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