The major lesson to be learned for soil ecologists is one of paying attention to details yet considering them in a holistic perspective. Certainly we are past the time when measurement of the "soil biomass" (referring to the microbial biomass) alone, by whatever method, is considered adequate (Coleman, 1994a). Small groups of organisms, perhaps highly aggregated within the ecosystem, may be facilitating (or retarding) turnover of other organisms, or of major nutrients such as nitrogen, phosphorus, and sulfur. In fact, as Darwin observed more than a century ago, these seemingly small biological processes operating over long time periods and large spatial scales can make profound changes in the world around us, including the formation of soil.

Decomposition rates, along with nutrient dynamics, soil respiration, and formation of soil structure, are integrating variables. They are generalized measurements of the functional properties of ecosystems, and they summarize the combined actions of soil microflora, fauna, abiotic variables, and resource quality factors. Litter breakdown rates can be compared using simple first-order models, so that rate variations between ecosystems or between different substrates may be compared. Litter breakdown rates are easily measured using bagged leaf litter ("litterbags"). Decomposition per se is due to microbial activities, but experiments show that fauna have a strong influence on litter breakdown rates, especially for more resistant substrates. The interaction between microflora and fauna is especially important for nutrient cycling mechanisms. Organic matter dynamics are strongly influenced by soil fauna. Termites and earthworms are well known for their influences on nutrient dynamics, soil organic matter, and soil structure. But the entire soil fauna is involved in these processes and, through their interactions with soil microbes, must be considered in a holistic perspective.

Was this article helpful?

0 0

Post a comment