The contribution of soil organisms to ecosystem goods and services is determined by a suite of hierarchically organized abiotic factors, and by the nature of the plant community (Lavelle et al. 1993; Figure 2.1). At the highest level of the hierarchy, climate determines soil processes at regional and global scales (Gonzalez & Seastedt 2001). Climatic limitations, such as drought or low temperatures, directly determine the rates of the main physical, chemical, and microbiological reactions (Lavelle et al. 1997). At the second level in the hierarchy, the landscape and the original nature of parent material largely influence soil ecosystem goods and services. Nutrient heterogeneity of the substrate, along with the amount and quality of clay minerals, are the most important characteristics.
The third level in the hierarchy is the quality and quantity of the organic matter produced, and this depends on the nature and composition of plant communities. The release of energy and nutrients stored in dead organic matter depends strongly on the proportion of support tissues rich in lignin and lignocellulose; the proportion of sec ondary chemical compounds, such as tannins or polyphenols; and the ratio of nutrients to carbon (Grime 1979; Swift et al. 1979). Production of secondary products potentially affecting the decomposability of the organic matter may be enhanced by nutrient deficiencies and/or attack by herbivores (Waterman 1983; Baas 1989). The chemical composition of plants is, therefore, an important determinant of the composition and activity of the soil organism community. At the lowest hierarchical level, the soil organisms themselves operate within functional domains. A functional domain comprises a subset of the soil community that has similar functions or effects on, for example, soil structure (Lavelle 2002). The influence of each factor affecting soil ecosystems varies over temporal scales, from millimeters to kilometers.
Information on the sustainable delivery of goods and services originating from one region may not be directly applicable to another region; information on intensively managed soils, where functional domains differ considerably from those under extensive management, should not be generalized a priori. Therefore, our comparison of ecosystem management strategies for sustainable delivery of ecosystem goods and services as provided by soils should be regarded as a template, rather than as results that apply to the whole globe.
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