In evaluating the consequences of management options for ecosystem services, it is impossible to consider all possible combinations of potentially interacting factors, such as soil type, vegetation type, and climate. Therefore specific examples were chosen, which we believe may be adopted for any type of ecosystem at any place on earth. Tabulating our information (see Tables 2.2-2.4) gives us the opportunity to quickly assess where specific soil organisms contribute positively, neutrally, or negatively (relative to abiotic factors) to the sustainable delivery of specific ecosystem goods or services.
In the specific sections for grassland, forest and arable land, we discuss trade-offs for management versus no (or extensive) management. In the case of arable land, we compare tilled land with non-tilled land. There is little consistency across studies with regard to the role of species diversity within functional groups of soil organisms on ecosystem processes (Mikola et al. 2002). However, our method of representation enables us to draw some general conclusions about the importance of functional diversity of soil organisms for the sustainable delivery of ecosystem goods and services in the three major types of ecosystems considered.
Temperate systems were selected because they are the best characterized. We appreciate that the assessment is imperfect, as perceptions of the services provided by each system in a locale differ and we therefore cannot list and evaluate precisely the same services in each ecosystem. We have compared the extremes of unmanaged and managed systems to highlight the service trade-offs, which are implicitly brought about by management. In reality, there is usually a gradient of possible interventions.
The relative importance of ecosystem goods and services ranking from -3 (strongly negative) to +3 (strongly positive) under both unmanaged (pristine, semi-natural, or zero-input) and managed (with significant human inputs and/or anthropogenic disturbance) states are presented. We compare three specimen temperate ecosystems: grassland, forest, and arable land. Under each category we have distinguished between biotic (mediated by living organisms) and abiotic (mediated by chemical, physical, and geologically historical factors, over which living organisms have, essentially, no overwhelming control on the short- and medium-term) processes. This is done by allocating each an asterisk rating from * (weak) to *** (strong) relative importance in determining the impact of the biotic and abiotic process on the specific ecosystem good or service identified. Habitat support functions, such as decomposition, bioturbation, and so on, are included in the allocation of drivers to biotic and abiotic categories. This level of resolution indicates those systems in which the manipulation of soil biodiversity (within or between groups of soil organisms that perform specific functions) could be effective in reinforcing a particular service, and where the services appear most vulnerable to changes in the biological soil community (see Wardle et al., Chapter 5, where some processes have been valued slightly different owing to the comparison between non-perturbed and perturbed systems).
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