Identifying soil health baselines in the Anthropocene

Abstract:

Soil health defines the continued capacity of soils to sustain diverse biological, chemical, and physical functions; soil health indicators are intended to weight and combine these functions quantitatively. Because soil health addresses disparate soil functions, its exact meaning is dependent on both geographic context and on management objectives. This flexibility is a strength of the soil health concept, but also makes intercomparison of soil health indicators across space and time complicated. To evaluate changes in soil health, measured soil properties and processes might in principle be evaluated against four different baselines: (1) natural or unmanaged conditions, to the extent that these are identifiable; (2) recent conditions under the current management regime; (3) contemporary conditions under alternative management regimes; (4) potential conditions simulated by process-based models. All four of these baseline states are useful, but they yield different interpretations of soil health. Baseline definitions (1) and (2) are important because they identify changes in soil properties and processes over time, while baseline definition (3) is useful because it emphasizes alternative management scenarios as they are actually implemented. Case (4)–predictive models of soil health—is underexplored, in part because existing process-based biogeochemical models are optimized to represent specific aspects of soil health (e.g. C and N cycling) but none are designed to represent soil health in its entirety. While soil health remains dependent on both geographic context and on management objectives, identifying the relevant baseline definition(s) applied when evaluating soil health will facilitate intercomparison across geographic contexts.