Worldwide Relevance

Concerns about the influence of Ca depletion on forest health exist for industrialized regions around the world including Europe, Eastern North America, and increasingly China (Driscoll and others 2001, Duan and others 2000, Kirchner and Lydersen 1995, Likens and others 1996, Schulze 1989, Tao and Feng 2000). Growing experimental evidence and examples from the field indicate that the threat posed to forest ecosystems from anthropogenic Ca depletion is real and potentially widespread. Knowledge of the influence of pollution loading on the cation pools that sustain forest health and productivity provides further scientific grounding and impetus for policy makers to modify existing pollution control measures. In addition, an increased recognition of the potential consequences of Ca depletion has functional relevance to managers in the field. Especially in regions with low inherent soil fertility or high precipitation leaching, or both, management options that either add Ca to systems or decrease its removal are increasingly being examined and employed. Indeed, in some tropical forests where native precipitation-based leaching has historically been high, and pollution-induced acidity is on the increase, sustainable forestry is not currently possible without the addition of Ca after logging (Nykvist 2000). The output of tested models that simulate the complexities of Ca cycling could greatly enhance the capabilities of policy makers and managers to integrate the influences of factors adding to or removing Ca from forest ecosystems. As such, these models could play a critical role in guiding adaptive policy and management decisions that prevent or mitigate pollution-induced damage to forest ecosystems.