Imbalanced forest ecosystems: assessments and consequences

Few ecosystems can maintain an ideal balance of available resources for primaryproducers, decomposing organisms, and consumers. When nutrition is optimal for plants,their tissue may be toxic for many consumers and their detritus nutritionally imbalancedfor decomposers. Even conditions favoring high rates of primary production soon leadto limitation in light and possibly other resources. Because of the integrated nature ofecosystems, stress induced in one part permeates the entire system. With chronic stressinduced by climatic change or air pollution, we might expect reductions in canopy leafarea, decomposition rates, and root mineral uptake, and increases in herbivory,pathological activity, and leaching of material into or through the rooting zone. Each ofthe six responses can be simply assessed. As a general index of stress to forest ecosystems,we may monitor changes in the ability of foliage to produce wood. Below a particularlevel of production, trees become susceptible to a variety of insects and diseases. Throughan experimental approach, we can identify the relative importance of constraining factorsand predict the consequences of management options.