Indicators of change in the organic matter in arid soils.

Soil organic matter is a key component in ecosystems, as it is the essential part of a set of relevant processes and constitutes an important carbon pool contributing to Global Change. The design of environmental monitoring programmes should include indicators of the current status of ecosystems, alerting to incipient changes in them. In this context, a sampling scheme has been designed taking into account the main processes and soil uses affecting the dynamics of soil organic matter.