ABSTRACT
The near-surface region of Earth, extending from plant canopies through the soil matrix to underlying bedrock, has been referred to as the “critical zone” (NRC 2001; Brantley et al. 2007). It is a focal point of human activities in terms of both its support of life processes and its response to impacts of land and water management. The quality of human life and the global environment are highly dependent on processes in soils; rapidly expanding systems of food, fi ber, water, and energy production and waste disposal are now based on the management of Earth’s near-surface. The emerging paradigm is that of the critical zone as the controlling medium for surface and subsurface water dynamics; transformation, storage, and release of bioactive elements; maintenance of biological productivity and diversity; and regulation of gas fl uxes between the biosphere and atmosphere (Brantley et al. 2007).
