Climate-Change Induced Organic and Inorganic Carbon Cycling in Soils: Processes and Reactions at Different Scales.

Climate change variables such as higher atmospheric CO₂ concentration (over 400 ppm), long periods of drought, very intensive rainfall and increasing air temperature (2-4°C or greater) are causing and will continue to cause short- and long-lasting, poorly understood changes in carbon and elemental cycling in soils. The soil responses to climate change would be complex because of the intricate network of simultaneous, coupled and/or sequential soil chemical, biological and hydrological reactions and processes. In addition, chemical elements, nutrients and contaminants involved in these reactions and processes (which are often time-dependent) are distributed in the soil’s three phases (i.e., solid, liquid and gas phases). This paper will look at chemical reactions occurring in soils at small scales (molecular, nano and micron scales) which may affect and/or control organic matter interaction with soil mineral; inorganic carbon cycling between atmosphere and soils and fluxes among different soil pools; climate change induced accelerated weathering of soil minerals and changes in soil chemical properties; and the source/sink behavior of soil in terms of carbon storage and elemental cycling. Data generated from small scale measurements can be used in modeling efforts to describe and predict climate change induced changes in physical, chemical and mineralogical properties of the soil. This paper will include a discussion about important and challenging aspects of climate effects on soils, report recent discoveries, identify key research needs, and highlight research opportunities offered by the changing climate.