ABSTRACT
The often-cited positive relationship between soil organic carbon (SOC) content and soil quality is based on contributions which SOC makes as a constituent of soil organic matter (SOM) to critical soil properties, processes and functions. The chapter aims to explore the relationships between SOM and soil quality by defining the basic contributions of SOM to soil functions as related to soil quality. It highlights the role of SOM composition and spatial distribution in determining the effect of SOM on soil quality. SOM exhibits strong spatial dependence in both agricultural and rangeland systems at scales ranging from the microaggregate. SOM affects soil functions by causing or mediating changes in soil properties and processes which are related to soil physical integrity, soil fertility and productivity, and environmental quality. SOM contributes to, and is affected by, biological productivity in natural and managed ecosystems.
