Soil organic matter has long been recognized as one of the most important components in maintaining soil fertility, soil quality, and agricultural sustainability. The soil zone strongly influenced by plant roots, the rhizosphere, plays an important role in regulating soil organic matter decomposition and nutrient cycling. Processes that are largely controlled or directly influenced by roots are often referred to as rhizosphere processes. These processes may include exudation of soluble compounds, water uptake, nutrient mobilization by roots and microorganisms, rhizosphere-mediated soil organic matter decomposition, and the subsequent release of CO2 through respiration. Rhizosphere processes are major gateways for nutrients and water. At the global scale, rhizosphere processes utilize approximately 50% of the energy fixed by photosynthesis in terrestrial ecosystems, contribute roughly 50% of the total CO2 emitted from terrestrial ecosystems, and mediate virtually all aspects of nutrient cycling. Therefore, plant roots and their rhizosphere interactions are at the center of many ecosystem processes. However, the linkage between rhizosphere processes and soil organic matter decomposition is not well understood. Because of the lack of appropriate methods, rates of soil organic matter decomposition are commonly assessed by incubating soil samples in the absence of vegetation and live roots with an implicit assumption that rhizosphere processes have little impact on the results. Our recent studies have overwhelmingly proved that this implicit assumption is often invalid, because the rate of soil organic matter decomposition can be accelerated by as much as 380% or inhibited by as much as 50% by the presence of live roots. The rhizosphere effect on soil organic matter decomposition is often large in magnitude and significant in mediating plant-soil interactions.