Mechanisms controlling soil carbon turnover and their potential application for enhancing carbon sequestration

Abstract

In addition to increasing plant C inputs, strategies for enhancing soil C sequestration include reducing C turnover and increasing its residence time in soils. Two major mechanisms, (bio)chemical alteration and physicochemical protection, stabilize soil organic C (SOC) and thereby control its turnover. With (bio)chemical alteration, SOC is transformed by biotic and abiotic processes to chemical forms that are more resistant to decomposition and, in some cases, more easily retained by sorption to soil solids. With physicochemical protection, biochemical attack of SOC is inhibited by organomineral interactions at molecular to millimeter scales. Stabilization of otherwise decomposable SOC can occur via sorption to mineral and organic soil surfaces, occlusion within aggregates, and deposition in pores or other locations inaccessible to decomposers and extracellular enzymes. Soil structure is a master integrating variable that both controls and indicates the SOC stabilization status of a soil. One potential option for reducing SOC turnover and enhancing sequestration, is to modify the soil physicochemical environment to favor the activities of fungi. Specific practices that could accomplish this include manipulating the quality of plant C inputs, planting perennial species, minimizing tillage and other disturbances, maintaining a near-neutral soil pH and adequate amounts of exchangeable base cations (particularly calcium), ensuring adequate drainage, and minimizing erosion. In some soils, amendment with micro-and mesoporous sorbents that have a high specific surface -such as fly ash or charcoal -can be beneficial.

Plant diversity increases soil microbial activity and soil carbon storage

“…In general, the amount of carbon stored in soil represents the balance between plant shoot and root litter production, root exudates and their microbial decomposition 16 . The observed increase in carbon storage with plant diversity 17 therefore either reflects higher primary production 18,19 or longer persistence of plant-derived organic materials due to slower decomposition 10,16 .…”

“…The observed increase in carbon storage with plant diversity 17 therefore either reflects higher primary production 18,19 or longer persistence of plant-derived organic materials due to slower decomposition 10,16 . Increased plant residue inputs also provide more substrate for soil microorganisms, resulting in a more active and more abundant microbial community 20 .…”

Isothermal Microcalorimetry Provides New Insight into Terrestrial Carbon Cycling

“…In ecosystems dominated by K-83 strategists, it is assumed that more of the organic material is sequestered in soils through carbon 84 allocation to microbial cell maintenance and synthesis of extracellular components such as 85 enzymes, polysaccharides, metabolites, proteins etc. 22 . Consequently, different soil microbial 86 communities are likely to call upon different biochemical pathways resulting in different carbon 87 and energy flows through the communities and ecosystems.…”

Annual cycle of humic substances in a temperate estuarine system affected by agricultural practices

“…This allowed accumulation of organic matter on soils which is certainly enhanced in this season by falling leaves and other plant debris. Furthermore, the residence time of organic matter in soils has been identified as being one of the key factors for its humification (Jastrow et al, 2007). Another element that could contribute to the export of organic matter and HS under autumnal floods is the fall tillage which is known to increase soil sensitivity to erosion (Robert, 2001).…”