Geomorphology and Soil Carbon Sequestration Potential

Introduction
Geomorphology—the science of landforms and the processes that sculpt them—plays a central, though often understated, role in shaping soil carbon dynamics. The arrangement of hills and valleys, slopes and plains, and the distribution of sediments created by rivers, glaciers, winds, and tectonics create a mosaic of microclimates, soil types, hydrology, organic matter inputs, and microbial communities. Each of these factors influences how carbon is stabilized, stored, or mineralized in soils. By examining geomorphology, researchers and land managers gain crucial insights into where soil carbon can accumulate most effectively, how long it can persist, and how land-use changes might either enhance or erode this sequestration potential. The interplay between landscape form and soil processes is complex and context-dependent, requiring integrated approaches that consider topography, soils, climate, vegetation, and disturbance regimes. This article maps the main geomorphic factors that govern soil carbon storage, discusses measurable pathways of carbon sequestration across landform types, and highlights the implications for conservation, restoration, and policy.

The role of topography in carbon stabilization

Topography sets the stage for soil formation and carbon dynamics by controlling water movement, erosion risk, sediment deposition, and microhabitat creation. Slopes influence leaching depth, drainage, and oxygen availability, which in turn affect microbial respiration, root growth, and the stabilization of organic matter. Convex slope positions tend to experience slower soil development and thinner horizons, while concave depressions often accumulate finer sediments and higher soil organic carbon (SOC) due to reduced runoff and enhanced moisture retention. Slope aspect, or the direction a slope faces relative to sun exposure, also modulates temperature and evapotranspiration, shaping plant productivity and litter input—two key inputs of carbon to soils. Steep terrains can act as rapid conduits for erosion, exporting soil carbon downslope or into waterways, whereas gentler terrains may foster longer residence times. Terracing, benching, and other landscape modifications alter natural hydrological gradients, creating microenvironments that can improve SOC stabilization in agricultural and rehabilitated landscapes. Understanding topographic position index, curvature, downslope flow paths, and landform-specific hydrology helps anticipate where carbon inputs diversify, where losses might be minimized, and where enhancement strategies may be most effective.

geomorphic controls on soil formation and SOC inputs

Soil formation, or pedogenesis, is intrinsically linked to geomorphic setting. Parent material delivered by rivers, glaciers, wind, or gravity provides the mineral substrate for carbon stabilization processes. The mineralogy, texture, and weathering susceptibility of parent material influence the surface area available for organic matter adsorption, stabilization with mineral surfaces, and the capacity of soils to retain decomposed organic residues. In alluvial plains, floodplain terraces, and deltaic environments, periodic sediment deposition introduces fresh mineral surfaces and organic inputs, often increasing SOC stocks temporarily or over longer timescales if vegetation cover is appropriate. In colluvial and slowly weathering soils on hillslopes, carbon input from litter and root turnover may accumulate at depth, with stabilization enhanced by clay- and mineral-organic associations. Pedogenic processes—soil formation and horizon development—are often interrupted by geomorphic disturbances such as landslides, avalanches, or river avulsions, creating mosaic soil sites with contrasting SOC stocks along a single landscape. The rates of carbon input, stabilization, and decomposition are controlled by moisture regimes, temperature, and soil texture, all of which are patterned by the underlying geomorphic framework.

hydrology, drainage, and carbon storage

Hydrology acts as a primary mediator of carbon fate in soils. Soil moisture governs microbial activity, root respiration, and the chemical pathways that stabilize or mineralize organic carbon. In landscapes with well-drained soils, aerobic conditions tend to favor decomposition, potentially lowering SOC stocks. In contrast, poorly drained or waterlogged soils create reducing environments that slow decomposition and promote the accumulation of organic matter in saturated horizons. Geomorphic features such as drainage networks, groundwater depth, seasonal flooding, and perched water tables shape the distribution of SOC across a landscape. Wetland-adjacent soils and floodplains, for example, often host higher SOC due to sustained anoxic conditions that inhibit decomposition and favor peat formation or longer residence times for organic carbon. Conversely, rapidly draining soils in arid or mountainous zones may exhibit lower SOC due to faster turnover or erosion of carbon-rich horizons. The interplay between terrain-driven hydrology and vegetation productivity ultimately determines the balance of carbon inputs and losses across landforms.

sediment transport and carbon redistribution

Sediment transport processes move carbon-rich material within and between landscapes. Rivers, ice, wind, and mass wasting can erode, transport, and redeposit soil carbon, creating spatially heterogeneous SOC patterns. Floodplain deposition, alluvial fans, and deltaic lobes can act as carbon sinks when vegetation and ongoing sediment supply stabilize deposited organic matter. Erosion from upland areas can export soil carbon to downslope ecosystems or aquatic systems, potentially increasing burial or mineralization along transport pathways. The residence time of carbon in a given soil profile is thus linked to geomorphic connectivity—the extent to which landforms are linked through sediment routing networks. In landscapes with frequent disturbance or rapid sediment flux, carbon may be stored transiently in depositional zones or buried within fine-grained layers where mineral surfaces provide stabilization. In more stable terrains, SOC may accumulate gradually over centuries as soils develop and organic inputs persist. The net effect of sediment transport on SOC depends on the rates of deposition, stabilization, decomposition, and the duration of storage in receiving environments.

role of landforms in soil organic matter stabilization mechanisms

Soil organic matter stabilization occurs through a suite of physical and chemical interactions, many of which are mediated by mineralogy and texture—factors that are themselves shaped by landform history. Clay minerals, iron and aluminum oxides, and mineral surfaces offer sites for organomineral associations that protect carbon from rapid microbial decomposition. The availability of reactive mineral surfaces is often enhanced in soils formed on certain parent materials and under particular geomorphic conditions that promote weathering. Additionally, physical protection arises from soil aggregation and occlusion within stable pore networks, which can be influenced by root architecture and bioturbation, processes that in turn reflect the microclimates created by slope position, aspect, and drainage. Vegetation type and productivity, themselves influenced by terrain, provide fresh litter and root carbon that become incorporated into soil organic matter. The balance between stabilization and decomposition is dynamic and highly sensitive to disturbance regimes—soil erosion, fire, land-use change, and climate shifts can disrupt stabilization pathways and alter SOC trajectories across landforms.

climate interactions and geomorphic context

Climate interacts with geomorphology to shape soil carbon sequestration potential in several ways. Temperature and precipitation patterns modulate primary productivity, litter quality, and decomposition rates, with terrain amplifying or dampening these climatic effects. Elevation gradients alter temperature regimes and moisture availability, creating distinct soil carbon dynamics across altitudinal belts. Microclimates produced by topography—such as cold-air pools in valley bottoms or sun-exposed ridges—can create niches where SOC accumulates differently. Glacially carved landscapes, karst terrains, and desert landforms each present unique climate–geomorphology couplings that influence SOC. In many regions, climate change alters precipitation timing and intensity, snowmelt dynamics, and drought frequency, which, when combined with existing geomorphic heterogeneity, leads to shifts in SOC stocks and turnover rates. Anticipating these changes requires integrating geomorphic mapping with climate projections to identify vulnerable zones and resilient landforms for carbon sequestration initiatives.

disturbances and resilience of geomorphically controlled SOC

Disturbances such as wildfires, floods, landslides, engineering works, and agricultural practices directly affect soil carbon reservoirs. Fire, for example, can volatilize carbon and alter soil properties, but post-fire vegetation regrowth and soil microbial changes can also lead to recovery or re-accumulation of SOC in certain landforms. Flooding and sediment pulses can bury carbon-rich materials and protect them within depositional layers, while erosive events may export SOC away from landscapes. The resilience of SOC to disturbance is often strongly related to geomorphic setting: flat, well-vegetated floodplains may recover SOC more quickly after disturbance than steep, unstable terrains where erosion is frequent. Moreover, landform-associated soil depth, texture, and mineralogy influence the capacity for SOC to rebound over time after perturbations. Recognizing these patterns is essential for designing land management and restoration projects that aim to maintain or increase carbon stocks amid a changing disturbance regime.

measuring SOC and linking it to geomorphic units

Quantifying soil carbon stocks in a geomorphically heterogeneous landscape requires a stratified sampling approach that respects landform units. Geomorphic units—such as hilltops, shoulder slopes, backslope zones, toe slopes, floodplains, terraces, dunes, and karst depressions—often host distinct SOC stocks and turnover rates. Standard soil sampling protocols may need adaptation to capture vertical and horizontal gradients created by landforms, including depth profiles down to horizons where SOC stabilizes or decomposes rapidly. Analytical approaches include measuring total organic carbon, particulate organic carbon, microbial biomass, and carbon in mineral-associated forms. Geospatial tools like digital elevation models, slope and aspect analyses, and watershed-scale hydrological modeling help delineate geomorphic units and predict SOC distribution. Long-term monitoring across landform classes supports understanding of sequestration potential under variable climate and land-use scenarios, enabling targeted management actions.

land management implications and restoration opportunities

Geomorphology-informed land management can optimize carbon sequestration outcomes by aligning restoration and conservation actions with landscape form. In floodplains and deltaic environments, preserving natural hydrology and vegetation can maintain high SOC stocks, while restoring wetland function or reestablishing native plant communities can enhance carbon burial. In hillslope and terrace landscapes, soil conservation practices—such as reduced tillage, cover cropping, and terracing—can minimize erosion losses and promote SOC stabilization on sloping terrain. In degraded landscapes, reestablishing vegetation on sediment-rich surfaces where deposition processes dominate can accelerate SOC accrual. Restorative actions should also consider potential trade-offs with other ecosystem services, such as biodiversity, water quality, and flood mitigation, ensuring that carbon-focused strategies integrate with broader landscape objectives. The geomorphic context provides a framework for prioritizing areas with the greatest potential for durable SOC gains and for selecting interventions that complement natural stabilization processes.

integrating geomorphology into policy and assessment

Policies aimed at enhancing soil carbon sequestration benefit from incorporating geomorphological understanding into landscape-scale assessments. Carbon accounting frameworks should differentiate SOC dynamics across landform classes and account for differences in residence time, potential for stabilization, and susceptibility to erosion or disturbance. Spatial prioritization guided by geomorphic mapping can inform land-use zoning, restoration funding, and conservation incentives, directing resources toward regions with high sequestration potential or those most vulnerable to SOC loss. Monitoring programs that track SOC changes should stratify sampling by landform type to detect region-specific responses to climate change and management. Integrating geomorphology into policy fosters more realistic projections of carbon sequestration potential, improves the precision of inventories, and supports the design of resilient, climate-smart land management strategies.

synthesis and future directions

Geomorphology shapes soil carbon sequestration potential by setting the hydrological, mineralogical, and ecological context in which soils form, evolve, and store organic matter. From topographic position and drainage patterns to sediment transport and stabilization mechanisms, landforms regulate the supply and fate of carbon inputs, the persistence of stored carbon, and the resilience of SOC stocks to disturbances. Future research will benefit from high-resolution geomorphic mapping combined with long-term SOC monitoring, enabling more accurate predictions of sequestration potential under environmental change. Advancements in soil analytics, remote sensing, and landscape modeling will further illuminate how diverse landforms contribute to a planet-wide carbon budget, guiding effective, equitable, and sustainable climate interventions.

Conclusion
The connection between geomorphology and soil carbon sequestration is a cornerstone of understanding how landscapes store carbon over time. Recognizing how topography, hydrology, sediment dynamics, and stabilization processes interact across landforms allows for more precise assessments of where carbon can accumulate and persist. This perspective supports targeted restoration and conservation actions that align with natural landscape processes, enhancing the durability and scale of sequestration outcomes. As climates shift and human pressures intensify, integrating geomorphic insight into land management and policy will be crucial for sustaining soil carbon stocks and maximizing climate benefits.