Transitions between alternative states have been shown to occur across geomorphic systems, such as alluvial fans. Our ability to identify shifts in the soil carbon dynamics has improved through advances in theory and statistical methods. Recent studies suggest that several indicators may be used as early-warnings of an approaching transition. The interrelation between climate and weathering plays an important role in C cycling. This study quantified mechanisms controlling soil carbon dynamics and their tipping points across the Quaternary alluvial fans evolution. Chemical weathering rates depend on the percolation rate and surface erosion. Weathering processes can affect the quality and resilience of soil systems by influencing the SOC pool. As chemical weathering proceeds, mineral (trans)formations and the formation of aggregates occur that support carbon fixation. SOC improves the soil structure and alters the chemical composition of the soil by the interaction with microbial communities. Severe erosion causes a reduction of the plant-available water capacity, the loss of the effective rooting depth, often a decline in soil structure and, subsequently, a reduction of soil quality. As a consequence, carbon is removed from the soil and sequestration reduced. Off-site impacts of erosion are due to sediment transfer and deposition, and emission of greenhouse gases into the atmosphere. Thus, land management decisions on soil conservation and increased C sequestration would improve soil quality. This study quantified mechanisms controlling soil carbon dynamics and their tipping points across the Quaternary alluvial fans evolution. Thus, land management decisions on soil conservation and increased C sequestration would improve soil quality.

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