Biogeochemical Cycling of Soil Calcium and Carbon

The biogeochemical cycling of soil calcium and carbon encompasses a series of interlinked processes that regulate the storage, transformation and movement of these elements in terrestrial ecosystems. Calcium, derived from mineral weathering and organic sources, influences soil pH, nutrient availability and the stability of soil organic matter. Carbon exists in soils as organic compounds within plant residues, microbial biomass and as inorganic forms such as carbonate minerals. Microbial communities and plant–microbe interactions drive organic matter decomposition, oxalate production and the oxalate-carbonate pathway, by which calcium oxalate is oxidised to precipitate calcium carbonate. This transformation not only sequesters CO₂ as stable mineral carbon but also modifies soil structure and local pH, with feedbacks on nutrient cycling. Land-use change, climate variation and pedogenic factors further modulate rates of carbon turnover and calcium dynamics, affecting soil fertility and the capacity of soils to act as carbon sinks. Understanding these coupled cycles is essential for predicting ecosystem responses to global change and for designing management practices that enhance carbon sequestration while maintaining nutrient balance. Practical applications include the optimisation of agroforestry systems to harness oxalotrophic microbial activity, the design of land-use regimes that favour carbonate precipitation, and the assessment of soil amendments to stabilise organic carbon and maintain calcium availability.

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Biogeochemical Cycling of Soil Calcium and Carbon publication trend

The graph below shows the total number of articles in biogeochemical cycling of soil calcium and carbon across all publications each year (not limited to Nature Index journals).

Technical terms

Oxalate-carbonate pathway: A biogeochemical process converting calcium oxalate into calcium carbonate, thereby fixing CO₂ as mineral carbon.

Oxalotrophic bacteria: Microorganisms that utilise oxalate as a carbon and energy source, catalysing oxalate oxidation.

Humic substances: Complex organic molecules formed during the decomposition of plant and microbial residues, encompassing humic acids and fulvic acids.

Biomineralisation: The formation of mineral phases by biological activity, such as precipitation of carbonate minerals by soil organisms.

Soil organic matter: The fraction of soil composed of decomposed plant and animal residues, microbial biomass and humified products.

References

1. Oxalate Carbonate Pathway—Conversion and Fixation of Soil Carbon—A Potential Scenario for Sustainability. Frontiers in Plant Science (2020).
2. Changes in Soil Organic Matter Associated with Land Use of Arenosols from Southern Botswana. Agronomy (2024).
3. Calcium Oxalates in Soils within Disturbed Landscapes and Rock on the Territory of Yakutia (Russia), Formation Conditions in a Sharply Continental Cryoarid Climate. Minerals (2023).
4. Functional Diversity of the Litter-Associated Fungi from an Oxalate-Carbonate Pathway Ecosystem in Madagascar. Microorganisms (2021).