Soil Organic Matter: A Carbon Champion

Soil organic matter (SOM) plays a pivotal role in the global carbon cycle, acting as a vital reservoir for storing carbon captured from the atmosphere. This stored carbon, known as soil organic carbon (SOC), makes up a significant portion of the terrestrial carbon pool, exceeding the amount found in all living organisms combined!

Here's how SOM contributes to carbon storage:

• Plant Input: Plants absorb atmospheric CO2 through photosynthesis and convert it into organic compounds. These compounds, along with dead plant tissues like leaves and roots, are deposited onto the soil surface.
• Decomposition: Microorganisms in the soil, like bacteria and fungi, decompose this organic matter. While some carbon is released back into the atmosphere as CO2, a significant portion gets stabilized and incorporated into SOM.
• Stabilization: The composition and structure of SOM influence its stability. Lignin, a complex molecule in plant cell walls, is resistant to decomposition and contributes to long-term carbon storage. Additionally, SOM can become physically protected within soil aggregates, further shielding it from microbial breakdown.

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Soil organic matter layers

This stored SOC plays a crucial role in ecosystem productivity in several ways:

• Nutrient Cycling: SOM decomposition releases essential nutrients like nitrogen, phosphorus, and potassium for plant uptake. This nutrient cycling is crucial for plant growth and overall ecosystem health.
• Soil Structure: SOM binds soil particles together, improving soil aggregation and aeration. This enhances water infiltration and retention, preventing erosion and creating a more hospitable environment for plant roots.
• Water Holding Capacity: SOM increases the soil's ability to hold water, making it more resilient to drought. This is particularly important in dry regions and during periods of water scarcity.
• Biodiversity: A healthy soil rich in SOM supports a diverse community of microorganisms, insects, and other soil organisms. This biodiversity underpins various ecosystem functions, including nutrient cycling, decomposition, and disease suppression.

Therefore, maintaining and enhancing soil organic carbon content is vital for mitigating climate change by sequestering atmospheric CO2. It also contributes to improved soil health, increased agricultural productivity, and overall ecosystem resilience.

By understanding and appreciating the vital roles of SOM in carbon storage and ecosystem health, we can implement practices like reduced tillage, cover cropping, and compost application to promote its formation and contribute to a more sustainable future.

Dr Murtadha Shukur thank you for your contribution to discussion

Soil organic carbon not only improves soil nutrient bioavailability but also affects soil fertility by various other mechanisms and is of central importance for the global C-cycle, which may strongly affect atmospheric CO2-concentrations. Through the process of photosynthesis, plants assimilate carbon and return some of it to the atmosphere through respiration. The carbon that remains as plant tissue is then consumed by animals or added to the soil as litter when plants die and decompose. Currently, soils remove about 25 percent of the world's fossil fuel emissions each year. Most soil carbon is stored as permafrost and peat in Arctic areas, and in most regions like the boreal ecosystems of Northern Eurasia and North America. Soils in hot or dry areas store less carbon. Surface soil carbon (C) in the form of organic matter supports essential ecosystem services such as climate regulation, plant production, nutrient cycling and water storage and purification. Global data show that soil C content is larger in cold and mesic than in warm and xeric ecosystems. Soil organic C plays an important role in water filtration and purification and soil water holding capacity by improving soil structural stability and microbial activity. Most studies show a positive relationship between SOC and water holding capacity. Soil organic matter significantly improves the soil's capacity to store and supply essential nutrients, and to retain toxic elements. It allows the soil to cope with changes in soil acidity, and helps soil minerals to decompose faster. Soil carbon provides a source of nutrients through mineralization, helps to aggregate soil particles to provide resilience to physical degradation, increases microbial activity, increases water storage and availability to plants, and protects soil from erosion. SOM is a reservoir of essential plant nutrients such as nitrogen, phosphorus, and sulfur. Microorganisms in the soil break down SOM into forms that plants can use, thus maintaining soil fertility. SOM helps to improve soil structure by creating aggregates that increase porosity and water-holding capacity. This improves water infiltration and reduces erosion and an important component of the carbon cycle, as it stores carbon in the soil. This helps to mitigate the effects of climate change by removing carbon dioxide from the atmosphere. By understanding the roles of SOM in soil fertility and carbon storage, farmers and land managers can work to maintain and improve SOM levels in their soil. This can be done through conservation tillage, crop rotation, and the incorporation of cover crops and organic matter into the soil. Soil carbon sequestration helps restore degraded soils, which can improve agricultural productivity. Increased climate resilience: healthier soils make farms more resilient against both droughts and heavy rainfall. Carbon storage is closely related to other vital ecological processes such as primary productivity. Because carbon dioxide is the primary greenhouse gas emitted by human activities, changes in forest carbon can help to mitigate climate change or they can exacerbate the problem. Disturbances, climate, topography, stand age, availability of nutrient elements, biological diversity, changes in species composition, and ecosystem structure are some important factors that directly or indirectly influence carbon storage in these ecosystems. Soil organic carbon is an important indicator of soil quality, and helps to regulate nutrient supply, microbial activity, and soil moisture content. Soil organic carbon levels come from the interaction of ecosystem processes such as photosynthesis, respiration, and decomposition.Surface soil carbon (C) in the form of organic matter supports essential ecosystem services such as climate regulation, plant production, nutrient cycling and water storage and purification. The productivity of the primary producers is especially important in any ecosystem because these organisms bring energy to other living organisms by photoautotrophy or chemoautotrophy.