12.2 Soil carbon sequestration and climate change mitigation

Soil carbon sequestration is a powerful tool in the fight against climate change. By capturing atmospheric CO2 and storing it in soil, we can reduce greenhouse gases while improving soil health. This process involves various mechanisms, from photosynthesis to organic matter additions, and can be enhanced through smart management practices.

Factors like temperature, soil texture, and land use intensity affect how well carbon stays put in soil. While sequestration offers benefits like better water retention and increased biodiversity, it can also present challenges. Balancing these trade-offs is key to making soil carbon sequestration a successful climate mitigation strategy.

Soil Carbon Sequestration Mechanisms and Potential

Mechanisms of soil carbon sequestration

Top images from around the web for Mechanisms of soil carbon sequestration

• 

  Soil carbon | Environment, land and water | Queensland Government View original

  Is this image relevant?

• 

  Biogeochemical Cycles and the Flow of Energy in the Earth System | Sustainability: A ... View original

  Is this image relevant?

• 

  Frontiers | Crops for Carbon Farming View original

  Is this image relevant?

• 

  Soil carbon | Environment, land and water | Queensland Government View original

  Is this image relevant?

• 

  Biogeochemical Cycles and the Flow of Energy in the Earth System | Sustainability: A ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Mechanisms of soil carbon sequestration

• 

  Soil carbon | Environment, land and water | Queensland Government View original

  Is this image relevant?

• 

  Biogeochemical Cycles and the Flow of Energy in the Earth System | Sustainability: A ... View original

  Is this image relevant?

• 

  Frontiers | Crops for Carbon Farming View original

  Is this image relevant?

• 

  Soil carbon | Environment, land and water | Queensland Government View original

  Is this image relevant?

• 

  Biogeochemical Cycles and the Flow of Energy in the Earth System | Sustainability: A ... View original

  Is this image relevant?

1 of 3

• Carbon input mechanisms
  • Photosynthesis captures atmospheric CO2 converts it to organic compounds incorporated into soil through plant residues
  • Root exudates release carbon-rich compounds nurture soil microbes increase microbial biomass
  • Organic matter additions enrich soil with carbon (compost, manure)
• Carbon stabilization processes
  • Physical protection within soil aggregates shields organic matter from decomposition
  • Chemical bonding with clay minerals forms stable organo-mineral complexes
  • Biochemical recalcitrance of organic compounds resists microbial breakdown (lignin, humic substances)
• Potential for climate change mitigation
  • Atmospheric CO2 reduction draws down greenhouse gases mitigates global warming
  • Increased soil organic matter content improves soil fertility enhances crop productivity
  • Enhanced soil water retention capacity boosts drought resilience reduces irrigation needs
• Carbon sequestration rates
  • Variation by ecosystem and management practices depends on climate soil type land use
  • Typical range: 0.1 to 1 Mg C ha$^{-1}$ yr$^{-1}$ with higher rates in tropical regions lower in arid areas

Management practices for carbon sequestration

• Agricultural ecosystems
  • Conservation tillage and no-till farming minimize soil disturbance preserve soil structure
  • Cover cropping and crop rotation increase biomass input improve soil health
  • Agroforestry and alley cropping integrate trees with crops enhance carbon storage
  • Precision nutrient management optimizes fertilizer use reduces emissions
  • Improved grazing management rotational grazing prevents overgrazing promotes grassland health
• Natural ecosystems
  • Reforestation and afforestation establish new forests increase carbon sinks
  • Wetland restoration revives carbon-rich ecosystems enhances biodiversity
  • Grassland management and fire control prevent carbon loss maintain ecosystem balance
  • Invasive species management preserves native plant communities protects soil carbon stocks
• Comparison of practices
  • Implementation costs and feasibility vary by region resource availability farmer expertise
  • Sequestration potential and timeframe differ based on practice climate soil conditions
  • Adaptability to different climates and soil types requires tailored approaches local knowledge

Factors Affecting Soil Carbon Sequestration

Stability of sequestered soil carbon

• Environmental factors
  • Temperature and moisture regimes influence microbial activity decomposition rates
  • Soil texture and mineralogy affect organic matter protection (clay content)
  • Microbial community composition determines carbon cycling efficiency
• Management factors
  • Land use intensity and disturbance frequency impact soil carbon stability
  • Nutrient availability and fertilization practices alter decomposition rates
  • Organic matter input quantity and quality affect carbon stabilization potential
• Carbon pool dynamics
  • Labile vs. recalcitrant carbon fractions have different turnover rates
  • Turnover rates of different soil organic matter pools vary from days to millennia
  • Priming effects stimulate or inhibit soil organic matter decomposition
• Climate change impacts
  • Altered precipitation patterns affect soil moisture carbon mineralization
  • Increased temperatures accelerate decomposition potentially lead to carbon loss
  • Extreme weather events increase soil erosion risk threaten carbon stocks

Co-benefits vs trade-offs in sequestration

• Co-benefits
  • Improved soil structure and water-holding capacity enhance crop resilience
  • Enhanced nutrient cycling and fertility reduce fertilizer dependence
  • Increased biodiversity and ecosystem services support pollination pest control
  • Reduced soil erosion and improved water quality protect aquatic ecosystems
• Trade-offs
  • Potential decrease in crop yields during transition periods as soil health rebuilds
  • Increased labor and management requirements demand farmer education resources
  • Possible conflicts with other land use objectives (urbanization, biofuel production)
  • Short-term economic costs vs. long-term benefits require careful planning
• Policy considerations
  • Carbon markets and incentive programs provide financial motivation for farmers
  • Monitoring, reporting, and verification challenges need robust systems
  • Integration with broader climate change mitigation strategies ensures cohesive approach
• Socioeconomic impacts
  • Food security implications balance carbon sequestration with agricultural productivity
  • Rural livelihoods and agricultural sustainability benefit from improved soil health
  • Equity issues in carbon credit distribution require fair accessible programs