9.4 Arctic and Alpine Ecosystem Biogeochemistry

Arctic and alpine ecosystems are unique environments shaped by extreme cold and short growing seasons. Permafrost dynamics, nutrient limitations, and seasonal freeze-thaw cycles play crucial roles in their biogeochemistry.

These ecosystems are significant players in the global carbon cycle, storing vast amounts of carbon in permafrost. Climate change threatens this balance, potentially releasing stored carbon and altering vegetation patterns, which could lead to far-reaching consequences for global climate systems.

Arctic and Alpine Ecosystem Biogeochemistry

Biogeochemistry of arctic and alpine ecosystems

Top images from around the web for Biogeochemistry of arctic and alpine ecosystems

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Biogeochemistry of arctic and alpine ecosystems

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

• 

  TC - Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in ... View original

  Is this image relevant?

1 of 3

• Permafrost dynamics shape soil processes permanently frozen ground for two or more years affects nutrient cycling
  • Active layer seasonally thawed upper soil allows for biological activity (typically 0.5-2 m deep)
  • Cryoturbation mixes soil due to freeze-thaw cycles redistributes organic matter and nutrients
• Seasonal freeze-thaw cycles alter physical and chemical soil properties
  • Physical changes in soil structure affect water retention and gas exchange
  • Impacts microbial activity and nutrient availability fluctuates with temperature changes
• Nutrient limitations constrain ecosystem productivity
  • Nitrogen and phosphorus scarcity limits plant growth (tundra, alpine meadows)
  • Slow decomposition rates reduce nutrient turnover in cold environments
• Short growing seasons necessitate rapid nutrient uptake
  • Plants adapt to brief periods of growth with efficient nutrient acquisition strategies
• Soil organic matter accumulation contributes to carbon storage
  • Slow decomposition in cold climates leads to peat formation and carbon sequestration
• Methane production in wetlands increases with permafrost thaw
  • Anaerobic conditions in thawed permafrost promote methanogenesis (thermokarst lakes)

Arctic and alpine ecosystems in global carbon cycle

• Carbon storage in permafrost represents significant global reservoir
  • Estimated 1300-1600 Pg of carbon stored globally equals more than current atmospheric carbon
• Carbon dioxide and methane fluxes vary seasonally
  • Sources include soil respiration and plant respiration increase with warming
  • Sinks involve photosynthesis and soil carbon sequestration affected by growing season length
• Vulnerability to warming threatens carbon balance
  • Permafrost thaw releases stored carbon increases greenhouse gas emissions
  • Increased microbial activity and decomposition rates accelerate carbon turnover
• Albedo changes amplify warming effects
  • Reduced snow cover leads to increased heat absorption darker surfaces absorb more solar radiation
• Vegetation shifts alter carbon dynamics
  • Expansion of shrubs and trees in tundra ecosystems increases above-ground carbon storage

Climate change effects on arctic and alpine environments

• Enhanced nutrient mineralization alters nutrient availability
  • Increased microbial activity releases nutrients from organic matter
• Changes in plant community composition shift ecosystem structure
  • Transition from lichens and mosses to vascular plants alters nutrient cycling patterns
• Altered hydrological cycles impact water availability
  • Earlier snowmelt and changes in soil moisture affect plant growth and microbial activity
• Extended growing seasons increase biological activity duration
  • Longer periods of photosynthesis and nutrient uptake change ecosystem productivity
• Increased nitrogen fixation enhances nitrogen availability
  • Enhanced activity of nitrogen-fixing microorganisms (cyanobacteria in cryptogamic crusts)
• Soil erosion and nutrient loss threaten ecosystem stability
  • Thawing permafrost leads to landscape instability and potential loss of nutrients

Permafrost thaw and climate feedbacks

• Release of stored carbon accelerates greenhouse gas emissions
  • Conversion of organic matter to CO2 and CH4 through microbial decomposition
• Positive feedback loop amplifies warming effects
  • Increased emissions lead to further warming creating a self-reinforcing cycle
• Changes in soil hydrology alter landscape characteristics
  • Formation of thermokarst lakes and wetlands creates new aquatic habitats
• Methane production in anaerobic conditions increases emissions
  • Newly formed water bodies become hotspots of methane production
• Nitrous oxide emissions contribute to greenhouse effect
  • Enhanced microbial activity in thawed soils produces N2O a potent greenhouse gas
• Impacts on global climate models require updated predictions
  • Incorporation of permafrost thaw dynamics improves climate change projections
• Potential tipping points pose risks of abrupt changes
  • Irreversible changes in arctic and alpine ecosystems may occur with continued warming (loss of sea ice, glacier retreat)