Climate change

Climate change

1. positive feedback loop?

   • increased greenhouse effects
     • warmer soils
       • accelerated mineralisation of SOM
         • higher CO2 and methane emissions
           • goes in circle

2. Carbon cycle

   • C pool in soil = 2x that in atmosphere, ~3x that in biomass
   • rates of CO2 emitted from soils balanced by CO2 uptake by plants
   • NPP affected by CO2 and climate change
     • affected by veg type and soil conditions
       • affected by latitude

3. Biomass

   • tropical forest = HIGHEST
   • all forests much higher than grasslands
   • tundra = LOW

4. Carbon sequestering

   • soil restoration
   • woodland regeneration
   • no-till farming
   • cover crops
   • nutrient management
   • manuring and sludge application
   • improved grazing and agroforestry practices
   • growing energy crops on 'spare' land
   • reversing C loss => INCR in productivity

5. Methane

   • 25-30x as powerful a greenhouse effect as CO2
   • emitted from soils under wet anaerobic conditions
     • paddy fields
   • under aerobic conditions can be SINK
   • livestock
   • melting permafrost

6. Nitrous oxide

   • 300x more powerful than CO2 as g.g
   • escapes from N cycle - aerobic and anaerobic conditions (denitrification and nitrification)
   • emission rates strongly influenced by rates and pathways by which N enters soil
   • fertilisers