Geography - Earths Life Support Systems - Case Studies

What is the Amazon Rainforest Case Study on the Water Cycle?

Water Cycle-

* High precipitation (>2000mm/year),
* High humidity levels,
* High temperatures (25-30°C),
* Trade winds blow moisture from Atlantic to Amazon basin,
* Dense vegetation - tall, hardwood trees,
* High evapotranspiration levels due to high rainfall and temperature,
* Cloud cover stabilizes forest albedo,
* High interception from trees and vegetation (10% of rainfall intercepted),
* Low seasonal variation in climate,
* Rapid nutrient cycling in soil - intense rainfall can lead to rapid surface run-off.

What is the Amazon Rainforest Case Study on the Carbon Cycle?

Carbon Cycle-

* Rapid decomposition due to high levels of organic matter,
* 400bn trees store 68bn tonnes of Carbon - massive Carbon sink,
* 60% of rainforest carbon is stored in above ground biomass,
* Lots of respiration due to high biodiversity (30% of worlds species),
* Leached and acidic soil contains limited amount of carbon and nutrients,
* NPP (Net Primary Productivity) is 2000grams/m squared/year,
* High levels of Carbon fixation and rapid carbon changes.

What is the Arctic Tundra Case Study on the Water Cycle?

Water Cycle-

* Low precipitation (50-350mm/yr) with most falling as snow,
* Low humidity and small atmospheric stores of moisture,
* Temperatures reach -40°C,
* Limited evapotranspiration due to lack of vegetation with some areas having no vegetation at all,
* High albedo - lots of sunlight reflected, sunlight used in summer to melt snow,
* Sun remains below horizon for weeks during the winter, long daylight hours in summer,
* Very little seasonal variation in climate,
* Permafrost locks percolation meaning limited groundwater stores.

What is the Arctic Tundra Case Study on the Carbon Cycle?

Carbon Cycle-

* Very slow decomposition rates (no organic matter) but snow cover insulates microorganisms, allowing for some decomposition,
* Permafrost accumulates carbon (permafrost contains 1600GT globally) - unfrozen soil releases methane (25x stronger than CO2),
* Limited photosynthesis and respiration due to lack of flora/fauna - short growing season where plants flower for a few weeks,
* NPP of tundra is 200grams/m squared/year,
* Plant remains lock away carbon for 500,000 years.