The land surface type is described in the model and is different for certain locations on the Earth. The JULES model divides the land surface into 7 categories to model the carbon dioxide fluxes at the land-atmosphere interface. There are 5 plant type divisions to capture the net carbon and competition with other plant types. For more detail see: JULES Vegetation
Representing vegetation in a model is important because plants play a significant role in the water balance since plants require water for growth. Plants draw in water through their root system to use in driving photosynthesis. Unfortunately for the plant a large amount is lost to the air as water vapour in order to allow CO2 to enter. This process of transpiration is similar to "sweating" and also works to cool a leaf. Plants also shade the soil which reducing solar energy which is a driver of evaporation from bare earth.
The process of photosynthesis is used by plants to fix carbon and make sugars used in their growth. Two pathways exist to fix carbon:
a 3 carbon pathway common to all plants (Calvin cycle first fixes carbon dioxide into a 3-carbon compound)
a 4 carbon-fixing pathway (Hatch-Slack pathway describesCO2 fixed into a 4-carbon compound)
C3 grasses: dominate in moderate temperatures, sunlight and where water is not scarce
C4 grasses: dominate in the tropics where high sunlight levels occur because the C4 pathway uses more energy than the C3 pathway but C4 plants are more efficient at fixing C02 than C3 plants
Land Cover Legend