Cycles case studies

Rainforests

Water + carbon cycles Unique to tropical rain forest

 Water- high average annual temp. 30degrees – 2000mm high average annual rain fall

Cloud cover ensure maximum temp. don’t reach levels of deserts

·         Precipitation- High and evenly dist. Throughout year – high intensity convectional rainfall

·         Interception- high around 10% of precipitation

·         Evapotranspiration-High- half of all incoming rain is returned to the atmosphere via transpiration due to high temperature, abundant moisture + dense vegetation

·         Run-off – RAPID – high and intensive rainfall + well drained soil

Carbon-

Exchanges of carbon are very rapid due to – speedy decomposition – rate of carbon fixation through photosynthesis high

Rainforest absorbs 2.4 billion tonnes of carbon a year

Large trees can store around 220tonnes c/ha a year

Physical factors affecting flows and storage of water cycle

·         Geology- Large parts of the Amazon basin is located on impermeable crystalline rocks – rapid run-off

·         Relief- Andes to the west create a steep catchment with rapid run-off , inundations across extensive floodplains like the Pantanal in Mato Grosso Du Sol state store water for several months slowing its movement in rivers

·         Temperature- means rates of evapotranspiration and precipitation is high  

Physical Factors affecting the flows and storage of carbon cycle

100 billion tonnes of carbon locked up in Amazon rainforest

Absorbs 2.4 billion tonnes of CO2 a year and release 1.7 back – THUS A CARBON SINK- 60% above ground 40% under – High temp. prec. Lead to high primary product – 25% of all terrestrial NPP

Quick decomposition released into atmosphere or into soil where it’s quickly absorbed by tree roots

Patches of Limestone in western Amazonia in the context of the slow carbon cycle are significant regional stores

Human impact on water cycle

Since 1970 1/5^th of rainforest deforested

For instance- Deforestation on the edges of Amazonia in the foothills of the Andes in Bolivia and Peru – Cattle and subsistence farming -  has led to a massive reduction in water storage (in plants, roots trees, soil)  - led to flooding in the madeira river basin 2016 60 died

Run-off has increased by 27x

Deforestation leads to a decrease in evapotranspiration which intern means lower precipitation

Predicted 20% fall in rainfall

This can result in permanent climate change – the amazon becoming drier and hotter

Human impact on Carbon cycle

Biomass of trees represent 60% of all carbon in ecosystem – deforestation exhausts the carbon bio-mass store and the pasture + grassland which replaces it contains only a small amount carbon in comparison

Nutrients- rainforest soil only contains a small amount of nutrients most quickly extracted by plant roots

Deforestation removes the main nutrients store – soil…