AMAZON - water + carbon cycle

Question 1

what type of system is a tropical rainforest?

Answer 1

open system

Question 2

what is the water cycle input

Answer 2

daily rainfalls

Question 3

outline location of Amazon

Answer 3

The Amazon River drainage basin encompasses 7million square kilometres of which 5.5million is covered by tropical rainforest. 60% of the forest is in Brazil, 13% in Peru and 10% in Colombia. The rest is found in neighbouring countries. The Amazon rainforest is the largest and most biodiverse tract of tropical rainforest in the world with 16,000 species of trees.

Question 4

what type of ecosystem is the Amazon?

Answer 4

Biome - large scale ecosystem

Question 5

how does the Amazon play a role in the water cycle?

Answer 5

Approx 8 trillion tonnes of water evaporates from Amazon rainforests each year. The rest of the rainfall entering the Amazon basin flows into the Atlantic Ocean, accounting for 15-20% of the worldwide continental freshwater runoff to oceans

Question 6

Outline the Amazon’s climate

Answer 6

Amazonia lies between 5 degrees N and 10 degrees S of the equator. The majority of the rainforest therefore has an equatorial climate.
For example, Manaus, the capital city of the Brazilian state of Amazonas, has an average temperature of 31degrees C. The hottest months are September and October, averaging 33 degrees C; the coldest months are January to March, averaging 26.3 degrees C.
As a result, Amazonia has a high potential rate of evaporation leading to high rates of precipitation (because as water evaporates it rises, cools and condenses).
Average rainfall across the whole Amazon basin is around 2300 mm of rain annually - can reach 6000mm - due to ground being heated up by high temperatures and warm air rising to condense and create rainfall means the majority of rainfall is convection rainfall
Lots of rainfall = lots of growth as water is needed for photosynthesis = dense vegetation known as evergreen trees meaning they don’t lose their leaves all year round = high interception rates

Question 7

How is the Amazon’s precipitation produced?

Answer 7

One third of the Amazon’s precipitation is produced in the recycling of water through evapo-transpiration. The other two-thirds arrives as moisture laden air form the Atlantic.

Question 8

Outline water cycle in Amazon

Answer 8

The dense forest canopy intercepts up to 75% of this rainfall. Some drips to the ground from leaves or flows down tree trunks as stemflow. About 25% of the rainfall is evaporated. Of the remaining 75%, about half is used by the plants and eventually returned to the atmosphere by evapotranspiration. The other half either infiltrates into the soil, is stored on the ground surface or flows overland to river channels as runoff.

Question 9

what stores is water transferring between?

Answer 9

rapidly recycling through atmosphere and the biosphere

Question 10

example of a negative feedback loop

Answer 10

When it rains for a long period of time, because temperatures are high, the water is fed back into the atmosphere, causing more rainfall, leading to more evapotranspiration - maintains a dynamic equilibrium

Question 11

how much carbon stored in amazon

Answer 11

In a typical year the Amazon rainforest absorbs 2.2 billion tons of CO2 while emitting 1.9 billion tons through decomposition and organic respiration, making it a major carbon sink.

Question 12

how much biomass growing

Answer 12

Studies show that tropical rainforests have been increasing in above ground biomass by 0.3 – 0.5% per year and that the rising productivity of tropical forests is due to sequestering of increased CO2 concentrations in the atmosphere.

Question 13

how has amazon carbon sink changed over time

Answer 13

By 2015 it only drew down just over 1 billion tonnes of CO2, meaning it no longer represents a continental carbon sink.

Question 14

Faster growth through carbon fertilisation on tree mortality

Answer 14

Trees will reach mortality quicker - one of the reasons why the amazon might be drawing less carbon

Question 15

Recurrent drought

Answer 15

Trees will reach mortality as the trees are so tall they need regular amounts of water as they are more vulnerable, if they are growing taller and faster because of this carbon fertilisation, they become less resilient to periods of drought, reducing their potential to store carbon. Current periods of drought means they will die and won’t sequester as much carbon from atmosphere.

Question 16

High temperatures

Answer 16

Increased temperatures could lead to increased forest fires, thinning the forest, making the forest more vulnerable to fires in the future as the canopy opens up meaning more solar radiation can reach the forest floor leading to more forest fires. This means there is less living biomass in the forest that would usually sequester carbon.

Question 17

Conversion to agriculture and illegal logging

Answer 17

Large areas are cleared for cattle and soya production, often done by burning - the removal of vegetation that could sequester that carbon and the impact that the clearance has on the local ecosystem can trigger other issues like draught which can change the forest ecosystem likely to brush vegetation, which is much smaller therefore as a carbon sink it has less capacity than the taller trees would.