L2 - Leaching your Limits

Question 1

describe the setting in Manaus (Brazil)?

Answer 1

• tropical rainforest
• high temps of 28°c
• daily falls of convection rain (ie. Inten thunderstorms)
• biodiversity is extremely high

Question 2

what is the problem in Manaus?

Answer 2

there are threats of DEGRATION (character and quality being lowered) due to deforestation

Question 3

what is deforestation?

Answer 3

the cutting down of trees and forests to allow a different land use

Question 4

list 4 human causes of deforestation in Brazil?

Answer 4

• increasing population = growth rate 1.5% p/yr
• 20 mil people migrating to the Amazon / tributaries
• fringe of settlements (Manaus) expand daily -> make way for shanty towns
• overfishing

Question 5

why does increasing population cause deforestation?

Answer 5

trees are being cut down as land is needed for farming and housing

Question 6

how does overfishing cause deforestation?

Answer 6

1) on the edge of the forest, there is a giant wetland (Pantanal)
2) the Pacu fish in Panatal are in decline
3) they usually help disperse seeds of some rainforest trees
4) there are spiral effects because not enough Pacu fish to disperse seeds

Question 7

list 4 climate change causes of deforestation in Brazil?

Answer 7

• nature beginning to be on the move
• droughts in seasonal rainfall areas
• unusual northerly shift of rainbearing winds
• amphibians, reptiles and frogs are highly sensitive to environmental change (temp changes cause disease in frogs)

Question 8

explain impact of droughts on tropical rainforests (Manaus)?

Answer 8

• during drought, the tropical rainforest emits CO2 instead of absorbing it
• there were two major droughts in 2005 + 2010
• longer lasting droughts in West Amazon

Question 9

list 6 indirect effects of deforestation

Answer 9

1) leaching
2) less CO2 absorbed (& wood burned)
3) CO2 is released
4) destruction of habitats
5) less evapotranspiration
6) increase in water run-off + soil erosion

Question 10

how does deforestation cause CO2 to be released?

Answer 10

1) less trees to cover forest floor
2) there is an increase in light energy reaching the forest floor
3) results in organic matter to decompose at a quicker rate
4) CO2 is released

Question 11

what is leaching?

Answer 11

the downward movement of rainwater through soil

Question 12

eventually, what does leaching result in for the tropical rainforest?

Answer 12

• organic material washed out (+ nutrients)
• the soil becomes infertile
• poorer-quality vegetation grows
• massive erosion occurs
-> this prevents new vegetation being able to grow (to eventually protect the soil again)

Question 13

even with the protection of the forest canopy, what is much higher than what?

Answer 13

rainfall is much higher than evapotranspiration

Question 14

what are latosols?

Answer 14

soils forming under tropical rainforest (20-30m deep)

Question 15

what colour are latosols and why?

Answer 15

latosols are red/yellow
-> because they come from the oxides of iron and aluminium (which remain in soil after other minerals are washed away due to leaching)

Question 16

what is the only fertile part of latosols? what does this mean?

Answer 16

a black humus layer (narrow horizon of organic material)

-> this means trees have shallow roots

Question 17

what does deforestation do to the black humus layer?

Answer 17

there are fewer leaves so there is a thinner humus and fewer nutrients are added to the soil

Question 18

with a decrease in nutrients, less vegetation grows - what does this result in?

Answer 18

there is less interception, heavier rainfall and downward leaching

Question 19

describe how there is lots of rainfall in rainforests?

Answer 19

1) rainforests are situated near the equator where it is very hot
2) as a result, evaporation occurs and this leads to convection
3) cumulonimbus (fluffy) rain clouds form
4) leads to more vegetation growth

Question 20

overall, what is the biosphere’s role in rainforests?

Answer 20

• living matter provides humus (soil formation)
• vegetation cover = protection against soil erosion
• soil is held together by plant roots
• organic matter slows down leaching
• decomposing organic matter adds nutrients to soil
• insects and animals burrow into soil -> help circulation of water
• nitrogen fixing plants (turnips)