tropical rainforests

Question 1

how much carbon does amazonia hold per year

Answer 1

2.4bn tonnes/year

Question 2

what are the differences between how much carbon woodland and cropland hold

Answer 2

woodland, 180000 tonnes/hector

cropland 16.4 tonnes/hector

Question 3

how is water stored in the ground in tropical rainforests

Answer 3

Aquifers, a store of water underground (permeable rock)

Question 4

what is the heat balance

Answer 4

inputs of solar energy and heat outputs from terrestrial land and gas

Question 5

why are equatorial regions hot

Answer 5

• receives the most concentrated solar radiation
• earth’s surface heats up and re radiates this heat out as long wave radiation warming the air above the thermal equator

Question 6

how much land does the amazon occupy

Answer 6

6 million km squared

Question 7

describe the distribution of the forest across different countries

Answer 7

70% occupies brazil but the forest also extends to neighboring countries such as Venezuela, Peru, Columbia, Bolivia

Question 8

describe the temperature in amazonia

Answer 8

high, between 25-35 degrees Celsius

Question 9

describe rainfall in amazonia

Answer 9

• high annual rainfall >2000mm, with no fully dry season
• 50-60% of rainfall is recycled by evapotranspiration in a strong feedback loop, 48% of this will fall again as rain
• interception by trees is significant, around 10%

Question 10

why are tropical temperatures not as extreme as sub-tropical deserts

Answer 10

significant cloud coverage

Question 11

why are rates of evapotranspiration high

Answer 11

high temperatures, abundant moisture, dense vegetation, most evaporation is from interception moisture on leaf surfaces

Question 12

describe the quality of soil nutrients in the forest

Answer 12

heavy rainfall means there is leaching of the nutrients in the soil but rapid decomposition nourishes trees for growth

Question 13

describe plant growth in amazonia

Answer 13

humid equatorial climate creates perfect conditions for plant growth, net primary productivity is high with a biomass between 400 and 700 tonnes/hector

Question 14

how much carbon does the amazon rainforest absorb per year

Answer 14

Amazonia absorbs 2.4 billion tonnes of carbon per year

Question 15

describe the exchanges of carbon in the forest

Answer 15

• rapid exchanges of carbon between the atmosphere, biosphere and soil
• warm, humid conditions ensure the rapid decomposition of material and quick release of CO2
• meanwhile the rates of carbon fixation are high from photosynthesis
• the forests leached and acidic soils contain only limited carbon and nutrient stores, the fact that such poor soils support a biome with the highest NNP emphasises the speed with which organic material is broken down

Question 16

how does geology impact the water and carbon cycles

Answer 16

impermeable catchments have minimal storage capacity so there will be rapid run off. Expanses of permeable porous rock such as chalk and limestone will have slow run off. The geology of the amazon is mainly dominated by metamorphic and igneous rock (impermeable, carbonates largely absent from mineral composition), although towards the Andes there are expanses of limestone (permeable, mineral composition largely dominate by carbonates).

Question 17

describe relief in the amazon

Answer 17

Mainly lowlands. In areas of gentle relief water moves cross the surface horizontally through the soil. The west Andes create steep catchments with rapid runoff. In the lower Amazon, at the mouth of Rio Negro the river level at low water season is only 15m above sea level, and the slope is about 1cm per kilometre.

Question 18

give figures that show the global significance of the amazon as a carbon sink

Answer 18

absorbs 2.4billion tonnes of carbon a year and releases around 1.7 billion from decomposition

Question 19

explain the dominating element of amazonia’s biomass

Answer 19

forest trees dominate the biomass with 60% of all carbon stored being in the above ground biomass of tree stems, branches and leaves. The remainder is below ground, mainly in roots and organic soil matter

Question 20

give two facts that show the scale of the amazons carbon cycle

Answer 20

NPP is 2500grams/m2/year

amazonia alone accounts for 15-25% of all NPP in terrestrial ecosystems

Question 21

explain the decomposition of material

Answer 21

high temperatures and humid conditions promote rapid decomposition by bacteria, fungi and other soil organisms, mainly of leaf litter and dead organic matter that temporarily accumulates at the soil surface. Decomposition releases nutrients into the soil that is quickly absorbed by tree roots and emits CO2 that is released into the atmosphere.

Question 22

give two facts that show the extent of deforestation in the amazon

Answer 22

Deforestation averaged around 17500km2/year between 1970 and 2013
since 1970 almost 1/5 of the primary rainforest has been destroyed or degraded.

Question 23

describe the flood on the madeira river

Answer 23

devastating floods in 2014 on the madeira river, the largest tributary (stream or river coming off a main river) of the amazon river.
60 people died
68,000 families were evacuated
outbreaks of cholera and leptospirosis

Question 24

describe the human influences that caused the madeira flood

Answer 24

deforestation has modified stores of water in trees, permeable rocks (due to rapid run off), and the atmosphere (less intercepted water on tree trunks and leaves that is easily evaporated). At the same time fewer trees means less evapotranspiration and therefore less rainfall. Run off speeds have increased, raising flood risks throughout the basin.
The main driver of the floods was deforestation in bolivia and peru; between 2000 and 2012, 30,000km2 of bolivian rainforest was deforested. Most of this occured on the steep slopes of the andes ( rapid run off= higher flood risk)

Question 25

why are rainforest trees such a crucial part of the water cycle

Answer 25

extracting moisture from soil, intercepting rainfall and releasing it through transpiration. The cycle sustains high atmospheric humidity which leads to cloud formation and convectional rainfall, deforestation can break this cycle and lead to permeant climate change. The effects of this are not just local, future projections of deforestation predict a 20% decline in regional rainfall as the rainforest dries out.

Question 26

describe the human factors effecting carbon cycle

Answer 26

• deforestation exhausts the carbon biomass store; the biomass of trees represents 60% of the carbon in the ecosystem, the rest is occupied by the soil in roots or dead organic material
• at the same time, deforestation massively reduces inputs of organic material to the soil. Soils, depleted of carbon and exposed to strong sunlight will support fewer decomposer organisms thus reducing the flow of carbon into the atmosphere

Question 27

what are the three categories strategies to recover the rainforest can fall into

Answer 27

1. protection through legislation of large expanses of primary forest unaffected by commercial developments
2. projects to reforest areas destroyed or degraded by subsidence farming
3. Improving agricultural techniques to make permanent cultivation possible.

Question 28

describe the brazillian conservation areas of the forest

Answer 28

by 2015, 44% of the brazillian amazon was occupied by national parks, wildlife reserves and indigenous reserves.

Question 29

describe a project to reforest an area

Answer 29

the sustainable forestry scheme aims to develop a 1000km2 commercial timber plantation using fast growing trees on government owned, deforested land.

Question 30

what has happened with improved agricultural techniques

Answer 30

• due to the low fertility of the soil, permanent cultivation proved unsustainable
• however one response has been diversification, soil fertility can be sustained by crop rotation and combined livestock