Give an approximate figure for the carbon held in tropical rainforest.

In the order of 180 to 200 tonnes of carbon per hectare, most of it above ground in the trees.

Why is rainforest soil a relatively small carbon store despite the biomass above it?

Hot, wet conditions make decomposition extremely rapid, so litter breaks down and its nutrients are taken straight back up rather than accumulating in the soil.

Where is most of the carbon in a temperate grassland held?

Below ground, in deep root systems and in the organic matter of the soil.

How does temperature influence the size of a biome's carbon store?

Warmth raises the rate of photosynthesis, but it raises decomposition faster still, so hot biomes cycle carbon quickly and retain little of it in the soil.

WJEC A-Level Geography 601-8455-3

Coastal Landscapes

Glaciated Landscapes

Topic overview The glacier as an open system Climate change and the glacier budget Glacier movement Types of ice mass and their distribution Glacial weathering and erosion processes Macro-scale erosional landforms Glacial transport and depositional landforms Fluvioglacial landforms Suites of landforms in glacial landscapes Periglacial processes and ground ice Periglacial action of water and wind Glacial change over different timescales Glacial environments and human activity

Tectonic Hazards

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Changing Places

Topic overview What gives a place its character Flows and connections that shape places Meaning, perception and attachment to place How places are represented Economic restructuring and the Clark Fisher model Deindustrialisation and social inequality The service economy and its impacts The knowledge economy and clusters Rebranding rural places Managing change in rural places Rebranding urban places Managing change in urban places Comparing a home place with a contrasting place How place change affects people's lives

Water and Carbon Cycles

Topic overview The water cycle as a global system and mass balance Global water stores and residence times Cryospheric processes and sea-level change Drainage basin inputs, stores and outputs Flows within the drainage basin River regimes and their controls Storm hydrographs and hydrograph shape Air uplift, cloud formation and precipitation Excess runoff and flooding Deficit in the water cycle and aquifer recharge The global carbon cycle and its stores Carbon pathways between land and the atmosphere Carbon transfers involving the oceans Carbon stores in biomes and land-use change Changing carbon stores in peatlands Rising atmospheric carbon and its impacts Feedback within and between the water and carbon cycles

Global Migration

Topic overview Globalisation and a shrinking world Classifying and mapping migration Causes of international economic migration Consequences and management of economic migration Refugee movements and internal displacement Rural-urban migration in developing countries Superpowers and global hub cities Migration policy and public debate in the UK Managing refugee crises Informal settlements in developing cities

Global Governance of the Oceans

Topic overview Supranational institutions and global governance Laws and agreements governing the oceans Strategic value of the oceans and maritime security Shipping, cables and illicit flows Sovereignty over ocean resources Managing marine environments Ocean pollution and its management Governance across scales: an ocean case study

EcosystemsContemporary theme

Topic overview The value of ecosystems to people The distribution of global biomes Ecosystem structure, energy flow and productivity Nutrient cycling in contrasting biomes Measuring and threatening biodiversity Conserving biodiversity Succession and local ecosystems The Arctic tundra biome Sustainable use of the Arctic tundra

Economic Growth and Challenge: IndiaContemporary theme

Topic overview India's relief, drainage and climate India's population, society and governance India's resources, hazards and economic geography India's global role and economic growth Environmental pressures of India's growth Sustainable development strategies in India

Economic Growth and Challenge: ChinaContemporary theme

Topic overview China's relief, drainage and climate China's population, society and governance China's resources, hazards and economic geography China's global role and economic growth Environmental pressures of China's growth Sustainable development strategies in China

Development in an African ContextContemporary theme

Topic overview Defining and measuring development Physical factors influencing development Economic factors influencing development Political, social and cultural factors in development The environmental cost of development Desertification Strategies to promote development

Energy Challenges and DilemmasContemporary theme

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Weather and ClimateContemporary theme

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Fieldwork and Geographical Skills

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Key Concepts in Geography

Topic overview Systems, equilibrium and feedback Causality, interdependence and mitigation Resilience, risk and sustainability Place, space, scale and representation

Water and Carbon Cycles

Carbon stores in biomes and land-use change

2 things to know
A2 Unit 3

Overview

Why temperate grassland soils accumulate so much carbon, three ways in which deforestation reduces a carbon store and how afforestation increases a carbon store.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain why temperate grassland soils accumulate so much carbon.

Key term

Which biome holds the largest carbon store in its vegetation?

Questions from this subtopic

Each one with the model answer underneath.

1
Which biome holds the largest carbon store in its vegetation?
Model answer
The tropical rainforest, whose tall, dense, year-round growth accumulates an exceptionally large biomass.
2
Give an approximate figure for the carbon held in tropical rainforest.
Model answer
In the order of 180 to 200 tonnes of carbon per hectare, most of it above ground in the trees.
3
Why is rainforest soil a relatively small carbon store despite the biomass above it?
Model answer
Hot, wet conditions make decomposition extremely rapid, so litter breaks down and its nutrients are taken straight back up rather than accumulating in the soil.
4
Where is most of the carbon in a temperate grassland held?
Model answer
Below ground, in deep root systems and in the organic matter of the soil.
5
Explain why temperate grassland soils accumulate so much carbon.
Model answer
Grasses die back each year and add organic matter below ground, while cooler conditions and a dry season slow decomposition, so carbon builds up in the soil.
6
How does temperature influence the size of a biome's carbon store?
Model answer
Warmth raises the rate of photosynthesis, but it raises decomposition faster still, so hot biomes cycle carbon quickly and retain little of it in the soil.

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