Carbon and Water Cycles in Tropical Rainforests

Transcription

1 Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby Carbon and Water Cycles in Tropical Rainforests Guidance Notes for Teachers This is one of two programmes produced by Pumpkin Interactive about water and carbon cycles. This programme is concerned with the carbon cycle. Filmed in Borneo. It focuses on rainforests, and how the carbon cycle could alter drastically as a result of human activities, e.g. logging or oil palm cultivation. The second concerns the Tundra biome, the changes which are taking place there resulting from climate change, and potential implications for the carbon cycle. PUMPKIN Specialist producers of high quality DVDs. Phone: + 44 (0) Post: 22A Backfields, Lane, St Pauls, Bristol, BS2 8QW Web: orders@pumpkin-interactive.co.uk Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 1

2 Contents p.3-6 p.7-9 p p Part 1 The Global Carbon Balance: Student Resources Part 2 Measuring Carbon in Tropical Rainforests: Student Resources Part 3 Deforestation and the Carbon Cycle: Student Resources Part 4 Deforestation and the Water Cycle: Student Resources Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 2

3 Part 1 The Global Carbon Balance: Student Resources A Knowing the key terms Define these key terms from the programme: 1. Anthropogenic 2. Atmosphere 3. Biosphere 4. Canopy 5. Carbon balance 6. Carbon capture 7. Carbon cycle 8. Carbon sinks 9. Carbon stores 10. Carbon use efficiency 11. Ecosystem 12. Emergent 13. Flux 14. Flux tower 15. Greenhouse gas 16. Gross Primary Productivity (GPP) 17. Net Primary Productivity (NPP) 18. Photosynthesis 19. Primary tropical rainforest 20. Respiration 21. Shrub Layer 22. Stratified structure 23. Understorey Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 3

4 B Odd one out In pairs, discuss the following groups of terms. In each case, identify the odd one out, and explain what makes it so: a) anthropogenic, atmosphere, biosphere b) canopy, shrub layer, emergent c) flux, respiration, greenhouse gas d) carbon sink, carbon store, carbon capture e) ecosystem, photosynthesis, respiration f) shrub layer, stratified structure, understorey g) GPP, NPP, Ecosystem h) atmosphere, biosphere, ecosystem i) carbon balance, carbon store, flux C Understanding the programme These questions are designed to aid your understanding of the programme 1. Flux towers what purpose do they have? Why locate them in the midst of a rainforest? Why do they need to be so tall? 2. Explain how rainforests play a crucial part in slowing the pace of climate change and helping to maintain the global carbon balance. 3. Explain two reasons why photosynthesis is fundamental to the carbon cycle. 4. In what ways are rainforests incredibly efficient carbon capture machines? 5. Explain the difference between Gross Primary Productivity (GPP) and Net Primary Productivity (NPP). 6. Why does CPP remain high all year in rainforests, but is only high for a few months in the boreal forests of Russia and Canada? 7. What is the significance of respiration in plants in terms of the carbon cycle? 8. Why is carbon use efficiency an important element of the carbon cycle? 9. Why are rainforests such effective carbon sinks? 10. Globally, what is the significance of rainforests in the carbon cycle? Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 4

5 D Understanding the structure of rainforests Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 5

6 Activity Study the four photos above. They show the four different layers in the structure of the rainforest. Place each of the following descriptions next to a photo by writing it in the spaces provided. A discontinuous cover Buttress roots are common here Crossing the layers are creepers such as lianas From ground level to 10m up is the shrub layer. Less than 3% of the light striking the trees above gets to the forest floor Most of the mature trees are here Plants here have to be tolerant to shade and are usually slow growing There s relatively little undergrowth here These two layers are sometimes called the under-storey. This extends from 20 to 40 metres in height This extends up to about 20m. This layer is also called the emergent layer Trees here can be over 50 metres high Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 6

7 Part 2 Measuring Carbon in Tropical Rainforests: Student Resources A Knowing the key terms Refer to the key words for Part 1 of this programme, plus the following: 1. Carbon source 2. Heterotrophs 3. Leaf area index 4. Logging Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 7

8 B How productive are different biomes? The table below shows eight major biomes and their NPP but, with the exception of rainforests, the data about NPP have been scrambled. In pairs, discuss and decide a) Which missing number goes where in the table b) Its rank (i.e. the lowest NPP is 8 th ) Mean Net Primary Production by Biome Vegetation type Mean Net Primary Productivity Rank [g/(sq m x yr)] Boreal forest Savanna Temperate deciduous forest Temperate evergreen forest Temperate grassland Tropical rainforest Tropical seasonal forest Tundra Choose from these values: C Understanding the programme 1. Flux towers why are they so tall? what instruments are used there, and what data do they collect? Why the need for three sets of data? What do the data tell Tehri? 2. Explain how the carbon balance varies between day and night. 3. Why do readings from the flux tower show falling CO2 but increasing water vapour during the day, but the reverse at night? 4. Explain how CO2 and water vapour readings might alter during a drought period. 5. Explain why the following data are essential to monitor the effects of logging: a) the total amount of CO2 fixed by plants, b) how much CO2 is returned during respiration, and c) how much CO2 is used for plant growth and repair. 6. Outline and explain the formula for calculating Net Primary Productivity 7. How do photographs help Tehri calculate how much carbon is being fixed by leaves? Explain how photographs, leaves collected in litter traps, and measurements of tree and root growth help Tehri to estimate NPP. 8. What s the significance of Tehri spending much of her time collecting CO2 data from tree roots and trunks? 9. How does Tehri know whether a particular rainforest is a carbon source or sink? 10. Explain why the billions of insects and fungi and the countless microbes in the soil are just as important in assessing carbon stores and sinks. D Activity Study Figure 2 below, which shows the carbon cycle and the relative importance of different inputs, flows, stores and outputs. The amount of Earth s carbon is measured in gigatonnes (Gt) or petagrams (Pg). Each Gt or Pg of carbon equals one billion tonnes. The units shown in Figure 2 are in petagrams (Pg) of carbon. Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 8

9 Store sizes are shown in blue, and annual fluxes in red. Source of diagram: Activity 1. Using a scale of 100 petagrams = 10 mm, re-draw Figure 2 as a flow diagram with flow arrows in proportion to the volume of fluxes shown. For small amounts, just use a pencil line. 2. a) Using the values shown, construct a system diagram to show inputs, flows, stores and outputs. b) To what extent is the carbon cycle in balance? Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 9

10 Part 3 Deforestation and the Carbon Cycle: Student Resources A Knowing the key terms Refer to the key words for Parts 1-2 of this programme, plus the following: 1. Biomass 2. Selective logging 3. Detritivores 4. Secondary forest 5. Colonisers Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 10

11 B Understanding the programme 1. Right now the world seems to have an insatiable appetite for the palm oil. Research the range of uses to which oil palm is put. 2. Explain the purpose of building a flux tower in the middle of an oil palm plantation. 3. What is Tehri talking about when she says if we didn t have this sink the concentration in the atmosphere would be rising at twice the rate that it currently is? 4. What investigative question is Tehri researching in the oil palm plantation, and why? 5. Why can the removal of just one large tree reduce the amount of carbon being stored in the rainforest by 50%? 6. Explain the impact of logging on a) GPP, b) the amount of CO2, c) the balance between the rainforest as a carbon sink versus a carbon source. 7. a) Why in spite of the removal of a large specimen tree can a rainforest quickly return to being a carbon sink, in theory at least? b) Why then following the removal of a large specimen tree does a rainforest NOT rapidly return to being a carbon sink? 8. The impacts of logging don t disappear that quickly.. Explain the meaning behind this statement. 9. Explain how the development of an oil palm plantation can result in a) changes in leaf cover, b) changes in how much CO2 is fixed compared to primary forest. 10. Explain why oil palms must be replaced every 20 to 30 years, and the impact that this has on the carbon cycle. C The impacts of different futures for the rainforest Impacts on Selective logging Clearance for palm oil plantations Conservation i.e. rainforest remains 1. Carbon balance (carbon source vs carbon sink) 2. Density of leaf cover 3. Biomass 4. Amount of CO2 fixed by Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 11

12 photosynthesis 5. Amount of CO2 released 6. Climate 7. Soil 8. Any other variable Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 12

13 Part 4 Deforestation and the Water Cycle: Student Resources A Knowing the key terms Refer to the key words in the teachers notes for Parts 1 to 3 of this programme, plus the following: 5. Drip tips 6. Evapotranspiration 7. Intercept 8. Leaching 9. Positive feedback loop 10. Stem flow 11. Through fall 12. Water cycle B Understanding the programme 1. Explain how a) drip tips and b) smooth bark have allowed some trees to adapt to climatic conditions in the rainforest 2. Explain how heavy rainfall results in soils becoming poorer in primary rainforest 3. Explain how plants cope with poor soils in rainforests 4. Explain how the soil pit bug by Tehri reveals how poor rainforest soils actually are 5. Why do compounds like iron and aluminium oxides remain and increase in concentration in rainforest soils? 6. Why is Tehri measuring water vapour being given off by the rainforest? 7. Explain how the following impact upon the hydrological cycle of rainforests: a) deforestation, b) further development (e.g. road construction and building of storage areas) 8. Assess the impacts of palm oil plantations on areas of former primary rainforest 9. Explain how deforestation and the establishment of palm oil plantations can actually alter the weather in rainforest regions 10. Explain how deforestation and the establishment of plantations can a) reduce rainfall, b) cause drought, and c) create a positive feedback loop in the hydrological cycle. Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 13

14 C Understanding the nutrient cycle Soil health or fertility is maintained within an ecosystem by the nutrient cycle shown below. It is usually known as Gersmehl's nutrient cycle (after Gersmehl who developed the idea). It s shown as a generic idea the circles are theoretically equal in size though this may vary depending upon particular ecosystems and their physical circumstances. A C B 1. Explain the ways in which Biomass, Litter and Soil are linked in the diagram. 2. Explain how the following process occur: Fallout Decay Growth (or uptake) 3. The following phrases belong on boxes A, B, and C. Decide which belongs where. Litter decomposes, returning nutrients to the soil Plants take up nutrients as they grow Dead plant matter fall to become known as leaf litter on the ground 4. Explain a) how deforestation break the nutrient cycle, b) why rainforest soils become infertile very quickly. Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 14

15 a) b) 5. Based on these answers, construct a new version of Gersmehl s nutrient cycle below, this time drawing proportional circles to show how each may vary within a rainforest ecosystem. Explain your thinking in how you decided to represent each part of the cycle Date: 20-Jan-2018 RCYCLE: Teaching Materials Author: Bob Digby 15