Nutrient cycles and global ecosystems Getting started Youll

Nutrient cycles and global ecosystems

Getting started You’ll need a notepad on which to make notes as you go along, or you could make notes, paste images, etc. on your device. You can view these slides: • as a slide-show for any animations and to follow links • in ‘normal’ view if you want to add call-outs or extra slides to make notes, paste images, answer questions, etc. © Geographical Association, 2020

What are nutrient cycles? • Plants take up nutrients from the soil to help them grow. • Nitrogen is an example of a very important nutrient. • The nutrients are returned to the soil when plants die or lose leaves. • Then new plants take them up again. • Nutrients go round and round an ecosystem in a cycle: the nutrient cycle. © Geographical Association, 2020 Resource How does the nitrogen cycle work? Activity Watch this Super Science video. Then explain the nitrogen cycle to someone else. You could draw a quick sketch to help your explanation.

Nutrient cycle diagrams – the stores • Nutrient cycle diagrams illustrate the nutrient cycle of an ecosystem. • There are three stores – soil (S), biomass (B) and litter (L). • The soil store is the soil – easy! • Biomass is all the living (biotic) organisms. • Litter is the layer of dead bits of biomass on top of the soil. © Geographical Association, 2020

Nutrient cycle diagrams – the transfers The arrows show the transfer of nutrients between the stores. Decomposition is bacteria releasing the nutrients from dead things back into the soil. Rainfall (precipitation) can bring nutrients into the ecosystem. Surface runoff can wash nutrients out of the litter store and into rivers /out of the ecosystem Leaching washes nutrients out of the © Geographical Association, 2020 soil. Littering is dead bits falling off biomass onto the litter layer. Plant uptake is plants taking nutrients up from the soil. Weathering releases nutrients from bedrock into the soil.

What was that again…? Sometimes, nutrient cycle diagrams only use letters for the stores and transfers. P B Li L U D R © Geographical Association, 2020 S Le Activity Without going back a screen, can you remember what all these letters stand for? Label a copy of this diagram to find out! Hint: P = precipitation

Differences between ecosystems Nutrient cycle diagrams are a great way to understand the features of ecosystems and the differences between ecosystems. These types of nutrient cycle diagrams are called Gersmehl diagrams. P Li B P Li L U D S R R Le Ecosystem 1 © Geographical Association, 2020 Score: 1– 2 differences = OK 3– 5 differences = good 6+ differences = excellent B L U Activity What differences can you spot between these two ecosystems? Ecosystem 2

Gersmehl diagrams • Now watch the video in the Resource box. • Some of the information will be familiar to you. • Some will be new and will explain what Gersmehl diagrams show about ecosystems. P B Li P Li L U D S D B S R R Le Ecosystem 1 © Geographical Association, 2020 Ecosystem 2 Resource Gersmehl diagrams Activity Once you’ve watched the video through, look again at Ecosystem 1 and Ecosystem 2. • Which one shows a rainforest ecosystem? Why? • Why is the other one a desert ecosystem?

This graph shows how nutrient cycles are affected by temperature and precipitation. The tropical rainforest ecosystem has high temperatures and high precipitation. The warm, wet conditions mean that decomposition happens rapidly. Litter breaks down rapidly in the litter layer, so nutrients do not stay in the litter layer for long = small litter store. Plants grow rapidly in the warm, wet conditions. So nutrients do not stay in the TROPICAL RAINFOREST soil for long = small soil store. Plants store nutrients in their tissues. Biomass = biggest store. © Geographical Association, 2020

The desert ecosystem has high temperatures but low precipitation. The dry conditions mean that few plants can survive. Biomass is very small. There is little litter produced so the litter layer is small. TROPICAL RAINFOREST There is very little rain so nutrients are not lost from runoff or leaching. With few plants and no leaching, nutrients build up in the soil. Soil = the biggest store. © Geographical Association, 2020

Activity Now it’s over to you. Try to explain the Gersmehl diagram for the taiga ecosystem. • What are temperatures and precipitation amounts like in the taiga? • Why would biomass be small in the taiga? • Why would decomposition be slow in the taiga? • How might this explain the biggest store? TROPICAL RAINFOREST Resource Taiga Adaptations. © Geographical Association, 2020

Summary • Nutrients cycle round and round in ecosystems – a nutrient cycle. Nitrogen is an example of an important nutrient. • Nutrient cycle diagrams are used to illustrate the nutrient cycle of an ecosystem. • Because different ecosystems have different nutrient cycles, these diagrams can be used to compare ecosystems – Gersmehl diagrams. © Geographical Association, 2020 Activity Gersmehl diagrams are a great way of explaining differences between ecosystems. Use the terms climate, stores and transfers to explain why.

Links Awarding organisations Topic AQA 3. 1. 2. 1 Ecosystems Edexcel A 3: Ecosystems, biodiversity and management Edexcel B 7: People and the biosphere Eduqas A 5. 3: Processes and interactions within ecosystems Eduqas B 3. 1: How ecosystems function OCR A 2. 1 Ecosystems of the planet (tropical rain forests) OCR B 4. 1. Why are natural ecosystems important? (the concept of an ecosystem) WJEC 5. 3: Processes and interactions within © Geographical Association, 2020 Find out more • National Geographic has lots of material on biomes: you could start here • Try out NASA’s biome interactive • BBC Bitesize has coverage of ecosystems for each specification.

Acknowledgements This presentation has been written by Rob Bircher, an experienced author, publisher and secretary of the Worcester Branch of the GA. Figures • Slides 4– 8: Diagrams from Wikipedia (CC-By-SA-3. 00) • Slides 9– 11: Diagram source http: //thestudent. blogspot. com/2012/05/structure-ofecosystems. html © Geographical Association, 2020