Nutrient cycles describe the movement of nutrients through biotic and abiotic components of ecosystems. Nutrients are absorbed by plants and animals from the environment, enter the soil through decaying matter, and are recycled through uptake by plants, decomposition, and other pathways. The rate and pathways of nutrient cycling vary between biomes, with forests generally having slower cycling than rainforests due to differences in climate and litter decomposition rates.

2. E.g. Carbon Cycle

3. Nutrient Cycle BIOMASS SOIL LITTER Uptake Pathway Gain from weathering Loss by leaching Loss by runoff Gain from precipitation Decay Pathway Fallout Pathway

4. Biomass BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Decay Pathway Fallout Pathway Gain from weathering Gain from precipitation

5. Soil BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Decay Pathway Fallout Pathway Gain from precipitation

6. Litter BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Decay Pathway Fallout Pathway Gain from weathering Gain from precipitation

7. Uptake Pathway: Absorption and take-up of elements from soil by plant roots BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Gain from precipitation Decay Pathway Fallout Pathway

8. Fallout Pathway: Death of plants and animals and the addition of nutrients to the litter store BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Gain from precipitation Decay Pathway Fallout Pathway Gain from weathering

9. Decay Pathway: Decomposition of litter to humus and return of nutrients to soil BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Gain from precipitation Decay Pathway Fallout Pathway Gain from weathering

10. Gain from Weathering: Chemical elements added to soil by weathering of rocks BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Gain from precipitation Decay Pathway Fallout Pathway Gain from weathering

11. Gain from Precipitation: Additional nutrients from precipitation, lightning or wind-blown dust etc. BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Decay Pathway Fallout Pathway Gain from precipitation Gain from weathering

12. Loss by Runoff and Leaching: N utrient removal through the erosive movement and chemical action of water. BIOMASS SOIL LITTER Uptake Pathway Loss by leaching Loss by runoff Decay Pathway Fallout Pathway Gain from precipitation Gain from weathering

15. Nutrient Cycles – Biomes Compared

20. Nutrient Cycling models for BIOMES (Gersmehl)