In some ecosystems, the climax community is not stable and is regularly and repeatedly replaced in a process of cyclical succession

• These periodic changes may be caused by recurring events (e.g. seasonal conditions) or changing interactions between animal and plant species

Cyclical succession can be observed between two species of desert plant (creosote bush and Christmas cactus) 

• Via the dispersal of wind, seeds from the creosote bush colonise an open space
  

• This draws birds and rodents, which transfer seeds from the Christmas cactus
  

• The cactus grows under the creosote bush and begins to compete for available water
  

• The cactus has a shallower root system which is more effective at absorbing water – meaning the creosote bush dies off
  

• Without a deeper root system, the soil begins to erode and the catcus roots become exposed – causing the plant to die 
  

• This re-establishes an open space, allowing the succession cycle to begin anew
  

Cyclical Succession

1. Shrub seeds

2. Shrub grows

3. Cactus seeds

4. Cactus grows

5. Shrub dies

6. Cactus dies