Woodland Nutrient Cycle
A deciduous woodland runs its nutrient cycle to the beat of the seasons. Follow the Gersmehl stores through autumn leaf fall and slow winter decay, and see why a woodland is not just a colder rainforest.
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A woodland through the seasons 🌳
A **deciduous woodland**, like an English oak wood, changes with the seasons: leaves burst out in spring and fall in autumn. Nutrients move through it in a **nutrient cycle**. The **Gersmehl model** shows that cycle as three stores linked by arrows. This module follows the cycle and, importantly, shows how a woodland differs from a tropical **rainforest**.
The three stores 🔑
In the Gersmehl model, nutrients are held in three stores, drawn as circles:
Match each transfer 🔗
- Uptake
- Litterfall
- Decomposition
- Leaching
- Roots absorb nutrients from the soil into the biomass
- Dead leaves fall from the biomass to the litter
- Decomposers break down litter, returning nutrients to the soil
- Water washes nutrients down out of the soil and away
Go round the cycle 🔄
An interactive activity.
Why so much litter? 🍂
Compared with a tropical rainforest, the litter store in a deciduous woodland is much larger. Why?
- Leaves fall together in autumn and the cold slows decomposition, so litter builds up
- Deciduous trees never drop their leaves
- The climate is hotter, so leaves pile up faster
- There is no soil for the nutrients to go into
Rainforest vs deciduous woodland ⚖️
Both biomes use the same Gersmehl model, but the sizes of the stores are very different.
Which describe a woodland? ✅
Select the TWO statements that describe a deciduous woodland nutrient cycle.
- The three stores are more balanced in size
- A large litter store builds up after autumn leaf fall
- The biomass store completely dominates the other two
- Litter decomposes almost instantly all year round
The seasons drive the cycle ❄️
The big difference is the **seasons**. In autumn, deciduous trees **drop all their leaves at once**, so the litter store suddenly grows. Through the **cold winter**, decomposers work **slowly**, so the litter and soil stores stay larger than in a warm rainforest. In spring, nutrients are taken back up as new leaves grow. The cycle is **seasonal**, not constant.
Complete the cycle 🧱
The Gersmehl model shows three stores: biomass, _____ and soil. Nutrients move from soil into the trees when roots carry out _____. In a deciduous woodland, decomposition is _____ because the winters are cold. Compared with a rainforest, the three stores are more _____. When the woodland is cleared, the cycle is broken and the soil becomes less _____.
True for a woodland? 🖍️
An interactive activity.
Clearing the woodland 🔀
An interactive activity.
Compare the cycles ✍️
An interactive activity.