Rainforest Lesson 4-7 (copy)

Lesson 4: Nutrient cycling

Rainforest soil is nutrient poor, thin and has a high iron content. This is because of the nutrient cycle (more details further in the text) uptake of nutrients by trees and plants, washing away of nutrients by rainfall but the nutrients are supplied by litter usually which is decaying plant matter.

Nutrient cycling in the rainforest:

The three main stores of nutrients where the nutrients will “sit” for a while are: litter (decaying/dead plant material on the forest floor), biomass (trees/shrubs) and the soil.

Rainfall can add a reasonable amount of nutrients to the litter. (1) (rainfall to litter)

But when it rains the rain water will run along the ground and remove some nutrients from the litter, this process is called run off. (5) (litter being destroyed)

Biomass adds some nutrients when their trees’ leaves fall to the floor to become litter. This is how biomass turns into litter and more nutrients and this process is called fall out. (2) (biomass to litter)

But, litter can break down and lots of its nutrients go to the soil. This process is called decay. (3) (litter to soil)

Little amounts of nutrients can leave the soil when it rains and the rain water washes nutrients down and out of the soil. This process is called leaching. (4) (soil being destroyed)

But, a small amount of nutrients can be added to the soil when rocks decompose because of the atmosphere, giving its nutrients to the soil. This process is called weathering (of rocks). (7) (rocks to soil)

Biomass can draw up a large amount of nutrients from the soil due to their roots actually being in the soil which gives the biomass the soil’s nutrients. (6) (soil to biomass)

All of these processes of gathering nutrients from different things for different stores all come together to become one big nutrient cycle.

This cycle can be useful to understand where nutrients can go from one place to another. For example, the nutrients of rocks are weathered to the soil and the roots of biomass suck up the nutrients and the leaves of the biomass will fall and decay into litter giving the soil more nutrients or getting ran off by the rainfall. The cycle is extremely useful and is like a route for the nutrients and where they go. It is important to bear in mind that, some processes gather more nutrients than others which can affect the routes of nutrients.

In theory:

Decay and trees drawing up nutrients are the most effective for nutrient gathering.

Rainfall adding nutrients in quite effective for nutrient gathering.

Fall out, run off, weathering and leaching are less effective in gathering/destroying nutrients.

The rainforest nutrient cycle is rapid. The hot and damp conditions on the forest floor can help the speed of decay in dead plant material which provides plentiful nutrients that can be easily absorbed by plant roots when the nutrients reach the soil. These nutrients are always in high demand because of the speed in which rainforest plants grow. The nutrients are not in the soil for long and stay close to the surface of the soil. Rainforest soil also does not make good farmland because of how vulnerable it is to erosion when plants are removed and how the soil always contains low nutrients.

THE WATER CYCLE:

When heavy convectional rainfall occurs because of the amount of plants in the rainforest some trees actually intercept that water and use it as nutrients. Some rain will reach the ground and the trees take up the water. If not, the water will evaporate and convectional rainfall follows.

Lesson 5/6: Plant adaptations and case study figures

What are adaptations?

Adaptations are features organisms have to survive in different climates.

Examples of plant adaptations:

• Buttress roots and still roots turn shallow to soak up nutrients because of how thin the rainforest soils are. Both buttress and still roots, also play a part in stabilising trees in the canopy.

• Red leaves can turn red when they are young to give protection from sunlight while their internal organs are developing. The red layer acts as a sunscreen, basically.

• Lianas use other trees to climb up the rainforest canopy to get as much sunlight as they can.

• Leaf angling - leaves arranged at different angles - is used so that a plant avoids shading its own leaves as the competition for sunlight is intense.

• Drip tips - leaves have a waxy surface to allow the excess rainwater to run-off easily to prevent algae, which blocks sunlight.

• Epiphytes live on the surface of other plants to help them get more sunlight - similar to lianas. And, epiphytes are not parasites so they can grow on other plants without harm.

• Trees have thin bark to help growth and they do not need thick bark as they do not need to prevent moisture

• Some plants attract insects using nectar and trap them and the walls of the plant are usually waxy killing the insect using microbes and enzymes giving the plant more nutrients. This plant is called the pitcher plant.

• Mimosa pudica wilts its leaves when touched to scare off predators and it deflects water too, to prevent waterlogging.

• Flowers have brightly coloured petals to attract attention for nectar.

TOP TIP FROM MISS CAMPBELL: Always put lots of points and explanations during high-mark questions as they are always worth a mark and add examples too; statistics and figures. Use acroynm TEA or OBE for graphs (Trend - what is the trend, Evidence - give figures, Anomaly - different) and PEE/PE/PEEL for high marks. Use the three types of geography to help. (Human, Physical, Environmental) Or reasons: Environmental, social, economic.

Why do plants have to adapt; what challenges are in the rainforest that plants have to face?

They have to adapt due to the climate and how moist and damp and humid it is, with high rainfall and low sunlight (2%) in forest floors and shrub layers. Challenges plants in the rainforest have to face include: ensuring future generations survive, avoiding pests and disease, competition for resources like sunlight and nutrients and avoiding waterlogging.

Around 50% of all known species of animals and plants live in the rainforest.

When old trees die it opens space for little plants to take over.

Only 2% of light reaches forest floor.

Balsa tree is the fastest growing tree in the rainforest.

Rainforests cover 2% of the planet.

Lesson 7: Animal adaptations

There are 6 key major types of adaptations:

Camouflage - a technique to disguise yourself, which can be useful to avoid predators. Examples: Sloths have green algae which grows on its fur to camouflage to avoid predators and being attacked or the leaf tailed gecko.

Poison and bright colours - bright colours scare off predators and poison can kill too, which can also be useful to scare off/avoid predators. Examples: poison dart frogs are only 1.5cm in length but holds enough poison to kill 100 humans!

Prehensile tails - are tails that allow animals to swing around easily, practically using it as a fifth limb. They also allow ease of living in the canopy where it can be used to hang and swing onto trees. It is useful to avoid flooding and fires and allows access to foods. Examples: sloths and spider monkeys have prehensile tails and live in the canopy.

Picky eating - reduces the competition for food as animals can eat some foods that other animals cannot because of diet and accessibility. Examples: toucans snatch hard-to-reach fruit which is not accessible to some other animals as toucans have long and narrow beaks which give it a slight advantage.

Reduced size - advantageous due to limited space in the rainforest therefore animals need to be smaller to move quicker. Example: frogs and birds

Nocturnal living - advantageous due to the high levels of competition during daytime so if you can exploit the night when everyone else is sleeping then you have less competition for resources. Example: sloths and bats

Other animal adaptations and examples:

Piranhas: super fast swimming and sharp teeth to catch prey and avoid predators.

Anteater (type of bird): sharp beaks to crack open and crunch nuts and seeds.

Gibbons: can rotate their shoulder joint completely to use it as a hook which can hold their whole body weight, they live in the canopy which gives the “hook” a chance to thrive.

Spider Monkeys: small thumbs to use hands as hooks, they also live in the canopy which gives the "hook” chances to thrive too.

Sloths: triple stomach to preserve energy from little foods.