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Marlborough Forest Ecosystems

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Marlborough Forest Ecosystems

You are helping a conservation team investigate a beech forest in Marlborough, Aotearoa New Zealand. Use the field notes, food web and sample data below to explain how the ecosystem works. In the food web, arrows point from the food to the organism that eats it.

Field notes and food web

The team surveys a patch of red and silver beech forest. Sunlight reaches the forest floor through gaps in the canopy. Rainfall and soil moisture vary across the slope. Beech trees produce seeds; seedlings need light, water and nutrients to grow. Invertebrates such as caterpillars feed on leaves. A forest bird, the toutouwai (South Island robin), eats invertebrates. The introduced ship rat eats seeds and invertebrates. Decomposers, including fungi and bacteria, break down dead material and return nutrients to the soil.

Beech seeds

→

Ship rat

Beech leaves

→

Caterpillar

Invertebrates

→

Toutouwai

Dead leaves and organisms

→

Fungi and bacteria

Survey results

A team used five 1 m² quadrats at random locations in each area (ten quadrats total). They counted living beech seedlings in every quadrat.

Interior: 8

Interior: 7

Interior: 9

Interior: 6

Interior: 10

Track edge: 4

Track edge: 3

Track edge: 5

Track edge: 2

Track edge: 6

1.From the field notes, identify one biotic factor and one abiotic factor. Explain how they could interact to affect beech seedlings.

2.Which sequence best describes a beech tree’s life cycle?

Seed → seedling → mature tree → death → decomposition
Seedling → seed → decomposition → mature tree → death
Mature tree → seedling → seed → death → decomposition
Seed → mature tree → decomposition → seedling → death

3.The team records sunlight, soil moisture, beech seedlings, caterpillars and ship rats. Sort these into abiotic and biotic factors.

4.In the food web, what does an arrow from beech leaves to a caterpillar mean?

The caterpillar provides energy to the beech tree.
The beech leaves are a food source that transfers energy to the caterpillar.
The beech tree hunts the caterpillar.
Both organisms eat decomposers.

5.Suppose ship rat numbers rise sharply. Predict one possible effect on beech seeds and one possible knock-on effect for another organism in the food web. Explain your reasoning.

6.Why might ecologists use quadrats and sample locations rather than count every seedling across the whole forest?

A sample is quicker and more practical in a large forest.
A sample always gives the exact total number of seedlings.
Quadrats make seedlings grow at the same rate.
Sampling removes the need to record methods.

7.The team chose quadrat locations by chance. What is one benefit of random sampling?

8.Calculate the mean number of seedlings per quadrat in the forest interior. Show your working.

9.Calculate the mean number of seedlings per quadrat at the track edge. Then compare it with the interior mean.

10.The track-edge mean is lower. Can the team conclude that walking tracks caused the difference? Give one reason for your answer and one improvement to the investigation.

11.Fungi and bacteria decompose dead leaves. Explain how this process can help the forest ecosystem continue functioning.