1.1. A student investigated the decomposition of leaves from different types of tree.

Decomposers in the soil convert...

1.2. The student collected and weighed some fresh leaves from a beech tree.

• The leaves were placed on top of soil in a tray.

• This was repeated for leaves from three other types of tree.

• The trays were kept in the same abiotic conditions for 40 days.

• The leaves were reweighed after 40 days.

(i) State two abiotic factors that should be kept the same in this investigation.

(2)

(ii) Explain how this investigation could be improved to make the results more comparable.

(2)

1.3. Figure 1 shows the mean rate of decomposition for this investigation.

Figure 1

(i) Which leaves would produce compost in the least time?

(1)

(ii) The same investigation was extended to include the leaves of a silver birch tree.

The starting mass of the leaves was 28.2 grams.

After 40 days the mass of the leaves was 19.7 grams.

Calculate the rate of decomposition of the leaves of the silver birch tree.

Give your answer to three significant figures and include the units.

(3)

1.4. Explain how the concentration of oxygen in a compost bin would affect the rate of decomposition.