Leatherjackets (the larvae of crane flies):

• live in the upper layers of soil
• feed on the roots and stems of grasses
• require damp soil conditions to survive
• are sensitive to extreme dry conditions.

Give two abiotic factors and two biotic factors that could affect the size of a leatherjacket population.

Students investigated the population of leatherjackets in the soil of two different green spaces:

• Site A: a domestic grass lawn
• Site B: a golf course fairway

A mild liquid, Solution Y, can be poured onto the turf. This solution causes the larvae to rise to the surface of the soil within a few minutes but does not harm them.

Plan an investigation using Solution Y to compare the number of leatherjackets per $m^2$ in Site A and Site B.