OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What role do leafy branches of trees play in soil moisture retention?

1. They absorb water from the soil

2. They prevent quick evaporation of water from the soil

3. They create shade which decreases transpiration

4. They act as barriers to wind

The correct answer is: They prevent quick evaporation of water from the soil

Leafy branches of trees play a crucial role in soil moisture retention by preventing quick evaporation of water from the soil. The presence of leaves creates a microenvironment that reduces the amount of sunlight directly hitting the soil surface. This shade helps to lower soil temperatures, which in turn decreases the rate of evaporation. Additionally, trees can also increase humidity levels in the air through transpiration, which can help maintain moisture in the surrounding environment. When the shady environment created by the leafy branches combines with the reduction in direct sunlight exposure, it significantly slows down the loss of water from the soil, making it more available for vegetation and other organisms. While the other options touch on important aspects of tree function, they do not directly pertain to moisture retention in the soil as effectively as the correct choice. For example, tree branches do not absorb water from the soil; instead, they utilize water through transpiration. Shading affects transpiration indirectly but does not decrease it to the same extent as the evaporation process. Lastly, while trees can act as barriers to wind, this primarily influences wind speed and soil erosion, rather than directly impacting soil moisture retention.