In a mature forest, how can a tree-fall gap increase species diversity?

• A. By providing a habitat for shade-tolerant plants to thrive
• B. By providing a habitat for shade-intolerant plants to grow
• C. By increasing soil moisture
• D. By reducing light for understory plants

Answer: (B)

A tree-fall gap creates a patch of forest floor with much more light and warmth, opening up new niches that the shaded understory couldn’t support. In a mature forest, many plants are adapted to low light and can’t grow when the canopy is intact. When a gap appears, shade-intolerant, or light-demanding, plants can germinate and establish themselves in that bright spot. As these sun-loving species take root alongside the existing shade-tolerant plants, the variety of species in the area increases, boosting overall diversity.

The other ideas don’t fit as neatly. Shade-tolerant plants were able to thrive before the gap, so merely having them grow there doesn’t add new species. Gaps don’t typically increase soil moisture; they often lead to more evaporation and drier conditions in the exposed spot. And gaps don’t reduce light—they increase it, which is the key driver for inviting those new, light-loving species.