Passage:
In temperate forest ecosystems, certain coniferous trees depend on intense environmental events to reproduce. The lodgepole pine (Pinus contorta), for example, produces serotinous cones that remain tightly sealed with a thick resin coating for many years. Under normal climate conditions, these cones stay closed and retain their viable seeds indefinitely, protecting them from seed-eating birds and rodents.
However, when a severe forest fire sweeps through the canopy, the intense thermal energy generated by the flames raises the temperature within the canopy above critical thresholds. This extreme heat melts the protective resin bond sealing the cone scales. As the resin liquefies and breaks down, the scales flex outward and release thousands of seeds onto the newly cleared, nutrient-rich forest floor. Because the fire also consumes competing understory vegetation and opens up the canopy to direct sunlight, the released seeds encounter ideal conditions for rapid germination and seedling growth.
Based on the passage, what directly causes the scales of lodgepole pine cones to flex outward and release their seeds?
- AThe rapid growth of seedlings following the removal of competing understory vegetation
- The melting of the protective resin seal by extreme heat from a forest fireCevap
- CThe foraging behavior of seed-eating birds and rodents under normal climate conditions
- DThe direct exposure of closed cones to sunlight prior to the occurrence of a fire