Are fine fuels or heavy fuels affected more by changes in relative humidity?

Fine fuels are indeed affected more by changes in relative humidity due to their smaller size and lower moisture content. Fine fuels, which include grasses, leaves, and small twigs, can absorb and lose moisture rapidly. As relative humidity decreases, fine fuels can dry out quickly, increasing their combustibility and making ignition easier. Conversely, when relative humidity is high, these fuels retain moisture, which can hinder their ability to ignite and sustain combustion.

Heavy fuels, such as logs and larger branches, have a higher moisture content and generally take longer to dry out or absorb moisture. These heavier fuels respond more slowly to changes in environmental conditions, such as relative humidity, making them less sensitive to immediate changes compared to fine fuels.

Understanding how fine fuels react to changes in humidity is critical for fire behavior prediction and wildfire management strategies. It highlights the importance of monitoring weather conditions, as low humidity can significantly increase fire risk, particularly in areas with abundant fine fuels.