How is fuel loading expressed?

Fuel loading is expressed in terms of tons per acre or pounds per acre, which quantifies the mass of combustible materials available in a given area. This measurement directly relates to fire behavior, as it indicates how much fuel is present to sustain a fire. Understanding fuel loading is crucial for fire behavior predictions, as heavier fuel loads can lead to more intense and longer-lasting fires due to the increased amount of material available to burn.

The other options, while related to different aspects of fire behavior and fuel characteristics, do not accurately represent the concept of fuel loading. For instance, moisture content is critical for assessing how easily fuels can ignite and burn but does not indicate the quantity of fuel available. Similarly, the percentage of living plants might provide insight into the ecological characteristics of an area but does not quantify the amount of fuel present for combustion. Therefore, the correct expression of fuel loading as tons per acre or pounds per acre provides clear and actionable data for fire management and planning.