Fire directly affects tree carbon balance and indirectly affects hydraulic function: consequences for post-fire...

Area of Science:

• Forest Ecology
• Fire Ecology
• Plant Physiology

Background:

• Mechanistic links between fire injuries and post-fire tree mortality remain unclear.
• Hypotheses focus on carbon balance and hydraulic function, but their interaction and relative importance are uncertain.

Purpose of the Study:

• Investigate fire's impact on tree carbon dynamics and hydraulic function.
• Relate these impacts to fire injuries and post-fire mortality.
• Examine species- and timing-dependent variations in fire effects.

Main Methods:

• Utilized two prescribed burns involving Douglas-fir and ponderosa pine.
• Assessed changes in non-structural carbohydrates (NSC) and hydraulic function.
• Correlated impacts with crown injury severity and burn timing (fall vs. spring).

Main Results:

• Fire-caused impacts on NSC were immediate, persistent, and strongly correlated with mortality.
• Hydraulic impacts were delayed and not directly linked to fire injuries.
• Some burned trees showed increased hydraulic dysfunction and water stress before death.

Conclusions:

• Fire directly impacts NSC, which is a primary driver of post-fire mortality.
• Hydraulic dysfunction may be an indirect consequence of fire's effect on NSC.
• Findings improve understanding of fire's complex effects on forest ecosystems facing increased fire activity.