1.    Direct effects of climate change (i.e., temperature rise, changes in seasonal precipitation, wind patterns, and atmospheric stability) affect fire regimes of boreal forests by altering fire behavior, fire seasons, and fuel moisture. Climate change also alters species composition and fuel characteristics, which subsequently alter fire regimes. However, indirect effects of climate change are often simplified or neglected in the direct climate-fire relationship models and dynamic global vegetation models. This may result in high uncertainties associated with existing projections of fire regimes for climate change scenarios. Moreover, few studies have examined fire regime predictions beyond the 21st century, and consequently, how the fire regimes of boreal forests would respond to climate change at the long-term (>100 years) is not clear.

2.    We develop a coupled modeling framework integrating direct and indirect effects of climate change to predict fire occurrence probability and burned area for boreal forests in northeastern China. We applied repeated-measures ANOVA to quantify direct and indirect effects of climate change on fire regimes in the short (0-50 years), medium (60-100 years), and long-term (150-200 years).

3.    Results showed that for the 21st century, direct effects of climate change are likely to exert a stronger influence on fire regimes than indirect effects. However, increases in fire occurrence probability and burned area will accelerate the transition of boreal forests to temperate forests in the period 2100-2200, and thereby reduce fire occurrence probability and burned area. This suggests that vegetation change will mediate direct effects of climate change on fire regimes of boreal forests in the long-term.

4.    Synthesis and applications. Vegetation change will mediate direct effects of climate change on fire regimes of boreal forests in the long-term. This finding suggested that policy makers may consider adaptive management by planting deciduous species to reduce fire occurrence probability and resistant management by reducing competition to promote boreal species under changing climate conditions.

Details of the methods can be found in the manuscripts.