Climate-induced Shifts in Fire Frequency, and Resulting Effects on Stand Composition Carissa D. Brown Northern Biogeography Lab Department of Geography, Memorial University

Black spruce (Picea mariana)

Fire drives secondary succession and species distribution in boreal forests

Short window of opportunity

Temperature trends ( ) Burrows et al Science; Chapin et al Science

Climate-fire regimes Flannigan et al Ratio of 3xCO2 / 1xCO2 area burned:

Climate-fire-succession Balshi et al Kasischke and Turetsky 2006

Fire drives secondary succession and species distribution in boreal forests What happens if fire regimes change?

How will changes in fire-climate interactions effect black spruce distribution?

mature forest long- interval fire short- interval fire

mature forest

long-interval fire

short-interval fire

mature forestlong-interval burnshort-interval burn Post-fire colonisation: is seed available?

Seed availability mature forest LISI short interval Number of viable seeds/m 2 /year Brown and Johnstone, 2012, For. Ecol. Man. long interval Fire history

Will seed germinate and survive?

Number of emerged seedlings Fire history Brown and Johnstone, 2012, For. Ecol. Man. Black spruce emergence

fire return interval seed availability establishment growth and survival long short seed Closely timed fires short-circuit regeneration cycles

A failure in two parts 1.Lack of seed 2.Unsuitable substrate

A failure in two parts Long-term disruption

Indirect climate effects caused by a change to the disturbance regime may initiate vegetation shifts of a larger magnitude or opposite direction than would happen due to climate alone

mammal

Carbon storage

wood organic horizon 1990/ mature forestlong-interval burnshort-interval burn Fire history

How will shifting fire regimes influence tree distributions in the boreal forest? If serotiny loses its advantage (ecosystems become less resilient), what will succeed?

The prediction Regions that have experienced a novel disturbance regime will become more suitable for alternative tree species dominance

Dalton Complex, Alaska Boundary Fire, Alaska Taylor Complex, AlaskaEagle Plains, Yukon Black spruce ecosystems

Future scenarios for successional shifts black spruce self-replacement historic regime severity frequency BS seed severity frequency BS seed moisture In the absence of seed limitation

Current distributions Black spruce

Current distributions Black spruce White spruce

Current distributions Black spruce White spruce Paper birch

50 km Black spruce White spruce Paper birch

Shifting regimes in Labrador

…and many, many field assistants, labmates, and colleagues. ACKNOWLEDGEMENTS Dr. Jill Johnstone, University of Saskatchewan

Mean stand age Seedling density. m 2 Stand recovery to 4000 trees/ha Viglas, Brown, et al. in review, Can. J. Forest Research High severity fire (good post-fire seedbed) Low severity fire (poor post-fire seedbed) Thresholds for stand recovery Range of seed requirements Threshold for recovery: 50 – 150 years

Patterns between species: Alaska Number of seedlings Soil moisture (%) Black spruceAlaskan birch Species-specific optimal seed bed conditions