Fire effects on vegetation recovery Summary of Results and Project Deliverables Jill Johnstone, Teresa Hollingsworth, Emily Bernhart & Katie Villano

All sites grouped by severity Burn severity is HIGHLY correlated with the Axis 1

Significant changes key species pre to post-fire Increase in Salix pulchra Increase in Salix diversity (4 Salix sps. that only occur post-fire (Feltleaf, Bebb’s, Firmleaf, and Scouler’s) Decrease in moss abundance and diversity including Sphagnum sps. Decrease in lichen abundance and diversity including 3 Cladonia species

Wildfire as a conduit for invasive species colonization

Are black spruce forests more susceptible to invasion after fire? In the greenhouse, invasive plants in burned soil cores showed higher survival than in unburned cores.

Does burn severity and soil moisture influence the success of invasive plant establishment? No significant differences between invasive biomass (or survival) in different burn site types at any point in the experiment.

MANAGEMENT IMPLICATIONS Burned areas with both high invasive propogule pressure and most suitable soils should take highest management priority (i.e. Dalton Highway). Even low severity burns are susceptible to invasive species

Fire and Site Effects on Tree Regeneration

drainage elevation resid.org BS WSLP TA PB conifer deciduous Model χ 2 =19.2, df=15, p=0.2 (no significant lack of fit) R 2 =0.57 R 2 = Modeling Seedling Recruitment

Drivers of forest regeneration Differential sensitivity of functional groups –Deciduous most sensitive to post-fire seedbeds –Conifers more responsive to site moisture Important role of fire severity in potentially tipping the balance between deciduous and conifer dominance

Successional trajectories modelling How might changes in fire severity affect landscape forest composition? Simulation experiments: –ALFRESCO (Alaska frame-based ecosystem model) –2004 Boundary Fire –Examine potential patterns of forest recovery

2004 Boundary Fire Start with pre- fire vegetation black spruce white spruce deciduous

2004 Boundary Fire Start with pre-fire vegetation Add on fire severity (NBR) Include scenarios for low or high surface severity high crown low surface moderate or low crown severity high crown high surface

2004 Boundary Fire Start with pre-fire vegetation Add on fire severity (NBR) Include scenarios for low or high surface severity high crown low surface moderate or low crown severity high crown high surface

2004 Boundary Fire Start with pre-fire vegetation Add on fire severity (NBR) Include scenarios for low or high surface severity Model black spruce recovery trajectories –extended deciduous phase under high surface severity

Scenario 1: High surface fire severity Scenario 2: Low surface fire severity Scenario 3: 50% High-low surface fire severity 50 years post-fire75 years post-fire 100 years post-fire

Boundary Fire Simulations Possible to use real landscape and fire data to project future forest composition Including variations in surface fire severity –Alters projections of future forest cover –Leads to vegetation effects on fire propagation – even in conservative scenarios Can this knowledge be made useful to managers?

Successional trajectories workbook Aim: to predict potential changes in post-fire trajectories –Focused on black spruce forest –Integrates moisture and severity effects –Rapid assessment of post-fire stands –Identify conditions leading to change

Subhygri c Mesic to subhygric Mesic Subxeric to mesic Subxeric Very Considerable Moisture; saturated by with less than <5% standing water <10cm deep Considerable moisture; depressions Moderate moisture; flat or shallow depressions Very noticable moisture; flat to gently sloping Noticable moisture; well- drained slopes ridges Little moisture; stabilized sand dunes, dry ridge tops Xeric Shallow permafrost % Gravel of soil

Moist site with intact organic layer Rapid assessment: –thick organics but good moisture –trees standing with cones intact Predicted recruitment: –very little deciduous –low to high black spruce (depending on quality of organics) Trajectory: open to closed black spruce

Moist site with low residual organics Rapid assessment: –shallow organics with good moisture –trees fallen (reduced seed dispersal) –deciduous seed source within 1-2 km Predicted recruitment: –high deciduous –low to moderate black spruce Trajectory: mixed deciduous – black spruce

Well drained site with intact organics Rapid assessment: –thick organics with low surface moisture –trees standing with cones intact –no deciduous seed source nearby Predicted recruitment: –very little deciduous –moderate black spruce Trajectory: open to intermediate black spruce

Well-drained site with low organics Rapid assessment: –shallow organics with low surface moisture –trees fallen –strong nearby deciduous seed source Predicted recruitment: –dense deciduous –very low black spruce Trajectory: deciduous forest

Conditions leading to trajectory shifts Substantial combustion of surface organic layers => exposed mineral soil –favors deciduous recruitment Deep charring of cone balls or toppling of trees –reduces black spruce seed rain Adjacent unburned stands of alternative species –provides strong propagule pressure