Fire in the boreal mixedwood: highlights for mixedwood managers. Steve Cumming, Meg Krawchuk and Cecilia Arienti June 21 2006 Edmonton, Alberta

Time passages 1992? 2006 Phil Burton Meg Krawchuk Cecilia Arienti

What distribution of stands do we want to maintain?

How should these be brought about… (e.g. some ways to get a spruce stand) Easy, very slow, unreliable Very hard, slow F. Schmiegelow Canadian Forest Service

…though time and space, given abiotic constraints… ~10,000 sq km

… and fire? Fire risk depends on: frequency, size, composition and severity; Risk components can be quantified; They are not exogenous; Fire and the forest mosaic interact in space and time.

What do fires burn? Pre-fire inventory maps!

Compositional analysis Fire composition depends on the landscape where it occurs. Fires are selective foragers. Selection is strongest amongst mixedwood stands: Leading deciduous: ICK Leading white spruce: YUM Photo: N. Lavoie, Canadian Forest Service

Landscape management can partially control outcomes of future fires A little calculus says how Landscape-specific assessments and prescriptions for mixed stand management?

Where do fires start? Fire arrivals registered to township Ignition potential (joint lightning and fire weather indices) Forest inventory data Elevation, Location, SSR, etc. Scaled counts: 10,000ha per year (counts / 10,000ha 1yr)

Fire occurrence probability (annual, per township) Sw->Aw Sb->Aw Forest composition effects are dominant. Main contrasts: Aw () Sw (++) Sb(+). Recent burns () Krawchuk et al. 2006

Count models agree (same area, different period) Burns Roads Aw Sw Arienti, in prep.

Mixed stands have two opposite and extremal fire “modes” The “switch” is species composition Aw: fires start rarely, spread poorly Sw: start frequently, spread readily Good news: managers can control species mix at stand and landscape scales

Fire counts increase in harvested landscapes for up to 30yr Recent Cuts Recent Burns

These models can be rolled up to map fire risk From 10,000 1yr simulations of veg-specific fire arrivals, natural escape p. and “correct” growth, we get mapped point estimates of burn probability/yr. Note huge spatial variation (> 1 order of magnitude).

Mixedwood management is fire management Implications Spatially variable risks from fires in noncommercial forests and wetlands can be accounted for and possibly exploited. Roads & harvesting increase fire starts. Controlling species composition of mixed stands has largest effect on fire risk. Mixedwood management is fire management

Don’t un-mix the mixedwood Risky and expensive Managing for mature DC stands can sustain both Sw harvest and ecological values.