L8 Post-disturbance succession in boreal forest Dr. Han Chen Office: BB-1009F Phone: 343-8342 Email: han.chen@lakeheadu.ca Reading material Chen, H.Y.H., S. Vasiliauskas, G.J. Kayahara, and T. Ilisson. 2009. Wildfire promotes broadleaves and species mixtures in boreal forest. Forest Ecology and Management 257:343-350. Ilisson, T., and H.Y.H. Chen. 2009. Response of six boreal tree species to fire and clearcutting. Ecosystems 12:820-829. Ilisson, T., and H.Y.H. Chen. 2009. The direct regeneration hypothesis in northern forests. Journal of Vegetation Science 20:735-744. Senici, D., H.Y.H. Chen, Y. Bergeron, and D. Cyr. 2010. Spatiotemporal variations of fire frequency in central boreal forest. Ecosystems 13:1227-1238. FORE3215, L5

Questions How frequent is fire in central boreal forest? How forest composition change after disturbance? –post-disturbance succession

Spatiotemporal fire regimes What is the fire cycle in central boreal forest? Does fire cycle change with time? Does fire cycle change spatially? Parisien & Moritz. 2009, Ecol Monogr 79:127-154) FORE3215, L5

The Forest and Methods Burn rate Dendro-chronology 11,600-km2

Time period investigated Temporal regimes Method Time period investigated 1820-2008 1820-1920 1921-2008 Burning rate N/A 158 Inverse hazard 150 (126-188)* 295 (229-499) 96 (84-111) 1921-1970 1971-2008 140 69

Spatial drivers for fire Variable Full Model   Prob > χ2 FF ratio Latitude 0.041 2.203 Longitude 0.105 0.619 Soil Order 0.004 1.78 Surficial Deposit 0.96 1.025 Mean Firebreak Distance 0.011 1.382 Aspect (west-east axis) 0.794 0.971 Aspect (north-south axis) 0.377 0.903 Elevation 0.19 0.997

What is the fire cycle in central boreal forest? Approximately 100 years for the period of 1921-2008, but shorter (69 years) for 1971-2008, much longer (295 years) for 1820-1920 Changes spatially, longer for stands closer to water bodies in south (due to fire suppression and landscape fragmentation) Brunisols (more likely dominated by broadleaves and mixedwoods) Intermediate to east and west boreal forests (75 vs. 150 years), supporting climatic top-down control

Context-Postfire succession Does a postfire stand have the same species composition as the prefire stand? Yes! Based on Direct Regeneration Hypothesis Proposed by Hanes (1971) Recognized in fire-prone Mediterranean and Chaparral ecosystems

Direct regeneration in boreal forest Species-specific post-fire regeneration density is proportional to its pre-fire basal area (Greene & Johnson. 1999. Can. J. For. Res. 29: 462-473) A pure post-fire aspen stand may be expected when the pre-fire stand has  20% aspen (Foresters’ prediction) FORE3215, L5

Drivers Propogule availability (seeds, root suckers, or stem sprouts) Substrates Competitive ability Species-specific prefire basal area Fire variability within a burn

Questions Can DRH be used in boreal forest? Do different tree species respond in a similar way? Is fire intensity as a result of fire season and weather important in affecting postfire regeneration? Used build-up index

Sampling A wide range of stand conditions on uplands A wide range of fire season, thus build-up index Prefire stands were mature and of naturally origin with no silvicultural treatments Plots > 100 m from fire edges

Burns between 5 to 20 years

Field measurement Prefire stand Postfire regeneration Determined by snags and down woody debris in a 400 m2 circular plot Basal area by species Stand age by counting rings of least shade tolerant species By three 25 m2 circular subplots Species Height class

Characteristics of postfire sites Prefire dominance # of sites Age of burn (yrs) Prefire stand age (yrs) Prefire basal area (m2/ha) Jack pine 18 7.3 (2.8) 107 (43) 23.9 (7.3) Trembling aspen 16 7.3 (2.3) 109 (53) 26.1 (9.1) White birch 17 8.2 (3.3) 151 (52) 17.5 (6.5) Black spruce 32 10.1 (4.2) 139 (45) 16.3 (5.6) White spruce 6 6.8 (1.5) 154 (47) 23.7 (6.9) Balsam fir 5 7.8 (0.4) 165 (69) 17.3 (9)

Species-specific postfire regeneration density

Regeneration density and buildup index Jack pine Trembling aspen White birch Black spruce White spruce Balsam fir

Other covariates for postfire regeneration density Age of burn (5-20 yrs) affected positively black spruce regeneration density, and also marginally white birch and balsam fir Moist sites had marginally greater jack pine regeneration density than dry and fresh sites when other factors (i.e., prefire jack pine basal area and BUI) are equal Distance to fire edge and prefire stand age were insignificant

Can we conclude now? Postfire regeneration density is linearly related to prefire basal area for jack pine, trembling aspen, white birch, and black spruce, not for white spruce and balsam fire Build-up index also positively affect postfire regeneration for early successional species Deep burn creates better substrates for regeneration of seed origin and perhaps reduces shrub competition for both sexual and asexual regeneration But This has not address DRH (i.e., the postfire stand has same compositions as the prefire)

Definition of CD For a given species, compositional difference between the postfire and prefire stand (CD) = Relative postfire regeneration density – Relative prefire basal area DRH CD = 0

Species-specific responses

CD in relation to prefire composition

Conclusions DRH is true for jack pine Fire promotes trembling aspen and white birch in the expenses of black spruce, white spruce, and balsam fir Fire promotes species mixtures

Postfire stand type distribution based on prefire stand type

Postfire and post-clearcutting succession Do post-disturbance regeneration behave in a similar way after fire and logging? Ilisson, T., and H.Y.H. Chen. 2009. Response of six boreal tree species to fire and clearcutting. Ecosystems 12:820-829.

Ilisson & Chen. 2009. Ecosystems 12: 820-829 D 0.872 BA <0.001 D x BA 0.57 D 0.969 BA <0.001 D x BA 0.137 D 0.009 BA 0.001 D x BA 0.676 D <0.001 BA 0.692 D x BA 0.865 D 0.117 BA 0.149 D x BA 0.226 D 0.006 BA <0.001 D x BA 0.364 Ilisson & Chen. 2009. Ecosystems 12: 820-829

Postfire and postlogging composition **

Post-disturbance succession conclusions All stand-replacing disturbances promote broadleaves and species mixtures Direct regeneration is applicable only to species with serotinous cones (e.g., jack pine and lodgepole pine) Future landscapes will be more dominated by broadleaves because of a shorter fire return intervals

How does wind disturbance differ from fire and clearcutting Ilisson, T., and H.Y.H. Chen. 2009. The direct regeneration hypothesis in northern forests. Journal of Vegetation Science 20:735-744.

Direct regeneration hypothesis in northern forests Q1: How do species regeneration strategy and/or shade-tolerance influence compositional development after stand replacing fire, clearcutting and wind disturbances? Q2: Does disturbance type have effect? A meta-analysis of 21 studies in northern forests

Regeneration strategy Species Broadleaves with strong vegetative reproduction ability SV-B Betula papyrifera, Populus balsamifera, P. grandidentata, P. tremuloides, Prunus serotina, Caraya spp, Quercus ellipsoidalis, Q. alba, Q. macrocarpa, Q. rubra, Acer rubrum, A. negundo, A. saccharum, Fagus grandifolia, Ostrya virginiana Broadleaves with weak vegetative reproduction ability WV-B Betula lenta, B. nigra, B. alleghaniensis, Fraxinus nigra, F. americana, Prunus pennsylvanica, Ulmus americana, U. rubra, Tilia americana Conifers with serotinous cones S-C Pinus banksiana, P. contorta Conifers with semi-serotinous cones SS-C Picea mariana Conifers without serotinous cones NS-C Larix laricina, Pinus resinosa, P. strobes, Picea glauca, Abies balsamea, Tsuga canadensis, Thuja occidentalis

Conclusions – Direct regeneration hypothesis in northern forests Species regeneration strategy defines the success/failure of species after disturbances, less so does disturbance type A species’ ability to regenerate vegetatively enables domination over species with other regeneration strategies Data lacking for serotinous and semi-serotinous species after clearcutting