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Boreal forest

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  1. Boreal forest • Biophysical environments • Biotic interactions • Fire regimes & post-fire succession • Floodplain succession & paludification • Forest clearance and succession • Climate change: natural & anthropogenic

  2. Boreal forest biome-------Scandinavia70% Russia70% Alaska50% Canada Fairbanks Chicoutimi Pr. Albert Kapuskasing Note latitudinal variation

  3. Mean monthly temperature J F M A M J J A S O N D

  4. Monthly precipitation (mm)

  5. Mean annual snowfall (mm) Boreal forest zone

  6. Boreal forest and permafrost distribution -2.8° Mean annual temperature 0.6° 3.0° 0.7° Discontinuous permafrost limit ~ -2°C

  7. Mean location Polar Front tree growth Jan July 120 30 Mean #d >10°C pollen/seed viability 150 240Mean #d <0°C Boreal forest Tundra Permafrost patchy discontinuous continuous

  8. Boreal forest-environment interactions Biota Climate Physical template Soil

  9. The boreal forest biome in Canada “Taiga” Boreal forest

  10. Trees of the N. American boreal forest Evergreens Deciduous

  11. Boreal forest vegetation types (North America)

  12. Forest structureBoreal forest Taiga spruce-lichen woodland spruce/birch/pine forest mosaic

  13. Boreal forest soils Underlain by coarse-textured deposits or bedrock. Well-drained, warm fairly rapidly in summer, more rapid breakdown of organics, strongly-leached, acidic, low nutrient availability. Underlain by fine-textured deposits / permafrost. Poorly-drained, cold in summer; little microbial activity, slow breakdown of organics, low nutrient availability. 100 gleysols, cryosols O Ae Bf O BC Cg % cover Podzols, regosols 0 south north boreal forest taiga

  14. Forest community segregation in the boreal forest white spruce - birch-aspen- balsam fir jack pine black spruce tamarack mosses site: wet mesic dry soil: gleys podzols active: thin (<0.3m) thick (>2m) layer (or no permafrost) organic thick thin layer

  15. Biomass and productivity paper birch black spruce white spruce poplar aspen

  16. Nutrient cycling and storage (nitrogen) paper birch black spruce white spruce poplar aspen

  17. Herbivory and boreal forest dynamics Moose population Nitrogen mineralization Browse biomass Wolf population soil microbiota phytotoxins enhancements reductions

  18. Insect outbreaks(e.g. spruce budworm; Siberian silkworm) Climate (early summer drought) Fire hazard Forest structure* and biomass Insect populations (larvae) *suitable host trees (e.g. balsam fir for spruce budworm) enhancements reductions

  19. Fire regime Fire cycle • Natural fire cycle averages 50-200 years • Length of the cycle controlled by moisture balance • Most fires small (~70% in AK & YK <5 ha). • Severe fires can cover 200,000 ha. • Most boreal forests equally flammable regardless of age (after first decade).

  20. Forestfire weather zones

  21. Precipitation and wildfire frequency Precip. Fire RI

  22. Fire regime Fire intensity • Most tree species are not fire resistant. Thick bark protects pines. • Tendency of fire to crown dependent on tree canopy architecture and understorey vegetation. Crown fires common in spruce and pine forests, rare in deciduous forests.

  23. Fire resistance: protective role of tree bark paper birch black spruce jack pine resistance

  24. Fire regime Post-fire regeneration • Many trees dependent on recurring fires. • Post-fire reproduction by means of: light, wind-dispersed seeds (e.g. birches, poplars)serotinous or semiserotinous cones (e.g. jack pine, black spruce)stump sprouting or suckering (aspen, paper birch)

  25. Post-fire regeneration from suckers from serotinous cones

  26. Fire succession no

  27. Birch (Betula papyrifera) forest with spruce (Picea sp.) understorey on mesic site

  28. Fire regime Fire severity • Removal of thecanopy and surface organic layer increases surface energy receipt. Thickness of active layer may increase substantially for first few years following fire. • Nutrients in surface mat and soil released by fire (N and P increase most in moderately burned areas).

  29. Succession schematic

  30. Floodplain succession, Alaska

  31. Floodplain succession( pioneer phase)

  32. Floodplain succession( pioneer phase) Balsam poplar white spruce herbs

  33. Floodplain succession(climax phase) mature white spruce on scroll bars

  34. Floodplain succession, NE BC

  35. Influence of forest cover on soil temperature

  36. In the absence of disturbance paludification may occur • Moss-organic layers > 5cm thick preclude spruce regeneration from seed. • Spruce stands may reproduce vegetatively by layering (regrowth of low branchesburied in the moss-organic mat). • If moss-organic layer continue to increase in depth, paludification (bog-formation) may occur. In W. Siberia ~1/3 of the taiga is forested bog.

  37. Paludification: a double feedback loop soil water table Sphagnum nutrient uptake peat development Sphagnum moss growth ironpan formation soil acidity tree growth enhancements reductions

  38. Sphagnum bog formation

  39. Effects of successional paludification of boreal forest soils(in western Québec) Data: Simard et al., 2007. Ecological Applications17, 1619-1637.

  40. Effects of paludification on forest timber production Left: stand opens up over time, and Right: wood production declines (especially in stands >200-yr old) Data: Simard et al., 2007. Ecological Applications17, 1619-1637.

  41. Forest clearance in NW Europe

  42. Farm clearance-abandonment cycle (data from New England)

  43. Wood production areas

  44. Effects of harvesting on forest cover in accessed areas of boreal forest poplars balsam fir birch other % change pine spruce

  45. North American vegetation at the Last Glacial Maximum(18 000 14C yr BP= 20 000 yrs BP)

  46. Postglacial migration of the boreal forest plant community from pollen evidence Pollen Viewer http://www.ncdc.noaa.gov/paleo/pollen/viewer/webviewer.html

  47. LGM and Late Glacial distribution of boreal and mixed forest from pollen evidence Boreal = dark green Mixed forest = light green No analogue Overpeck et al., 1992. Geology20, 1071-1074.

  48. Ranges, clades and postglacial migrations of New World tree squirrels (T = Tamiasciurus) ? Douglas squirrel T. douglasii ? easternclade Red squirrel T. hudsonicus SW clade “T. mearnsii” Simplified from data in Abrogast et al., 2001. J. Mammalogy82, 302-319

  49. Range, fossil sites and inferred postglacial migration of American marten Martes americana varieties: americanaandcaurina • fossils Stone et al., 2002. Molecular Ecology11, 2049–2063

  50. Sphyrapicus (sapsuckers) Dendroica (warblers) Vermivora (warblers) Passerella (warblers) Vireo (vireos) Empidonax (flycatchers) Opopornis (warblers) Poecile (chickadees) “Superspecies” complexes of boreal forest birds: note repetitive distribution patterns Weir and Schluter, 2004. Proc. Roy. Soc. London B, 217, 1881-1887.