Boreal Forest Structure & Disturbance
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Communities change due to many different reasons. Is it predictable? Explain 2 hypotheses
According to Clements or Elger: yes - succession is predictable - mosses/ lichens colonize first after glacier - then trees - conifers drop needles –> acidify soils –> hard for other trees to survive According to Gleason: it’s sometimes random - wind - who arrives first to colonize
succession= primary- secondary-
= changes in communities over time (at one place) Primary= absence of soil –> creation of soil after glaciation Secondary= still soil present (eg after a fire)- seed banks= vegetation comes back
3 steps of primary succession:
• rock weathering • soil formation- lichens and moss die • successional stages- grasses, shrubs, trees
What are autogenic and allogenic influences of succession?
Autogenic= inside influence= enviro change is a result of species in the community eg. light changes in a forest as a result of changing forest canopy Allogenic= outside influence= enviro change is a result of the physical enviro eg changing temps with increase in elevation/ flooding/ drought
What are the 3 major subdivisions of north American boreal forests?
• Open lichen woodland (northern-most) • Northern coniferous forest • Mixed forest (southern-most)
3 forms of open lichen woodland
A. typical lichen-spruce woodland B. spruce-moss woodland C. Open tamarack wetlands
lichen-spruce woodlands have __ canopies. Why?
open lots of lichen= spruce germination inhibited caribou disturb lichen= allows some spruce to colonize
spruce-moss woodlands have near ___ soils (___ order0 resulting from a high water table
saturated gleysolic
Open tamarack wetlands are ___ and dominated by ___ bogs and tamarack ___
saturated sphagnum bog tamarack fen
northern coniferous forests have a ___ canopy and includes ___, pine, and ___ ___
closed spruce balsam fir
Floodplain succession order (over time): 1 2 3 4 5 6
• silt • willow • balsam poplar • white spruce • black spruce • bog
Mixed forests include both ___ and broadleaf ___ trees (which are very good at ___). This is __-most
conifers deciduous southern