Lecture 10- Boreal Forest Succession and Disturbances Flashcards
What are the three steps of primary succession of boreal forests?
- Rock weathering
- Soil formation (lichens and mosses die)
- Successional stages (grasses, shrubs, trees)
Give an in depth description of plant life during primary succession in boreal forests
(Pioneer stages)
1. Bare rock
2. Lichens
3. Small annual plants, lichens
4. Perennial herbs, grasses
(Intermediate stages)
5. Grasses, shrubs, shade intolerant trees
(Climax community)
6. Shade tolerant trees
When does secondary succession occur?
-Occurs on previously vegetated substrates (secondary growth, soil is already present)
-Occurs after a disturbance (regrowth of a forest after a disturbance)
What are the two things that influence succession in boreal forests?
1.Autogenic
2.Allogenic
What is the difference between autogenic and allogenic?
Autogenic- Environmental change is a result of species in the community (light changes in a forest as a result of changing forest canopy)
Allogenic- Environmental change is a result of the physical environment (changing temperatures with increases in elevation or flooding or drought)
Describe climax communities
-Vegetation changes is predictable over time
-All ecosystems have endpoint community
-Communities shift together to reach endpoint (no intermediate communities)
-After disturbance, ecosystem returns to stable, endpoint communities
Describe multiple steady states
-Ecosystems are driven by disturbances
-No baseline community that ecosystems is returning to
-Ecosystem = patchwork of communities at various times since disturbance
What is the successional stages of mesic upland boreals?
-Aspen colonizes after disturbance (fast growing, short lived)
-White spruce slowly grows in understory (slow growing, long lived)
-Aspen slowly dies, spruce becomes dominant
-Disturbance can set back to aspen
What is the successional steps for boreal petlands?
-Peat accumulates higher above the water table
-Surface of peatland dies
-Becomes ombrotrophic
-Disturbances removes peat
What would a disturbance in the successional process of boreal peatlands do?
Disturbance removes peat (wetter sites become more fen like)
What would a disturbance in the successional process of mesic upland boreal do?
Disturbance set back to aspen
What are the successional steps for xeric upland boreal?
-Aspen can dominate after disturbance
-Jack pine grows in high diversity
-Jack pine thins over time (density dependence)
-Understory stays open and low diversity (lichens inhibit tree growth, seeds cant penetrate)
What would a disturbance in the successional process of xeric upland boreal do?
Aspen would dominate
What are the steps to density dependent growth?
- Free growth (no competitive interaction, tree growth at potential, stand growth less than potential)
2.On set of competition (competitive interactions, tree growth less than potential, size class differentiation, stand growth less than potential)
3.Full sit occupancy (complete canopy closure, substantial competitive interactions, tree growth much reduced from potential, substantial size class differentiation, stand growth at potential)
4.Self thinning (suppression mortality)
5.Stem reinitiating (establishment of new cohorts, increased structural diversity)
Disturbances determine ______
Successional path
