Lecture 5 Habitats

Question 1

9 dominate tree species (area and adaptation)

Answer 1

1. Black Spruce: Low-lying, poorly drained areas, can grow in active layer only 25cm thick
2. White spruce: Well-drained, dry uplands, can grow in active layer only 25cm thick
3. Jack Pine: sandy outwash plains and former dune areas. (low nutrient and water)
4. Lodgepole Pine :common in western North America.
5. Balsam Fur: found on a wide range soil soften in mixed stands with other species.
6. Tamarack: found on thin, waterlogged substrate in level areas underlain with
   permafrost. Deciduous confer (has needles but loses them in winter)
7. Paper Bitch: broadleaf trees, often found early successional forest or along waterways
8. Trembling aspen: broadleaf trees, often found early successional forest or along waterways
9. balsam poplar: broadleaf trees, often found early successional forest or along waterways

Question 2

Confer adaptations to short growing season (6 + what is a growing season)

Answer 2

*Growing season: period in the year during which temperatures are high enough for photosynthesis

*Conifers photosynthesize whenever weather is warm enough.

• Not as efficient at photosynthesis as broadleaf plants, but don’t spend energy to grow new leaves

*Evergreens have a special, sticky, thick resinous sap that doesn’t freeze like broadleaf trees do

*Conical shape – promotes shedding of snow & prevents loss of branches

*Dark color – helps the foliage absorb maximum heat from the sun and begin photosynthesis as early as possible

*Needles reduce surface area of leaves, have thick waterproof coating and shrunken stomas = less net water loss

Question 3

Mycorrhizae (2)

Answer 3

*Most taiga plants have mycorrhizae – interweaving of fungal mycelium and root tissue

*Mycorrhizae are a mutualism between plants and fungi.
* the plant provides the fungus with carbohydrates
* the fungus helps the plant get nutrients from the soil, like nitrogen

Question 4

Fire (3)

Answer 4

Fire is the primary agent of change in the boreal forest

1. releases nutrients
   * fires reduce litter (leaves, logs & conifer needles) on the forest floor, and release nutrients that have been tied up in these materials.
2. allows sunlight
   * Fires also open the canopy to sunlight, which in turn stimulates regeneration from seeds and roots.
   * Stimulates growth and reproduction

Question 5

Succession (3)

Answer 5

*Succession is the replacement of one community by another
*Primary succession takes place on land where no organic soil exists
*Secondary succession takes place after an ecological disturbance (ie fire)

Question 6

Boreal Forest: 3 zones based on tree cover

Answer 6

1. Closed boreal forest (southern): Dense forest, trees form a closed canopy
2. Open boreal forest (northern):Trees grow far enough apart that a canopy never forms. ground layer dominated by lichen
3. Forest-tundra ecotone: Russians often treat it as a separate biome, not a transition between 2 biomes (north America)

Question 7

The Tree line (3)

Answer 7

• the zone where ‘forest with patches of tundra’ merges into ‘tundra with patches of forest’
• the northern limit of the growth of trees >5m high
  *caused by The lack of summer warmth – not cold winters. Photosynthesis can only happen if plant tissues are warm enough.

Question 8

Boreal Peatlands (3)

Answer 8

*Peat: an accumulation of partially decayed vegetation
*Peatlands occur mainly in boreal regions, covering 25-30% of the boreal forest region globally
*Many plant species are unique to these areas because of the acidic water and its other unique physical conditions.

Question 9

How Peatlands formed (4)

Answer 9

*Retreating glaciers left behind holes created by melting blocks of ice
* Water could not drain into the underlying rock strata because of permafrost.
* The layer of cold water was colonized by sphagnum moss.
* Over time, develops a floating mat of vegetation that may support shrubs and small trees

Question 10

Peatlands as carbon sinks (3)

Answer 10

*Peat is important because it stores organic carbon that otherwise could be released into the atmosphere as carbon dioxide or methane

*Higher temperatures could increase the rate of decomposition, releasing carbon

*Increased fire frequency could release more carbon trapped in peat

Question 11

Peatland communities (4)

Answer 11

Bog : High soil moisture, low nutrients
Fen: High soil moisture, high nutrients
Muskeg: low soil moisture, low nutrients
Swamp: low soil moisture, high nutrients

Question 12

sphagnum (4)

Answer 12

*responsible for most of the organic buildup in the extensive peatlands of the north.

*covers more of the world’s land surface than any other single plant genus.

*Dominance of Sphagnum based on its ability to absorb and retain water (up to 8 times it’s weight in water) (cant hold as much when dead)

*Closely packed sphagnum creates wick-like columns of moss, which lift
water to the top of a sphagnum hummock (capillary action).

Question 13

Peatlands and permafrost (3)

Answer 13

*Peatlands are growing points for permafrost throughout the taiga
*In summer, sphagnum dries out, insulates against incoming heat.
*In autumn, heavy rains and freeze-thaw cycles: sphagnum becomes
water-saturated, conducts outgoing heat.