Lecture 6 CM

Question 1

What have most biomes been substantially altered by?

Answer 1

by human activity, however the ‘footprint’ (or impact) of this activity varies across different biomes

Question 2

Arctic Tundra

Answer 2

(look at slides)
- occurs above 60 degrees N&S of the equator
- characterised by vegetation
- surface defrosts but the inside doesn’t
- high pressure zone so there is very little precipitation
- many plants rely on the blanket of snow as it may be warmer underneath the snow cover which is on the inside

Question 3

Boreal Forest

Answer 3

(look at slides)
- 50-65 degrees North
- most extensive forest system as distribution is scarce
- tree growth form reflects environmental stresses: in the smi-frozen boreal environment, conical tree shapes has 3 distinct advantages over branching shape

Question 4

What are the 3 advantages of the conical tree shape?

Answer 4

1. snow accumulation is prevented and limbs do not break
   –> the tree has adapted to snow accumulation which allows the snow to fall off, so the branches don’t break
2. the lower surface-to-volume area minimises the exposure and transpiration stress, especially outside the summer
3. the vertical orientation of canopy limbs instead of horizontal orientation improves the efficiency of low-angle light conditions. the reverse is true in lower latitude/higher light angle environments

Question 5

Temperate deciduous forest

Answer 5

(look at slides)
- 30-50 degrees North
- the trees drop their leaves because of the water stress
- the leaves form in autumn and inflate/expand in spring & summer
- vertebrates are more abundant and diverse than in the boreal forest
- herbs with underground storage organs are abundant

Question 6

Temperate evergreen forest/rainforest

Answer 6

(look at slides)
- 45-50 degrees N&S
- there is no limit of growth per plant
- native forests in west and southwest Ireland display a climate and evergreen moss/fern vegetation is more typical of rainforests

Question 7

Temperate shrubland: Mediterranean scrub, Chapparal

Answer 7

(look at slides)
- 30-40 degrees N&S
- plant can survive the summer drought using a variety of strategies

Question 8

What ways can plants survive the summer drought in temperate shrubland?

Answer 8

• they can have a sclerophyllous habit comprising small waxy leaves (often semi-deciduous), which limit transpiration stress
• deep roots (to tap permanent water table)
• limited size (to maintain sustainable biomass)
• trees can be very long-lived

Question 9

What is another way plants survive the summer drought in temperate shrubland?

Answer 9

• they use dormancy either as the seeds in the top soil layer (which germinate and reproduce quickly in spring)
• or they use underground storage organs (like bulbs, tubers) which allow the plants to achieve large biomass in a short growing period

Question 10

What is the contrasting appearance of the temperate shrubland in the mild, wet spring and the hot, dry summer due to?

Answer 10

• it is caused by this switch between growth/leaf development and dormancy/leaf loss.
• this switch also determines the behaviour, life cycle and abundance of all animals in the biome

Question 11

Temperate grassland: prairie, steppe, pampas

Answer 11

(look at slides)
- 30-50 degrees N&S

Question 12

What does the relative proportion of apical meristems at ground/below ground level impact?

Answer 12

• it impacts the ability of each habitat to cope with physical disturbance, especially fire and excessive grazing
• after the fire or grazing, aboveground plant tissue is destroyed
• afterwards, grasses regenerate quickly, but trees and shrubs are often destroyed

Question 13

How do seeds play a major role in helping vegetation recover?

Answer 13

• the seed bank in the soil is crucial
• weeds are seed bank specialists