L7

Question 1

What is the devensian cold stage?

Answer 1

115,000- 10,000 BP

Generally cold but considerable temperature fluctuation

Interstadials

Question 2

Interstadials

Answer 2

warm periods

• Summer temperatures similar to now
  • Winter temperatures much colder
  • Some interstadials had forest, others not
  • Rich vertebrate fauna, including temperate and boreal species

Question 3

Dimlington stadial

Answer 3

Extensive ice sheets

- Polar desert or tundra in the periglacial fridge

- Large herbivores probably forced south

- But some mammoths remained

Question 4

Loch Lomond stadial

Answer 4

• Ice sheet retreat
  • Patchy permafrost
  • Not fully artic
  • Brings us to about 10,000 years ago
  • Tree birches and pine survived

Question 5

Goodwin zonation (pollen)

Answer 5

• Pollen analysis in peat cores
  • Gradual appearance of increasingly thermophilous (warm loving) trees (elm, oak etc)
  • Birch is cold tolerant - often forms northern tree line
  • Emergence of pine as temperatures increases slightly
  • Leads to the forest ‘maximum’
  • UK essentially was totally forest covered

Question 6

The forest maximum conditions

Answer 6

• Warm and wet
  • 2.5c warmer than today
  • Followed by cooler, wetter conditions resulting in some tree decline
  • Only 5000 years ago
  • Development of other UK systems is linked to the fall of the forest maximum

Question 7

Uk woodland cover over the years

Answer 7

5000BP uk largely covered by woodland

2000BP end of iron age = 50% woodland

1400 = 10% woodland cover

1900 = 5% woodland cover

currently = 13%

Question 8

what is the woodland today composed of in the UK?

Answer 8

52% conifer plantation, remainder largely broadleaf

= 50 native species of trees and shrubs

Question 9

woodland types

Answer 9

ancient woodland

semi-natural woodland / primary

recent and plantation woodland (planted)

Question 10

Ancient woodland

Answer 10

• Continually wooded since before 1600
  • 2.4% of land area

Question 11

Semi-natural woodland

Answer 11

• Largely native species and largely not planted

Question 12

Recent and plantation woodland

Answer 12

• Commercial forestry
  • Conservation/ amenity value

Question 13

woodland soils

Answer 13

brown forest soil (or brown Earth)

typical soil in UK woodland

relatively good quality, rich soil

highly valued for agriculture -many lowland forest cleared

very fertile land

Question 14

vertical structure

Answer 14

• Most complex vertical structure of any vegetation type
  • Typically seen in many woodlands

Question 15

what are the two main approaches plants have for survival on the forest floor?

Answer 15

shade tolerance

complementary resource use

Question 16

shade tolerance mechanisms

Answer 16

altered leaf morphology

- Often have large, thin leaves

- Single palisade layer reduces light travel distance to reach chloroplasts

- Minimises CO2 travel distance

- Larger SA to weight ratio

Question 17

Morphological plasticity to shading

Answer 17

• Typical of plants in partial shade conditions

Question 18

lower respiration

Answer 18

• Carbon gain = photosynthesis - respiration
  • The amount of light where photosynthesis = respiration is the light compensation point
  • Shade tolerant plants may have a lower light compensation point than plants adapted to sunny areas as they have a low respiration point
  • Shade leaves have advantage at low levels
  • Disadvantage is that it cannot reach high photosynthesis
  • However shade plants are always unlikely to so it is not that significant

Question 19

Being evergreen

Answer 19

• Lower energy requirements
  • This means they do not have to have shade type leaves

Question 20

Way hair grass

Answer 20

• Narrow , bristle like leaves
  • Tolerates partial shade
  • But these leaves must respire through winter so have a low respiration rate and therefore grow slowly

Question 21

Complementary resource use

Answer 21

• Early growth and flowering, occurring before canopy becomes too dense
  • Eg dog’s mercury
  • Their flowering finishes prior to tree canopy growth
  • Resource use of light and avoids shade