Development of Britain's anthropogenic landscape Flashcards
1
Q
Early Mesolithic
A
- 10-5,000 BP
- hunter gatherers
- first evidence for human impact
- use of fire
- spread of hazel
- impact of fire favours hazel, evidence of charcoal
- forest still relatively open 10-8Ka
- mosaic of different successional stage
- high flora diversity
2
Q
Later Mesolithic
A
- 6000 years ago
- most tree species had arrived
- lowlands, closed canopy forest
- upland areas, more open woodland
- near attitudinal ecotones
- climatically stressed
- unstable slopes
- more burning in late Mesolithic, dense closed canopy forest
- little undergrowth, less food
- used fire as forest management tool to keep forest in early stages of succession
3
Q
Fire
A
- natural fires are very rare, with return interval of several thousand years
- charcoal evidence of repeated fires, suggests human cause
- Mesolithic people used fire as a hunting tool and driving game
- frequency burning maintains forest in early stages of succession
- young growth with succulent shoots
- full light favours herbs/shrubs
4
Q
Mesolithic/Neolithic transition
A
- 5000 BP
- first evidence of cereal cultivation in UK
- adoption of agriculture economy
- widespread elm decline
5
Q
Mid Holocene elm decline: dutch elm disease
A
- ascomycete fungus
- spread by 2 beetle species found in Holocene deposits
- blocks xylem, causing wilt and death
- rapid spread, high tree mortality
- 1965-1973: 60% of UK elms killed
- combination of factors resulting in disappearance
6
Q
patterns of forest clearance
A
Before 3.5ka BP - forest clearance in chalk land of Wessex, east Anglia and limestone area in Ireland Bronze age (3.5-2.5ka BP) - southern Britain and moorland areas Late Iron Age/Roman period - 50% of woodland removed
7
Q
consequences of farming and clearance
A
- contributed to decline in lime and elm
- promoted expansion of beech and hornbeam
- introduction of disease, parasites, weed species associated with crops and domesticated animals
- late Holocene extinction f beaver, bear, wolf and boar
8
Q
Blanket Bogs
A
- blanket of peat over the landscape
- where rainfall >1200mm
- in previously forested area
- expansion 7-3ka BP
- climate change: increase precipitation
- can cause; leaching/alkali removal, development of podzols and increased acidity
- areas of very high rainfall
- natural vegetation succession
- human land use accelerated transformation of soil to peat
9
Q
Heathland
A
- Bronze age
- lower elevations and lower rainfall than peat
- found on sandy podzolic soils
- dominated by Ericaeae family
- previously forested areas
- anthropogenic
10
Q
chronology of mid Holocene elm decline
A
- analysis of 150 dates from 139 sites
- mean date of 5000 years BP
- 50% drop in elm pollen percentage is very sudden less than 40yrs
11
Q
Climate cooling (elm decline)
A
- conflicting evidence from different proxies
- reduction in northerly range of thermophilous taxa
- advance of alpine glaciers
- dendroclimatological records from scots pine show 1oC increase in fennoscandia
- colder winter but warmer summers
- climate change not fast enough to account for elm decline
12
Q
Human activity (elm decline)
A
- elm decline coincides with onset agriculture
- not simple deforestation as other tree species unaffected
- use of elm twigs, branches, leaves for cattle fodder in winter
- elms found on most fertile soils, so may have been selectively removed for farming
13
Q
problem with anthropogenic explanation (elm decline)
A
- fails to account for scale of elm decline
- elms covered 12% of total British woodland (25 million hectares)
- pollarding this area would need human population of 500,000 no evidence for this
14
Q
clearance by early farmers
A
- following elm decline ever increasing scale of forest clearance
- fire
- agriculture
- increase grazing pressure
- neolithic peoples domesticated animals: goats, sheep, cattle, pigs
15
Q
people cause
A
- deforestation
- nutrient leaching
Causes: - expansion of Sphagum
- initiation in upland area
- spread downslope
