L8 Flashcards
Developments of grasslands is linked to…
Forest decline after the forest maximum
What value types does grassland have?
- Agricultural
- Ecological
- Social/ amenity
Grassland History Post-Glacial period
- Tundra and grass / tall herb communities were dominant in the post-glacial period
- Grasslands supported a range of sun-loving (heliophile) species
Developments of forests confined heliophiles to…
Naturally open habitats
- above the treeline - Disturbed areas eg river margins - Steep slopes/ cliffs - Glades/ clearings - Was ideal for trees not heliophiles
Forests declined after what period?
The atlantic period
- It got cooler - Less ideal temperatures for growth - But increased recognition o the role of natural grazers
Vera cycle importance
- Important role in initial breaking up of the forest
- Herbivores begin to open up an area and create a light loving environment
- More herbivores then attracted
- Area then expands
- Quality of grazing declines(degraded)
- Scrubby habitat then forms
- Loss of grassland
- Trees then reinvade
- Herbivore may then open it up again many years later
- Important in early stages of forest decline
Neolithic period
- Late forest maximum
- Early Human influence (later on)
Landnam clearances
- Small temporary clearances
- Slash and burn by neolithic farmers
Where do we have evidence of landnam clearances?
- Decline in tree pollen
- Increase in arable weed pollen
- Cereal pollen records
- Someties a charcoal layer
- First types of human influence in driving forest decline
Neolithic clearances
- Proposed neolithic farmers took advantage of vera cyclesHumans may have also removed large predators excacerbating the cycles
Where do we have evidence of neolithic clearances?
- Longer periods each time
- Cycles of clearance
- More extensive and permanent deforestation in some parts of Britain
- Associated with well populated areas
- Greater agriculture demand and industry (mines etc)
Bronze age
- Agricultural expansion and population increase
- Continuous deforestation in more populated areas and where soils allow for easy deforestation
Iron age
- Climatic change- more rainfall
- Migrant from Europe - better technology
- Permanent settlements
- Wetter soils could be cultivated
Present day grasslands
- Makes up approximately 40% of the UK
- 50% permanent pasture
- 40% rough grazing (lower productivity)
- 10% grass ley (temporary cover eg arable land)
- Small amounts of ‘amenity grassland’
- Most grassland is agricultural - most grass is a crop
How much of grassland is of the UK?
40% of the UK
How much of the UK grassland is permanent pasture?
50%
How much of the UK grassland is rough grazing?
40% (this is lower productivity)
How much of the UK grassland is grass ley?
10% grass ley (temporary cover eg arable land)
Most grassland is…?
Agricultural crop
small amounts of ‘amenity grassland’ exist
Graminoids
- Grasses, sedges, rushes
- Herbs (forbs)
- Woody areas can still be in grasslands
Altitude
- Upland/lowland (300m contour)
pH of substrate
- Acidic/neutral (mesotrophic) / calcareous
Improved grassland (for agricultural purposes) features
- Drained
- Fertilised
- Reseeded with more desirable species (more productive)
- More nitrogen
- Sometimes not so biodiverse
Semi improved grassland vs improved grassland?
Semi- improved grassland is the same but has no reseeded plants
Semi-natural / unimproved grassland state of management?
- Only managed to maintain it as a grassland (grazing/cutting)
- Stay as grassland
- If no grazing/cutting they would go back to woodland
- 100,000 ha out of 4.5 million in the UK
- Can be very biodiverse
Are semi-natural / unimproved adapted to stays as grasslands?
yes
- Adapted to stay as grasslands - Evolved as grazed/ burnt systems - Historically adapted to stay as grasslands, now humans interfere and keep as grassland - Copes with biomass removal - Grazing and nutrient takes away nutrients - Often not used for hay cutting as this requires fertiliser addition
Adaptations of grassland plants
- Grazing/mowing results in the repeated partial defoliation of plants or avoid defoliation
Intercalary meristem
Rhizomes (soil)
Adpressed growth
Low palatability
Ephemeral
Intercalary meristem
- Base meristem
- Only in graminoids and horsetails
- Grazed plants can easily regrow from basal meristem
- Removal of new growth doesn’t matter
- Apical meristems leaves behind new growth, so meristem is removed when cut
Rhizomes (soil)
- Rootstalks provide new nodes for growth
- Grazed plants can spread without flowers
- Herbs, Grasses, woody plants
Adpressed growth
- Negatively phototropic rosettes
- Plant is flat to the ground
Not easily grazed
Low palatability
- Spines
- Woody tissues
- Distastefulness and toxins
Ephemeral
- Grow when the opportunity arises
- Exploit bare patches of soil
- Grow/reproduce during periods of limited grazing
- Avoiding grazing period
Importance of pH
- Has an effect upon grassland plant species composition
- Some species grow over a very wide pH range
- Calcifuge species grow in acidic soils
- Calcicole species grow in calcareous soils (alkaline)
Importance of pH on nutrients
- Effect of pH on plants largely mediated by its influence on availability of other ions
- Some of these ions can be toxic, whilst some are crucial to plant growth
- Toxic compounds are more bioavailable in acidic soils
Distribution of the calcicole and limestone grasslands
- Cant grow in an acidic soil
Grimes Humpback curve
- Curve of productivity and species richness
- Harsh environments and low productivity results in few species
- Productive ecosystems have dominance of a few species
- Few species will go rapidly leading to competitive exclusion
Maximum potential biodiversity
- Intermediate productivity
- No harsh environment
- Not enough productivity for competitive exclusion
Shown in many areas of the world
what is the reservoir effect?
small pool of species that can cope with acidic soil
high nutrients favours…
dominance and hence low diversity
soil pH leads to less…
actual biodiversity as few species are adapted
