Theme B Flashcards
When was the Devensian cold stage?
115,000 to 10,000 BP, Arctic conditions and periods of warm were similar to boreal conditions
What are stadials and interstadials?
stadials= embedded periods of cold conditions
interstadials = embedded periods of temporarily warm conditions
What were the conditions like at the start of the Devensian cold stage?
- Coldest, permafrost in arctic and shrubby wildlife
- interstadials allow for some productive vegetation to come in
- 16 degree in summer and -10 in winter
- Rich vertebrae such as mammoth, bison, woolly rhino
What was the dimlington stadial?
- 21,000 ya wit extensive ice sheets and polar deserts and tundra
- large herbivores forced south but some mammoths remained
What was the loch Lomond Stadial?
- Last period of proper intense cold
- The species that survived went on to form species we have now
- Occurred after teeny warm period
When did the Forest form?
10,000 BC
How can we see the forest forming?
- Pollen gets trapped in the peat, take pollen in different layers by taking peat cores and look at the abundance of different tree species
- Gradual appearance of increasingly thermophilous trees (warm-loving trees)
- Birch starts to decline as its the most cold-tolerant
- As things warm up even more (moving up the peat core) we get elms, limes start to come in and oak which stays very abundant
When was the ‘Forest Maximum’ and what were its characteristics?
7,500,5000 years BP
- ‘Warm and Wet’
It was about 2.5 degree warmer than it is today
What happened after the forest maximum?
- Slightly cooler period resulting in some tree decline
brought us to about 2500 years ago
What is our % woodland cover now?
13% (compared to 50% 2000 ya)
Around 52% of this is conifer plantation and the rest is mainly broadleaf
What are the different woodland types and their characteristics?
Ancient Woodland:
Continuously wooded since before 1600
2.4% of land area
Semi-natural Woodland:
Largely native species and largely not planted
A bit more recent than ancient
Recent and plantation Woodland:
Commercial forestry
Conservation values
What is the difference between primary and secondary forest?
Primary= Semi-natural/ancient woodland
Secondary = Woodland or forest developed on cleared land
What are the characteristics of brown forest soil?
- High quality from deciduous leaf litter
- Transpiring trees stop wet soil
- Typical Uk woodland soil
- Highly valued for agriculture
- Invertebrates aid soil cycling and nutrient burying/lifting
What is the vertical structure of forests?
Tree layer
Shrub layer
Field layer
ground layer
(Not all of these layers will be present depending on habitat conditions e.g. too much leaf litter stops a ground layer from forming)
What are the three main distribution types for horizontal structure?
Regular = overdispersed and widely spread
Random = Small random groups of individuals
Clumped = underdispersed (most common) patches of species clumped together
What is varied horizontal structure caused by?
Morphology and growth characteristics of the plant species
Seed dispersal mechanisms (e.g. by wind or by animals)
Environmental heterogeneity
Species interactions (e.g. competition)
What are the two main approaches for plants for survival on the forest floor?
Shade tolerance
Complementary resource use
Explain how shade tolerance is a survival mechanism
- Shade plants often have a single palisade layer and large thin leaves
- Large surface area to weight ratio
- High photosynthesis but low respiration (low compensation point)
- Evergreen - low energy requirements
- Grow slowly as the leaves must respire through winter
What does a low compensation point mean?
Don’t need much light before photosynthesis outweighs respiration
Don’t lose much carbon in dark conditions
How is Complementary resource use a survival mechanism?
Early growth and flowering of ground species before trees dump loads of litter and have coverage
So they use the light levels in early spring to the best of their ability e.g. bluebells
How were heliophiles supported in the post glacial period?
Grasslands supporting heliophiles
Development of forests confined helophiles to open habitats
Explain the vera cycle
a way grazers make an open habitat within woodlands
Open → scrub → woodland → breakup through disturbance leading to expansion of open area good for heliophile species
What is the evidence of a ‘slash and burn’ agricultural approach in the neolithic period
Decline in tree pollen
Increase in arable weed pollen
Cereal pollen recorded
Sometimes a charcoal layer
How was the vera cycle enhanced under neolithic influence?
neolithic used advantage of woodland areas cleared by animals
(vera cycles)
hunting and removing top predators, vera cycles are enhanced as herbivore populations increase
Leads to permanent deforestation
How did human influence affect agriculture during the iron age?
- Continued agricultural expansion and continuous deforestation
- Migration from Europe, permanent settlements and better technology for ploughing
What percent of landcover in the UK in present day is grassland?
40%
What are the main plant types in grassland ecology and what are the most basic classifications?
- Graminoids and Herbs
- Most basic classifications are altitude and acidity of the soil
What does calcareous mean?
alkaline (limestone&chalk)
What is improved grassland?
intervening to make the grassland better e.g. drained, fertilised, seeded with more productive species e.g Lolium perenne
What is semi-improved grassland?
Drained/fertilised but no reseeding
What is semi-natural/unimproved grassland?
Contain natural grassland species but only manages by having grazing on them or cut for hay
Why is intercalary meristem an adaption of grassland plants to repeated defoliation?
- Means grazed plants can easily regrow from basal meristem
-Plant grows from this point, even if it gets mowed it will just produce more growth and push up
Why are rhizozomes an adaption of grassland plants to repeated defoliation?
- Also help the plant grow from low down
- Underground rhizome branching system are the source of new shoots, not effected by mowing
How is adpressed growth an adaptation of grassland plants to repeated defoliation?
- growing tip is close to the ground e.g. plantego
- gets missed by grazing and mowing
How is low palatability an adaptation of grassland plants to repeated defoliation?
Spines and woody tissue with distastefulness and toxins to deter grazings
How is being ephermal and adaptation of grassland plants to repeated defoliation?
Exploit bare patches of soil
Grow/reproduce during periods of limited grazing
What are calcifuges and calcicoles?
Calcifuges = acidic soil species
Calcicoles= alkaline soil species
Why is soil pH important?
- Acidity decreases the bioavailability of nutrients such as N and P
- Leads to low levels of productivity and species richness
What is the difference in species abundance between intermediate and high levels of crop+litter productivity?
Intermediate = Ideal window of intermediate productivity, not too competitive so species can occur together
High = Low levels of species richness due to extreme growth of one or two species (lots of competition)
How much degraded, eroded soil is lost annually?
2.9 million ha tonnes
What does compaction by heavy machinery do to the soil?
reduces nutrient cycling and ability to mitigate flooding
How much money does degradation cost the economy?
1.2 billion due to loss of C
What is meant by horiculture?
the art or practice of garden cultivation and management
How much of the peat profile are we using each year to grow fruit and veg?
1.2cm
Describe the different ways to restore quality in agricultural land
Organic farming = no chemical input into the systems
Regenerative agriculture = restoring soil health, self sustaining ecosystems
Conservation agriculture = soil health specific focus but to increase yields
How much of our fruit and veg do we grow domestically?
Fruit = 18%
Veg = 56%
What is urban horticulture and why is it a good option for sustainability?
- People growing their own food in allotments
- less degradation, organic C is 250% higher than on arable/pasture land
- We have lost 65% of allotment usage since 1950
What percentage of greenspace is peoples gardens?
38%- Local gardens could feed into the local food economy
What are vegetation patchworks?
- Patchwork of types, differing in species composition and appearance
- Requires some form of sampling
What are Stands?
Patches of relatively uniform vegetation separated by boundaries
Boundaries may be sharp (ecotones) or diffuse (ecolines)
What is stratified random sampling?
- Includes the decision to only sample within the main stands
- Sample more in areas your more interested in
What is releve sampling and what are the rules?
Not a fixed size or shape- single sample to represent a stand
- Be ‘representative’ of the stand as a whole
- Be ‘uniform’, away from the stand boundaries
- Be sufficiently large to include most species (concept of the ‘minimum area’)
Why does releve sampling plateau at a certain amount of square metres?
Gets to a point where there is a biggest point where most of the species have already been captured
What does the number and area of samples required depend on?
- Purpose of the study
- Measurements being made
- Size of individual plant species
- Evenness of distribution of species (e.g. uneven patterns may require a larger sample size)
- Sample area and number may be interrelated
What are the different quadrat methods and their pros and cons?
Quadrat:
- Quick but lower accuracy
Subdivided Quadrat:
- % cover in each sq then an average
- Slower
- greater accuracy
Point survey:
- Drop lots of large pins in a regular grid
- You need lots 100 is too small
What ways can you characterise vegetation?
Species composition
Species richness (number of species)
Species diversity
Explain the plant strategy theory
Low stress low disturbance = competitors
Low stress high disturbance = ruderals (weeds)
High stress low disturbance = stress tolerator (acid species)
