APS124 Dyson Flashcards
British woodlands are normally…
broadleaved and deciduous
In the past woodland covered most of the UK. Now just … of the UK is wooded.
12%
What are the 3 main types of woodland?
Native, ancient and recent
Around … of uk woodlands are native. Most is broadleaf deciduous woodland. Native trees are trees that….
40%,
have grown in the UK naturally since the last ice age - not introduced - usually birch dominated
The UK has around … species of native trees and shrubs
50
Ancient woodland is..
woodland that has been continually wooded since 1600AD
- as planting became more common after 1600AD, and therefore pre-1600 woodland is likely to be natural and native
Recent woodland is woodland that..
has been planted or established naturally (e.g. on former heathland)
British trees produce very high quality…
leaf litter, and woodland has relatively good quality, rich soil. - this soil type covers 45% of land in the UK, showing where woodlands have previously been
- highly valued for agriculture
- lots of invertebrates and organic matter
- many lowland forests cleared
Similar plant communities occur in similar environments because of…
- similar environmental factors/stresses
- community processes
- competitive exclusion
- co-existence through tolerance
- co-existence through complementary resource use
- dependence
What are the 3 components of the structures of plant communities?
- Vertical structure (stratification)
- Horizontal structure (pattern)
- species abundance
Woodland has the most…
complex structure of any british vegetation type
What are the four layers of woodland (vertical structure)
- tree layer
- shrub layer
- field layer
i. tall herbs and undershrubs
ii. layer of low herbs - ground layer (mosses and small herbs)
When looking at horizontal structure, what are the 3 main distribution types?
- Regular (overdispersed)
- Random
- Clumped (underdispersed - the most common type)
The pattern shown by a species is a product of…
- morphology and growth characteristics (e.g. individual vs spreading species)
- seed dispersal mechanisms
- environmental heterogeneity
- species interactions
Species abundance is…
the amount a species contributes to the vegetation in an area
- this can be used to define a vegetation type
Species abundance can be measured using…
- Abundance ‘guestimates’ (subjective) - e.g. DAFOR: Dominant, Abundant, Frequent, Occasional, Rare
- Density - number of individuals per unit area - easier with young plants but not spreaders
- Frequency - chance of finding a particular species in a sample of vegetation - estimated by examining several samples - “shoot frequency” and “root frequency”
- Cover - generally expressed as a % - can be more than 100% if count overlapping vegetation
Plants have two main approaches to survival on the forest floor:
- shade tolerance
- Complementary resource use
What are the 3 ways to be shade tolerant?
- absorb as much light as possible
- reduce your energy requirements
- both
Shade plants often have …, … leaves with a single … layer - they have a large … … to … ratio
large, thin, palisade, surface area, weight
Shade plants often have … … to shading - typical of plants in partial shade conditions and less so for species in consistently deep shade
morphological plasticity
Evergreen plants have lower…
energy requirements as they do not need to make new leaves every year - this means they do not have to have shade type leaves
Shade tolerant species may respire more …, as this level has to be maintained at both high and low light intensities - this means that shade tolerant species have lower … …
slowly, growth rates
carbon gain =
photosynthesis - respiration
The amount of light where photosynthesis overtakes respiration is called the…
light compensation point
Shade tolerant plants may have a … light compensation point than plants adapted to sunny areas. This gives shade leaves an advantage at low light levels - but disadvantage at higher light levels
lower
Vernal species grow in …
spring
Aestival species grow in…
summer
Autumnal species grow in…
autumn
hiemal species grow in…
winter
Vera cycles are natural processes involving..
herbivores that regulate woodland formation and die off
- take around 500 years to complete
There were widespread grasslands during the…
Devensian/ last glacial period (~100,000-11650ya)
Sun-loving species are known as…
heliophile species
What is the current epoch called?
holocene (last 11,650 years)
What is a modern major driver of ecosystem change into grassland?
establishment of farming (agriculture)
What declines in the fossil record when grassland is established?
elm (pollen)
What are the hypothesised reasons for elm decline?
- disease?
- climate change?
- trees pollarded to provide winter feed for livestock
- areas of diseased trees easier to clear for farming
still debated, but likely a combination of human impacts on the landscape and disease
In the moors west of sheffield, there are … peaks of … pollen between the elm decline and the iron age (500BC) - suggests…
5, Plantago,
5 clearance phases, progressively larger and longer
- ‘landnam’ clearances
It is thought that Neolithic farmers took advantage of of … … …. They would clear land at the edges of … …. Humans also removed large …, exacerbating the cycles. There was an interaction between plant communities, large herbivores and humans.
natural vera cycles, dying woodlands, predators
Grasslands are…
dominated by grasses
- subject to natural or artificial grazing - results in the partial defoliation of plants
Graminoids are..
grasses, rushes and sedges
- “grassy things”
What are grassland plant adaptations?
- Intercalary meristem
- spread by rhizomes
- adpressed growth
- low palatability
- ephemeral life history
intercalary meristem is only present in..
graminoids and horsetails
- meristem present at the base of each leaf - grazed plants can easily regrow from basal meristem
Rhizomes…
- rootstalks provide new nodes for growth - grazed plants can spread without flowers
Adpressed growth…
- negatively-phototropic rosettes - leaves tightly adpressed to the ground - not easily grazed
Examples of low palatability include…
spines, woody tissues, distastefulness and toxins
Ephemeral plants…
exploit bare patches of soil and grow during periods of limited grazing
What are the 2 grassland types in the uk defined by?
soil pH - acidic and alkaline grassland
Calcifuge species grow in…
acidic soils
Calcicole species grow in..
calcareous (alkaline) soils
Why does pH have such a large impact on plant growth?
Influences availability of ions - some can be toxic, whilst others are crucial to healthy plant growth
Most of the peak district grasslands, including the derbyshire dales, are based on..
limestone (calcareous, and therefore alkaline, soils)
Limestone grassland is often very species..
rich
The characteristic soil of limestone grassland is called..
rendzina
- no subsoil, just surface soil, substrate, then bedrock
- tends to mean rendzina soil is very shallow, and often bleeding of bedrock into upper layers of soil
- low fertility
The ‘thin-ness’ of the soil is particularly due to the…
purity of the bedrock - pure limestone provides very little insoluble residue on dissolution - little material to contribute to the development of a deep soil profile
The shape of the land formed through the rock is called the…
toposequence
Biodiverse limestone grasslands tend to form on…
slopes, rather than plateaus and valley bottoms
Plateaus have…
more acidic podzol soils (pH < 5) and very low fertility (<10 species/m2
Slopes have…
rendzina soils (pH >7) and low fertility but high species richness (20 species/m2)
Valley bottoms have…
alluvial soils (pH 5.5-7.5) and medium fertility, and (5-15 species/m2)
Globally, heathland and moorland is very…
rare
Heathland refers to a physiognomically-distict type of vegetation, dominated by…
ericoid dwarf shrubs
Ericoid =
Ericaceae and related families = heathers
- normally dominated by C. vulgaris
Heathland in the UK has low … … but high … …
floristic diversity,
conservation status
Heathland has low … status and … soil
nutrient, acidic
Upland heaths are known as…
moors
What are the characteristics of upland heaths?
- ~300-400m above sea level
- up to montane zone (the tree-line)
- 2 to 3 million hectares in the UK
- 75% of entire world’s total
What are the characteristics of lowland heaths?
- 58,000 ha in UK
- 20% of world’s total
- altitudes less than 300m above sea level
Heathlands typically occur on … … soils
acidic podzol
Podzol soils are typical of…
boreal forests and heathland
What are the characteristics of podzol soil?
- acidic (pH < 5.5)
- little mixing of mineral and organic matter by organisms
- not much cycling of nutrients
- sharp boundaries between distinct horizons
- intense eluviation of surface horizons (nutrients and bases leached from upper horizons
- much deeper soil than rendzina soils (+ deep organic (peat) layer)
- iron pan prevents drainage
Peatlands are the largest…
carbon reserve in the uk
- 3 billion tonnes C
- more C stored in UK peat than forests of Britain and France combined
- peat degradation is a climate change risk
Podzolisation may have occured in response to…
forest clearance and cultivation
- so not really a fully natural habitat
Most moorlands don’t exist without some form of…
management
Red grouse is … to the UK
endemic - high conservation status and economic value
- eats heather
- grouse shooting popular sport
Grouse shooting is worth about … per year to the UK economy
£100 million
Grouse are completely reliant on…
young shoots of heather
How is heathland managed for grouse shooting?
rotational burning used on an 8-15 year cycle
- maximises the amount of edible biomass
- provides patches of more mature heather for nesting
Prescribed burning…
removes the top layer of heather
- done in winter
- controlled areas
- avoids burning the peat underneath
What are the advantages of burning moorland?
- Management to avoid succession
- ash provides nutrients to soil
- nutrients also return to soil via precipitation
- can increase plant diversity
- can increase insect diversity in the long term
What are the disadvantages of burning moorland?
- even careful burning can cause loss of peat
- burning increases soil temperature for up to 7 years
- burning reduces insect populations initially
- burning reduces water table in burned areas
- burning reduces plant health and nutrients
- substantial loss of some nutrients in the smoke, especially nitrogen (N)
Wildfires burn …, happen in … weather, and can be uncontrolled and burn through underlying …
deeper, hot, peat
- climate change –> hotter summers –> more fires
What are the two types of wetland in the UK?
- Aquatic wetlands - shallow water ecosystems
- Telmatic wetlands - wet terrestrial ecosystems
Telmatic wetlands can be…
permanent wetlands or seasonal wetlands
Permanent telmatic wetlands can be classed as…
- Bog - fed by rainfall only, acidic
- Swamp - flooded for most of the year, supports graminoids
- Fen - fed by groundwater and rainfall, base-rich
Seasonal wetlands tend to be called…
Marshes - dry for part of the year, can support meadow and pasture
Telmatic wetlands all have … in them
peat - organic plant material at varying stages of decomposition
Succession is…
a gradual, directional change in the composition of vegetation
populations of different plant species successively replace one another
usually accompanied by environmental change
Allogenic means…
succession is driven by environmental change
Autogenic means…
succesion when the vegetation itself induces environmental change - vegetation creates conditions conducive to its own replacement
Primary succession occurs…
on surfaces that have not previously supported vegetation, e.g. bedrock exposed by erosion, newly created pools, lava flows
secondary succession occurs..
on surfaces that have previously supported soil and vegetation, e.g. recolonisation of set-aside farmland
Wetland succession (peat accumulation) occurs in two ways. What are they?
- Terrestrialisation - infilling of lakes and pools with mud and peat
- Paludification - the process by which ‘dry’ land gets wetter - caused by impeded drainage or increased precipitation - responsible for the largest areas of wetland in Britain
What are the two types of terrestrialisation?
- Rooting (normal) terrestrialisation - water gradually shallows by the accumulation of mud and peat - allows progressive colonisation by species more suited to shallow-water conditions
- rafting terrestrialisation - open water becomes overgrown directly by a buoyant mat of peat - reduces the dependency of the succession on shallowing caused by the accumulation of mud and peat
What plant is often the first to colonise wetlands (especially in the UK)?
Sphagnum moss
- most of our peat made from sphagnum
When does a raised bog form?
When acidic ombrotrophic peat accumulated above the level of the fen water table - usually up to five metres high in the centre
What type of bog is most often formed by paludification?
blanket bog - normal terrestrialisation in a bog but vegetation starts to spread further and further away from the original open water source - need significant amount of rainfall for this to occur (200+ days of rainfall per year and/or high humidity)
ombrogenous formation means…
rain-fed
It is now considered that much blanket bog was initiated by…
forest clearance (as tree removal increases water table)
What are some plant adaptations to the waterlogged and oxygen-deficient wetland environments?
- Anaerobic respiration in roots (produce less toxic malic acid rather than ethanol), transport of oxygen to roots (high root porosity), release of oxygen into the rhizosphere (soil around roots)
In bogs, decomposition is …, meaning bodies can be incredibly well-preserved (known as … …, e.g. the tollund and lindow men)
retarded, bog bodies
Dead stems of reed in winter may have an important function as…
snorkels
- cutting dead stems below water level in winter can cause plants to ‘drown’ and sometimes die
Oxygen release by plants with high rates of … … … can sometimes oxidise the soil sufficiently well to permit the growth of others
radial oxygen loss
