7-11: Temperate Forests, Forest Floor, Forests in the Future Flashcards
What is the temperate zone?
Seasons of spring, summer, autumn, winter
Moderate climate
Long growing season
40 and 60/70 degrees North and South of the equator
What is the average temperature in temperate zones?
5-20 degrees C
What is the temperate zone mean annual rainfall?
25-200cm
What is a biome?
A region defined by vegetation type and climate
Development of the biome concept
Merriam 'life zones': Focused on animals Temperature varied with altitude Loldridge 'life zones': - Focused on plants - Introduced water availability and evapotranspiration (tendency of water leave surface) Whittaker: - Plotted temperature vs. precipitation - Simplification of Holdridge
Debate about whether Europe is really a temperate forest
2000 Frans Vera An open savannah with woodland glades? But lots of trees that are wind pollinated In savannah, grasses- don't flower often
2 types of forest
Evergreen
Deciduous
Temperate rainforest requirements
Precipitation over 1400mm
Mean annual temp 4-12 degrees C
Mostly evergreen
Advantages of having deciduous leaves
Reduced area for water loss
Buds are cheaper to produce
Can get rid of disease/damaged tissue
Disadvantages of having deciduous leaves
Nutrients are lot in autumn
Slow start in spring
Advantages of having evergreen leaves
Quick start in spring
Can photosynthesise over winter
No lost nutrients
Keeps the understory in the shade
Disadvantages of having evergreen leaves
Generally lower capacity for photosynthesis
Lower N-use efficiency
Poorly optimised photosynthesis
What is Gause’s Law of Competitive Exclusion?
No 2 spcies can occupy the same ecological niche and co-exist
One will always out-compete the other
How do trees in the same forest all grow together?
All use same resources- do they occupy same niche?
No- have a mixture of tree species
What is succession?
Where the structure of a biological community evolves over time
Example of primary succession
Sand dunes
Example of secondary succssion
Recovery after a forest fire
What is cyclical succession?
A small number of species tend to replace each other over time in the absence of large-scale disturbance
Disturbances include wind, fire, grazing, and human, fire, felling, management
What is primary succession?
A rapid transition from bare rock to broad-leafed forest
Previous plants create soil for new, bigger plants
Does not stop!
Primary succession of birch
Birch seeds are very light, disperse by wind well
Grow quickly, are very tolerant
What is secondary succession?
Development of an ecosystem on previously vegetated land
Typically scrub -> birch -> oak in the UK
Filling the forest gaps
If a big tree falls, everything in the space will grow
Beech falls = large gap, replaced by ash, birch, sycamore
Fallen ash = little gap, replaced by tolerant beech that doesn’t require much sun
The replacement plant will depend on…
The year (mast years, where only seeds every 2 years) The weather- rainfall, temperature
Strategy theory
r_____________K
r: reproduction, like disturbed habitats eg. birch
K: carrying capacity, like stability eg. oak
What was the ‘Great Storm’ of 1987?
134mph winds
22 people killed
15 million trees felled
On Toys Hill, Kent, new growth was dominated by birch
What is Dutch Elm Disease?
Killed most elm trees in the UK in the 70s
Fungus carried by elm bark beetle
Elm is clonal, so little genetic variation
What is Sudden Oak Death?
Not serious in British oaks
Oomycete (fungus-like)
What is ‘Acute Oak Decine’?
Bacterial disease
Kill British Oak
What is Ash dieback?
Caused by airborne fungus
Took 20 years to reach the UK from central Europe
Expected to kill most UK ash trees
Disturbance by insects
Leaf eaters eg. Ash sawfly
Sap feeders eg. Aphids
Disturbance by small mammals and birds
Seed eaters- prevent dispersal
Some eat bark/buds
Disturbance by large herbivores
May eat seedlings/leaves
Stop forest regeneration
Eg. Fallow deer in UK browse seedlings, fraying (rub antlers against bark), pull up recently planted trees
Human disturbance
Eg. coppicing- where trees are cut close to the base
How to stop large herbivores
Culling
Re-introduction of predators eg. wolves
What is the Manchester museum Alderley Edge project?
1997-2003
Tree planting happened 1745-1755
Over 1000 plant species identified
19 tree species identified
What trees were mainly found at Alderley Edge?
Oak
Birch
Beech
Scots Pine
What was the most common tree at Alderley Edge?
Oak (followed by beech)
Where does beech grow?
Moist climates
Well drained soil
What plants were found at Alderley Edge?
Brambles (blackberries) found in clearings, hedgerows
Important food for lepidoptera
Examples of indicator species
Rowan
Holly
Wood sorrel
What is Grime’s triangle?
Theories of surviving on the forest floor
Three strategies:
Competitor
Stress tolerator
Ruderal
These strategies each thrive best in a unique combination of either high or low intensities of stress and disturbance
What light is shade light enriched in?
Green
Far red
What is partial shade rich in?
Green
Far red
Blue
How do sun plants grow?
Sense far red light
Try to outgrow the shade
This is a shade avoidance response
What photoreceptor senses red/far red light?
Phytochrome
Do shade plants respond to phytochrome signals telling them to get taller?
No
What is different about shade plant chlorophyll?
Shade plants have a lower Chl a : b ratio
So have more Chl b per Chl a
Chl b absorbs different wavelengths, so can absorb light ‘missed’ by sun plants
Shade plant leaves
Shade plants have thinner leaves
Leaves are arranged in a single layer
Leaves don’t overlap
Fewer roots in relation to shoots (higher shoot : root ratio)
Stinging nettle features
High N requirement
High protein content
High photosynthetic rates
Good competitor- fast growing, dense but dies down in winter
Types of light foraging
Vertical foraging
Horizontal foraging
What is vertical foraging
Growing up trees
Eg. ivy
What is horizontal foraging?
Stolons (runners)- take roots at points along length to form new plants
Eg. blackberries
Plants that do seasonal shade avoidance
Deciduous understory plants
They leaf/flower in spring or autumn before trees leaf
Have underground storage tissues eg bulbs, so ready for a quick start in spring
Eg. bluebells
Examples of human activities that affect distribution and nature of forests
Coppicing
Plantations
Forest clearance- eg for livestock
Urbanisation
What does elevated CO2 lead to
Changing climates
What does an increasing human population do
Increase food and fuel demand
3 ways of measuring the effects of elevated CO2 on forests
Expose a leaf to high CO2
Expose a whole plant to high CO2
Expose a whole ecosystem to high CO2
Expose leaf to CO2 theory
Ci = conc of CO2 in leaf
In the day, Ci decreases due to use by photosynthesis
Replaced by CO2 from stomata
Conc gradient as lower CO2 inside leaf
Elevating CO2 levels = increase in photosynthesis
Increased Ci = increased Rubisco activity
3 ways to expose a whole plant to high CO2
Growth chamber studies
Greenhouse studies
Open top chambers
What are growth chamber studies?
Limited space
Stable environment
Can change CO2 conc and light
But can’t grow tall or provide natural light
Light only to the top of plant- doesn’t reflect nature
What are greenhouse studies?
More space
More natural light
Temperature is buffered
Can grow taller plants
What are open top chambers?
Near a natural environment Still buffered from the wind Basically a big tent with a fan CO2 is added Can use for small trees The best
What effect does elevated CO2 have on Ponderosa Pine saplings?
More photosynthesis in natural environment when there is an increased CO2
Actual phot. is elevated, but capacity is reduced
Change investment in different processes
Invest less in carbon capture
This is called acclimation
What happens when there is acclimation of photosynthesis?
Less Rubisco
So lower protein content
How do you expose a whole ecosystem to high CO2?
‘FACE’- free air CO2 enrichment
Pipes pump out CO2 to trees based on wind direction
What is POP-FACE?
Exposing a poplar coppice to high CO2
Looked at 3 species over 3 months
Why use poplar for POP-FACE?
Grows 10m every 10 years- fast growing
What did POP-FACE find?
Trees with increased CO2 were doing more photosynthesis
But increased photosynthesis does not necessarily mean increased growth (more wood)
Effects of elevated CO2 on leaf litter
Accumulation of leaf litter
Trees producing more and so dropping more leaves?
Or because fallen leaves are decaying slower?
FACE conclusions
Fast growing trees maintained enhanced growth
Leaves were greener longer
Increased P in soil
40-45% increase in net Carbon sequestration 3-5 years after CO2 increase
7 year study on temp increase
Up to 2010
5 degree rise in soil temp
2 plots, one heated, one not
Only soil warmed- no direct effects on canopy
Found that warming will reduce C in soil, but increase C in trees
But effects on photo. not considered
