1
Q
What is a Biome?
A
A way of classifying the ecosystems based on what lives there
2
Q
What are some examples of Biomes?
A
Polar tundra
Boreal forest
Temperate forest
Tropical forest
Tropical savanna
Desert
3
Q
What are needleleaf and broadleaf trees?
A
Needleleaf= ‘conifer’ and can be evergreen or deciduous
Broadleaf = ‘angiosperm’ and can also be evergreen or deciduous
4
Q
What did Humboldt say about the relationship between biomes and climate?
A
- Particular vegetation types are associated with climate and support similar life forms
- To get the same temperature and biome you have varying altitudes depending on the climate e.g. to get no trees in the tropical biome you have to go higher up the mountain than you would in the arctic biome
5
Q
Why cant a cold AND wet climate occur?
A
Warm air holds more moisture: why climate change is an issue for rainfall
6
Q
What are the ‘rules’ for biome distribution?
A
- Environmental filters: Survival of cold or dry environmental extremes requires specialist adaptations, it’s about the extremes rather than the averages as its the extremes that are causing the exclusion
- Competition: Specialists are excluded from warmer/wetter environments by stronger competitors
7
Q
What are some examples of cold-sensitive plants?
A
- Bananas and mangos as they are tropical plants with no tolerance to chilling
8
Q
What are the mechanisms of freezing resistance?
A
- Metabolic adaptations e.g. solute accumulation to depress freezing point, anti-freeze protein synthesis, resource allocation etc.
- Structural adaptations e.g. thick-walled cells, narrow xylem vessels to resist freezing injury
- ‘Trade-off’ with climate resistance and growth as the energy used to adapt could have been used for growth with photosynthesis
9
Q
Why do some species not survive in the tropical rainforest despite its good conditions?
A
- Competition, causes species specific growth
- In colder/direr conditions ‘environmental filters’ play their part
10
Q
What does a ‘eurocentric’ view of biomes mean?
A
Theory that forests are most important vegetation and exist everywhere, if they don’t its because of fires and deforestation
11
Q
Why are Savannas perceived as ‘unnatural’?
A
- Deforestation and fires in tropical forests can lead to savanna-like vegetation - Savannisation
- Therefore gives perception that savannas are ‘unnatural’ and are always caused by degraded tropical forests through anthropogenic causes or fires
12
Q
What are some characteristics of Savannas?
A
Tree-grass coexistence
Continuous grass cover but discontinuous tree cover
13
Q
How are Savannas functionally different to forests?
A
Savanna:
- Open tree canopy
- Ground cover of light demanding grasses
- Frequent grass fires
- Fire adapted ground flora
Forests:
- Closed tree canopy
- No grasses
- No fires
- Trees intolerant of fires and killed
- No fire adaptation in ground flora
14
Q
What is an endemic species?
A
Lives in a particular, small area and grow nowhere else
15
Q
What do endemic species imply about Savannas?
A
Fire and herbivory are ancient mechanisms of maintaining savannas
E.g. Savanna grass communities in madagascar are adapted to grazing and are rich in endemic species
16
Q
How do Savanna trees survive wildfires?
A
- Little trees engulfed by fire but have underground organs so when fire goes it tries again
- When no fire, the canopy goes above the ‘escape height’ and grow taller as the trunk is fireproof
- ‘Demographic Bottleneck’
17
Q
What causes savanna ‘mosaics’ with the forests?
A
- Grass means fire which leads to open canopy
- No fire for a bit and the trees grow up and close the canopy then there is no fire and grass doesn’t grow
- Leads to forest and savanna in close proximity
18
Q
What is involved in the misclassification of Savannas?
A
- Forest -savanna mosaics implied to colonists that savannas are degraded forests
- Colonists had a ‘forest-centric’ view
- No account for the savanna biome which functions in a completely different way to northern temperate biome
- Leads to mismanagement such as planting trees
19
Q
What is ‘woody plant enorachment’?
A
- A consequence of climate change in the Savanna
- Rising C02 promotes growth meaning they can escape the fire easier and means trees move into savannas
20
Q
Why is woody plant encroachment bad?
A
-Depletes savanna groundwater and threaten soil carbon stocks
- Woody plant densities impact livelihoods, cannot graze domestic animals etc.
21
Q
How can trees entering the savanna reduce diversity?
A
Their canopy covers up floor species which need light meaning floor species die
22
Q
What are land surface models?
A
Numerical models solve coupled fluxes of water, energy and carbon between the land-surface and the atmosphere (direct and indirect human forcings)
23
Q
How are Land surface models run?
A
Through coding in high performance computing systems (HPC)
24
Q
What kind of feedbacks can land models cover?
A
- Snow cover and climate
- Soil moisture-evapotranspiration-precipitation
- Land use and land cover change
- Carbon cycle
- Reactive nitrogen
- Biomass burning
25
What is the global carbon budget?
Total amount of carbon dioxide emissions that can be released into the atmosphere while still limiting global warming to a certain target
26
Brief evolution of land models
- Complexity has increased as years have progressed
- Able to distinguish between different species of plants etc.
- In the 2000s water starts to be included
- 2010s + we start including crops, cities, human disturbance etc.
27
What information does a land model provide in an earth system model?
1. Land-atmosphere changes (energy, water ,carbon ,energy)
2. Land surface states (soil moisture, temp, snow cover
3. Land surface characteristics (soil texture, roughness, albedo)
28
What are the main components of a land model?
- Surface energy balance
- Surface water balance
- Carbon balance
29
What will happen if the surface energy input/output aren't balanced?
Global warming
30
What are the energy output longwaves?
Latent heat flux
Sensible heat flux
Ground heat flux
31
Which processes/properties affects the energy balance of land surfaces?
- Albedo
- Surface roughness
- Evapotranspiration
32
What are the indirect influences of deforestation on climate?
DEPENDS ON THE REGION
- Removing all trees leads to cooling as there is less albedo
- Removing all trees leads to no evapotranspiration which means warming as water vapour would cool the atmosphere
- Surface roughness due to trees, when removed lead to increase in temp
33
What are some inputs/outputs included in surface carbon balance land models?
- Photosynthesis
- Autotrophic and heterotrophic respiration
- Carbon flux due to fire
- Carbon flux due to land use change
34
How do we look at land surface heterogenity?
Subgrid tiling: dividing larger grid or cells into smaller sub cells to better capture spatial variability of land use within them
35
Where do parameterizations in the land models come from?
Lab understanding of plant processes
Empiral relationships
Optimality theory
36
How can we predict how much photosynthesis accounts for carbon uptake in certain land use models?
- Light, energy, transport of sugars
- Measuring of C02 uptake of plants in the ecosystem
37
How can we look at land use model uncertainty?
- Model intracomparison
- Model benchmarking (model evaluation against observations)
- Model-data fusion
- Manipulative experiments
- Model intercomparisons (carbon cycle, land use, land -atmosphere interactions.)
- Tower flux data, subsequent correlation plots to see how well the model reflects real data
38
What is meant by ecosystem structure?
Biophysical architecture of an ecosystem
39
Give some examples of ecosystem structure
LAI
Canopy height
Tree density
‘Clumping’
40
What is the LAI?
- Total one sided green leaf are per unit ground surface area
- Defines the area that interacts with solar radiation and provides the remote sensing signal
- Surface responsible for carbon and water exchanges within the atmosphere
41
What is ecosystem function and some ways to measure it?
Processes that occur within the ecosystem
I.e.:
Productivity
Carbon sequestration
Decomposition
Energy flows
Nutrient cycling
42
What is remote sensing?
Getting info about an ecosystem without touching it - using reflected or emitted radiation to quantify properties of ecosystems
43
What are some remote sensing techniques?
- LiDAR
- Optical remote sensing (400-700nm reflected radiation)
- Microwave RS (soil moisture)
44
What are vegetation indicies?
Mathematical formula to measure structure, condition etc. of vegetation
45
How do leaves interact with different wavelengths of light?
- Green is reflected straight back
- Red and blue penetrates deeper into spongey mesophyll
- Infrared goes deeper but it doesn’t matter because we cant see than anyway
Good because exploits differences between reflectance at wavelengths for remote sensing
46
What are the three main types of vegetation indices derived from?
1. Simple ratio (density)
2. Normalized difference (density)
3. Red edge (chlorophyll)
47
What are 3 applications of vegetation indicies?
1. Indicators of seasonal and inter-annual variations in vegetation (phenology)
2. Change detection studies (human/ climate)
3. Tool for monitoring and mapping vegetation
48
How is normalized difference measued?
NDVI = (NIR- Red)/ (NIR + Red)
NIR= Near infrared reflectanc e
Red = red reflectance
High NDVI = High density, can be mapped to look at biomass distribution
49
What are the limitations of NDVI?
- Once certain density is hit, its saturated so it plateaus, cant tell difference between high density and higher density
- Atmospheric scattering and soil wetness can influence the red and NIR
- Doesnt reflect plant-scale processes and NDVI may vary according to vegetation species
50
What is the equation for simple ratio and how is it different from normalized difference?
SR = NIR/Red
Takes the ratio, not the difference and doesn't normalize for differences atmospheric conditions
51
What relationship is there with SR and LAI and what does this enable?
Linear relationship, can be used to map the LAI of a space without going there
52
What are the different types of plant pigments?
- Chlorophyll (green)
- Cartenoids and favlonoids (yellow)
- Carotenoids (orange)
- Anthocyanins and carotenoids (red)
53
How does absorption vary depending on pigment?
- Chlorophyll absorbs red and blue (reflects green)
- B-carotene reflects green orange and yellow and absorbs blue
- Anthocyanin absorbs around 500 nm
54
What is used to map chlorophyll as a vegetation indicy?
MTCI
55
What can remote sensing tell us about ecosystem function?
- Affected by human and abiotic drivers
- Can model carbon fluxes with climate change
- NDVI, photosynthesis and transpiration to work out carbon exchange
56
What is LUE and why is it good?
Light use efficiency = how well plants convert light energy into chemical energy via photosynthesis
- linear relationships between NDVI and photosynthesis but LUE is better as it analyses daily and not annual fluxes
57
What is LUE influenced by?
air temperature, water, atmospheric Co2 concentration
58
What is the limitation of process based models?
- Only as good as the data that you put into them e.g. canopy height and LAI
- Hard to parametrize due to diff process being dynamic
- We also need to understand the factors limiting the process and therefore output
59
What are the conditions needed for wildfires?
1. Dry weather
2. Fuel load
3. Ignition (e.g lightening or humans)
60
What is a crown fire?
- Climb up into tree canopy and everything dies
- Hot
- Many mature trees die (crown of tree is burning)
61
What is a surface fire?
- Burn fuel on the ground surface i.e. grass and litter
- Cooler
- Many mature trees survive
62
What is a ground fire?
- Organic matter smoulders underground in organic soils such as peat that dries out
- Burn slowly over a long period as there isn’t much oxygen available
63
What are pyromes?
A way to classify vegetation around the world depending on how the vegetation burns
64
What are seeders and sprouters?
‘Seeders’ = Seed release or germination triggered by fire
‘Sprouters’ = Resprouting of surviving plants
65
What is refractory seed?
TYPE OF SEEDER
- Some kind of cue related to fire which means it sits dormant until a fire and the fire breaks the dormancy
- Cue= heat shock but can be related to the chemistry of smoke
This same strategy has evolved independently on different continents
66
What is serotinity?
TYPE OF SEEDER
Retain seeds on the plant and the fire causes the seed to be released e.g. the frog mouth plant which opens with fire and ‘spits’ the seed out
67
What is a lignotuber?
TYPE OF SPROUTER
Wood that sits on/under the surface full of energy which the shrub uses to resprout shoots after the fire burns
68
What is an epicormic bud?
TYPE OF SPROUTER
A way of reshooting from the crown of the tree (little buds with shoots)
69
What does it mean if a plant has adapted to be non flammable?
Thick, insulating bark (cork) or fibrous bark layers (redwood)
- Cork keeps epicormic buds safe with spongey insulating wood
- Thick bark protects the vascular cambium
70
What is the vascular cambium?
main growth tissue in stems and roots of plants
71
What does it mean if a plant has adapted to have a fast flammable strategy?
- Ignite easily, burn very fast and not much biomass
- Means there isnt much damage to meristems below the ground
- This means the buds underground can resprout
E.g. savanna grasses
72
What does it mean if a plant has a hot flammable strategy?
- Dense biomass burning slowly meaning high heat release
- Seed dispersal (need heat to germinate)
- May burn species not fire adapted- competitive advantage
73
What are the fire characteristics of Savannas?
- Fast flammable grasses and non-flammable trees
- Corky trees, the bark protects the underneath store and the trees survive meaning grass and small trees can resprout
- Savannas need fire to maintain ecosystem, burned land decreasing over time due to agriculture :(((
74
What are the fire characteristics of Mediterranean ecosystems?
- Winter rain and hot summer
-Combination of hot flammable plants which are seeders and non flammable plants which are sprouters
- Tends to have crown fires
75
What are the fire characteristics of temperate forests?
- Dry litter fuel and thick bark, serotinous cones which release seeds with fire
- Fibrous Redwood domination
- Fires important to remove dry litter so released seeds can germinate
- Without small fires that reduce litter it means crown fires occur due to less adaptation
76
How can plant traits influence fire regimes in north America boreal forests?
- Hot flammable trees
- Branches close to ground + flammable for ladder fuels (jump to canopy)
- Not defended against fire but have serotinous cones
E.g. Jack pine
77
How do plant traits influence the fire regime in Eurasia boreal forests?
- Non flammable trees
- Self pruning branches with moister needles + thicker bark
- Trees survive fires
E.g. Siberian larch and Scots pine
78
How does albedo link with fires?
Northern fires clean the surface of vegetation which increases the surface albedo increasing the reflectance of the surface
Ecosystems and Sustainability
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