1
Q
What are the spectral curves of different material dependent upon?
A
- Reflection, Absorption, and Transmittance of their constituents
2
Q
What is a general guide for image processes?
A
- DN
- Calibration
- Correction
- Reflectance
3
Q
How many visual cones do humans have?
A
3 (visible range)
4
Q
How many visual cones to butterflies have?
A
5 (Visible, UV and Violet)
- UV spectrum may be used for mating purposes (wings look attractive etc.)
5
Q
What is the difference between human and butterfly vision?
A
- Butterflies see more cones and into UV spectrum
- Butterflies have ‘narrower bands’
- Narrow is generally better
6
Q
Mantis shrimp
A
- Extraordinary vision
- Approximately 16 visual cones
- Many narrow bands in the visual range
7
Q
What can knowledge about variations in species and vegetation distribution patterns, vegetation growth cycles, and plant physiology and morphology provide insight into?
A
- Climatic, geologic, and physiographic characteristics of a region
8
Q
Total incident irradiation = ?
A
Total Reflected plus Total Absorbed plus Total Transmitted
- Depending on spectrum, light will be 1 of these 3
9
Q
How does light reach the understory?
A
- Transmittance through leaves of canopy
10
Q
What are the potential fates of EM radiation absorbed by a pigment?
A
- Usually blue and red absorbed:
- Dissipated as heat
- Emitted in longer wavelength (fluorescence)
- Used for photosynthesis (trigger chemical reaction)
- Depends on amount of energy
11
Q
What is the general chemical eqn for photosynthesis?
A
6 Carbon Dioxides plus 6 waters plus light energy (PAR spectra) = Carbohydrate (sugar, c6H12O6) plus 6 Oxygens
12
Q
What does PAR stand for?
A
Photosynthetically Active Radiation
13
Q
What is PAR?
A
- Spectral range 400 - 700nm that organisms can use for photosynth
14
Q
Why is the spectral range for PAR the way it is?
A
- Photons at shorter wavelength too energetic and damage cells and absorbed by atmospheric ozone
- Longer Photons don’t have enough energy to fuel photosynth
15
Q
Plant cuticle
A
- 1st layer
- Holds water on surface
- Regulates light
- But doesn’t play much role
16
Q
Stoma (Stomata)
A
- Hole on bottom of leaf that releases carbon dioxide
17
Q
Parenchyma
A
- 2nd layer
- Holds chlorophyl in chloroplasts
- Absorbs light (red and blue)
- Unabsorbed transmits to spongy mesophyll
18
Q
Chloroplasts and Granum
A
- Found in Parenchyma and spongy parenchyma mesophyll
- Where light reaction occurs
- Absorb red and blue light
- Granum (stack of thylakoids) in chloroplast has chlorophyl and pigments, where photosynth begins
19
Q
What are the 7 main factors that affect leaf optical properties?
A
- Pigment composition
- Internal and external leaf structure
- Water content
- Age
- Nutrient Stress
- Healthiness
- Background
20
Q
What is the dominant factor controlling leaf reflectance?
A
- Leaf pigments in the palisade mesophyll:
- Chlorophyll a and b
- Beta carotene etc.
21
Q
What wavelengths does chlorophyl a absorb?
A
0.43 and 0.66
22
Q
What wavelengths does chlorophyl b absorb?
A
0.45 and 0.65
23
Q
What is the overall perception of transmitted wavelengths after chlorophyl a and b has absorbed their corresponding wavelengths?
A
- Overall green perception
- Lack of absorption in the 0.5 to about 0.6 range
24
Q
Carotene
A
- 35 to 0.5 micrometers
- Transmits/reflects orange colour
25
Phycoerythrin
0. 55 micrometers
| - Transmits/reflects red with a bit of purple
26
Phycocyanin
0. 6 micrometers
| - Transmits/reflects bluish-green (cyan)
27
Xantophyll
0. 35 to 0.5
| - Transmits/reflects yellow
28
What does pigmentation depend on?
- Seasonal senescence
| - Environmental stress
29
What does a green leaf represent? Yellow? Red? Brown?
```
G = Photosynthesizing,
Y = Beginning of senescence
R = Late stage senescence
B = Fallen, dieing
```
30
What happens to the spectral response as a leaf dies?
- Less chlorophyl absorption at 0.43 and0.66 micrometers
| - Blue shift of the red edge from just above 700nm to just below 700nm
31
What are the ranges that indicate stress?
535 - 640nm and 685 - 700nm
32
Blue shift of the red edge
- Red edge = sharp increase from red to NIR reflectance
| - As pigmentation changes the sharp edge shits towards blue range
33
Can the blue shift be detected on Landsat 7, 8, or Sentinel-2?
Might not be able to see with Sentinel-2 b/c red band is very narrow
- Landsat 8 might be best with a larger red band?
34
What happens in the spongy mesophyll?
- NIR energy interaction
- High reflectance at 0.7 to 1.4 micrometers b/c of internal scattering at the cell wall-air interfaces within the leaf (high NIR)
- Refractive index (n) - hydrated cells: 1.4
- Intracellular air: n = 1.0003
35
Healthy mature leaves...?
- Absorb radiation very efficiently in blue and red
| - Chlorophyll a = photosynthesis
36
Why do plants have high reflectance and transmittance in the NIR? i.e. low absorption
- If NIR was absorbed as efficiently as visible plant would be too warm and proteins denatured
- Evolutionary adaptation of spongy mesophyll allow most NIR to reflect or transmit
37
Why is the scattering in NIR possible and satellite bands important to be in that location?
- Less atmospheric water absorption in those wavelengths/bands
38
What are the generalized interactions of blue, red, and NIR light with plant tissue of young, mature, and old leaf?
- Young: G and IR reflected, R and B absorbed
- Mature: G reflected, R and B absorbed, More scattering of IR as spongy mesophyll has more air spaces
- Old/senesced: B, R, G, and IR reflected, spongy mesophyll broken down
39
What is the spectral behaviour of vegetation at the leaf level mostly dependent on?
- Visible range (400 - 700nm): Absorption of chlorophyll a (430 and 660) and chlorophyl b (450 and 650), green colour from chlorophyl not absorbing green light
- NIR (700-1200nm): Cell structure and interstitial air spaces (index of refraction) act to scatter radiation, prevents heat damage
- MIR (1200-2700nm): Plant water content, strong absorption bands at 1450 and 1940nm
40
MIR
1.3 - 2.5 micrometers
41
Water conditions: turgid vs. relatively turgid
- Turgid = high water content
- Relatively turgid = low water content
- More water content = more IR absorption
- Less water content = More reflection
42
Water absorption bands (nm)
- 970
- 1190
- 1450
- 1780
- 1940
- 2700
43
Why are landsat bands 6 and 7 located where they are?
- Because that is where interactions with MIR and leaf water content occur
- Atmospheric window where wavelengths are not absorbed by atmospheric water
44
Plant response to parasites
- Change in pigments (visible)
- Necrosis: NIR
- Water content: NIR, SWIR
- Parasites in the intercellular spaces therefore compacts the internal structures, NIR
45
Plant response to fungus
- Loses chlorophyll pigments (visible)
| - Water content, NIR, SWIR
46
What do insect vectors do?
- Carry fungus from infected to healthy trees
| - Fungus blocks the water translocation
47
What does a mountain pine beetle do?
- Blocks water translocation
48
Beetle infestation: Endemic
A few trees, isolated
49
Beetle infestation: Incipient
A stand of trees infected, at least a few dozen
50
Beetle infestation: Outbreak
Entire stands of forest infected, large areas
51
Why is there an increase in MIR reflection when a plant is infected with fungus?
- Less water is absorbing in the leaves
52
Why is remote sensing a good option for monitoring mountain pine beetle infestation?
- Tree can still look fine in visible range
- But early, green, attack stage shows very decreased IR absorbance
- Red attack is late stage and only then can damage bee seen by eye
53
General vegetation senescence
- NIR begins to decrease
| - Red reflection increases b/c no longer absorbing chlorophyll
54
Advantages of handheld spectral radiometer? Disadvantage?
- Achieve ideal curves
- Separate desiccated mixed with healthy veg
- No atm. involved
- No pixel mixing
- Not as good spatial and spectral resolution
55
What are possible causes for the blue shift of the red edge?
- Natural senescence
- Water deficiency
- Toxic materials
- Disease
- Decrease chlorophyl a and the red absorption shifts to shorter wavelength and width of absorption band decreases
56
Vegetation index
- Indicator of relative abundance and activity of green vegetation
- Dimensionless
- Radiometric measures that function as indicators
57
What does the vegetation index indicate
- Leaf-area index
- Precent green cover
- Chlorophyll content
- Green biomass
58
Advantages of Vegetation index
- Minimize effects of atmosphere
| - Normalize canopy background and topography
59
LAI
Leaf-Area Index
- Amount of vegetation
- Function of Simple Ratio
60
Simple Ratio
= NIR/R
- NIR represents vegetation
- R represents soil reflectance and chlorophyll absorption
- Looks at vegetation present and LAI
61
High LAI (biomass) = what SR?
- High SR, lots of vegetation
| - Senesced would be much smaller than healthy veg
62
Problems with SR
- Unitless w/ no range
- Depends on digital number in image being worked with therefore is image dependent
- Cannot compare output on 2 different scales
- Only usable for 1 image and cannot compare images, especially 8 vs. 16 bit
63
NDVI
- Normal Distribution Vegetation Index
- Normalized SR into 0 - 1 range
= NIR - R/NIR plus R
- Good indicator of a good growing year for healthy veg
- Increase in NDVI = Increased biomass
64
What is the difference for healthy and unhealthy veg relating to the NDVI
- Healthy absorbs most visible and reflects large portion of NIR, high NDVI
- Unhealthy/sparse reflects more visible and less NIR, low NDVI
65
Applications of NDVI
- Growing seasons (compare years) health/yield in subsaharan Africa
- Drought in California (compare years)
- Input for global carbon models, LAI APAR percent cover biomass
66
Problems with NDVI
- Saturation
- Soil colour
- Moisture content
- Atmospheric content
- Atmospheric conditions
- Presence of dead material in canopy
- All the above change regionally and/or seasonally
67
Why is soil colour a problem for NDVI?
- If soil shows and depending on type (brown vs red-iron rich) gives a different signal
68
How does presence of dead material affect NDVI?
- NDVI can see a dead branch but cannot detect that it isn't affecting the plant and that the plant is still healthy
69
How can problems with the NDVI be fixed?
- Soil adjustments
| - Blue band for atmospheric normalization
70
SARVI
Soil and Atmosphere Resistant Vegetation Index
- Soil calibration factor uses the blue channel
= 2(densityNIR - densityR)/(L plus densityNIR plus C1densityR - C2densityBlue)
71
Relationship between vegetation and soil during growing season for SR
- Planted, watered moist soil, no veg yet, low red
- Intermetiate biomass/canopy closure less red and more NIR, moves up centre of shark fin graph
- Almost ripe is closer to peak, more NIR, less R
- Ripe/high canopy closure/biomass is peak, high NIR, less R
- Harvested is back to soil line but more R b/c not moist, no longer watered
72
In false colour, what does results in cyan?
- Green plus red
| - Closer to bare soil
73
Leaf additive reflection
- Leaf reflects 40 - 60 percent incident NIR from spongy mesphyll
- Transmits remaining 45 - 50 percent through to layer below
- Transmitted can then be reflected once again by leaves in lower canopy
- More leaves in the canopy means more NIR reflectance
