Lecture 13

Question 1

What limits plant development

Answer 1

Dominant Controls water availability 40% temperature 33% solar radiation (cloud cover prevents sunlight reaching canopy. other areas water availability influences plant growth. 27% Total vegetated area: 117 M km2
Plant growth is limited by : * temperature and radiation (cold winters and cloudy summers) over Eurasia * temperature and water (cold winters and dry summers) * radiation and water (wet-cloudy and dry hot periods induced by rainfall seasonality) in the tropics

Question 2

Give an example of other vegetation indexes

Answer 2

• Enhanced Vegetation index (EVI)

Question 3

What is (EVI)

Answer 3

• Enhanced Vegetation index (EVI) sensitive to dense vegetation* MODIS instrument - also applied to landsat
  EVI is deigned to estimate Leaf Area Index (LAI) and canopy structure, thus provide information on vegetation amount
• LAI is defined as the one-sided green leaf area per unit ground area. Can range from 0 – about 8 over dense forest. amount for green leaf material per 1x1m on the ground.
• Designed to overcome some of the limitations of the NDVI: NIR – RED/ NIR + C1 *RED – C2 *Blue +L. used blue to try and account for atmospheric scattering. C and L– trying to account for soil background correction

Question 4

What is (MTCI)

Answer 4

• MERIS Terrestrial Chlorophyll Index (MTCI) sensitive to chlorophyll concentration in vegetation. * MERIS instrument. MTCI is designed to estimate chlorophyll content in vegetation canopy, thus provide information on vegetation condition.

Question 5

Why is NDVI different from other VI

Answer 5

NDVI – indicates healthy vegetation these indices show the biophysical characteristics of vegetation.

Question 6

What are the advantages of EVI

Answer 6

Advantages
1. It includes a blue band, which allows accounting for residual
atmospheric contamination
2. Minimise soil background effect
3. Sensitive to high biomass area
more responsive to dense vegetation, doesn’t saturate - more applicable globally

Question 7

Why do we need information on chlorophyll content?

Answer 7

▪ Chlorophyll is a leaf pigment and the reason why healthy plants are green in colour.
▪ Plays an important role in the productivity of green plants ▪ photosynthetic capacity (conversion of light to energy)

Measuring vegetation chlorophyll content important for understanding (e.g.):
▪ Nutrient cycling ▪ Carbon budgets – how productive is vegetation ▪ Vegetation productivity Net primary productivity – how can canopies remove CO2

Question 8

What is chlorophyll an indicator of

Answer 8

▪ Indicator of :
▪ biotic stress factors (viruses, bacteria, insects) ▪
abiotic stress factors (drought or light stress

Question 9

Explain which satellite MERIS Terrestrial Chlorophyll Index (MTCI) needs and why

Answer 9

• Designed for used with a satellite sensor called Medium Resolution Imaging Spectrometer (MERIS) * Contains 15 wavebands includes four in the ‘red-edge’ between 665nm – 778nm
  ▪ Red-edge position is sensitive to chlorophyll concentration
  ▪ The position and the slope of red-edge change under stress conditions
  ▪ shift towards shorter wavelengths to the left) if you measure this shift you can work out how much chlorophyll is in vegetation.
  doesn’t directly measure chlorophyll content - you can estimate a relationship.
• lower values in the winter - less vegetation

Question 10

Advantages of Vegetation Indices for monitoring vegetation

Answer 10

▪ Simplicity
▪ Many sensors have wavebands in the red and NIR for calculating a number of indices
▪ Relationships developed in the field translate directly (or scale-up easily) to the satellite data sets. ▪ E.g. relationship between LAI and VI can be extrapolated to larger area
▪ Widely used from land cover, climate models, and operational applications.

Question 11

What is Plant phenology

Answer 11

• Phenology is the study of the timing of recurring life cycle events
• For plants such events are budburst, leaf unfolding, blossoming, fruit ripening, leaf colouring

Question 12

Why monitor it phenological cycle

Answer 12

• Track biotic response to climate change
• Estimating biological productivity (because you manage full seasonal cycle)
• Understanding land-atmosphere interactions
• Modelling vegetative inputs into biogeochemical cycle.

Question 13

What happens to the ENDVI in the phenological cycle

Answer 13

endvi can track phenological cycle as indicative of greeness.
Plants harvested = decrease in ENDVI

Question 14

Why is ENDVI useful for growing season

Answer 14

Provides information on the length of the growing season
NDVI values change with phenology stage
Time series data were helpful in estimating various phenological variables

Question 15

Time of Start of Season (SOS) / Onset
of Greeness:

Answer 15

beginning (end) of measurable
photosynthesis.

Question 16

Length of the growing season:

Answer 16

duration of photosynthetic activity.

Question 17

Time of Maximum NDVI:

Answer 17

time of maximum photosynthesis.

Question 18

NDVI at End of Season / End of Greeness:

Answer 18

level of photosynthetic activity at EOS

Question 19

Seasonal integrated NDVI:

Answer 19

photosynthetic activity during the growing season.

Question 20

Rate of Greenup (senescence):

Answer 20

speed of increase (decrease) of photosynthesis