Phenology Week TalkOctober 3, 2014
Cynthia WallaceResearch Geographer, U.S. Geological Survey, Tucson AZ
Buffelgrass Phenology Project:When and Where Buffelgrass is Green
The Sonoran Desert Ecosystem
Wide spacing between individual plants means that fires that start do not spread
Natural fires are infrequent and of low intensity
Credit: Caroline Patrick-Birdwell
Buffelgrass (Pennisetum ciliare) invasion in the foothills of the Santa Catalina Mts.
north of Tucson
Credit: Caroline Patrick-Birdwell
Get it while it’s Green: Using MODIS satellite data to capture dynamics of buffelgrass (Pennisetum ciliare) phenology for eradication and management
USGS science and funds directed toward NPS management issue
Working with Saguaro National Park
Coupling field-based observation of buffelgrass phenology with satellite “land surface phenology” and climate
Model when and where buffelgrass is green
Alert managers in a timely manner to treat optimally with herbicides
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
Passive Sensors A passive sensor records reflected or emitted energy. Usually, the energy source is the sun.
Examples include aerial and satellite images.
Note: Photographs and image data are different. Photos are recorded on sensitized film whereas images are recorded as electronic data. From: Shane Brandt, Geospatial Extension Agent, U of New Hampshire
Digital Format & Brightness Values
Digital format: the subdivision of an image into small equal-sized and shaped areas, called picture elements or pixels, and representing the
brightness of each area with a numeric value or digital number.
Canada Center for Remote Sensing
Pixel: Sensor:
1 m IKONOS
1 m Quickbird
30 m TM, ETM+
250 m MODIS
1 km AVHRR
How a Satellite Image is Made
Energy
Data
Display
Per
cent
Ref
lect
ance
Near Infrared (0.83 um)
DA
TA
Green Gun
Green (0.56 um)
SWIRNIRB G R
Red (0.66 um)
Blue Gun Red Gun
Composing a Satellite ImageE
NE
RG
Y
DIS
PLA
Y
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 um
50
40
30
20
10
1 2 3 4 5 7TM Bands
Basalt
Vegetation
Soil
Dar
k --
----
----
----
-- B
right
$T
Per
cent R
efle
ctan
ce
Near Infrared (0.83 um)
DA
TA
Green Gun
Green (0.56 um)
SWIRNIRB G R
Red (0.66 um)
Blue Gun Red Gun
Composing a Satellite ImageE
NE
RG
Y
DIS
PLA
Y
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 um
50
40
30
20
10
1 2 3 4 5 7TM Bands
Basalt
Vegetation
Soil
Dark
---
----
----
----
- B
right
$T
Energy
Blue band
Green
band
Red band
NIR
band
A band of an image is the measurements taken in a specific region of the electromagnetic spectrum.
Per
cen
t R
efle
ctan
ce
Near Infrared (0.83 um)
DA
TA
Green Gun
Green (0.56 um)
SWIRNIRB G R
Red (0.66 um)
Blue Gun Red Gun
Composing a Satellite Image
EN
ER
GY
DIS
PLA
Y
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 um
50
40
30
20
10
1 2 3 4 5 7TM Bands
Basalt
Vegetation
Soil
Da
rk -
----
----
----
---
Bri
ght
$T
Data (from 3 bands of energy)
In this case, we are creating a “false color” composite, where by convention, green band energy is assigned the color blue, red band
energy is assigned the color green, and near infrared energy (which is directly undetectable by the human eye) is assigned the color red,
Per
cent
Ref
lect
ance
Near Infrared (0.83 um)
DA
TA
Green Gun
Green (0.56 um)
SWIRNIRB G R
Red (0.66 um)
Blue Gun Red Gun
Composing a Satellite Image
EN
ER
GY
DIS
PLA
Y
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 um
50
40
30
20
10
1 2 3 4 5 7TM Bands
Basalt
Vegetation
Soil
Da
rk -
----
----
----
---
Bri
ght
$T
Display – a “False Color Composite”
Near-IR (band 4) Red (band 3) Green (band 2)Blue (band 1)
SATELLITE
COMPUTER
From: Shane Brandt, U of New Hampshire
Per
cent R
efle
ctan
ce
Near Infrared (0.83 um)
DA
TA
Green Gun
Green (0.56 um)
SWIRNIRB G R
Red (0.66 um)
Blue Gun Red Gun
Composing a Satellite ImageE
NE
RG
Y
DIS
PLA
Y
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 um
50
40
30
20
10
1 2 3 4 5 7TM Bands
Basalt
Vegetation
Soil
Dark
---
----
----
----
- B
right
$T
Spectral Signature
Blue band
Green
band
Red band
NIR
band
The pattern of reflectance characteristic of a surface. Vegetation has a distinctive spectral signature.
Plant Phenology and Spectral Response – One Species
• Chlorophyll in green leaves absorbs blue and red, reflects green and NIR
• Senescent leaves reflect more red, less NIR
• Band ratio can distinguish actively photosynthesizing vegetation from senescent
• Observing seasonal patterns can identify plant species, guide management decisions
(From: Jensen, John R. Remote Sensing of the Environment: An Earth Resource Perspective.)
Vegetation Indices
V.I.s are Remote sensing surrogates for
estimating certain biophysical parameters of
plants (e.g., percent cover, biomass, LAI)
From: Paul Pinter,USDA, ARS, US Water Conservation Laboratory
For example:Normalized Difference Vegetation Index
NDVI = (NIR - Red)/(NIR + Red)
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
Areas in red outline patches of dense buffelgrass from 2008 aerial mapping of the western Santa Catalina foothills area of Tucson AZ.
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
The spatial pattern of rainfall is highly variable in the Sonoran Desert
Photo Credit: Zack Guido, CLIMAS, The University of Arizona
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
Get it while it’s Green: Preliminary Results
Observed buffelgrass greenness, MODIS-EVI and Precipitation (PPT) data for 16-day periods
10-1
310
-17
10-2
111
-02
11-0
611
-10
11-1
411
-18
11-2
212
-03
12-0
712
-11
12-1
512
-19
12-2
313
-04
13-0
813
-12
13-1
613
-20
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
MODIS-EVI
Pct_green
10-1
310
-17
10-2
111
-02
11-0
611
-10
11-1
411
-18
11-2
212
-03
12-0
712
-11
12-1
512
-19
12-2
313
-04
13-0
813
-12
13-1
613
-20
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
0
0.5
1
1.5
2
2.5
3
3.5
Pct_green
PPT Total (in)
2011 2012 2013
2011 2012 2013
Fourier Harmonics of Annual Phenology
Fourier Harmonic Analysis of a Waveform
Forest Shrubland Grassland Wetland Forest Shrubland Grassland Wetland
1998 1999
Temporal NDVI profiles for selected SE Arizona landscapes
Get it while it’s Green: Harmonics analysis of each variable by year
2011
• MODIS and Greenness patterns align• PPT pattern precedes Greenness
Get it while it’s Green: Harmonics analysis comparing variables
• Timing of PPT always earlier, Timing of Greenness and MODIS typically coincide
Preliminary Results
Buffelgrass greenness observed on the ground is strongly correlated to contemporaneous MODIS-EVI greenness.
Buffelgrass greenness observed on the ground is highly correlated to precipitation of the prior time-period and the prior two time periods (prior 16 day total and prior 32 day total).
Annual harmonics resonance between greenness-MODIS-PPT show consistent patterns, with PPT peaks preceding others and with greenness and MODIS in synchronicity.
Saguaro National Park: so far, we have found lower MODIS-EVI values for some vegetation types with buffelgrass invasion vs. areas without buffelgrass.
Data MODIS Satellite Data
Buffelgrass Phenology Observations
SNP Mapping of Buffelgrass
Climate Data
Preliminary Results
Next Steps
1 2 3 4 5 6 7 8 9 10 11 120
1
2
3
4
5
2002 (7.47") Ave(11.28")
2002
1 2 3 4 5 6 7 8 9 10 11 120
1
2
3
4
5
2005 (11.55") Ave(11.28")
Precipitation (UA Station)
2005
MODIS NDVI Profiles
1. Join Nature’s Notebook
2. Find a site to monitor buffelgrass – Choose a location that you will visit once every week or two. I can help you select a site or you can have your own site added to the network.
3. Sign up as an observer – Become an official participant with Nature’s Notebook and set your username and password. All you need is an email address and Internet access. When you are registering, identify yourself as part of this effort by selecting “Buffelgrass Monitoring Network, Tucson” from the Partner Organization drop-down menu.
How to participate…..