global rangelands and their role in food security temuulen “teki” sankey northern arizona...
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Global rangelands and their role in food security
Temuulen “Teki” SankeyNorthern Arizona University
Flagstaff, AZ
Background
• I am a plant ecologist/dendrochronologist/RS
• I study rangeland use/land cover changes:– Intermountain USA: grassland-forest ecotones,
aspen and pinyon-juniper woodlands– Great Basin: sagebrush shrublands– Sonoran Desert: desert invasive forbs– Central Asia: grassland steppe
Western US Rangelands• Climate change and land
management-induced changes– Fire – Woody encroachment
Post-fire recovery in sagebrush• 16 fires since 1937• SPOT image
Sankey et al. 2008. Post-fire recovery of sagebrush communities: Assessment using SPOT5 and Very Large Scale Aerial Imagery. Rangeland Ecology and Management 61: 598-604
Post-fire recovery in sagebrush
Mountain big sagebrushMean cover = 38%
Time = 27 years
Sankey et al. 2008. Post-fire recovery of sagebrush communities: Assessment using SPOT5 and Very Large Scale Aerial Imagery. Rangeland Ecology and Management 61: 598-604
Sagebrush characterization - Lidar
• Classify sagebrush communities
• Shrub height
Sankey, T. and P. Bond. 2010. Lidar-based classification of sagebrush community types. Rangeland Ecology and Management 64: 92-98
Sagebrush Height - Lidar
Field-based maximum shrub height (cm)
0 50 100 150 200 250 300
LiD
AR
-der
ived
max
imu
m s
hru
b h
eigh
t (c
m)
0
50
100
150
200
250
300
y= -24.52 +0.94XAdj. R2 = 0.77SB = 9%NU = 3%LC = 84%
Sankey, T. and P. Bond. 2010. Lidar-based classification of sagebrush community types. Rangeland Ecology and Management 64: 92-98
Sagebrush Height - Lidar
Vegetation classes
Herb ARAR ARTR PUTR Other
Veg
etat
ion
heig
ht (
cm)
0
100
200
300
400
500
600
Lidar measurementField measurement
a b
c
d
a
Sankey, T. and P. Bond. 2010. Lidar-based classification of sagebrush community types. Rangeland Ecology and Management 64: 92-98
Western Rangelands: Juniper encroachment• Juniper cover increase: 30-600%• Encroachment leads to:– Understory vegetation loss– Soil erosion– Habitat loss– Fire hazard
• Control treatment– Prescribed fire– Cutting– Shredding
Juniper encroachment• Quantify encroachment rates and patterns• Identify priority areas for control treatment
Juniper encroachment
Sankey et al. 2010. Characterizing western juniper expansion via a fusion of Landsat 5 Thematic Mapper and lidar data. Rangeland Ecology and Management 63: 514-523
-
A
C
B
0 100 M
Legend
Juniper absenceJuniper presence
! Juniper trees
Landsat
Fusion
Lidar
Vegetation associations
ARTRV/PUTR
ARTRV/SYOR
ARTRV/PSSP
ARAR/PSSP
ARAR/FEID
Juni
per
cano
py c
over
(%
)
0
10
20
30
40
50
ab
cd
e
Sankey et al. 2010. Characterizing western juniper expansion via a fusion of Landsat 5 Thematic Mapper and lidar data. Rangeland Ecology and Management 63: 514-523
Juniper encroachment
Juniper encroachment
Shrubland Grassland
Juni
per
incr
ease
(%
)
0
10
20
30
40
50
Grazed Ungrazed
Sankey, T. and M. Germino. 2008. Assessment of juniper encroachment with the use of satellite imagery and geospatial data. Rangeland Ecology and Management 61: 412-418
Decades
1700 1750 1800 1850 1900 1950 2000
Rel
ativ
e di
stri
buti
on o
f tr
ee a
ge (
%)
0
2
4
6
8
10
12
14
16
N=228
Juniper encroachment
Sankey et al. 2013. Lidar-derived carbon estimates in woody encroachment. Journal of Geophysical Research (In Press)
Field-measured tree height (m)
0 4 8 12 16
Lid
ar-d
eriv
ed tr
ee h
eigh
t (m
)
0
4
8
12
16
y = -0.14 + 0.82XR2 = 0.84p < 0.001RMSE = 4.9
Juniper encroachment
Sankey et al. 2013. Lidar-derived carbon estimates in woody encroachment. Journal of Geophysical Research (In Press)
Field-measured tree canopy cover
0 20 40 60 80 100
Lid
ar-d
eriv
ed tr
ee c
anop
y co
ver
0
20
40
60
80
100
y = 6.72 + 1.44XR2 = 0.82p = 0.04
Juniper encroachment
Sankey et al. 2013. Lidar-derived carbon estimates in woody encroachment. Journal of Geophysical Research (In Press)
Field-measured juniper tree density
0 10 20 30 40 50 60
Lid
ar-d
eriv
ed j
un
iper
tre
e d
ensi
ty
0
10
20
30
40
50
60
R2=0.79y=8.38+0.59*X
Juniper encroachment
Sankey et al. 2013. Lidar-derived carbon estimates in woody encroachment. Journal of Geophysical Research (In Press)
Juniper encroachment
0 2 4 6 80
2
4
6
8
Ground-predicted biomass (ln(kg))
Lid
ar-p
red
icte
d b
iom
ass
(ln
(kg)
)Y= 0.85 + 0.77*XR2 =0.77p <0.001RMSE = 0.5
Sankey et al. 2013. Lidar-derived carbon estimates in woody encroachment. Journal of Geophysical Research (In Press)
Central Asian Rangelands• Mongolia’s political
changes• Changes in herding
practices• Livestock numbers
tripled
Effects on rangelands• Landsat 5 TM• 6 years: 1986,
1989,1990,…...shift… 2001, 2002, 2007
• Collective vs post-collective
• Significant decrease
Rangelands vs Croplands• Many abandoned fields in former socialist
countries• Abandoned fields were used as rangelands• New shift now