Impacts of large-scale drought and deluge on phenology and vegetation productivity in Southeastern Australia

Impacts of large-scale drought and
deluge on phenology and vegetation
productivity in Southeastern Australia
Xuanlong Ma
1
, Alfredo Huete
1
, Susan Moran
2
,
Guillermo Ponce-Campos
2
, Derek Eamus
3
1 Plant Functional Biology & Climate Change Cluster
University ofTechnology Sydney
2 SouthwestWatershed Research Centre,
USDA Agriculture Research Service
3 School of Life Sciences, University ofTechnology Sydney
6 October 2015 @ Kusadasi, Turkey
Xuanlong Ma xuanlong.ma@uts.edu.au 1
International Conference on Phenology Impact of Climate Extremes on Phenology

MOTIVATION

IN THE NEWS
Lake Hume (NSW), 2007
Credit:TimJKeegan
Xuanlong Ma xuanlong.ma@uts.edu.au
Credit:EpocTinmes
Stockman Gordon Litchﬁeld at
Leigh Creek (SA), 2006
33

Drought had significant impacts, including
dramatic reduction in agricultural
production, reduced water availability for
industrial and civil consumptions, increased
forest die-back and bushfire (Sempel et al., 2010).

There is an increasing trend in the
frequency and spatial extent of extreme
climate events around globe and in Australia,
yet the impacts of these extreme climate on
ecosystem function remains uncertain.

Vegetation phenology and primary productivity
represent key functions of an ecosystem,
potential changes in phenology and primary
productivity under climate change will have
great implications to regional & global climate
and biogeochemical cycles.

Phenology is the study of life cycles of
flora and fauna and their interactions
with seasonal and inter-annual
variations in climate and other factors.

Phenology is an integrative
indicator of vegetation
responses to climate variability
and change.

Vegetation phenology and
primary productivity together
represent key functions of an
ecosystem.

Therefore, understanding their
relationships with environment is of great
importance in global change studies that
aim to predict how ecosystem function will
be affected by future climate changes.

Remote Sensing uses satellites
to track seasonal changes in
vegetation activity on regional,
continental, and global scales.

Remote sensing provide unparalleled way for
detection and mapping vegetation phenological
and functional responses to climate over broad-
scales, which complement the restricted
coverage afforded by ground-based plots
observations.

The objective of this study
is to investigate the shifts in
phenology and vegetation
productivity under climatic
extremes.

DATA & METHOD

Southeastern Australia (SEA)
Land cover map of the SEA
Ma et al. (2015) JGR-Biogeosciences, in press
1.3 million km2

Southeastern Australia (SEA)
Land cover map of the SEA
Martin Wells
Broken Hill
Yanco
Tumbarumba
Warracknabeal
16
Chowilla
1.3 million km2

Satellite Data
• Moderate Resolution Imaging
Spectroradiometer (MODIS) onboard
NASA’s Terra satellite;
• EnhancedVegetation Index (EVI);
• MOD13C1, 16-day, 0.05° resolution;
• 2000-2014;
• Quality Control (QC) applied.

Wavelength (microns)
Reﬂectance

Reﬂectance

Vegetation Index is based on the
contrast between the reﬂectances at
NIR region and VIS region.
Reﬂectance

Standardised Precipitation-
Evapotranspiration Index (SPEI)
• SPEI is a multi-scaler drought index which takes into
account both precipitation (P) and potential
evapotranspiration (PET) in determine the drought
severity (Vicente-Serrano et al., 2011);
• SPEI reﬂect the cumulative effect of the imbalance
between atmospheric supply (P) and demand (PET);

Phenological Metrics Extraction
Seasonal maximum EVI
Prior Season Minimum EVI
10%
After Season Minimum EVI
10%
Soil background EVI = 0.08
(yellow shaded area)
Annual integrated EVI (iEVI)
(green shaded area)
SGS
PGS
EGS
LGS●
Warracknabeal (Cropland)
0.0
0.1
0.2
0.3
0.4
0.5
Feb−2003 Apr−2003 Jun−2003 Aug−2003 Oct−2003 Dec−2003
Date
EVI

RESULTS

First, we show the hydroclimatic
impacts on seasonality of
vegetation growth.

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(f)
Warracknabeal (Wheat cropland)
Broken Hill (Hummock grassland)
Martins Wells (Acacia shrublands)
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Sep−2000 Mar−2002 Sep−2003 Mar−2005 Sep−2006 Mar−2008 Sep−2009 Mar−2011 Sep−2012
Date
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Yanco (Pasture)
Chowilla (Mallee woodland)
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SPEI Dry Wet EVI
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EVIMODIS
● ●2002 (Drought) 2010 (Wet)
Seasonal and inter-annual variations in EVI and SPEI at local sites, 2000-2013
2525
All sites experienced severe and protracted drought condition throughout 2002
and 2003, as indicated by consecutive negative SPEI lasted for 9 - 14 monthsMa et al. (2015) JGR-Biogeosciences, in press

Second, we show the biogeographical
patterns in vegetation phenology and
productivity across drought and wet
years

SPEI
LGS (days)
iEVISD
27
In 2002, 87% areas of the SEA experienced drought impact,
76% areas experienced wet condition during the 2010

SPEI
LGS (days)
iEVISD
28
Within the areas that phenology was detected during both
2002 and 2010, there was an increasing trend in LGS over
70% areas of the SEA in the wet year.

SPEI
LGS (days)
iEVISD
29
Region-wide averaged productivity was reduced by 21%
in the 2002 drought year and was increased by 20% in the
2010 wet year relative to 2000-2013 average.
Within the areas that phenology was detected during both
2002 and 2010, there was an increasing trend in LGS over
70% areas of the SEA in the wet year.

Quite dramatically, we found drought
resulted in widespread reduction or
collapse in seasonality, associated with
no detectable phenology over vast
drylands ecosystems.

2002 drought year
2010 wet year
2002 drought year
2010 wet year
EVI
32

2002 drought year
2010 wet year
2002 drought year
2010 wet year
EVI
33
Length of greening season > 6 months in normal or wet year

2002 drought year
2010 wet year
2002 drought year
2010 wet year
EVI
34
Length of greening season = 0 day in drought year
Length of greening season > 6 months in normal or wet year

DISCUSSIONS

First…

Phenology:
the study of periodic plant and animal life
cycle events.

In temperate ecosystems,
phenology profile as observed
from satellite sensors normally
looks like…
Trends in Environmental Research Series (TIERS) 8 April 2015
3838

Harvard Forest, MA, USA, deciduous broadleaf forest Fisher & Mustad, 2007
Hmimina et al., 2013
3939

Fontainebleau, France, deciduous broadleaf forest Hmimina et al., 2013
4040

Fontainebleau, France, deciduous broadleaf forest Hmimina et al., 2013
Darwin, NT, Australia, tropical savanna Ma et al., 2013
4141

However, we found under
highly variable climate, such as
in Australia, phenology profile
looks like…

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0.14EVIMODIS
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Yanco (Pasture)
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0.5
0.14
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0.1
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0.4
0.5
0.08
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0.16
0.12
0.14EVIMODIS
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Jan Apr Jul Oct
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EVIMODIS
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Jan Apr Jul Oct
Date
EVIMODIS
Yanco, NSW (Pasture)
Warracknabeal, VIC (Wheat crop)
Broken Hill, NSW (Hummock grass)
Martin Wells, SA (Acacia shrubland)
Red: 2002
Blue: 2010
4444

Finding #1

Phenology is not repeated
event, at least for Australia’s
dryland ecosystems.
46
Trends in Environmental Research Series (TIERS) Impact of Climate Extremes on Terrestrial Ecosystems
46

Drought resulted in widespread
reductions or collapse in the normal
patterns of seasonality such that in
many cases there was no detectable
phenological cycle during drought years.
47
47

Implication of finding
#1
48
48

The direction of the gradual shifting in
ecosystem function and structure as induced by
global change (e.g., warming and CO2
fertilisation effect) in a long-run might be
suddenly altered, or even reversed direction, by
short-term extreme climatic events.
49
49

Our findings highlight the need for
models to explicitly take into account
climate-induced abrupt shifts in
phenology and productivity for
predicting future ecosystem states,
particularly in global semi-arid and
arid regions where climate is highly
variable and vegetation growth is not
or less limited by temperature but
rather limited by water-availability.
50
50

Second…
51
51

Agricultural ecosystems,
including cropland and
pastures, are important…
52
52

However, we found…
53
53

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Yanco (Pasture)
0.30
0.35
0.40
0.45
0.2
0.3
0.4
0.5
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0.14
0.16
0.18
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0.1
0.2
0.3
0.4
0.5
0.16
Red: 2002
Blue: 2010
Victoria wheat belt
54
54
Yanco
Warracknabeal

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Yanco (Pasture)
0.30
0.35
0.40
0.45
0.2
0.3
0.4
0.5
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0.14
0.16
0.18
0.20
0.1
0.2
0.3
0.4
0.5
0.16
Red: 2002
Blue: 2010
Victoria wheat belt
“We want to see the Murray ﬂow.”
NSW farmer Gilbert Bain is harvesting
his withered wheat near Deniliquin.
55
55
Yanco
Warracknabeal

(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Rainfed Cropland Rainfed Pasture
Hummock Grassland Shrubland
Open Forest Open Woodland
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.9
3
4
1.0
1.5
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Rainfed Cropland Rainfed Pasture T
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.9
3
4
1.0
1.5
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
0.0
0.5
1.0
1.5
0.0
0.5
1.0
0
1
2
3
4
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.0
0.3
0.6
0.9
0
1
2
3
4
0.0
0.5
1.0
1.5
−2 0 2 −2 0 2 −2
∆iEVIsd or ∆SPEI
Density
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Rainfed Cropland Rainfed Pasture Tussock Grassland
Hummock Grassland Shrubland Closed Forest
Open Forest Open Woodland Woodland
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.0
0.3
0.6
0.9
0
1
2
3
4
0.0
0.5
1.0
1.5
−2 0 2 −2 0 2 −2 0 2
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b)
(d) (e)
(g) (h)
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.6
0.9
2
3
4
0.5
1.0
1.5
Density
Red: 2002
Blue: 2010
Negative impact of drought
was ampliﬁed by cropland
56
56

(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.9
3
4
1.0
1.5
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Rainfed Cropland Rainfed Pasture T
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.9
3
4
1.0
1.5
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
0.0
0.5
1.0
1.5
0.0
0.5
1.0
0
1
2
3
4
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.0
0.3
0.6
0.9
0
1
2
3
4
0.0
0.5
1.0
1.5
−2 0 2 −2 0 2 −2
Density
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
Rainfed Cropland Rainfed Pasture Tussock Grassland
Hummock Grassland Shrubland Closed Forest
Open Forest Open Woodland Woodland
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.0
0.3
0.6
0.9
0
1
2
3
4
0.0
0.5
1.0
1.5
−2 0 2 −2 0 2 −2 0 2
Density
iEVI SPEI
2002 − Mean 2010 − Mean
(a) (b)
(d) (e)
(g) (h)
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0
1
2
3
4
5
0
1
2
3
0
1
2
0.0
0.3
0.6
0.9
1.2
0.6
0.9
2
3
4
0.5
1.0
1.5
Density
Red: 2002
Blue: 2010
Negative impact of drought
was ampliﬁed by cropland
57
57
Native dryland vegetation
buffered drought impact
very well Ma et al. (2015) JGR-Biogeosciences, in press

Finding #2:
58
58

SE Australia’s agricultural
ecosystems, including cropland and
pastures, didn’t buffer drought
impact as good as native
vegetations.
59
59

In a climate change perspective,
predicted increases in drought
frequency and intensity will have
great impact on Australia’s
agricultural ecosystems, resulted
in a series of consequences, such
as crop failures, forage loss, and
pasture degradation.
60
60

These pose concerns on their
sustainable ability to support
human livelihood and social
functioning, and suggested that
improved management and
adaption strategies should be
strengthened in these areas of
concerns.
61
61

Besides, our results highlighted the
significant role of native vegetations,
particularly hummock grassland
(spinifex) and shrubland (e.g., Acacia
shrubland, or Mulga), in buffering the
impacts of drought on regional carbon
balance and subsequent feedback to
regional and global climate.
6262

For example, the positive
anomaly in global land carbon sink
in 2010-11 was largely driven by
semi-arid ecosystems in Southern
Hemisphere, with 60% of global
carbon uptake anomaly was
attributed to Australia’s drylands
ecosystems (Poulter et al., 2014).
6363

Summary
64

Summary
65
• We found dramatic impacts were exerted
by drought and wet extremes on
vegetation phenology & productivity, with
abrupt change in phenology and
productivity between dry and wet years.
• We found agricultural ecosystems did not
buffer drought well, while native dryland
ecosystems were quite resistant and
resilient to hydroclimatic variations.

Summary
66
• We found dramatic impacts were exerted
by drought and wet extremes on
vegetation phenology & productivity, with
abrupt change in phenology and
productivity between dry and wet years.
• We found agricultural ecosystems did not
buffer drought well, while native dryland
ecosystems were quite resistant and
resilient to hydroclimatic variations.

Thanks!
Questions?
Trend in Environment ResearchTrends in Environmental Research Series (TIERS) Impact of Climate Extremes on Terrestrial Ecosystems
67
Murray-Darling National Park
Photo Credit: Ignacio Palacios/Lonely Planet

Impacts of large-scale drought and deluge on phenology and vegetation productivity in Southeastern Australia

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