ACRIS Landscape Function Update 2006-2010
Updated information to that provided in
Rangelands 2008 – Taking the pulse
Gary Bastin1, Phil Thomas2, Paul Novelly2, Mike Fleming3 and Craig Baulderstone3
1
2
ACRIS Management Unit, CSIRO, PO Box 2111, Alice Springs NT 0871
WA Department of Agriculture & Food, Locked Bag 4, Bentley Delivery Centre, WA 6983
3
SA Department of Environment & Natural Resources, GPO Box 1047, Adelaide SA 5001
This project is supported by Ninti One Limited,
through funding from the Australian Government's Caring for our Country.
1
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2
Landscape Function
Landscape function defines the capacity of landscapes to regulate (i.e. capture and retain, not leak)
rainwater and nutrients, the vital resources for plant growth which, in turn, provides food and
shelter for fauna. Continued ground-based pastoral monitoring in Western Australia and South
Australia allows more recent reporting of change in landscape function over a significant part of the
Australian rangelands.
Key points
Landscape function is monitored using a resource capture index as part of the Western Australian
Rangeland Monitoring System (WARMS). To enable cross-jurisdictional reporting however, we
infer landscape function from the persistence of perennial vegetation measured in different ways by
the separate monitoring systems of WA and SA.
Sites are reassessed at a three-to-five year interval in WA and this allows reasonable confidence in
attributing seasonal and management effects as likely causes of detected change. Explaining
probable causes of change is more difficult in SA because of the longer period between assessments
(generally >10 years).
Based on the vegetation data used to infer landscape function:





The majority of grassland monitoring sites in northern WA bioregions had maintained or
improved landscape function between 2006 and 2008. Approximately one third to a half of
monitoring sites were similarly categorised in the southern shrubland bioregions. A decline
in landscape function in the southern Western Australian rangelands was attributed to poorer
seasonal quality.
The density of longer-lived perennial vegetation species was maintained or increased at one
half to two thirds of pastoral monitoring sites in the southern pastoral bioregions of SA.
Allowing more explicitly for seasonal quality, ~25% of reassessed sites in the Gawler
bioregion (SA) and ~30% of sites in the Coolgardie 3 sub-IBRA (WA) had an increased
density of perennial vegetation (and inferred increase in landscape function) following
poorer seasonal quality. This increase in landscape function may relate to good
management as a decrease in landscape function was expected under poor seasonal
conditions.
Elsewhere in WA and the southern rangelands of SA, change was mostly as expected during
drier years (i.e. a low proportion of sites with an inferred increase in landscape function).
The following caveats accompany these general findings of the change in landscape
functions across parts of the Australian rangelands:
(i) monitoring is confined to pastoral areas within bioregions,
(ii) sites don’t represent all parts of the landscape,
3
(iii) sites in some bioregions are confined to a particular sub-region and reporting is only for
that area, and
(iv) bioregions (or sub-regions) had to have at least 12 reassessed sites for reporting.
More detail on the changes in landscape function for particular regions based on various data types
is provided in the body of this update.
4
Table of contents
Key points ............................................................................................................................................ 3
Tables ................................................................................................................................................... 6
Figures .................................................................................................................................................. 6
Landscape function .............................................................................................................................. 8
Site-based monitoring of landscape function ................................................................................... 9
More recent changes in landscape function ......................................................................................... 9
Gross change – all seasons ............................................................................................................. 10
Seasonally adjusted change ........................................................................................................ 12
Jurisdictional monitoring data in more detail .................................................................................... 13
Western Australia – WARMS sites ............................................................................................... 13
Grassland sites (northern bioregions) ........................................................................................ 14
Frequency change relative to seasonal quality....................................................................... 17
Shrubland sites (southern bioregions) ........................................................................................ 17
Change in shrub population relative to seasonal quality........................................................ 20
Landscape function based on the Resource Capture Index ........................................................ 20
Change in resource capture index relative to seasonal quality .............................................. 22
Compare indices of landscape function ..................................................................................... 22
South Australian Pastoral Monitoring System ............................................................................... 23
Bladder saltbush as a component of change .............................................................................. 26
References .......................................................................................................................................... 28
Appendix 1. Seasonal quality matrices for change in perennial grass frequency at WARMS
grassland sites .................................................................................................................................... 29
Appendix 2. Seasonal quality matrices for change in shrub density at WARMS shrubland sites.... 31
Appendix 3. Seasonal quality matrices for change in RCI ratio at WARMS sites ........................... 33
Northern grassland bioregions ....................................................................................................... 33
Southern shrubland bioregions....................................................................................................... 34
Appendix 4. Seasonal quality matrices for change in landscape function at SA pastoral
monitoring sites .................................................................................................................................. 36
5
Tables
Table 1. Numbers and types of sites by bioregion used for reporting more recent change in
landscape function. Seasonal quality preceding the most recent assessment is also indicated
by the percentage of sites classified into each seasonal-quality tercile. ............................................ 10
Table 2. Percentage of sites where the ratio of change in RCI during the most recent
assessment cycle was below a specified threshold. ........................................................................... 21
Table 3. Mean time interval and range (years) between reassessment of sites in each bioregion
(or sub-region).................................................................................................................................... 23
Figures
Figure 1. Dysfunctional (left) and functional (right) landscapes in tropical savanna woodlands
near Charters Towers, Queensland. ..................................................................................................... 8
Figure 2. Gross change in landscape function based on perennial vegetation monitored at sites
in WA and SA. ................................................................................................................................... 11
Figure 3. Seasonally-adjusted change in landscape function based on perennial vegetation
monitored at sites in WA and SA....................................................................................................... 12
Figure 4. Location of WARMS grassland and shrubland sites. ........................................................ 13
Figure 5. Mean and standard error of perennial grass frequency within bioregions at each
assessment of WARMS grassland sites. ............................................................................................ 14
Figure 6. Mean and standard error of the ratio of perennial grass frequency from one
assessment to the next at sites within bioregions. .............................................................................. 15
Figure 7. Change in site-level perennial grass frequency during the most recent assessment
cycle for the Central Kimberley and Pilbara bioregions. ................................................................... 16
Figure 8. Mean and standard error of population growth rate for the second assessment
cycle of shrubland bioregions. ........................................................................................................... 18
Figure 9. Change in site-level shrub population during the most recent assessment cycle
for the Carnarvon and Gascoyne bioregions. ..................................................................................... 19
Figure 10. Change in site-level shrub population during the most recent assessment cycle
for the Murchison bioregion. ............................................................................................................. 20
Figure 11. Ratio of site-level RCI values, averaged across pastoral bioregions, for the most
recent assessment cycle. Standard error of the mean is also shown. ................................................ 21
Figure 12. Mean and standard error of the density of perennial vegetation at the first and
second assessments of sites grouped by bioregion (or part region). .................................................. 24
6
Figure 13. Mean & SE of the ratio of densities of perennial vegetation at first and second
assessments of SA pastoral monitoring sites. The dashed line represents ‘no change’. ................... 24
Figure 14. Change in site-level population of perennial vegetation between the first and
second assessments for the Gawler bioregion and Flinders Lofty Block 3 sub-IBRA. ..................... 25
Figure 15. Change in density of bladder saltbush and all perennial species at SA pastoral
monitoring sites. ................................................................................................................................. 26
Figure 16. Compositional and structural changes in vegetation between 1993 and 2011
at a pastoral monitoring site in the Broken Hill Complex bioregion of SA....................................... 27
7
Landscape function
Landscape function defines the capacity of landscapes to regulate (i.e. capture and retain, not leak)
rainwater and nutrients (see the example for a savanna woodland below). Water and nutrients are
the vital resources for plant growth which, in turn, provides food and shelter for fauna.
Figure 1. Dysfunctional (left) and functional (right) landscapes in tropical savanna woodlands near
Charters Towers, Queensland.
Dense native perennial grasses (right) slow overland flows during intense rainfall events allowing
rainwater to infiltrate the soil surface. Runoff that does occur carries minimal sediment and thus soilborne nutrients are retained on site. The sparse cover on the left means that most rainfall is lost as
runoff. Rapidly flowing water has the energy to cause further erosion and loss of vital nutrients for
plant growth.
Photo: CSIRO Townsville.
The relative functionality of landscapes varies with environmental setting. Regions with higher or
more assured rainfall generally have higher ground cover with that cover comprising a greater
proportion of persistent species (grasses in northern Australia, chenopod shrubs in the south).
Ground cover and the proportion of perennial species both decline with increasing aridity with the
exception of some spinifex communities which can have a high cover of perennials under arid
conditions. Whatever the setting though, functional landscapes have a relatively higher cover of
patches of perennial vegetation which are spatially arranged to efficiently capture runoff and resist
wind erosion (Tongway and Ludwig 1997). Damaged or dysfunctional landscapes have reduced
cover and have lost much of their perennial component. They are generally unproductive for
grazing, have low biodiversity value and may remain highly vulnerable to continued erosion.
Functional landscapes are likely to maintain their vegetation cover through variable climatic
conditions and recover quickly from disturbances (e.g. drought, fire, grazing). Dysfunctional
landscapes take longer to recover. Changes in landscape functionality provide useful indicators for
assessing the effects of management on rangelands.
8
Site-based monitoring of landscape function
Site-based data are used for reporting change in landscape function in WA and SA. Each
monitoring system is focussed on pastoral land and most sites are located within an intermediate
grazing distance from water (e.g. 1.5-4 km).
Western Australian Rangeland Monitoring System (WARMS): Northern grassland sites are
assessed approximately every three years and change in the frequency of perennial grasses is
reported with respect to seasonal quality. The most recent assessment period was May 2006 to
October 2008 (number of sites assessed by bioregion shown in Table 1). Southern shrubland
sites are assessed approximately every five years, and were most recently monitored between
May 2005 and November 2009 (Table 1). Changes in shrub density are comparable with the
data collected at SA monitoring sites. A more direct measure of landscape function is obtained
at WARMS sites using the Resource Capture Index (RCI) and changes based on these data are
also reported.
South Australian Pastoral Monitoring System: Change in the density of longer-lived perennial
vegetation relative to seasonal quality in the southern (sheep-grazed) rangelands is reported (see
Table 1 for number of sites). Second-round assessment of sites commenced in 2005 and change
is evaluated against the first assessment, generally during the 1990s.
ACRIS uses a tercile scoring system based on long-term rainfall to indicate site seasonal quality1.
Rainfall contributing to the vegetation measured at the most recent assessment is compared to the
long-term record and classified as above average, average or below average. Regional seasonal
quality at the time of the most recent assessment is indicated in Table 1.
More recent changes in landscape function
Change in landscape function between 1992 and 2005 was reported in Chapter 3 of Rangelands
2008 – Taking the pulse (Bastin et al. 2008). Here, we update that reporting using further
measurements at monitoring sites in the pastoral country of WA and the southern sheep-grazed
rangelands of SA.
Two sets of maps are used to show changes in landscape function: the first (Fig. 2) shows overall or
‘gross’ changes and the second (Fig. 3) shows changes adjusted for seasonal quality. Although a
coloured value is applied to all of the grazed country in each pastoral bioregion, mapped change
applies only to the locations of monitoring sites. Change is not reported for bioregions with less
than 12 sites reassessed.
Seasonal quality and the way in which the tercile scoring system is applied are described in Rangelands 2008 – Taking
the pulse (see Box 2.1, page 13 and Ch. 3, page 31).
1
9
Table 1. Number and type of sites by bioregion used for reporting more recent change in landscape
function. The seasonal quality preceding the most recent site assessment is indicated by the
percentage of sites classified into each seasonal-quality tercile.
Bioregion (IBRA) or
sub-IBRA
No sites
assessed
% sites in each seasonal quality category
above average
average
below average
WARMS grassland sites – northern bioregions (assessment 5: May 2006 to October 2008)
Central Kimberley
68
90
10
130
81
19
Northern Kimberley 1
10
60
40
Ord Victoria Plain
80
82
18
Pilbara
99
56
30
Victoria Bonaparte 1
11
100
Dampierland
14
WARMS shrubland sites – southern bioregions (assessment 2: May 2005 to November 2009)
Carnarvon
Coolgardie 3
125
26
74
30
23
77
Gascoyne
181
36
31
33
Murchison
357
27
54
19
Nullarbor 2
116
17
36
47
38
62
Yalgoo
40
SA pastoral monitoring sites – sheep-grazed rangelands (2nd assessment: 2005 to 2010)
Gawler
693
5
43
52
Broken Hill Complex 1
16
38
63
Flinders Lofty Block 3
148
24
53
20
10
90
Stony Plains 1
a
a
23
reporting restricted to the area south of the Dog Fence.
Gross change – all seasons
A score indicating the percentage of sites in each bioregion that maintained or improved their level
of landscape function during the most recent assessment cycle is mapped in Fig. 2. In some cases,
reporting is restricted to a sub-IBRA of the bioregion.
10
Insufficient or no data
% sites with stable or
increased landscape function
0
25
50
75
100
Figure 2. Gross change in landscape function based on perennial vegetation monitored
at sites in WA and SA.
Non-pastoral areas in each bioregion are masked (in grey). Reporting is by sub-IBRA where sites
within some bioregions are confined to particular sub-IBRAs.
Data sources: DAFWA and SA DENR. Map compiled by the ACRIS-MU.
The majority of grassland monitoring sites in northern WA had maintained or improved landscape
function between 2006 and 2008 based on perennial grass frequency. Approximately one third to a
half of shrubland monitoring sites were similarly categorised. Poorer seasonal quality in the south
of the state contributed to the decline in landscape function based on shrub density (Fig. 3).
The density of longer-lived perennial vegetation was maintained or increased at one half to two
thirds of pastoral monitoring sites in each bioregion (or part bioregion) in the southern sheep-grazed
rangelands of SA (i.e. indicated by the shades of green colouring in Fig 2).
When interpreting this map of change in landscape function, it is important to note that: (i) to be
mapped, bioregions had to have at least 12 assessed sites; (ii) in some areas sites are confined to a
sub-IBRA and, where this is the case, only that part of the bioregion is reported on; (iii) sites don’t
represent all parts of the landscape and (iv) monitoring is confined to pastoral areas within
bioregions.
11
Seasonally adjusted change
Adjusting changes in landscape function by seasonal quality provides a useful longer-term view
because changes are corrected for recent rainfall. In Fig. 3, the top map shows that ~25% of
reassessed sites in the Gawler bioregion (SA) and ~30% of sites in the Coolgardie 3 sub-IBRA had
an increased density of perennial shrubs following poorer seasonal quality (decrease expected at
this time).
insufficient data or no data for
below-average seasonal conditions
no data
% sites with increased
landscape function
0
25
50
75
100
(a) Increase in landscape function following below-average seasonal quality
insufficient data or no data for
above-average seasonal conditions
no data
% sites with decreased
landscape function
0
25
50
75
100
(b) Decrease in landscape function following above-average seasonal quality
Figure 3. Seasonally-adjusted change in landscape function based on perennial vegetation monitored
at sites in WA and SA.
Data source: DAFWA, SA DENR. Maps compiled by the ACRIS-MU.
12
Elsewhere in WA and the southern rangelands of SA, change was mostly as expected during drier
years (i.e. few sites with increased landscape function). Note though that when interpreting the top
map, any value above 0% (coloured red) would be a positive result, even though red is typically
used by ACRIS in other maps to display negative results. Also note that the colour scheme is
reversed between the two maps so that in each case, the blue-purple end of the colour scheme
represents the most substantial improvement.
Excluding the Pilbara bioregion, most WARMS grassland sites experienced average to aboveaverage seasonal quality so change for these bioregions is not shown in the top map.
For the reverse situation, all pastoral bioregions in WA and SA had a low proportion (<20%) of
sites showing unexpected decline in landscape function when assessed following above-average
seasonal quality (Fig. 3, bottom map).
Jurisdictional monitoring data in more detail
Western Australia – WARMS sites
The locations of grassland and shrubland sites are shown in Fig. 4. The majority of sites were
monitored during the most recent reassessment cycle.
Figure 4. Location of WARMS grassland and
shrubland sites.
Data source: WA Dept Agriculture and Food. Map:
ACRIS Management Unit.
13
As noted earlier, landscape function in the northern grasslands is indicated by the frequency of
perennial grasses (i.e. percentage presence in quadrats relative to the total number assessed at each
site). In the southern shrublands, landscape function is indicated by the density of longer-lived
perennial vegetation. Higher frequencies of perennial grasses (in northern bioregions) and densities
of shrubs (in the south) indicate increased landscape function. WA also conducts formal landscape
function analysis (Tongway 1994 and Tongway and Hindley 1995) at WARMS sites and these data
are also reported here using a resource capture index (i.e. additional information to that presented in
Rangelands 2008 – Taking the pulse).
Grassland sites (northern bioregions)
Perennial grass frequency increased, on average, in the three most northern IBRAs in the 1990s and
early 2000s and then stabilised in the second half of the most recent decade above 80% frequency
(Fig. 5). By inference, landscape function also increased and then stabilised. In contrast, perennial
grass frequency decreased in the Pilbara bioregion, particularly between 2000 – 2002 and 2003 –
2005. This infers considerable loss of landscape function at this time. Note that change in
perennial grass frequency is not shown for the pastorally less productive Northern Kimberley 1 and
Victoria Bonaparte 1 sub-IBRAs because fewer than 12 sites were assessed in each region.
100
1994-1996
1997-1999
2000-2002
2003-2005
2006-2008
95
90
Frequency (%)
85
80
75
70
65
60
55
50
Central Kimberley
Dampierland
Ord Victoria Plain
Pilbara
Figure 5. Mean and standard error of perennial grass frequency within bioregions at each assessment
of WARMS grassland sites.
Data source: WA Rangeland Monitoring System (WA Dept. Agriculture and Food). Graph compiled
by the ACRIS-MU.
14
The period between pairs of assessments is a cycle and the most recent cycle (the fourth)
encompasses assessments four (2003-2005) and five (2006-2008). Change in perennial grass
frequency at each site is reported as a ratio (1 = no change, <1 represents decrease, >1 an increase)
with ratio values for all sites averaged for each IBRA into a cumulative index value (Fig. 6).
1.5
cycle 1 (1994-96 to 1997-99)
1.4
cycle 2 (1997-99 to 2000-02)
Figure 6. Mean and standard error of
cycle 3 (2000-02 to 2003-05)
1.3
cycle 4 (2003-05 to 2006-08)
the ratio of perennial grass frequency
from one assessment to the next at sites
Frequency Ratio
1.2
within bioregions.
1.1
The dashed line indicates no change.
1.0
Data source: WA Rangeland
0.9
Monitoring System (WA Dept.
0.8
Agriculture and Food). Graph
compiled by the ACRIS-MU.
0.7
0.6
Central Kimberley
Dampierland
Ord Victoria Plains
Pilbara
The frequency ratio has been consistently above one for the three most northern bioregions. This
indicates recruitment of perennial grasses at successive assessments and supports the inference of
increasing landscape function. The ratio has decreased since the first two cycles and in two cases
stabilised close to one; plausible because increase in perennial grass frequency must slow as it
approaches 100%.
The frequency ratio for the Pilbara bioregion declined appreciably (and to <1) in cycle 3 in line with
the lower perennial grass frequency at assessment 4 (Fig. 5). The small increase in absolute
frequency in cycle 4 (Fig. 5) then produced a substantial increase in the frequency ratio (Fig. 6).
This is largely attributable to a few sites: perennial grass frequency at one site increased from 9% to
90% and five other sites had an increase of >50%.
Site-level change in perennial grass frequency during the last cycle for two bioregions is shown in
Fig. 7. The Central Kimberley (top panel) was relatively unchanged compared with the Pilbara
(bottom panel). For the latter, there were several sites with a large decrease in frequency during the
cycle (bottom right of graph) and other sites with a large increase in frequency (top left of graph).
These changes were not always associated with seasonal quality: some sites with a large decrease
experienced good seasonal conditions while for a few sites, frequency increased following average
or below-average seasonal quality.
In interpreting the graphs, ‘c4a1’ means the first assessment in cycle 4 and ‘c4a2’ represents the
second assessment.
15
100
above average
average
Frequency c4a2 (2006, 2007 or 2008)
90
80
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
Frequency c4a1 (2003, 2004 or 2005)
Central Kimberley bioregion
100
Frequency c4a2 (2006, 2007 or 2008)
90
80
above average
average
below average
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
Frequency c4a1 (2003, 2004 or 2005)
Pilbara bioregion
Figure 7. Change in site-level perennial grass frequency during the most recent assessment cycle for
the Central Kimberley and Pilbara bioregions.
Sites positioned near the 1:1 line were relatively unchanged. Colours and symbols represent seasonal
quality preceding the most recent assessment. Data source: WA Rangeland Monitoring System (WA
Dept. Agriculture and Food). Graph compiled by the ACRIS-MU.
16
Frequency change relative to seasonal quality
ACRIS uses a ‘seasonal quality’ matrix to report the percentage of reassessed sites that had either
expected on unexpected change in the attribute monitored for seasonal conditions experienced.
Seasonal quality matrices for WARMS grassland sites during the most recent assessment cycle are
tabulated by bioregion in Appendix 1.
Shrubland sites (southern bioregions)
A complete census of shrubs is made at each assessment of shrubland sites and change in density is
reported as population growth rate (PGR). Values of less than one mean loss of some shrubs from
one assessment to the next and PGR > 1 indicates shrub recruitment.
Change in shrub density at WARMS sites for cycle 1 (for most sites, 1994-2000 to 2000-2004) was
reported in Rangelands 2008 – Taking the pulse. Cycle 2 change is reported here – 2000-2005 to
2005-2009.
Shrub density (i.e. PGR) declined on average in most bioregions between the first and second
halves of the most recent decade (Fig. 8). This decline was most marked in the Carnarvon IBRA.
The Murchison IBRA had a very small increase in shrub density (PGR=1.05±0.04).
The general decline in PGR for the Carnarvon and Gascoyne IBRAs is further illustrated by sitelevel change in shrub population during the second assessment cycle (Fig. 9) where the majority of
sites plot below the 1:1 line. Much of this decrease was associated with average to below-average
seasonal quality. In comparison, the Murchison IBRA had a more even and generally clumped
distribution of sites about the 1:1 line based on change in shrub population (Fig. 10) with some sites
that had increased shrub density having experienced below-average seasonal quality.
In interpreting the graphs, ‘c2a1’ means the first assessment of cycle 2 and ‘c2a2’ represents the
second assessment (duration of each assessment period also shown).
17
1.2
Population Growth Rate
1.1
1.0
0.9
0.8
0.7
0.6
Figure 8. Mean and standard error of population growth rate for the second assessment cycle of
shrubland bioregions.
Data source: WA Rangeland Monitoring System (WA Dept. Agriculture and Food). Graph compiled
by the ACRIS-MU.
18
300
No. plants c2a2 (5/05 to 9/08)
250
200
150
100
50
average
below average
0
0
50
100
150
200
250
300
No. plants c2a1 (9/99 to 8/02)
Carnarvon bioregion
350
No. plants c2a2 (5/05 to 5/08)
300
250
200
150
100
50
above average
average
below average
0
0
100
200
300
400
No. plants c2a1 (8/99 to 8/03)
Gascoyne bioregion
Figure 9. Change in site-level shrub population during the most recent assessment cycle for the
Carnarvon and Gascoyne bioregions.
Sites positioned near the 1:1 line were relatively unchanged. Colours and symbols represent seasonal
quality preceding the most recent assessment. Data source: WA Rangeland Monitoring System (WA
Dept. Agriculture and Food). Graph compiled by the ACRIS-MU.
19
450
No. plants c2a2 (9/05 to 9/09)
400
Figure 10. Change in site-level
shrub population during the most
350
recent assessment cycle for the
300
Murchison bioregion.
250
Sites positioned near the 1:1 line
were relatively unchanged.
200
Colours and symbols represent
seasonal quality preceding the
150
most recent assessment. Data
100
source: WA Rangeland
above average
50
Monitoring System (WA Dept.
average
Agriculture and Food). Graph
below average
0
0
50
100
150
200
250
300
350
400
450
compiled by the ACRIS-MU.
No. plants c2a1 (9/99 to 8/04)
Change in shrub population relative to seasonal quality
Seasonal quality matrices for WARMS shrubland sites during the most recent assessment cycle are
tabulated by bioregion in Appendix 2.
Landscape function based on the Resource Capture Index
Formal landscape function analysis (Tongway and Hindley 2004) has been conducted at WARMS
sites in recent years. This allows a Resource Capture Index (RCI) to be calculated from the
vegetation data where the index is the percentage of a measured down-slope transect length that is
occupied by resource-capturing patches (mainly perennial vegetation). Change during an
assessment cycle is reported as the ratio of RCI values for the previous and current assessments.
This allows aggregated data for grassland and shrubland sites to be compared; although RCI values
may differ considerably, the ratio provides a comparable index of change.
All bioregions with sufficient site-level data for reporting maintained or had a slightly increased
RCI value during the most recent assessment cycle (Fig. 11). This suggests that landscape function
(based on RCI) was maintained or slightly increased, on average, across all bioregions. Northern
bioregions appeared to have a larger increase in landscape function compared to southern IBRAs.
Better seasonal quality in the north (Table 1) probably contributed to this result.
20
1.8
1.7
Grassland sites, cycle 4
Shrubland sites, cycle 2
(2003-2005 to 2006-2008)
(2000-2005 to 2005-2009)
Average Change in RCI
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
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Pl
er
la
nd
pi
am
D
O
C
en
tra
lK
im
be
rle
y
0.8
Figure 11. Ratio of site-level RCI values, averaged across pastoral bioregions, for the most recent
assessment cycle. Standard error of the mean is also shown.
Data source: WA Rangeland Monitoring System (WA Dept. Agriculture and Food). Graph compiled
by the ACRIS-MU.
Grassland bioregions and the Carnarvon IBRA (i.e. shrubland) had relatively large standard errors
about their mean ratio of RCI values indicating that while the majority of sites within each IBRA
had an increased ratio value, others had a substantial decrease (Table 2).
Table 2. Percentage of sites where the ratio of change in RCI during the most recent assessment cycle
was below a specified threshold.
IBRA / sub-IBRA
Type
Central Kimberley
grassland
Dampierland
Number of sites
assessed in cycle
% sites where RCI ratio is
< 0.9
< 0.5
69
57
13
grassland
122
56
22
Ord Victoria Plain
grassland
78
42
13
Pilbara
grassland
93
34
15
Carnarvon
shrubland
124
38
2
Coolgardie 3
shrubland
30
37
3
Gascoyne
shrubland
180
33
6
Murchison
shrubland
352
28
5
Nullarbor 2
shrubland
116
20
3
Yalgoo
shrubland
40
28
0
21
Change in resource capture index relative to seasonal quality
Seasonally interpreted change in the RCI ratio during the most recent assessment cycle is reported
for WA pastoral bioregions in Appendix 3.
Compare indices of landscape function
Two accounts of landscape function have been provided based on WARMS data: (1) indices
derived from perennial vegetation measured across each site (perennial grass frequency, grassland
sites and shrub density, shrubland sites) and (2) a resource capture index calculated from the length
of resource-capturing patches measured downslope. Although both are based on attributes of the
perennial vegetation, they can provide different accounts of change in landscape function.
Perennial grass frequency remained relatively high and stable under conditions of predominantly
good seasonal quality during the most recent assessment cycle in the Central Kimberley,
Dampierland and Ord Victoria Plains bioregions (Fig. 5). The frequency ratio was close to, or a
little above, one (Fig. 6) inferring maintenance of, to a slight increase in, landscape function. The
RCI ratio suggested a small increase in landscape function for the Central Kimberley and
Dampierland bioregions and a more definite increase in the Ord Victoria Plain IBRA (Fig. 11).
Trend in landscape function in the Pilbara was more equivocal. The frequency ratio was higher
than for other grassland bioregions (Fig. 6) due to a small increase in mean frequency of perennial
grasses during the current cycle (Fig. 5, but this cycle’s frequency was much lower than for cycles
one and two). The RCI ratio for the current cycle suggested a definite increase in landscape
function (Fig. 11), albeit with a considerable standard error about the mean.
Of the shrubland bioregions, the Carnarvon IBRA had reduced shrub density (PGR<1, Fig. 8)
suggesting a decline in landscape function while there was a small increase in RCI (RCI ratio>1,
Fig. 11) suggesting improvement. Probable reasons for this apparent paradox include:
1. Considerable recruitment of perennial species following good seasons but small plant size
which had little influence on the landscape’s capacity to hold resources.
2. RCI includes ‘non live or dead’ obstructions such as fallen branches. Such obstacles are
included as capture zones at one assessment but may have largely disappeared by the
second.
3. Differences in measurement area. RCI is measured along a line transect and plant
recordings are within a wider belt.
4. Measurement and data differences apart, RCI provides a direct measure of landscape
function while PGR allows inference.
22
Both index values suggested slightly increased landscape function in the Murchison IBRA. PGR
was a little above one (Fig. 8), demonstrating shrub recruitment – as was the RCI ratio (i.e.
increased RCI throughout the cycle).
Landscape function appeared to be relatively stable across other shrubland bioregions given the size
of standard errors about mean values of PGR and the RCI ratio. The Coolgardie 3, Gascoyne,
Nullarbor 2 and Yalgoo bioregions had maintained or slightly reduced shrub densities on average
(0.88 ≤ PGR ≤ 0.97, Fig. 8) and an RCI ratio close to, or a little above, one (1.03 ≤ RCIratio ≤ 1.14,
Fig. 11).
South Australian Pastoral Monitoring System
Compared to WA, there was a longer period between reassessments of SA pastoral monitoring sites
(Table 3). There can be considerable rainfall variability during this time and we are less confident
that the ACRIS ‘seasonal quality’ matrix appropriately infers whether observed change is likely due
to season or grazing management. Nevertheless, we have assigned a seasonal quality score, based
on rainfall in the preceding three years, to each site at the time of the latest assessment to emphasise
where the direction of change may be counter to seasonal expectations (Fig. 3 and bioregion
summaries in Appendix 4).
Table 3. Mean time interval and range (years) between reassessment of sites in each bioregion (or subIBRA).
Bioregion (or sub-IBRA)
Mean interval (years)
Range (years)
693
15.1
6 – 17
Broken Hill Complex 1
16
14.4
9 – 16
Flinders Lofty Block 3
148
13.7
9 – 16
20
14.7
14 – 15
Gawler
Stony Plains 1 a
a
Number of sites
monitoring sites south of the Dog Fence.
Averaged across all reassessed sites in each bioregion (or part thereof), the density of perennial
vegetation at individual sites increased slightly in the Gawler bioregion and decreased elsewhere
between 1990-2000 and 2005-2010 (Fig. 12). The degree of site-level change is enhanced by
calculating a change ratio (density of perennials at 2nd assessment divided by density at 1st
assessment, as for the WARMS shrub data in Fig. 8). These data show that there was good
recruitment of perennial vegetation, on average, at sites in the Gawler bioregion and Barrier Range
subregion of the Broken Hill Complex (BHC1) (Fig. 13). This infers increased landscape function
at the time of the second assessment. There was little change in the density of perennial vegetation
23
(and, by inference, landscape function) at reassessed sites in the Olary Spur region (Flinders Lofty
Block 3 sub-IBRA) and the small area of Breakaways, Stony Plains (STP1 sub-IBRA).
Site-level densities of perennial species and their change over time with respect to seasonal
conditions are shown for the Gawler IBRA and Olary Spur (FLB3 sub-IBRA) in Fig. 14. Many
sites in the Gawler bioregion that experienced below-average seasonal quality prior to reassessment
had maintained or increased their density of perennials. Several sites experiencing average seasonal
quality during the same time had a considerably increased plant count at their second assessment.
Some sites with recent above-average seasonal quality lost perennial plants between their first and
second assessments (further information about change with respect to seasonal quality is
summarised in Appendix 4). As noted above, change may have occurred at some sites prior to the
three years preceding reassessment that was used to calculate site-level seasonal quality.
400
Figure 12. Mean and
1990-2000
350
standard error of the
2005-2010
density of perennial
Count of Perennial Plants
300
vegetation at the first and
250
second assessments of sites
grouped by bioregion (or
200
part region).
150
Data source: SA Dept.
100
Environment and Natural
Resources. Graph
50
compiled by the ACRIS-
0
Gawler
Broken Hill Complex 1
Flinders Lofty Block 3
Stony Plains 1
1.8
Figure 13. Mean & SE of
1.6
the ratio of densities of
1.4
perennial vegetation at first
and second assessments of
1.2
Change Ratio
MU.
SA pastoral monitoring
1.0
sites. The dashed line
0.8
represents ‘no change’.
0.6
Data source: SA Dept.
0.4
Environment & Natural
Resources. Graph:
0.2
ACRIS-MU.
0.0
Gawler
Broken Hill Complex 1
Flinders Lofty Block 3
Stony Plains 1
24
1500
No. plants (2001-2010)
1200
900
600
300
above average
average
below average
0
0
300
600
900
1200
1500
No. plants (1990-2000)
Gawler bioregion
900
800
No. plants (2001-2010)
700
600
500
400
300
200
above average
100
average
below average
0
0
100
200
300
400
500
600
700
800
900
No. plants (1990-2000)
Flinders Lofty Block 3 sub-IBRA (Olary Spur)
Figure 14. Change in site-level population of perennial vegetation between the first and second
assessments for the Gawler bioregion and Flinders Lofty Block 3 sub-IBRA.
Sites positioned near the 1:1 line were relatively unchanged. Colours and symbols represent seasonal
quality preceding the most recent assessment.
Data source: SA Dept. Environment and Natural Resources. Graph compiled by the ACRIS-MU.
25
As noted above, quite long intervals separated most reassessments and we are not confident as to
when (or why) actual changes in the densities of perennial vegetation occurred. However it is
encouraging that landscape function based on plant density was maintained or increased at many
sites in the Gawler bioregion and parts of other bioregions (BHC1, FLB3 and part STP1 subIBRAs) in generally below-average seasons.
Bladder saltbush as a component of change
Bladder saltbush (Atriplex vesicaria) is an important component of the perennial vegetation across
much of the southern chenopod rangelands. This shrub contributed the majority of the recorded
change at many reassessed sites in South Australia, as indicated by the general spread of sites along
the dashed 1:1 line in Fig. 15. This graph is a little different to the preceding scatter plot (Fig. 14)
in that it shows change in the density of bladder saltbush compared to that of all perennial species
regardless of seasonal quality.
Despite the general correspondence between density of bladder saltbush and all perennial species,
there was considerable variation at some sites. Of those sites that had >10% increase in density of
all perennial plants (shown by the green squares in Fig. 15), there was limited recruitment of
bladder saltbush at many sites and some sites had lost individuals at the second assessment (i.e.
sites represented by the green symbols plotting substantially below the 1:1 line in Fig. 15).
800
Figure 15. Change in density
600
of bladder saltbush and all
perennial species at SA
Density of bladder saltbush
400
-1000
pastoral monitoring sites.
Sites positioned near the
200
dashed 1:1 line had similar
changes in the density of
0
-500
0
500
1000
bladder saltbush and all
perennial vegetation.
-200
Colours and symbols
represent degree of change.
-400
-600
Data source: SA Dept.
increase
Environment & Natural
no change
Resources. Graph: compiled
decrease
by the ACRIS-MU.
-800
Density of all perennial plants
26
Conversely, where total plant density declined by more than 10% at sites (red diamond symbols in
Fig. 15), bladder saltbush persisted at some sites (shown by the red symbols plotting well above the
1:1 line).
Change at some sites was spectacular (Fig. 16) and serves to show how dynamic compositional and
structural change can be in the rangelands. The 2011 photo shows that this site was dominated by a
palatable biennial (i.e. relatively short-lived) grass, Enneapogon avenaceus) while the 1993 photo
had a good cover of chenopod shrubs (low bluebush, Maireana astrotricha, and bladder saltbush).
Plant density data confirm that bladder saltbush declined from 92 adults and 296 juvenile plants in
1993 to two adults in 2011. Low bluebush underwent similar change; from 160 adults and six
juveniles in 1993 to just 12 adults in 2011.
Anecdotal evidence strongly suggests that these changes were due to some very dry years in the last
decade. Prior to summer in 2001 and after a dry winter and low levels of ephemeral feed, the lessee
removed stock from the site area to minimise potential impacts on the valuable chenopod shrubs if
further rain was not received. Drought ensued and the shrubs succumbed to be replaced by the
more ephemeral E. avenaceus with recent good rains. This grass provided good ground cover when
the site was reassessed but it does not persist like the chenopod shrubs it has replaced and therefore
does not provide longer-term stability in landscape function.
1993
2011
Figure 16. Compositional and structural changes in vegetation between 1993 and 2011 at a pastoral
monitoring site in the Broken Hill Complex bioregion of SA.
Anecdotal evidence strongly indicates that loss of chenopod shrubs (which are evident in the left hand
photo) was due to drought during the last decade. Shorter-lived grasses responded to good rains prior
to the 2011 photo. In the long-term, chenopod shrubs provide better landscape function than the more
ephemeral grasses.
Photo: SA Dept. Environment & Natural Resources.
27
References
Bastin, G. & the ACRIS Management Committee (2008). Rangelands 2008 – Taking the Pulse.
Published on behalf of the ACRIS Management Committee by the National Land and Water
Resources Audit, Canberra. Available at:
http://www.environment.gov.au/land/rangelands/acris/index.html
Tongway, D.J. and Ludwig, J.A. (1997). The conservation of water and nutrients within
landscapes, Chapter 2. In J.A. Ludwig, D.T. Tongway, D. Freudenberger, J. Noble and K.
Hodgkinson (Editors), Landscape ecology, function and management: principles from
Australia’s rangelands. CSIRO Publishing, Melbourne, Australia, pp. 13-22.
Tongway, D. (1994). Rangeland Soil Condition Assessment Manual. CSIRO Division of Wildlife
and Ecology, Canberra.
Tongway, D., and Hindley, N. (1995). Manual for the Assessment of Soil Condition for Tropical
Grasslands. CSIRO Division of Wildlife and Ecology, Canberra.
28
Appendix 1. Seasonal quality matrices for change in perennial grass frequency
at WARMS grassland sites
The following tables report seasonally-interpreted change in perennial grass frequency for the most
recent assessment cycle (2003-2005 to 2006-2008). Tables are not included for the Northern
Kimberley 1 and Victoria Bonaparte 1 sub-IBRAs where less than 12 sites were assessed during
cycle 4. Cell values report the percentage of sites in each seasonal quality category that showed
decline, no change or improvement in frequency.
The red cell in each table emphasises the percentage of reassessed sites that had decreased
frequency following above-average seasonal quality (increase expected). Conversely, the green cell
highlights where improvement occurred when poor seasonal quality suggested a decrease in
frequency.
Central Kimberley
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
frequency < 90%
frequency between
frequency
90% and 110%
>=110%
Above average
61
15%
69%
16%
Average
7
14%
72%
14%
Number of sites
Decline.
No change.
Increase.
frequency < 90%
frequency between
frequency
90% and 110%
>=110%
Below average
Dampierland
Seasonal
Quality
Above average
105
9%
69%
22%
Average
25
4%
84%
12%
Number of sites
Decline.
No change.
Increase.
frequency < 90%
frequency between
frequency
90% and 110%
>=110%
Below average
Ord Victoria Plain
Seasonal
Quality
Above average
66
10%
70%
20%
Average
14
7%
93%
0%
Below average
29
Pilbara
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
frequency < 90%
frequency between
frequency
90% and 110%
>=110%
Above average
55
20%
38%
42%
Average
30
20%
43%
37%
Below average
14
7%
36%
57%
30
Appendix 2. Seasonal quality matrices for change in shrub density at WARMS
shrubland sites
The following tables report seasonally-interpreted change in shrub density (based on population
growth rate, PGR) for the most recent assessment cycle (2000-2005 to 2005-2009). Cell values
report the percentage of sites in each seasonal quality category that showed decline, no change or
improvement in PGR.
The red cell in each table emphasises the percentage of reassessed sites that had a decreased density
following above-average seasonal quality (increase expected). Conversely, the green cell highlights
where improvement occurred when poor seasonal quality suggested a decrease in density.
Carnarvon
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
and 1.05
Above average
Average
33
79%
6%
15%
Below average
92
67%
21%
12%
Number of sites
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
Coolgardie 3 sub-IBRA
Seasonal
Quality
and 1.05
Above average
Average
7
72%
14%
14%
Below average
23
44%
17%
39%
Number of sites
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
Gascoyne
Seasonal
Quality
and 1.05
Above average
65
43%
17%
40%
Average
57
68%
18%
14%
Below average
59
76%
12%
12%
31
Murchison
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
and 1.05
Above average
96
45%
20%
35%
Average
192
40%
26%
34%
Below average
69
41%
20%
39%
Number of sites
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
Nullarbor 2 sub-IBRA
Seasonal
Quality
and 1.05
Above average
20
40%
25%
35%
Average
42
62%
29%
9%
Below average
54
48%
32%
20%
Number of sites
Decline.
No change.
Increase.
PGR < 0.95
PGR between 0.95
PGR >= 1.05
Yalgoo
Seasonal
Quality
and 1.05
Above average
Average
15
33%
40%
27%
Below average
25
72%
12%
16%
32
Appendix 3. Seasonal quality matrices for change in RCI ratio at WARMS sites
The following tables report seasonally-interpreted change in the ratio of RCI for the most recent
assessment cycle. Tables are not included for the Northern Kimberley 1 and Victoria Bonaparte 1
sub-IBRAs where less than 12 sites were assessed during cycle 4. Cell values report the percentage
of sites in each seasonal quality category that showed decline, no change or improvement in RCI.
The red cell in each table emphasises the percentage of reassessed sites that had decreased RCI
following above-average seasonal quality (increase expected). Conversely, the green cell highlights
where improvement occurred when poor seasonal quality suggested a decrease in RCI.
Northern grassland bioregions
Assessment cycle: 2003-2005 to 2006-2008
Central Kimberley
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
and 1.0
Above average
62
55%
14%
31%
Average
7
72%
14%
14%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Below average
Dampierland
Seasonal
Quality
and 1.0
Above average
97
55%
13%
32%
Average
25
60%
8%
32%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Below average
Ord Victoria Plain
Seasonal
Quality
and 1.0
Above average
64
36%
14%
50%
Average
14
72%
7%
21%
Below average
33
Pilbara
Seasonal
Number of sites
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Quality
Decline.
and 1.0
Above average
52
27%
15%
58%
Average
30
40%
10%
50%
Below average
12
55%
9%
36%
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Southern shrubland bioregions
Assessment cycle: 2000-2005 to 2005-2009
Carnarvon
Seasonal
Number of sites
Quality
and 1.0
Above average
Average
33
27%
21%
52%
Below average
91
42%
25%
33%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Coolgardie 3 sub-IBRA
Seasonal
Quality
and 1.0
Above average
Average
7
14%
29%
57%
Below average
23
44%
39%
17%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Gascoyne
Seasonal
Quality
and 1.0
Above average
65
25%
28%
47%
Average
57
39%
28%
33%
Below average
58
36%
31%
33%
34
Murchison
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
and 1.0
Above average
93
29%
30%
41%
Average
192
26%
31%
43%
Below average
67
34%
33%
33%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Nullarbor 2 sub-IBRA
Seasonal
Quality
and 1.0
Above average
20
15%
25%
60%
Average
42
19%
29%
52%
Below average
54
22%
50%
28%
Number of sites
Decline.
No change.
Increase.
RCI < 0.9
RCI between 0.9
RCI ≥ 1.1
Yalgoo
Seasonal
Quality
and 1.0
Above average
Average
15
33%
60%
7%
Below average
25
24%
40%
36%
35
Appendix 4. Seasonal quality matrices for change in landscape function at SA
pastoral monitoring sites
As for previous appendices, the following tables report seasonally-interpreted change in the density
of longer-lived perennial shrubs at SA pastoral monitoring sites. Cell values report the percentage
of sites in each seasonal quality category that showed decline, no change or improvement in
landscape function.
Gawler (assessments between 1990-1999 and 2005-2009)
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
density < 90%
density between
density > 110%
90% and 110%
Above average
36
58%
11%
31%
Average
301
34%
13%
53%
Below average
356
34%
15%
51%
Broken Hill Complex 1 sub-IBRA (Barrier Range, assessments between 1994-1996 and 2005-2010)
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
density < 90%
density between
density > 110%
90% and 110%
Above average
6
50
17
33
Average
10
50%
20%
30%
Below average
Flinders Lofty Block 3 sub-IBRA (Olary Spur, assessments between 1994-2000 and 2009-2010)
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
density < 90%
density between
density > 110%
90% and 110%
Above average
35
63%
14%
23%
Average
79
42%
18%
40%
Below average
34
38%
24%
38%
36
part Stony Plains 1 sub-IBRA (Breakaways, assessments between 1990-1991 and 2005-2006)
Seasonal
Number of sites
Quality
Decline.
No change.
Increase.
density < 90%
density between
density > 110%
90% and 110%
Above average
2
50%
50%
Average
18
33%
17%
50%
Below average
37