1 Monitoring ecological indicators of rangeland functional integrity and biodiversity at local to regional scales John A. Ludwig, 1 David J. Tongway 2 Gary N. Bastin, 3 and Craig James 3 1 Tropical Savanna CRC and CSIRO, PO Box 780, Atherton, Qld 4883 Australia, 2 CSIRO, GPO 284, Canberra, ACT 2601 Australia, and 3 CSIRO, PO Box 2111, Alice Springs, NT 0871 Australia Abstract In Australia’s rangelands, clearing, grazing and fire have variously modified landscape functional integrity, which is the intactness of native vegetation and soil patterns and the processes that maintain these patterns. Intuitively, biodiversity should be strongly related to landscape functional integrity, that is, landscapes with high functional integrity should be maintaining biodiversity and altered, less functional landscapes may have lost some biodiversity, here defined as the variety and abundance of the plants, animals and micro-organisms of concern. Simple indicators of biodiversity and functional integrity are needed that can be monitored at a range of scales, from fine to coarse. In this paper, we use examples, primarily from Australia’s rangeland literature, to document that at finer patch and hillslope scales, a number of indicators of landscape functional integrity have been identified, and these indicators, based on the quantity and quality of vegetation patches and zones, are related to biodiversity. For example, a decrease in the cover and width (quantity) and condition (quality) of vegetation patches, and an increase in bare soil, near cattle watering points in a paddock, are significantly related to declines in plant and grasshopper diversity. These vegetation patch cover and bare soil indicators have traditionally been monitored with field-based methods, but new high-resolution, remotely-sensed imagery can be used in many rangeland areas for this fine-scale monitoring. At intermediate paddock and small watershed scales, indicators that can be derived from medium- resolution remote-sensing are also needed for efficient monitoring of rangeland condition (i.e. functional integrity) and biodiversity. For example, 30 to 100- m pixel Landsat imagery has been used to assess the condition of rangelands along grazing gradients extending out from watering-points. The variety and abundance of key taxa have been related to these gradients (the Biograze project). At still larger region and catchment scales, indicators of rangeland functional integrity can also be monitored by coarse-resolution remote-sensing and related to biodiversity. For example, the extent and greenness
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Monitoring ecological indicators of rangeland functional integrity and biodiversity at
local to regional scales
John A. Ludwig,1 David J. Tongway2 Gary N. Bastin,3 and Craig James 3
1Tropical Savanna CRC and CSIRO, PO Box 780, Atherton, Qld 4883 Australia, 2CSIRO,
GPO 284, Canberra, ACT 2601 Australia, and 3CSIRO, PO Box 2111, Alice Springs, NT
0871 Australia
Abstract In Australia’s rangelands, clearing, grazing and fire have variously modified
landscape functional integrity, which is the intactness of native vegetation and soil patterns
and the processes that maintain these patterns. Intuitively, biodiversity should be strongly
related to landscape functional integrity, that is, landscapes with high functional integrity
should be maintaining biodiversity and altered, less functional landscapes may have lost
some biodiversity, here defined as the variety and abundance of the plants, animals and
micro-organisms of concern. Simple indicators of biodiversity and functional integrity are
needed that can be monitored at a range of scales, from fine to coarse. In this paper, we use
examples, primarily from Australia’s rangeland literature, to document that at finer patch
and hillslope scales, a number of indicators of landscape functional integrity have been
identified, and these indicators, based on the quantity and quality of vegetation patches and
zones, are related to biodiversity. For example, a decrease in the cover and width (quantity)
and condition (quality) of vegetation patches, and an increase in bare soil, near cattle
watering points in a paddock, are significantly related to declines in plant and grasshopper
diversity. These vegetation patch cover and bare soil indicators have traditionally been
monitored with field-based methods, but new high-resolution, remotely-sensed imagery
can be used in many rangeland areas for this fine-scale monitoring. At intermediate
paddock and small watershed scales, indicators that can be derived from medium-
resolution remote-sensing are also needed for efficient monitoring of rangeland condition
(i.e. functional integrity) and biodiversity. For example, 30 to 100-m pixel Landsat
imagery has been used to assess the condition of rangelands along grazing gradients
extending out from watering-points. The variety and abundance of key taxa have been
related to these gradients (the Biograze project). At still larger region and catchment scales,
indicators of rangeland functional integrity can also be monitored by coarse-resolution
remote-sensing and related to biodiversity. For example, the extent and greenness
2
(condition) of different regional landscapes has been monitored with 1-km pixel NOAA
AVHRR satellite imagery. This regional information becomes more valuable when it
indicates differences due to land management. Although a dose of caution is needed,
measuring and monitoring landscape functional integrity at finer hillslope to small
watershed scales does provide emergent attributes and indicators for understanding
processes driving changes occurring at coarser region and catchment scales; this
understanding is essential for making sound management decisions such as whether to
rehabilitate an area of rangeland. Finally, we discuss potential future developments that
may improve proposed indicators of landscape functional integrity and biodiversity, hence,
1993). We also recognise the importance of nutrient cycling in maintaining plant
production, evident at the within-patch scale (Adams 2002), and across rangeland regions
(visible as greenness in imagery; Cridland & Fitzgerald 2001). Both water redistribution
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through runoff and runon and nutrient conservation and utilisation are vital for maintaining
biophysical functioning landscapes that are rich in habitat quality and populations of
organisms.
Advances in landscape functionality and rangeland restoration
Rangelands can be restored by building vegetation patches that function to retain resources
on hillslopes or at the base of hillslopes (e.g., Purvis 1986, Bastin 1991, Tongway &
Ludwig 1996, Noble et al. 1997, Karssies & Prosser 2001). However, when restoring many
rangelands, a broader landscape view is needed – a view that encompasses geomorphic and
hydrologic processes. For example, building on earlier erosion cell concepts (Pickup
1985), a hierarchical geo-ecological view is being advanced as an approach to restoring
and managing rangelands in Western Australia (Pringle & Tinley 2001, Tinley 2001,
Pringle 2002b). Basically, this approach assesses key geomorphic processes within a
drainage basin. It aims to identify and treat incision ‘nickpoints’ in the landscape where
disturbances have caused head-cutting gullies that literally ‘pull the plug’, diverting water
from landscape surfaces (Tinley 2001). These altered water regimes can cause vegetation
changes over large landscape areas in the basin (e.g., shrub encroachment). This altered
vegetation is likely to persist unless incision nickpoints are repaired to restore former
geomorphic and hydrologic processes and patterns. The ecological consequences of subtle
alterations in hydrological processes are now being studied in rangelands of Australia at
hillslope (e.g., Dunkerley 2002; Ludwig & Tongway 2002; Prosser et al. 2001), watershed
(e.g., Cramer & Hobbs 2002) and catchment scales (e.g., Pickup & Marks 2000; Prosser et
al. 2002). Practical applications to repair hydrological processes in rangelands include
retention banks being progressively built down a hillslope (Purvis 1986) and the
Ecosystem Management Unit (EMU) process (Pringle & Tinley 2001).
Future developments in relating landscape functionality and biodiversity
In this paper we explored landscape functionality, as defined by resource retention, and the
integrity of landscape structure, as defined by patchiness, and whether these concepts
provided useful indicators and information about the status of biodiversity. We used
Australian rangeland examples to suggest that highly intact landscapes are highly
functional and diverse, whereas degraded landscapes have lost some functionality and
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species variety and abundance. To progress future developments in this area, we suggest
that further studies are needed to relate biodiversity to landscape functional integrity. We
need to better understand at what level a landscape is sufficiently intact to provide a variety
of habitats suitable to maintain viable populations of species at scales appropriate to a
given rangeland region. We would anticipate finding significant relationships between
patch obstructions viewed at many scales, from log mounds on a hillslope to wetlands on a
floodplain, where these patch obstructions capture and hold resources and maintain habitat
quality (food and shelter) for biodiversity.
To better determine the potential role of patch obstructions for conserving biodiversity,
we suggest questions, such as the following, need to be addressed:
1. What conditions of resource supply are required for different key taxa to occur in
different places? For example, can a landscape on a given soil type, with its current
geomorphic structure, provide adequate soil water supply for these key taxa?
2. When is resource redistribution needed in a landscape to allow key taxa to persist and
prosper where otherwise they would not?
3. What are the functional relationships between degree and frequency of disturbances
such as clearing, grazing and fire, and the amount of landscape needed to support
these key taxa?
These questions should be addressed within analytical frameworks that should include, but
not be limited to:
1. The trigger-transfer-reserve-pulse framework, which has spatial and temporal
components that relate landscape patterns to processes at finer patch-hillslope scales
(Ludwig et al. 1997); this framework has proven useful for identifying ecological
indicators of landscape functionality applicable for monitoring rangelands (Tongway
& Hindley 2000); and
2. Biodiversity monitoring frameworks specifically designed for Australian rangelands
(e.g., ACRIS 2001, Smyth et al. 2003); these frameworks should accommodate a
range of inputs and include components that can be refined with time (Whitehead
2000).
ACKNOWLEDGEMENTS
We particularly thank Mark Stafford Smith for his intellectual input into the development
of relationships shown in Figure 4, and Hugh Pringle for enlightening us about his work
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with Ken Tinley on their hierarchical geo-ecological approach to landscape ecology and
rangeland restoration.
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