The University of Melbourne
207-35/EVSC2007 Integrated Landscape Problem Solving and 451-342/ GEOM30012 Integrated Spatial Systems, 2010.

 

ABSTRACT (Snell)

Merri Creek is an inner urban river that has been significantly degraded over time. This is largely a result due to the wide range of human induced impacts that the riverine ecosystem is exposed to. The state of most of the vegetation along the riparian zone of the water way is either non-existent or highly degraded. The Merri Creek Management Committee has engaged Team Revegetation to develop a revegetation recommendations paper for a small riparian zone in Northcote, Melbourne. Team Revegetation aimed to provide precise and accurate information on the current condition of the site, identify and prioritise areas for improvement, provide a weed analysis with accompanying mitigation plan, as well as providing an extensive range of practical recommendations to restore the site to a good to excellent condition over time.

A desk-top analysis was conducted to develop a sound knowledge of the area before infield assessments commenced. To evaluate the condition of the site and its vegetation structure a flora field survey and habitat hectare assessment were undertaken by Team Revegetation. The site was found to have a high level of foreign and exotic herbaceous understorey species, as well as a predominant absence of native species. Overall, the site was considered to be of poor quality. To illustrate the vegetation condition of the site the vegetation communities and high priority weed infestations were spatially represented, along with any assets and/or infrastructure of significance to the management plan. The identified exotic weed species were prioritised categorically, under federal and state weed frameworks (i.e the Weeds of National Significance framework and Noxious weeds listing). Concretion amongst Team Revegetation resulted in the development of recommendations that target the lowest quality regions of the site. The recommendations provide clear, informed and integrated methods to eradicate high priority weed species (such as Rubus discolour, Salix sp., Plantago lanceolata), revegetate the area with key native species and provide a spatial representation of an integrated vegetation management plan.

 

Glossary of Abbreviations
Abbreviation Description:
TR Team Revegetation
MCMC Merri Creek Management Committee
MCRMP Merri Creek Revegetation Management Plan
EVC Ecological Vegetation Classification
DSE Department of Sustainability and Environment
RTK Real Time Kinematic
GPS Global Positioning System
DPI Department of Primary Industries
IVM Integrated Vegetation Management

 

1 INTRODUCTION (Burrows)

1.1 CONTEXT

An increasing awareness of the importance of biodiversity has seen much of Australia’s southern land care and conservation groups expending their efforts to reduce the rate of biodiversity loss and to rehabilitate/revegetate deteriorating ecosystem services (Possingham, 2001).

However, it is essential that the natural resource managers who are in control of revegetation and conservation practices have a conceptual and systematic understanding of contemporary landscape ecology theories, natural resource management frameworks and revegetation issues Landscape ecology explores the development and dynamics of spatial heterogeneity, spatial and temporal interactions and the exchanges across heterogeneous landscapes of abiotic and biotic processes (Turner et al, 2001). Understanding the concepts and theories of landscape ecology that drive these aspects is essential for natural resource managers to make successful decisions and implementmanagement plans that benefit the environment, as well as benefiting the social and economic aspects associated with a project. Equally important is the development and use of management frameworks that use a multi-disciplinary approach to identify the ‘best approach’ method for natural resource management.

With the emergence of, and improvements to new technologies such as GPS and satellite imagery, the way in which natural resource management has been carried out has also changed. This technology is now used increasingly in the planning, implementation and monitoring stages of natural resource management (Apan et al, 2004). Apan also suggests that given the cost of revegetating deteriorating ecosystems, and often the limited funds that are allocated, that money and efforts should be targeted at the most affected areas and where the problems are most likely to reoccur.

To help do this, existing maps with DEM data, vegetation overlays, satellite imagery, land use overlays and other GIS data layers are often used to construct a GIS analysis that enables natural resource managers to make more informed decisions that can help prioritise the areas where their efforts should be focused. At a more basic level, this revegetation framework will be applied to the Merri Creek site that is the basis of our revegetation plan (see Figure 2).

In addition to this, the Merri Creek Management Committee (MCMC) have outlined their own set of revegetation priorities. These include the protection and restoration of remnant vegetation, the maintenance of existing plantings and the establishment of new revegetated areas (MCMC, 2010). Team Revegetation (TR) has formulated their aims in accordance with the MCMC’s, with the intent of utilising Global Positioning and Geographic Information System technology to assist in the prioritisation of management areas. Before a management plan can be developed however, a familiarity with the site’s geographical location and surrounding environment is fundamental. A brief history of the site’s land use, as well it’s ecological history also needs to be understood.

 

1.2 SITE HISTORY

The area concerning this project is located in the suburb of Northcote, and bounds Merri Creek between the Rushall Station rail bridge over the creek and the footbridge approximately 300m downstream. Merri Creek flows for about 60 kilometres from the Great Dividing Range near Wallan, in the far north of Melbourne, to the Yarra River at the heart of Melbourne. It lies mainly on sandy sediments, having cut through volcanic deposits over the last 5 million years. The main habitats within the Merri Creek catchment are grasslands and grassy woodlands (MCMC, 2010).

The indigenous flora that was once abundant and widespread, that the MCRMP is attempting to emulate, has obviously changed extensively over time with the growth of the urban environment and its influence on surrounding ecosystems. It is suggested that Melbourne’s renowned basalt plains in the north-west that were once covered in native grassland habitat, have become increasingly sparse, and are in general, show a poor to completely absent level of representation in reserves throughout Victoria (Wigney 1994). This particular void in local natural flora management has provided TR with the scope to develop a management plan that can hopefully create a precedent for indigenous flora representation in reserves throughout Victoria.

Today, large sections of the Merri Creek run through urbanized areas and it is therefore subjected to many urban processes and activities. The areas along the creek are used by people for industrial, residential and recreational reasons. These uses all have impacts on the health of the creek. Notable effects of these uses are pollutants in the water, such as heavy metals and oils; introduction of foreign flora species; and erosion. The lower section of the catchment especially, has become highly urbanized over the last 150 years and this has negatively affected the landscape processes that operate in the region significantly. Over the last 20 years the MCMC has gone to significant lengths to mitigate these consequences and restore the creek, as much as possible, to the healthy, sustainable state it was in when native indigenous flora dominated the landscape.

The particular section of the Merri Creek under investigation is situated adjacent to both residential and industrial development. A bicycle and pedestrian path runs along a portion of the site. The site is used regularly by cyclists, pedestrians, dog-walkers and nature enthusiasts and occasionally by homeless people seeking shelter. One of the purposes of this report, and of the MCMC in general, is to help manage the impact of human use on the creek, and its affect on the area’s vegetation.

 

1.3 PURPOSE & SCOPE

The purpose for the Merri Creek Revegetation Management Plan (MCRMP) is to complete fundamental field analyses and to provide realistic recommendations for the successful re- vegetation of the proposed project area (see Figure 2 below). Our proposal will simultaneously serve to minimise the extent of weed invasion, prevent the reestablishment of colonies and aim to increase the proportion of native species to the area.

However, the current state of vegetation at this particular site is unknown. A reconnaissance of the area will need to be undertaken to identify the local and pest species, and which native species would be appropriate for revegetation purposes needs to be determined. The main aims of the strategy will be the control of weeds throughout the reserve and to generally rehabilitate the native flora of the project area.

This project will use a range of key-stone literature, field surveying, a desktop analysis, management frameworks and innovative ideas to develop a revegetation management plan that is sustainable and effective in helping achieve the MCMC revegetation objectives, through our own specific macro- and micro- level aims.

 

2 AIMS (Sloan)

The MCRMP aims to improve the state of the area’s vegetation, using both revegetation and weed management methods. This will be achieved through a series of objectives at both a macro- and micro-scale. By taking this approach it will be easier to complete specific goals of the project and to evaluate the success of the project in delivering broader scale environmental benefits. The objectives set out by the MCRMP are:

 

Macro-Scale Objectives:

• To develop a management recommendations plan that could be used to effectively restore the site to a good to excellent vegetation condition, utilising Integration Vegetation Management (IVM) methods.
• To provide recommendations based on relevant literature, that ensures revegetation throughout the area will be ‘self sustaining’ or ‘viable’ indefinitely.
• To use the Ecological Vegetation Classes (EVC) and a habitat hectare assessment system to assist in evaluating the condition of the proposed area.
• To identify regions within the project site that share similar ecological characteristics and flora communities for spatial representation.

 

Micro-Scale Objectives:

• To identify the previous and current vegetation communities that exist at the project site. This will provide a catalogue of native species found at the area and any species that would appropriately match predicted previous indigenous floristic communities. This catalogue could be used for future vegetation management of the area, or for similar projects elsewhere.
• To identify areas of weed infestation and assess their severity/ priority for eradication.
• To discuss the limitations of the assessments used.
• To make recommendations on appropriate weed eradication methods and to minimise their impact on the sites native flora.
• To develop zoned spatial representations of the project site including; zonings of current foreign and local flora, zones to be revegetated, and the zones in need of future weed preventative measures.

 

 

 

 

 

 

 

4 RESULTS

4.1 PRESENT NATIVE CONDITION (Panozzo & Snell)

Vegetation Description (Panozzo)
This is a Eucalyptus melliodora and E. camaldulensis open woodland with an understorey comprised of a large number of exotic weed species. There are three strata in this vegetation, with a mosaic of native and exotic species present.

There are two parts to the upper strata on the site. At the northern end of the site it is dominated by E. melliodora and E. camaldulensis with mature heights up to 17m. These trees are situated in a cluster and only occupy a small area to the north of the site (estimated projected foliage cover of 6%) and appear to be part of a previous revegetation effort. At the southern end of the site the upper strata of vegetation is mostly comprised of Salix sp. height of 8-10 meters and a cover of 2%. Also at this end are a number of Pinus radiata which have a height of 3-25m and an estimated projected foliage cover of less than 1%.

The mid-strata is comprised of a number of native Acacia spp. and Eucalyptus spp. with heights of 3-7 meters the Acacia implexia, A. mearnsii and A. melanoxylon dominate this strata (estimated projected foliage cover of 8%). There are also a number of individuals of E. macrorhyncha. In the middle of the site there is a group of A. spp. which have been planted and are in amongst the highly weeded lower strata. The lower stratum is comprised of mostly exotic weeds species.

The dominant species in this strata are Ehrharta erecta and Ehrharta longifolia, with covers of up to 20% each and heights less than 50 cm. Numerous other exotic species are present at the site which are preventing the success of any native grass or shrub species. See a complete flora survey sheets at Appendix C and a flora list at Appendix D for further information.

 

Habitat Hectare Assessment (Snell)
A habitat hectare assessment was conducted on the 29th of September 2010 at the project site by TR (see Appendix E). The site overall condition was considered to be in very poor condition (total = 26/100 (26%)) with low scores across all components (see Figure 1). The two highest scoring components were ‘organic litter’ (4/5×100 = 80%) and ‘logs’ (4/5×100 = 80%). The two lowest scoring components were ‘neighbourhood’ (0%) and ‘distance to core area’ (0%). However, the landscape context component is realistically unable to be improved throughout the scope of this recommendations paper and would require radical improvements from a macro urban development scale. Two components of this assessment that were scored low and have potential to be improved on a local scale were the ‘understory’ (5/25 = 20%) and the ‘lack of weeds’ (2/15 = 13.3%) components. Refer to Figure 1.

 

Figure 1

 

4.2 WEED ASSESSMENT AND HIGH THREATS (Snell)

All exotic species identified at the project site are listed in Table 1 along with their commonwealth, state and local priority-status.

The project site has no state prohibited weeds, one regionally prohibited weed (Plantago lanceolata), three regionally controlled weeds (Plantago lanceolata; Rubus discolour; Silybum marianum (l)), six restricted weeds (Plantago lanceolata; Oxalis pes-caprae; Allium triquetrum; Rubus discolour; Silybum marianum (l); Salix sp.) and two WONS (Salix sp.; Rubus discolour). All species that fit the mentioned categories have been classified as ‘high priority’ weeds.

 

Table 1

 

4.3 SPATIAL DATA (Judd)

Native Vegetation Map (see Figure 2) (Judd)

Native Section 1 = Acacia sp. and Poa labillardieri.

Native Section 2 = Juvenile Eucalyptus melliodora and Poa labillardieri / Senecio glomeratu. Native Section 3 = Scattered Acacia and Eucalyptus sp. with Poa labillardieri / Senecio glomeratu.

Native Section 4 = Steep Slope of revegetated Acacia mearnsii and Solanum laciniatum shrubs.

 

Figure 2

 

Weed Infestation Map (see Figure 3) (Judd)

Weed Section 1 = High priority weed infestation with a mosaic of understory species and Salix sp.

Weed Section 2 = High Priority weed infestation with some Salix sp. and rich herbaceous and grassy understorey.

Weed Section 3 = Low Priority weed infestation covered in a mosaic of weedy herbaceous understory species.

Weed Section 4 = High priority area with Rubus discolour and Senecio mikanioides.

Weed Section 5 = Low priority weed infestation covered in a mosaic of weedy herbaceous understory species.

 

Figure 3

 

 

6 RECOMMENDATIONS (Panozzo, Snell & Judd)

TR has proposed three major recommendations that aim to improve the low scoring components identified in the habitat hectare assessment and to eradicate the high priority weeds. These recommendations focus on; 1) weed mitigation to improve the ‘understorey’ and ‘lack of weed’ components; 2) revegetation techniques to improve the ‘tree canopy cover’ and ‘large tree’ components; and 3) integrated management options to ensure different tools are used to achieve one overall management scheme.

 

6.1 WEED CONTROL OPTIONS (Snell)

6.1.1 Burning (Snell)
The use of fire is an effective tool that can be used by vegetation managers to control weeds, encourage natural regeneration and alter species compositions (Hajek and Johnson, 2002). Fire acts as a disturbance throughout the landscape that can have both positive and negative effects on natural ecosystems depending on its application and regimes (e.g intensity and what type of vegetation is burnt) (see Richards et al, 1999). The appropriate application of fire to the project site may be a successful tool to promote the regeneration of a native understorey and to eradicate some understorey weed species (i.e Plantago lanceolata). However, the small size of the area and the adjacent land restricts the use of fire on the edges of the site. Low intensity controlled fires should be introduced to the interior (10m from any infrastructure or Merri Creek) of the site during late Autumn to Spring (DSE, 2009) (see Figure 4).

 

6.1.2 Herbicides (Snell)
Herbicides (chemical controls) can be another effective tool for weed control. Herbicides have a rapid kill rate and can be safely and easily distributed throughout a site (DPI, 2007). The danger of applying herbicide varies with the chemical being used, the weather conditions and topographic aspects of a site. It is recommended by the Department of Primary Industries (DPI) to monitor and manage the use of chemicals around waterways and steep slopes (DPI, 2007). Although, for the purpose of this paper water safe herbicides (Round-up) could be safely used to eradicate understorey or thickets of weed populations around the edges of the site – the 10m strip around the edge of the area (e.g Rubus discolour) (see Figure 4).

 

Figure 4

 

6.1.3 Hand and machine removal (Snell)
Unfortunately, some herbicides are not effective at eradicating well established woody weed species (such as Salix sp.) or fragile areas (natives near water course). Physical controls such as machine removal for Salix sp. and hand pulling weeds from the water edge riparian zone may be a more practical method for weed eradication. Some fragile areas at the project site should be hand weeded to prevent natural vegetation being destroyed and Salix sp. should be removed by machines (see Figure 4).

 

6.2 RESTORATION

In order to guarantee the success of the active planting within the site, we have compiled a suggested species list. Information has been drawn from Watson (2004), Royal Botanic Gardens Cranbourne (n.d) and the Studley Park EVC (55) Plains grassy woodlands (see Appendix E) who provide insight into species that occur naturally and those which will maximise economic efficiency of the project. The history of the vegetation at the site as well as the typically successful species given the bioregion and soil composition have both been integral in selecting species. This will not only mean that they will have the greatest survival rate but will also create an environment which is closest to the predicted, once naturally occurring, indigenous habitat (see Figure 5).

 

Figure 5

 

6.2.1 Seed Provenance
The benefit of collecting and utilising the seed of local provenance is the local adaptive ability of the seed supply that it provides (Kiehl, K., et al 2010). However there also exist potential issues with adopting this strategy. It can lead to not only the failure of planted species to survive/thrive but it may also lead to outbreeding depression, where the reduced fitness of non-local individuals leads to the next generation of hybridised individuals being weakened.

 

6.2.2 Do nothing
A viable option is to take no action in terms of vegetation management. Depending on the land usage patterns of the site it may make more economic and social sense to leave the site as it is. The benefit of improving the ecological and aesthetic value of the site may be less than the financial cost of the project. Further research and/or a cost-benefit analysis needs to be conducted to assess the social benefit of revegetation plans.

 

6.3 INTEGRATED MANAGEMENT FOR MERRI CREEK REVEGETATION
(Snell, Panozzo & Judd)

Integrated Vegetation Management is a long term sustainable approach that uses a wide range of different options to achieve one overall management scheme, for landowners such as the MCMC (Johnstone, 2008). IVM avoids the use of single techniques and instead consists of different types of methods, over a long period of time to eventually deplete all weeds in the region (Johnstone, 2008). TR proposes a zoned management scheme for the site to use a mosaic of different techniques. This aims to target specific areas with certain techniques that would achieve the best results based on that areas characteristics.

 

Integrated Weed Mitigation Zones:

• Zone 1: Exterior zone. Use low intensity herbicide and hand pulling techniques throughout this zone. – This zone will also provide a buffer for burning regimes.
• Zone 2: Interior zone. Use low intensity burning to eradicate weeds and promote natural flora regeneration.
• Zone 2 a: Burn first year of management plan
• Zone 2 b: Burn third year of management plan
• Zone 2 c: Burn fifth year of management plan (repeat at again Zone 2a). NOTE: Implement weed hand removal techniques each year at previous burnt sites to allow natural regeneration.
• Zone 3: Use machine removal to eradicate this area. Also remove any Salix sp. along creek bed.

 

Integrated Revegetation Zones:

• Zone 1 (planting assisted revegetation): Exterior zone. Revegetated areas using the proposed species list (see Appendix D). Use grasses and shrub near creek bed immediately to reduce erosion.
• Zone 2 (Natural Revegetation): Use burning and weed prevention methods to allow natural revegetation of this area (see above section).

 

Acknowledgments
Team Revegetation would like to thank the Merri Creek Management Committee for their assistance throughout the project for providing historical information. Thanks also need to be given to the Department of Geomatics for the provision of GPS equipment, and especially Eldar Rubinov for help in processing the acquired spatial data. Lastly, cooperation between the students and coordinators of Integrated Spatial System (451-342) for support throughout the production of this report.