Case Study 1: Riparian revegetation and exclusion fencing.
Bessell Road, Rosa Glen
State NRM Capabilities
Farming – grazing of cattle and sheep
Justin Carroll & Marnie Hamilton
Brent Dennis, Landforms
Justin and Marnie bought their property in 2012. The previous land owner had grazed sheep and had planted poplar trees as wind breaks and to assist in the lamb’s nourishment. Since Marnie & Justin purchased the property they have predominantly grazed cattle, subsequently the poplars that were once controlled by grazing sheep became dominant in the landscape causing a number of issues that needed to be addressed. Poplars are deciduous trees, they cast intense shade in spring and summer which affect the ability for other native flora from growing beneath them. Hindering other flora species growth resulted in little if no understory vegetation, especially on the bank of the natural winter creek running through the property causing the bank to be more prone to erosion. Secondly the lack of understory meant there was little if no biodiversity, essentially a monoculture which reduced suitable habitat for native fauna. The area had become weed dominant.
Further to this, the brook was not fenced off, therefore effluent (from grazing cattle) was flowing downstream effecting local waterway quality.
Justin & Marnie heard about the opportunity to work with the Lower Blackwood Land Conservation District Committee through their neighbour Tim Crimp. Tim and his family helped Justin and Marnie out when they first started running cattle and suggested they take up the opportunity for soil testing to improve their soil’s health. Further, knowing the poplars had become a problem on the Carroll’s property, with an understanding of Justin and Marnie’s vision for future usage of their property, Tim also informed them of the Regional Estuaries Initiative opportunity to do some riparian revegetation work with the Lower Blackwood LCDC which could include stock exclusion fencing of their riparian zones.
Justin and Marnie had a clear vision of what they wanted to achieve on their piece of land. They had previously put in a dam wall; they wanted a dam for future water use, for aesthetics and recreation. Previous to the revegetation work the case study area had been in poor condition as previously described and inaccessible to them. With a young family, they were keen to improve their waterway’s health and create a sustainable natural landscape that could be utilised and appreciated in more ways than one.
Challenges: There were many challenges!
Firstly, the poplars didn't want to die, this is an ongoing challenge for the Justin and Marnie.
The revegetation area is an enormous, this in itself is a huge challenge. The site access is difficult as the site is very steep and the ground is loose and very muddy.
The steers are challenging to keep out. Unfortunately, they recently caused a severe setback. Cattle pushed their way into the revegetation area and did extensive damage to the whole revegetation area. Much work needs to be done to fix the damage and get to the point it was at before the damage was done.
Contractor Considerations, Recommendations & Advice
Owners objectives - Justin and Marnie wanted to create a revegetation landscape that was aesthetically pleasing, naturally sustainable and useful for outdoor recreation;
Site specific factors/conditions – length of the creekline, presence of perennial weeds (eg. kikuyu grass & cape weed), dry and windy summers, weed invasion, potential issues with neighbouring properties-sediment transport downstream and livestock invasion and pressure.
What resources were available
Specific farm considerations:
Weeds - being a farm there is a significant source of weeds – paddock species are weeds that if not grazed they out compete native plants.
Soil variability – this site had clay through to quartzy sands, thus plant choice must be species that can cope with the difference in soil moisture and chemistry.
Transition between seasons – a lot of moisture at the end of winter- water logged etc, however no sunshine means little growth. No rain for just a few days and the land dries out causing plants to struggle as no time to adjust to changing conditions.
Wind – especially the summer south easterlies. The biggest factor as wind strips foliage, reduces moisture availability – its more pervasive than the sun as is a problem 24 hours a day (can cause moisture evaporation at night as well as in the day) rather than just 11-12 hours a day.
Interactions between stock (cattle & sheep and horses) and the plantings. Can set a project back by 12 months. Cattle cause the most damage, their mass & numbers. Often cattle are a commercial venture thus the farmers put more value on the stock. If stock breakthrough the damage is quick. Thus, fencing work done previous to planting is integral to a successful revegetation planting.species are weeds that if not grazed they out compete native plants.
The biggest key to the success is the choice of plants and planting technique. Choosing plants that will require less follow up. Plants that can cope with the particular landscape. Plants chosen should be able to replicate a natural system, where in five to ten years visually it will not be obvious that the planting has been done. This does depend on the economic resources and the land owner’s objectives.
Plants used on this site:
Eucalyptus patens (Black Butt)
Corymbia Calophylla (Marri)
Agonis Flexuosa (Peppi tree),
Banksia Paludosa (swamp banksias)
Myoporum montanum (water bush)
Melaleuca Incana (grey honey myrtle)
Beaufortia sparsa (swamp bottle brush)
Callisachys lanceolata (Native Willow)
Hakea oleifolia (olive leaf hakea)
Taxandria linearifoli (swamp peppiment)
In this project, sedge species are the largest in number as they provide the initial structure and ground cover protection from weeds so better for other species to become established. Further sedges give protection to other species from wind, traps sediment and provides cover to invertebrates.
Read more about using rushes & sedges in the South West in this guide.
Sometime unfortunately compromise is necessary due to availability. However the choice needs to be made, do you do a big area with plants that are not so suited or do you plant out smaller areas with plants that are best suited well. First choice should always be to do a smaller area well and continue to the process at a later date when plants become available;
When the cattle made a breakthrough to the revegetation area, they did a lot of damage and unfortunately due to lack of availability some of the blackbutts will be replaced with Marris’.
Planting technique is integral to success. Different plants like different conditions, some like wet feet others need to be further away from the waterway so the planning and arrangement of the different plants is very important. Further, how you plant the plant, the planting hole preparation is also important to each plant’s success. The size and the depth as well as ensuring the soil edge is not compacted.
Read more on revegetating riparian zones in south-west Western Australia
The work done by the Lower Blackwood LCDC was a huge help. Financially it has helped, it has cost a lot more to do than Justin and Marnie originally thought. Further, more importantly the expertise and time given has been fantastic. Chiara, the LBLCDC Project Officer, has helped with keeping us on track and has purchased all the plants using her extensive knowledge and has organised for Brett and team to do the planting. If we were trying to do on our own it would not be as good and defiantly would not be as far along as we are now. The help has been awesome.
The planting is designed to reduce maintenance and for the area to become self-sustaining.
There will be some weed control necessary every few months;
Next year there will be some secondary planting;
Sedges should be established and we will be able to plant some colonising species, rapidly growing sedges spread from rhizomes in the base and out-compete which is very valuable for natural and ongoing weed control;
Watering of key species (especially the trees) initially in the warmer months of the year, this will assist in them getting established quicker.
Once Justin and Marnie recover from the recent damage to the area by the cows, environmentally, they would like to try and get their bush back to a more natural state. They have 25 acres of remnant bush which has been logged quite heavily. They would also like to plant some more trees, but at this stage there are no new projects imminent. Marnie and Justin will continue with soil testing on an ongoing basis.