1. s e s s i o n 4 p a r t 3 Riparian zone exotic flora

2. Riparian zone exotic flora
Problems caused by weeds
Types of weeds
Methods of control
Special case: Willow management
Discussion Point
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click links for examples

3. Problems caused by weeds
Weeds are adapted to be able to rapidly colonise degraded areas. Native species are not as competitive, and eventually are outgrown or cannot germinate because of the presence of weeds
Some weeds (eg willows) cast dense shade which prevents lower canopy plant species from surviving, therefore severely restricting the biodiversity of the site
Weeds such as blackberry are very prickly, and create an environment that, while it forms safe haven for birds (from pests such as cats), also create good habitat for other pests such as foxes and rabbits. Blackberries are also eaten by birds and foxes and the seeds are spread in their faeces.
Weeds reduce the aesthetic value of streams, and in some cases, can completely restrict access to the streamside
Aquatic weeds can cause excessive shading which restricts other macrophytic species from becoming established
Outcompete native species
Block waterways
Seeds are washed downstream and spread to other sites
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4. Example
IMPACT OF WILLOWS COMPARED WITH NATIVE SPECIES IN THE RIPARIAN ZONE
The slide shows a number of aspects in which these two types of vegetation differ. These include:
NATIVE VEGETATION
Many different species of plants can become established due to the comparative ‘openness’ of the canopy
This encourages a wide diversity of fauna which depend on a variety of flora to survive
Insects and plant debris constantly fall into the water, providing a continual supply of food for instream species
Riparian tree species ultimately form hollows which provide nesting sites for fauna
Fallen tree branches and trunks provide habitat for fauna
WILLOWS
Drop leaves only once a year
Excessive leaf litter causes water quality problems in autumn
Heavy shade in summer prevents other plant species from becoming established, thereby restricting habitat value for flora and fauna
The roots are invasive and can clog and block the stream
Birds are not attracted to willows
Get the students to look at the guide on page 41 of the reference for a summary.
< weeds

5. Types of weeds < weeds TYPES OF WEEDS ALONG WATERWAYS
WOODY OR HERBACEOUS:
WOODY
Examples of woody weeds are Blackberries and Willows
HERBACEOUS
Herbaceous weeds are those such as grasses which have the potential to outcompete and stifle native species
Other species such as Paterson’s Curse and St John’s Wort are a problem in the Eastern Riverina area where the river banks have been disturbed.
IN-STREAM WEEDS
A good example of an instream weed is water hyacinth, and, in places, native species such as cumbungi
These weeds are likely to be different in different environments and hence cannot be covered in detail for every situation/location in a course such as this.
< weeds

6. Methods of control < weeds next > WEED CONTROL Labour intensive
May include both physical and chemical methods
Are often specific to the weed and the location (both environmental and government)
METHODS OF WEED CONTROL
Chemical, (stem injection, foliar spraying or application to newly cut stumps)
(see the BEFORE and AFTER example on the slides)
Mechanical (hand pulling, chipping, removal with machinery (including in-stream weed removal))
Burning
Mulching (which effectively smothers the weeds)
Controlled grazing
Decreasing light levels over the water (ie shading) controls many in-stream weeds
Use of chemicals near waterways must be done:
With extreme care to prevent non target plant species from being affected
Only the permission of the manager, owner, or state government body who are responsible for the management of the zone
Particular caution should be exercised where amphibious animals such as frogs are found, as these animals directly absorb water (and dissolved chemicals) through their skin and can become rapidly affected.
Further information on this topic can be found in Guideline A: controlling nuisance plants
Fact Sheets on weed control can be sourced on the Internet and also from local/state government organisations.

7. Special case: willows next > SPECIAL CASE EXAMPLE: WILLOWS
WHERE DID AUSTRALIAN WILLOWS COME FROM?
Willows were planted along Australian creeks and rivers for:
Aesthetic reasons
In an attempt to control erosion
As another source of drought time feed for livestock
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8. Special case: willows Willows blocking creek next >
SPECIAL CASE EXAMPLE: WILLOWS
PROBLEMS WITH WILLOWS
Photo: Willows blocking creek
They are prolific growers
They can root from sticks and branches which wash up on the river/stream banks or they can grow from seed
Can grow in the stream bed where they are often surrounded by water and can eventually block it
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9. Special case: willows Willows in channel next >
SPECIAL CASE EXAMPLE: WILLOWS
Photo: Willows in channel
Blocking of the channel can itself cause erosion as the water is forced against the banks
Increases possibility of flooding as the channel capacity is reduced
Willow presence restricts growth of native plant species, and therefore restricts the potential for habitat diversity
Do not contribute to the large woody debris (hence in stream habitat) of the stream/river
The restriction of leaf fall to autumn, means that there is a problematic excess of organic material in the water over this time
As leaf fall provides a foodsource for many instream species, there is little food available except during autumn
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10. Special case: willows Basket willow next >
SPECIAL CASE EXAMPLE: WILLOWS
IDENTIFICATION OF WILLOW SPECIES
There are over 100 willow species in Australia which have all been introduced
Proper identification of willows (type and sex) is required for control to be fully effective
Willows can be either male or female plants, and where the two exist together, seed set and dispersal are issues that also need to be considered
The important things to look at when identifying willows are the flowers, form, leaves, bark branches and roots. (You may need to refer to a published willow identification guide for your area or contact someone who is experienced at willow identification if you have plants you wish to identify)
Photo
: Basket willow (S. fragilis)
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11. Special case: willows Weeping willow next >
SPECIAL CASE EXAMPLE: WILLOWS
WHERE DID AUSTRALIAN WILLOWS COME FROM?
Photo 1
Willows were planted along Australian creeks and rivers for:
Aesthetic reasons
In an attempt to control erosion
As another source of drought time feed for livestock
PROBLEMS WITH WILLOWS
Photo 2: Willows blocking creek
They are prolific growers
They can root from sticks and branches which wash up on the river/stream banks or they can grow from seed
Can grow in the stream bed where they are often surrounded by water and can eventually block it
Photo 3: Willows in channel
Blocking of the channel can itself cause erosion as the water is forced against the banks
Increases possibility of flooding as the channel capacity is reduced
Willow presence restricts growth of native plant species, and therefore restricts the potential for habitat diversity
Do not contribute to the large woody debris (hence in stream habitat) of the stream/river
The restriction of leaf fall to autumn, means that there is a problematic excess of organic material in the water over this time
As leaf fall provides a foodsource for many instream species, there is little food available except during autumn
IDENTIFICATION OF WILLOW SPECIES
There are over 100 willow species in Australia which have all been introduced
Proper identification of willows (type and sex) is required for control to be fully effective
Willows can be either male or female plants, and where the two exist together, seed set and dispersal are issues that also need to be considered
The important things to look at when identifying willows are the flowers, form, leaves, bark branches and roots. (You may need to refer to a published willow identification guide for your area or contact someone who is experienced at willow identification if you have plants you wish to identify)
Photo 4: Basket willow (S. fragilis)
Photo 5: Weeping willows (S. babylonica)
CONTROL OF WILLOWS
Maintenance of willows that are to be kept:
Regular inspections of watercourses will assist with willow management because:
New seedlings can be easily removed
Sticks and branches that may root can be easily removed
Identification of species and the sexes of trees can be established to assist with prioritisation of plant removal
Annual lopping and removal of material will help to control retained trees
Removal of willows:
Where the willows are not important because of issues such as stream stability, their removal is recommended
Removal should occur in conjunction with native vegetation replacement
Planning of the removal process is critical
ALONG WATERCOURSES IN NSW, IT IS ILLEGAL TO REMOVE ANY VEGETATION WITHOUT A PERMIT – if you do not live in NSW CHECK the laws in your state before undertaking any such activity
If possible, do not remove the willow roots
It is better to kill the tree before removing it, as this prevents the live branches and twigs from falling into the water
Killing of the trees can be done organically, or with the aid of herbicide (contact your state government organisation responsible for river/riparian management for guidance on the recommended techniques for your area)
Photos 6 and 7: another set of BEFORE and AFTER willow removal images
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12. Special case: willows AFTER BEFORE < back next >
SPECIAL CASE EXAMPLE: WILLOWS
CONTROL OF WILLOWS
Maintenance of willows that are to be kept:
Regular inspections of watercourses will assist with willow management because:
New seedlings can be easily removed
Sticks and branches that may root can be easily removed
Identification of species and the sexes of trees can be established to assist with prioritisation of plant removal
Annual lopping and removal of material will help to control retained trees
Removal of willows:
Where the willows are not important because of issues such as stream stability, their removal is recommended
Removal should occur in conjunction with native vegetation replacement
Planning of the removal process is critical
ALONG WATERCOURSES IN NSW, IT IS ILLEGAL TO REMOVE ANY VEGETATION WITHOUT A PERMIT – if you do not live in NSW CHECK the laws in your state before undertaking any such activity
If possible, do not remove the willow roots
It is better to kill the tree before removing it, as this prevents the live branches and twigs from falling into the water
Killing of the trees can be done organically, or with the aid of herbicide (contact your state government organisation responsible for river/riparian management for guidance on the recommended techniques for your area)
Photos: BEFORE and AFTER willow removal images

13. Discussion point
Landuse changes as one progresses from upstream towards the mouth of a river.
Why would this be, and how is it likely to affect the stream/river?
DISCUSSION POINT: REASONS FOR DEGRADED WATERWAYS AND THE IMPACT ON NATIVE FLORA AND FAUNA
(NOTE: discussion points provide a break for students and teachers, but should not exceed 15 minutes in length, as the topics are returned to in greater detail through the course).
The aim of this discussion point is to get the students to start thinking about the major issues of riparian restoration. Particular emphasis should be on the reasons for the poor condition of the sites – possibly as a result of either (1) inappropriate management (the landholder has attempted to manage the riparian area well, but failed) or (2) the most common cause of the problem – the manager has DELIBERATELY CHOSEN not to implement best practice riparian management.
Get the students to also start thinking about the implications of the degraded riparian areas on wildlife and native plant populations. This is the next area that will be focussed on in this session.
end session

14. end of session END OF SESSION
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