Invasiveness Assessment - Desert ash (Fraxinus angustifolia) in Victoria

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Desert ash.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
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Common Name: Desert ash
Scientific name: Fraxinus angustifolia

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	Seeds have a seasonal requirement for germination; it has been found that this species seeds germinate best during a period of fluctuating temperatures after a period of cold stratification such as early spring (Piotto & Piccini 1998). Mass germination occurs in spring (Blood 2001).	MH	H
Establishment requirements?	Seedlings prefer an area free of other vigorously growing ground flora and are unlikely to establish in dense shade (Muyt 2001). The species is however reported by Carr et al (1992) to invade grassy woodland and is therefore considered capable of establishing under a moderate canopy or litter cover.	MH	MH
How much disturbance is required?	The species may have a preference for disturbed sites however it has been described as having the potential to invade riparian vegetation in the Victorian high country (Muyt 2001; Richardson, Richardson & Shepherd 2006). Therefore the species is considered to be able to invade relatively intact ecosystems.	MH	MH
Growth/Competitive
Life form?	Other; a deciduous tree species able to grow to 20 m (Debussche & Lepart 1992).	L	H
Allelopathic properties?	Although there has been no evidence for this species reported, other species in the genus have been reported to have allelopathic properties (Rice 1984).	M	L
Tolerates herb pressure?	Trees cut down by beavers have regrown from the stump (Fustec et al 2001). The growth and form of seedlings exposed to heavy animal browsing was improved through a stumping technique (Çiçek & Tilki 2007). The species can therefore tolerate extreme biomass reduction events and is considered therefore to be capable to withstand moderate browsing pressure.	MH	MH
Normal growth rate?	The species is reported to have a very high growth rate (Carus & Çiçek 2007).	H	H
Stress tolerance to frost, drought, w/logg, sal. etc?	Frost can damage seedlings (Çiçek & Tilki 2007). Being deciduous the species may be able to withstand below zero winter temperatures but is however considered frost tender (Blood 2001). The species is considered one of the more drought resistant Fraxinus sp. however it is also reported to be drought tender (Blood 2001; Percival, Keary & Al-Habsi 2006). Waterlogging; The species can tolerate periodic inundation (Muyt 2001). The species tolerance to fire is not reported, however its ability to recover after being logged by beavers shows potential for recovery even if the above ground biomass is killed (Fustec et al 2001).	ML	MH
Reproduction
Reproductive system	The species reproduces sexually by producing seed and vegetatively through suckering (Blood 2001).	H	MH
Number of propagules produced?	The species is reported to be capable of producing thousands of seeds annually (Muyt 2001).	H	MH
Propagule longevity?	Unknown, the seeds are able to become dormant (Piotto 1997).	M	L
Reproductive period?	Can form monocultures (Muyt 2001). The plantation rotation time for this species is reported to be 40 years (Çiçek & Tilki 2007).	H	H
Time to reproductive maturity?	Unknown; however the species is described as very fast growing, therefore it is possibly not long,	M	L
Dispersal
Number of mechanisms?	Seeds are dispersed by wind and water (Debussche & Lepart 1992).	MH	H
How far do they disperse?	Seeds spread by water can be dispersed a number of kilometres (Debussche & Lepart 1992).	H	H

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