Title: Piptochaetium montevidense (Spreng.) Parodi

Scientific Name:

Piptochaetium montevidense (Spreng.) Parodi

Common Names:

Uruguayan rice grass



Image via GBIF

Habitat:

Temperate and subhumid climates. Prefers dry ground and will grow in crops, roads, streambanks, urban areas and natural environments such as grassy woodlands and lowland grasslands. (CRC for Australian Weed Management 2003)

Distribution:



Invasiveness Assessment

ESTABLISHMENT


1. Germination requirements? This species was successfully germinated in the temperate greenhouse at the Botanic Garden of the Institute of Botany in Graz (Austria, Europe), giving a “vague” impression of the conditions under which it was grown (Teppner, 2002). Not enough information was found to indicate germination requirements.

2. Establishment requirements? Observed as a dominant understorey species below Serrated tussock and Chilean needle grass in Argentina (David Maclaren, pers. comm.). Can establish under moderate canopy cover.

3. How much disturbance is required? Disturbed grassland…it can also invade relatively undisturbed vegetation (CRC Weed Management, 2003b). A weed of crops, natural areas, roadsides and urban areas (Cunningham et al, 2003).

GROWTH / COMPETITIVE


4. Life form? Perennial stipoid grass (Cunningham et al, 1993).

5. Allelopathic properties? No evidence found. There is little information available about this species, so a medium value was chosen.

6. Tolerates herb pressure? Resistant to grazing (CRC Weed Management, 2003a; Cunningham et al, 2003). Recorded as growing in a region of Brazil that has been grazed for the last 30 years by cattle, sheep and occasionally by horses (Maia et al, 2004). Unpalatable (David Maclaren, pers. comm.).

7. Normal growth rate? As an understorey to Nasella spp. in Argentina (David Maclaren, pers. comm.), indicates that it doesn’t grow as vigorously as these grasses, but no further information about its growth rate has been found.

8. Stress tolerance to frost, drought, w/logg, sal. etc? Burning stimulates development (Heringer & Jacques, 2002). Maia et al (2004) found this plant associated with less wet habitats and uplands and intermediate sites. Focht & Pillar (2003) found the plant growing mainly in the dryer slopes (moist only after rain) of a Brazilian grassland site, but it still appeared in almost 40% of the wet lowland areas that were almost always moist (although at half the abundance of the drier sites). This is a major species from the Salado River Basin, an area that is subject to frequent flooding and severe summer droughts (Sala et al., 1981). In Victoria, Australia it was growing at Cherry Lake, near Altona (Cunningham et al, 1993), a site that is 400 m from the saline Port Phillip Bay. A specimen of this plant was collected from 3,400 m up Chimborazo in Ecuador (Anon, 2005) at elevations that reach freezing in the Andes (Neill, 1999). The types of environments in which it is found suggests that P. montevidense is tolerant of drought, frost, salinity and waterlogging, and it appears to be tolerant of fire. It may not be susceptible to any of these stressors.

REPRODUCTION


9. Reproductive system? Plants are bisexual with bisexual spikelets and hermaphrodite florets (Cunningham et al, 2003). No evidence of vegetative reproduction was found.

10. Number of propagules produced? Produces many seeds. Although the exact volume or seed produced is unknown (CRC Weed Management, 2003a).

11. Propagule longevity? No information found.

12. Reproductive period? Dense sward (Cunningham et al, 2003), but this is not necessarily a monoculture. No further information was found.

13. Time to reproductive maturity? Germinates Spring and Autumn, flowers Sept-Dec, seeds form in Dec & dropped by early Autumn (CRC Weed Management, 2003b). Reaches reproductive maturity in under one year.

DISPERSAL


14. Number of mechanisms? Dispersed by wind and also by browsing animals ingesting the plant and excreting the viable seed elsewhere…anectodal evidence suggests that seeds are not carried or dispersed externally by stock (CRC Weed Management, 2003b).

15. How far do they disperse? Animals digesting the seed have the potential to transport them several kilometres.


Impact Assessment

RECREATION


1. Restrict human access? “Forms dense tussocks to about 0.5 m high” (CRC Weed Management, 2003), which would not restrict human access.

2. Reduce tourism? “Can be difficult to identify because of its similarity to native grasses and Austrostipa species” (CRC Weed Management, 2003). This weed would not be obvious to the average visitor.

3. Injurious to people?"The leaf blade is hairless but covered with minute rough protections” (CRC Weed Management, 2003), although these are not noted as sharp and so not likely to cause injury.

4. Damage to cultural sites? See Q. 2, as a “native-looking” grass, this species would not detract from cultural sites, nor damage structures.

ABIOTIC


5. Impact flow? Terrestrial species. Whilst this plant does invade streambanks (CRC Weed Management, 2003), the only documented occurrence in wet environments was in seasonally flooded, or “always” moist areas, rather than permanent waterways. This makes it unlikely to impact on water flow.

6. Impact water quality? See Q. 5, unlikely to impact on water quality.

7. Increase soil erosion? Predominantly a weed of crops. As “a perennial that forms tussocks” (CRC Weed Management, 2003), this plant should not increase erosion as it would not cause patches of exposed bare soil as dormant or annual species might.

8. Reduce biomass? Similar habit to the dominant kangaroo grass (Themeda triandra) that it was found invading near Altona (CRC Weed Management, 2003; Albrecht et al. (eds), 1991). Likely to replace tussock biomass in the grassland communities that it invades.

9. Change fire regime? As it is similar in habit to the vegetation that it displaces (see Q. 8) and “stimulated by fire” (CRC Weed Management, 2003) this plant is unlikely to change the fire regime in the communities that it invades.

COMMUNITY HABITAT


10(a) Impact on composition of high value EVC? EVC= Plain grassy woodland (E); CMA=Corangamite; Bioreg= Victorian Volcanic Plain; CLIMATE potential=VH. Formed a “dense sward” (Cunningham et al, 2003) where it invaded grassland in Victoria. Major displacement of some dominant species in the groundcover layer.

10(b) Impact on medium value EVC? EVC= Lowland Forest (D); CMA=Corangamite; Bioreg= Otway Plain; CLIMATE potential=VH. Formed a “dense sward” (Cunningham et al, 2003) where it invaded grassland in Victoria, however the forest canopy would be likely to reduce its density. Minor displacement of some dominant species in the groundcover layer.

10(c) Impact on low value EVC? EVC= Lowland Forest (LC); CMA=Glenelg Hopkins; Bioreg= Warrnambool Plain; CLIMATE potential=VH. Formed a “dense sward” (Cunningham et al, 2003) where it invaded grassland in Victoria, however the forest canopy would be likely to reduce its density. Minor displacement of some dominant species in the groundcover layer.

11. Impact on structure? Formed a “dense sward” (Cunningham et al, 2003) where it invaded grassland in Victoria. It has the potential to have a major impact on ground flora. Its ability to affect the germination of flora from other strata is not known.

12. Effect on threatened flora? No Information found.

FAUNA


13. Effect on threatened fauna? No Information found.

14. Effect on non-threatened fauna? Has the potential to reduce the availability of ground flora as fodder (see Q. 11.) and is “resistant to grazing” so could reduce food sources where it invades, forcing some species to forage elsewhere.

15. Benefits fauna? See Q.14- would provide little food for desirable species.

16. Injurious to fauna? Despite its resemblance and close association to Chilean needle grass, the seeds on this grass are not sharp and barbed (see illustration CRC Weed Management, 2003). Not noted for toxicity.

PEST ANIMAL


17. Food source to pests? “Resistant to grazing” (CRC Weed Management, 2003) so not likely to provide a significant food source to pests.

18. Provides harbor? As a perennial that “forms dense tussocks to about 0.5 m high,” (CRC Weed Management, 2003) this grass may provide harbour for entrances to rabbit warrens.

AGRICULTURE


19. Impact yield? In Argentina this plant is a dominant understorey to Chilean needle grass and serrated tussock (David Maclaren, pers. comm.) indicating that it has the potential to form a significant component of invaded grassland. As a grassland invader that is resistant to grazing (CRC Weed Management, 2003), this tussock may displace stock fodder, reducing the carrying capacity of the land. The degree of impact is unknown, so a medium value was chosen.

20. Impact quality? Despite its resemblance and close association to Chilean needle grass, the seeds on this grass are not sharp and barbed (see illustration CRC Weed Management, 2003), so it doesn’t pose a meat contamination risk. The plant “will grow in crops” (CRC Weed Management, 2003) however, which may impact quality, however, again the degree of impact is unknown, so a medium value was chosen.

21. Affect land values? Effect on land value will depend on level of infestation and ease of control, both of which are unknowns for this species.

22. Change land use? Change in land use may occur if the carrying capacity of pasture is significantly reduced or if crop quality is too badly affected. Without any indication of the potential degree of impact, a medium value was chosen.

23. Increase harvest costs? Harvest costs may be increased if a large degree of weed control is necessary.

24. Disease host/vector? Not known as a disease host or vector, however there is not much information about this species.




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Assessment ratings originally made by the Victorian Department of Primary Industries.
The entry of this assessment was made possible through the generous support of an anonymous donor.




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Date: 18 April 2023; 2:54:29 PM AEST

Author Name: David Low
Author ID: adminDavid