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Recovery Strategy : Forked Three-awned Grass (Aristida basiramea) au Canada
1. Species Information
Common Name: Forked Three-awned Grass
Scientific Name: Aristida basiramea
COSEWIC Status: Endangered
Reason for Designation: Few disjunct and fragmented populations found in very small habitats within populated areas subject to further habitat disruption and loss through activities such as sand extraction, recreational use and urban development.
Canadian Occurrence: Ontario and Québec
COSEWIC Status history: Designated Endangered in November 2002. Assessment based on a new status report.
1.1.1 Secies Information
Forked Three-awned Grass, or Ice Age Grass (Aristida basiramea) is an annual grass that grows in tufts. It has extremely narrow leaves (1 mm wide) which often have the margins curled inward, and wiry stems which reach 30-60 cm in height. Plants branch at the base and only sparingly above. The inflorescence is 10-20 cm long, borne at the end of erect stems. The glumes (two tiny bracts around at the base of the spikelets) each have a single vein and are unequal in length with the second being the longer. One of the bracts (i.e. lemma) subtending individual fruits has three awns: two relatively short lateral ones which are erect, and a longer middle awn which is coiled at the base and which sticks out at a divergent angle (Gleason and Cronquist, 1991). The species is late-developing, with flowering and fruit-set occurring from late August through October (COSEWIC, 2002).
1.1.2 Global Distribution and CanadianRange
The disjunct distribution of Canadian populations of A. basiramea is believed to be a relict of past climates. There is also the suggestion that the distribution of the species may be associated with the migration of Aboriginal peoples. The core range of the species is in the Midwestern United States, and less than 1% of the global population of A. basiramea occurs in Canada (Figure 1). The species has never been known to be more common in Canada. Only five sites have been discovered in Southern Ontario and Southern Québec since 1975.
A. basiramea is currently known from five naturally occurring sites: one in southwestern Québec and four others in Ontario in the southern Georgian Bay area (Table 1). A population discovered in 2001 in the Rainy River District of Ontario (COSEWIC 2002), believed to be introduced in gravel brought in to repave the road, did not persist (Wasyl Bakowsky, pers. comm. 2005, 2006), and no typical natural habitat is present in the environs (Michael Oldham, pers. comm., 2005).
The species currently has the following conservation rankings:
- G5 globally (NatureServe 2005).
- N4 in the United States (NatureServe 2005)
- N1 in Canada (NatureServe 2005)
- S1 in Ontario (Oldham 1999)
- S1 Québec (NatureServe 2005; Barbeau and Brisson, 2004)
It has been designated as “Endangered (not regulated)” on the Species at Risk in Ontario list, and is recommended for designation as "menacée" (threatened), the highest level of concern under Québec provincial legislation.
Figure 1. Global range of A. basiramea (from COSEWIC, 2002)
1.1.3 Population Size and Trend
As of fall 2005, the total number of plants in Canada is estimated to be in excess of 100,000, likely between 150,000 and 300,000. Most of the population occurs at only four sites and total occupancy (all sites) is about 20 km2 (Table 1, COSEWIC, 2002, Jones 2005). The largest population is that at Christian Island, where it was documented in 2005 as occurring in 15 sub-populations totaling over 100,000 individuals (Jones 2005). Because the majority of sites have only been known since 2001, it is not yet possible to determine if change is occurring in population size or geographical distribution. Also, because the species is an annual, the size of its populations have large yearly fluctuations.
|Site name (Province)||Land ownership||Number of subpopulations and area of occupancy1||Total number of plants (2005)2|
|Anten Mills (Ontario)||Privately owned by 2 or 3 owners, but one subpopulation under a conservation easement since 2004||1 population in 4 patches in 2002; not known how many still remain||< 100|
|Beausoleil Island (Ontario)||Georgian Bay Islands National Park||1 population; area of occupancy 100 x 50 m.||> 1500|
|Macey Lake (Ontario)||Privately owned by more than one owner; part is designated a provincial area of natural and scientific interest (ANSI)|
total area unknown
|Cazaville (Québec)||Privately owned by many owners; two lots in municipal control||6 subpopulations within 15 km2||> 10,000|
|Christian Island (Ontario)||Beausoleil First Nation: community-owned land, as well as Certificate of Possession lands||At least 15 subpopulations within about 4 km2||> 100,000|
1A subpopulation at Cazaville is equivalent to an element occurrence (EO) (See Barbeau and Brisson (2004) for a definition), while those at other sites aggregate to form one EO at each.
2 Numbers in COSEWIC (2002) were updated in 2005.
N1--Critically imperiled at the national level; N4--uncommon to locally common apparently secure nationally; S1--Critically imperiled at the provincial level; G5--stable, not at risk. See NHIC, 2005 for details.
1.1.4 Biologically Limiting Factors
A. basiramea is a very late-maturing annual, flowering in late August-September and setting fruit in September-October. It has been suggested that reproduction is naturally limited by the arrival of the end of the growing season, and that this climatic factor may also determine how far north the species is able to grow (COSEWIC, 2002). It has been speculated that climate is a limiting factor for A. basiramea in Québec since there is some suitable habitat north of the existing population of Cazaville (Line Couillard, pers. comm. 2005). Interference with the ecological processes required by the species to maintain populations or to colonize new areas may also be limiting factors. Availability of suitable habitat is considered the number one limiting factor for this species in Canada. See next section as well as 1.1.9 Threats.
1.1.5 Habitat Requirements
A. basiramea requires areas of sandy, open ground. It appears to be highly intolerant of shading and competition from other plants (COSEWIC, 2002). Barbeau and Brisson (2004) report that the species prefers areas where there is an average of 33% bare ground, and little other woody or herbaceous vegetation in the immediate surroundings. The species is found in open sand barrens, sandy forest openings and sandy fallow fields, as well as on the sandy edges of roads and trails. The pH of the substrate is presumably acidic.
All five of the Canadian sites with A. basiramea are on sand barrens on relict post-glacial shorelines or dunes. Barbeau and Brisson (2004) infer that the Cazaville area was originally a woodland of white pine (Pinus strobus) where a fire regime kept patches of ground in an open state, up until colonization ,when the white pines were cut and the area cleared.
In Michigan the species is known from dry, open sandy ground (Voss, 1972), specifically sandy open areas in oak woodlands or oak barrens (Penskar, pers. com. 2005). In the Great Plains region it is reported from “roadsides, pastures and waste ground” (McGregor, et al., 1986). These differing reports show a presence in both natural habitats and habitats altered by human use.
Natural disturbance processes are important for this species. Ecological processes that maintain sandy habitat in an open, barren state are considered habitat requirements. Fire may be required to create and maintain open, barren ground to sustain A. basiramea at some of the sites. For example, Beausoleil First Nation has conducted annual prescribed burns for years at one of their main sub-populations, as part of the maintenance of a baseball field. This low-intensity burning has successfully maintained a high quality sand barren in which A. basiramea thrives. At Georgian Bay Islands National Park there has been a historic role of fire in the ecosystem, but that role is not clearly understood yet (Quenneville, pers. comm. 2006). Drought and wind-throw of trees may also be naturally-occurring processes which help maintain open ground. Shoreline processes such as ice scours and changing lake levels may also play the same role.
Many sites on Christian Island where A. basiramea now grows were once ploughed fields. Whether or not a similar disturbance today would be able to create suitable habitat is unknown, as other species have been introduced that may preventA. basiramea from early colonization of newly disturbed ground.
Historically, A. basiramea's habitat may not necessarily have been maintained at any one spot by fire or other disturbances, but rather was maintained by being present within the overall landscape. Suitable habitat is an early successional vegetation type which once grew on naturally disturbed sites, colonizing when there was disturbance, gradually disappearing with the filling in of vegetation, and then reappearing somewhere else in the landscape after a new disturbance. This kind of regime has been documented for bur oak savanna on Manitoulin Island, Ontario (Jones, 2000). Since we may no longer have the natural dynamics that created suitable habitat on a landscape scale, recovery must look at maintaining the habitat that currently exists.
1.1.6 Residence Description
Damaging or destroying the location of individual plants ofA. basiramea will automatically damage or destroy the individuals, so there is no need for a description of residence for this species to enforce the general prohibitions of the Species at Risk Act.
1.1.7 Ecological Roles
The ecological role of the species has not been studied. Allred (2001) reports that quail and small mammals eat small amounts of the seed. Presumably A. basiramea could provide late season food or cover for insects preparing to over winter. As well, it may have some role in colonization or stabilization of dry, open substrates of coarse texture.
1.1.8 Importance to People
A. basiramea occurs at two locations where people of Beausoleil First Nation have lived (Christian and Beausoleil Islands). The possibility of a cultural link should be investigated as it may shed light on the origin or maintenance of key populations of the species in Canada. In addition,Aristida basiramea occurs at several sites of cultural significance to Beausoleil First Nation.
A. basiramea is not known to have any economic significance.
Habitat availability is considered the most important limiting factor for the species in Ontario. Nearly all threats to A. basiramea (Table 2) are threats to habitat, and with only five known sites, any habitat loss is extremely serious.
In addition to the threats to habitat described below, it is not known whether global climate change would affect this species. A. basiramea grows in high light and heat conditions, in dry substrate, with lots of exposure. As well, other species present in the habitat (especially Danthonia spicata) are similarly adapted. Therefore, it is difficult to speculate whether climate change would hinder or help A. basiramea until more is known about future conditions.
|Threat||Anten Mills||Beausoleil Island||Cazaville||ChristianIsland||Macey Lake|
|Succession & absence of ecological processes||High||Low||Low||Low||Medium|
|Planting of conifers||High||None||Low||Low||None|
Sources: Jones 2005, Barbeau and Brisson 2004, COSEWIC, 2002; and personal observations of Recovery Team members.
There is very little habitat currently available which fulfills the open, barren, sandy requirements of the species in Ontario. Sand barren vegetation communities in Ontario are critically imperiled and ranked S1 or S2 by Ontario’s Natural Heritage Information Centre (NHIC) (Bakowsky, 1996). In Québec, the Cazaville site is the only large sand opening in Southwestern Québec (Barbeau and Brisson, 2004). Further loss of suitable open sandy habitat continues to occur through fire suppression, changing shoreline processes, succession, and several other threats, explained below.
Open sandy areas are often suitable places for commercial extraction of sand. Sand extraction destroys both habitat and plants, although the disturbed open ground created by the process can be suitable habitat for the species after the fact (COSEWIC, 2002). Sand extraction is currently occurring at two of six Cazaville subpopulations (Barbeau and Brisson, 2004).
Successional Changes and Absence of Ecological Processes
Plant succession and eventual formation of forest canopy causes naturally open areas to become unsuitable for the species. The habitat of A. basiramea would normally be only early successional vegetation, although open habitat can be maintained for many years by fire, drought, shoreline processes such as ice scours and changing lake levels, or other natural disturbance. In the absence of these ecological processes, habitat becomes too densely vegetated and unsuitable. Successional changes are visible at all sites.
While some human disturbance has proved beneficial to the species by creating new open substrate, development damages and destroys habitat. Building and driveway construction eliminate open ground. Landscaping may cover barren patches and introduce invasive species. Human occupation of sandy areas also results in an increased need for fire suppression. Subdivision development (2003-2004) caused the loss of the majority of the Anten Mills population. Subdivision development may threaten other recovery habitat in the Simcoe County, Ontario area due to the rapid expansion of the nearby communities of Barrie and Wasaga Beach. Residential construction may threaten one subpopulation at the Macey Lake site. Results from a recent survey of the species on Christian Island (Jones 2005) indicate a moderate level of threat to the species from development or associated activities, especially where A. basiramea occurs in open spaces in and adjacent to the village.
Planting of Conifers
Since the 1920s many programs have sought to stabilize soils that are highly susceptible to wind erosion and improve barren ground. Plantations of conifers, ultimately becoming closed canopy stands, have eliminated previously suitable habitat at Anten Mills and at Cazaville (occurrence #2). Efforts to plant conifers continue to be a threat at Cazaville while at Anten Mills the continuing growth and closing-in of the forest canopy is further reducing the amount of open ground (COSEWIC 2002; Barbeau and Brisson, 2004).
Several invasive species have been reported in the habitat ofA. basiramea including:
- Glossy Buckthorn (Rhamnus frangula)
- Scot’s Pine (Pinus sylvestris)
- Spotted Knapweed (Centaurea maculosa)
- White Sweet Clover (Melilotus alba)
- Mouse-Ear Hawkweed (Hieracium pilosella)
- Sheep Sorrel (Rumex acetosella)
These species have the potential to quickly take over and vegetate the open ground that A. basiramea requires. Scot’s Pine in particular was noted to be spreading quickly at the Macey Lake and Anten Mills sites (COSEWIC, 2002). Spotted Knapweed is a dominant now on the periphery of the Macey Lake population (Gary Allen, pers. comm. 2005) and White Sweet Clover is spreading on Christian Island (Gary Allen, pers. comm. 2005). Mouse-ear hawkweed blankets the ground in open spaces between grass tufts (prime spots for A. basiramea growth), destroying the suitability of much habitat on Christian Island (Jones, 2005). Based on current knowledge, the threat of invasive species may be a key issue in habitat suitability. Studying the use of burning and other tools to mitigate the effects of invasive species on A. basiramea will be addressed in Action Plans.
All Terrain Vehicle (ATV) Use
Light use of ATVs may keep sandy habitats open and provide suitable habitat for the species; however, ATVs also trample plants and damage vegetation. At Cazaville, four out of six subpopulations have ATV trails through them. The increase in use and the number people riding off-trail threatens both plants and their habitats. (Barbeau and Brisson, 2004). The degree of ATV use at other sites is not known.
Most of the Cazaville site is surrounded by agricultural operations, and some of the Cazaville subpopulations are on fallow fields, testimony to agricultural use in the past. An area of formerly suitable habitat was leveled and worked up in 2003 for planting in 2004 (Barbeau and Brisson, 2004). The area of one of the main populations at Christian Island was used both for crops and pasture in the past. None of the known A. basirameasites is currently used as pasture, however, grazing by livestock sometimes causes introduction of weeds, reductions of native species presence, and is considered a threat to other naturally open habitats (Jones and Jalava, 2005; Reschke et al. 1999). Although some protection for the Macey Lake site is given in the Tiny Township Official Plan, agricultural use is not excluded (The Planning Partnership, 2000).
Dumping of Garbage
Natural barren lands often carry the misconception that they are waste land where indiscriminate usage does not matter. People do not see sand barrens as having the same beauty as a forest. This misconception can spur human-caused damage and destruction. In particular, barren grounds often become places for clandestine dumping of garbage.
1.1.10 Knowledge Gaps
- Recent discoveries of the species in the vicinity of Awenda Provincial Park (Fall 2005) are sub-populations of the Macey Lake site. However, these discoveries suggest there may be other sites in the Southern Georgian Bay area of Ontario, especially on other sandy islands and small sandy patches occurring randomly in the landscape. In spite of the fact that the region has historically been relatively well botanized, the species develops late in the growing season and does not fruit until late September, a time when comparatively less botanical work happens. A survey needs to be conducted for A. basiramea, in suitable habitat, at the time when it is most easily detected.
- Little is known about the species’ population dynamics, trends and viability, particularly the role of the soil seed bank. Several sites were only discovered in 2001, and most populations have not been re-surveyed since that time, so new data needs to be collected. This will be addressed by a monitoring program.
- There is a need for better understanding of ecological processes involved in maintaining habitat availability for the species. What is needed to maintain good quality habitat? Is controlled burning needed? What is the fire history and what were natural fire cycles like at these sites? Will other, more mechanical (anthropogenic) methods of clearing ground be sufficient? Monitoring the removal and reintroduction site at Christian Island will only begin to fill this knowledge gap.
- Is there traditional Native knowledge or history about this species? It could be important to know if there is a link between Native land use (historical and current) and the current distribution of A. basiramea, because it may show how the species came to be where it is, as well as whether some land use practices are beneficial to maintenance of the species.
- Date Modified: