Crooked-stem Aster (Symphyotrichum prenanthoides) : management plan 2018, proposed

Official title: Management Plan for the Crooked-stem Aster (Symphyotrichum prenanthoides) in Canada 2018 [proposed]

Species at Risk Act
Management plan series

Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996) agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of management plans for listed species of special concern and are required to report on progress within five years after the publication of the final document on the SAR Public Registry.

The Minister of Environment and Climate Change is the competent minister under SARA for the Crooked-stem Aster and has prepared this management plan, as per section 65 of SARA. To the extent possible, it has been prepared in cooperation with the Province of Ontario (Ontario Ministry of Natural Resources and Forestry), as per section 66(1) of SARA.

Success in the conservation of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this plan and will not be achieved by Environment and Climate Change Canada and Climate Change or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this plan for the benefit of the Crooked-stem Aster and Canadian society as a whole.

Implementation of this management plan is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

Acknowledgments

The initial draft of this management plan was completed by Judith Jones (Winter Spider Eco-Consulting). Subsequent drafts were developed by Elisabeth Shapiro (Environment and Climate Change Canada, Canadian Wildlife Service - Ontario (ECCC)) and Lauren Strybos (Formerly ECCC, Canadian Wildlife Service - Ontario). An earlier recovery strategy for this species was prepared by Jarmo Jalava in consultation with the Carolinian Woodlands Technical Committee. The following people are gratefully acknowledged for sharing information on this species: David J. Bradley and Eric Snyder (Ontario Ministry of Natural Resources and Forestry (OMNRF), Ron Gould (Ontario Parks), Allan Harris (Northern Bioscience), David Holmes (Long Point Region Conservation Authority), Daria Koscinski (Thames Talbot Land Trust), Will Van Hemessen (Private Consultant) and Mary Gartshore (Consulting Ecologist). This federal management plan benefited from input, review and suggestions from the following individuals and organizations: Justine Mannion, Marie-Claude Archambault, Burke Korol, Smeet Panchal, Christina Rohe, Judith Girard, Ken Corcoran, Krista Holmes and Elizabeth Rezek (ECCC - Canadian Wildlife Service - Ontario) and reviewers from the Ontario Ministry of Natural Resources and Forestry (OMNRF).

Acknowledgement and thanks are given to all other parties that provided advice and input used to help inform the development of this management plan. Those parties include various Indigenous organizations and individuals, landowners, citizens, and stakeholders who provided input and/or participated in consultation meetings.

Executive summary

Crooked-stem Aster (Symphyotrichum prenanthoides) is listed as a species of Special Concern under Schedule 1 of the Species at Risk Act (SARA) and under the Ontario Endangered Species Act 2007. In Canada, the Crooked-stem Aster is restricted to a small area of Carolinian forest near the shore of Lake Erie in southwestern Ontario. Crooked-stem Aster was initially designated as Special Concern by COSEWIC in 1999; however, the quantitative criteria currently used to define each risk category (endangered, threatened, etc.) were not applied until 2002. The application of these criteria resulted in the Crooked-stem Aster being uplisted to Threatened, based on the presumption that there were fewer than 1,000 mature individuals occurring in a small geographic area (COSEWIC 2002). However, Crooked-stem Aster is now known to have more than 1,000 mature individuals and ten new sites have been discovered, thus Crooked-stem Aster has been downlisted to Special Concern. NatureServe ranks this species as Globally Secure to Apparently Secure (G4G5), Nationally Imperiled in Canada (N2), and Imperiled in Ontario (S2). In Canada, Crooked-stem Aster is found in southwestern Ontario in Elgin County (18 populations), Norfolk County (two populations) and Middlesex County (two populations). Another nine populations are considered historical in occurrence with their current status unknown, and three are considered extirpated. As Crooked-stem Aster is a long-lived perennial plant, it is possible that the species may still be present at some historical sites.

Crooked-stem Aster is a long-lived perennial herb with flexuous (zig-zagging) stems and pale blue ray florets. The species grows in colonies of upright stems arising from creeping rhizomes^{Footnote 1}. Crooked-stem Aster has toothed leaves that vary from oval to lance-shaped and the bases of the upper leaves clasp the stem. Flowering occurs from late August through to early October.

A number of biological traits affect the needs of Crooked-stem Aster including its growth form as colonies of stems, need for cross pollination by insects, seed dispersal by wind, and tolerance for moderate disturbance. Crooked-stem Aster occurs in a wide range of habitats, including floodplains of creeks flowing into Lake Erie, at the edge of woods, along creek banks through riparian forest, in damp thickets, and on some roadsides. The species is commonly found in partial to full shade and requires wet to moist soil moisture regimes. Suitable habitat may be dynamic since floodplains are subject to periodic natural disturbance from inundation and fast currents.

The major threats to Crooked-stem Aster include habitat loss from invasive/non-native alien species which occur at most of its sites, roadwork that uses herbicide or involves large machinery for major reconstruction, and trampling from inappropriate ATV use and off-trail hiking. Residential development, livestock grazing, and logging are occasional or localized threats. Browsing by White-tailed Deer and a lack of pollinators may also be potential threats.

The management objective is to maintain or increase the distribution and abundance of all populations in Ontario, including any newly discovered populations, if biologically and technically feasible.

Broad strategies and conservation measures to meet this objective are presented in this management plan. Filling knowledge gaps regarding populations with unknown status, controlling inappropriate ATV use, partnering with organizations to protect habitat, and working with municipal and county agencies on other threats, are all high priority conservation measures.

1 Committee on the Status of Endangered Wildlife in Canada species assessment information

Date of assessment: November 2012

Common name (population): Crooked-stem Aster

Scientific name: Symphyotrichum prenanthoides

COSEWIC status: Special Concern

Reason for designation: This perennial aster is restricted in Canada to a small area of the Carolinian forest near the shore of Lake Erie in Ontario. The species has experienced historic declines, but no recent losses have been documented and overall numbers appear to be stable. Invasive plants occur at a number of sites and have the potential to negatively impact the species in the future. Additional threats include indirect impacts of Emerald Ash Borer, and roadside maintenance. The species has a restricted distribution in Canada, and its persistence will likely require ongoing monitoring and management of invasive species.

Canadian Occurrence: Ontario

COSEWIC Status History: Designated Special Concern in April 1999. Status re-examined and designated Threatened in May 2002. Status re-examined and designated Special Concern in November 2012.

In 1999, when Crooked-stem Aster (Symphyotrichum prenanthoides) was first designated Special Concern by COSEWIC, the quantitative criteria to define each risk category (endangered, threatened, etc.) had not yet been developed (Bennett pers. comm. 2015). When the first set of quantitative criteria were applied in 2002, Crooked-stem Aster was uplisted to Threatened based on the presumption that there were fewer than 1,000 mature individuals occurring in a small geographic area (COSEWIC 2002). However, the species is now known to have more than 1,000 mature individuals, and 10 new sites have been discovered (three in 2007, one in 2012, one in 2016 and five in 2017) (COSEWIC 2012; Gould pers. comm. 2016; Gartshore pers. comm. 2017; Koscinski pers. comm. 2017 and Van Hemessen pers. comm. 2017). It no longer meets COSEWIC's criteria for a Threatened species and has been re-designated to Special Concern (COSEWIC 2015).

2 Species status information

In Canada, Crooked-stem Aster is listed as Special Concern^{Footnote 2} on Schedule 1 of the federal Species at Risk Act (SARA). In Ontario, Crooked-stem Aster is listed as Special Concern^{Footnote 3} under Ontario’s Endangered Species Act, 2007 (ESA).

The global conservation rank for Crooked-stem Aster is currently Secure to Apparently Secure^{Footnote 4} (G4G5) (NatureServe 2017). It is nationally ranked as Imperiled^{Footnote 5} in Canada (N2), and sub-nationally ranked as Imperiled in Ontario (S2) (NHIC 2015a). According to NatureServe (2017), the species occurs in 21 states, and is ranked S1 to S3 in six states, possibly extirpated (SH) in one, and not ranked (SNR) or status unknown (SU) in nine others  (COSEWIC 2012; Appendix A).

3 Species information

3.1 Species description

Crooked-stem Aster is a perennial herb that forms colonies from rhizomes. The upright stems (20 to 90 cm tall) are usually bent at the nodes^{Footnote 6}, especially in the upper part of the stem, hence the common name for this species. The upper stem leaves are lance-shaped with sharply toothed edges and clasping leaf bases, which lack petioles (a stalk that joins leaf to stem) (Figure 1). The lower stem leaves usually fall off before flowering time (Semple et al. 2002; Brouillet et al. 2006).

Crooked-stem Aster blooms between late August and early October (COSEWIC 2012).
As with all species in the aster family, what appears to be a flower is actually a head of many tiny flowers of two types: ray florets that appear as flat petals around the outside of the head, and tubular disc florets that make up the centre of the head. In Crooked-stem Aster each head may have 17 to 30 pale blue ray florets and 40 to 65 disc florets which are yellow initially and become purple or brown with age. The few to many flowering heads are in a panicle (a branched arrangement). The peduncles (stalks of the heads) are sparsely to densely covered with long, thin hairs. The single-seeded fruit has one rib on each side (Semple et al. 2002; Brouillet et al. 2006).

Crooked-stem Aster may be confused with other asters, as its heads may appear similar to those of other asters. However, the clasping leaf-bases attached to a flexuous (bent at the nodes) stem distinguish it from other asters.

3.2 Species population and distribution

In Canada, Crooked-stem Aster is known from Elgin, Norfolk and Middlesex counties in southwestern Ontario. It is considered historic in Oxford County. There are a total of 22 populations that are extant, four of these populations have not been reconfirmed within the last 20 years, but are currently presumed to be extant. An additional nine populations are historic with their status unknown and three are known to be extirpated. The majority of these populations occur on the floodplains of several creeks which drain into the north shore of Lake Erie including: Kettle, Big Otter, Catfish, South Otter, Talbot, Silver and Dodd. Table 1 shows populations of Crooked-stem Aster and their status. The Canadian range of Crooked-stem Aster is shown in Figure 2.

For the purpose of this management plan, the status of some populations in Table 1 and Figure 2 may differ from what is shown in the COSEWIC report (2012), and are based on the most recent information. COSEWIC (2012) lists site 22 as extirpated; however, the NHIC provides a ranking of historical for the same site. This population has not been surveyed since 1997, but given this discrepancy in rank this population will be considered historic with status unknown until its status is confirmed

In addition, COSEWIC (2012) lists population numbers 4, 6, 13 and 15, last confirmed in 1997, as unknown. However, populations that have been confirmed within the last 20 years are generally considered extant unless there is evidence to the contrary (NatureServe 2015). Therefore, for the purpose of this management plan, these four populations are considered extant.

Since the publication of the COSEWIC report in 2012, six new populations of Crooked-stem Aster have been confirmed; three in Elgin County, two in Middlesex County and one in Norfolk County. These populations were found in 2016 and 2017 and based on available stem counts for five of the six populations represent an estimated 1317 to 1567 stems.  A survey conducted in September 2010 found approximately 2575 stems of Crooked-stem Aster among seven sites. These surveys along with ones completed in 1994, 1997 and 2007 provide a total estimated stem count of 4562 to 4812 stems for 19 of the 22 extant populations in Ontario. Numbers of flowering stems at sites visited varied from fewer than 20 to several hundred; however, due to the species’ clonal nature the number of genetically distinct individuals is likely much lower (COSEWIC 2012).

In addition to the known locations listed above, it is possible that Crooked-stem Aster may be present in other areas. Aster species can be difficult to identify, and may have been overlooked or gone undetected during field surveys. This species is easiest to identify while flowering from late August through October, but most biological field work is completed earlier in the season, and therefore incidental sightings may not be as frequent.

In the eastern United States, Crooked-stem Aster is present from New Hampshire south to North Carolina and west to eastern Kentucky and Tennessee, with a second centre of distribution in Wisconsin, Minnesota, and Iowa (Kartesz 2015). It has been reported that Crooked-stem Aster is at the northern limits of its range in southwestern Ontario (COSEWIC 2012). However, the species occurs at higher latitudes in New York and Wisconsin (approximately 2 to 4o further north) (Kartesz 2015). The North American Plant Atlas (Kartesz 2015) shows Crooked-stem Aster as being present in Alabama and Georgia while COSEWIC (2012) and NatureServe (2015) do not.

3.3 Needs of the Crooked-stem Aster

Biological needs

A number of biological traits affect the needs of Crooked-stem Aster. Most asters cannot self-pollinate and must be pollinated by a genetically different individual (Jones 1978). This species grows in colonies forming groups or "clones" of connected, upright stems, originating from elongated rhizomes (Semple et al. 2002). In order for pollination to occur, pollen must come from flowers on a stem that belongs to a separate clone.  Crooked-stem Aster is pollinated mainly by bees and butterflies (Zhang et al. 1999). Depending on the size of the clone and the spacing between clones, pollinators may be required to travel distances anywhere from a few centimetres to tens of metres or more between genetically different individuals. In Crooked-stem Aster, clones may grow as a dense cluster, with many stems in a few m², or they may grow with stems scattered over many m². Zhang et al. (1999) found Crooked-stem Aster clones ranged from fewer than 10 shoots in one or a few m², to 20 to 40 shoots in as much as 8 m², and one large clone had 50 shoots scattered along 20 m (linear measure) of ground. Some clones were noted as spaced 20 to 50 m apart. These growth traits may influence the size and shape of habitat requirements.

Fruits of Crooked-stem Aster are dispersed either by falling from the plants by gravity or by being blown off by wind. The fruits have bristles (collectively known as the pappus) which catch the wind and assist dispersal (Semple et al. 2002). No known dispersal studies have been conducted specifically on Crooked-stem Aster.  Dispersal distances are hard to define as they relate to a number of changeable factors including wind speed, weather conditions and humidity, release height, and the height of the surrounding vegetation (Soons et al. 2004). These factors may differ on particular days and in different habitat types. In general, dispersal in the Aster Family is most favourable in fair weather with low humidity, as the bristles on the fruits are open and stiff, however wind speeds are usually low in such conditions (Sheldon and Burrows 1973). Sheldon and Burrows (1973) concluded that long distance dispersal in the Aster Family is typically prevented unless convection currents can carry fruits high up in the air, though this is unlikely to occur in the treed habitats, which Crooked-stem Asters prefer. Information suggests that fruits may also be dispersed by water (e.g., carried by currents in creeks and streams) and could be deposited downstream (COSEWIC 2012).

Most aster seeds are reportedly short-lived with viability times of one to one and a half years and up to four years reported (Jones 1978; Cullina 2000). It is not known whether Crooked-stem Aster may maintain a seed bank in the soil longer than 4 years.

Habitat needs

In Canada, Crooked-stem Aster occurs in a wide range of habitats. In general, Crooked-stem Aster is found in the floodplains of streams and creeks flowing into Lake Erie, most commonly at the edge of woods or along creek banks through riparian forest, as well as in a few roadside and old field locations in that region. It is usually found in partial to full shade (Zhang et al. 1999; Semple et al. 2002; COSEWIC 2012). Figure 3 shows Crooked-stem Aster in a woodland roadside habitat. Soil conditions where Crooked-stem Aster occurs include rich sandy, loamy, or clayey soil (Zhang et al. 1999). In its greater global range, Crooked-stem Aster is found in moist or swampy grounds, woods, thickets, meadows, seeps, stream banks, and roadsides (Brouillet et al. 2006).

Crooked-stem Aster has been observed to tolerate moderate levels of disturbance and competition from weeds and taller plants, and is able to grow and reproduce in a broad range of light, canopy cover, and soil moisture conditions (Zhang et al. 1999; COSEWIC 2012; Harris pers. comm. 2015) (Figure 3). It is unknown whether Crooked-stem Aster requires disturbance to create suitable habitat patches, but if so, there may be a trade-off between a need for disturbance to occur and the occasional loss of individual plants when the disturbance happens. Disturbance activities would need to occur on a small scale and outside of the growing season with careful considerations of the seed bank.

Zhang et al. (1999) reported habitat data from their 1997 field work, as well as the habitat information listed on herbarium specimens of Crooked-stem Aster from Ontario. When these and other Canadian reports (COSEWIC 2012) are examined in detail, it is apparent that Crooked-stem Aster can be found in a variety of habitats, with different associate species, a range of canopy cover if any, and different species making up the canopy. A generalized list of reported habitats includes:

• creek and stream banks under forest canopy, at the edge of woods, or open
• open floodplains with no canopy
• floodplains in Black Maple Forest with Sycamore (Platanus occidentalis) and Black Walnut (Juglans nigra)
• openings in forest of Sugar Maple (Acer saccharum), American Beech (Fagus grandifolia) and Eastern Hemlock (Tsuga canadensis)
• open thickets on a slope in damp sandy loam
• wet-mesic thickets of Ninebark (Physocarpus opulifolius)andDiamond Willow (Salix eriocephala)
• wet-mesic grove of White Cedar (Thuja occidentalis)
• sandy moist soil, part shade
• roadside banks at the edge of woods or through woods
• gravelly soil of waste ground
• in a small ditch mixed up with horsetail (Equisetum spp.)
• moist seepage in road cut and ditch
• sandy embankment under ash trees
• and a mix of conditions within one area: "along an old road paralleling a creek through lowland forest, but a few plants also extend up the valley slope into beech-hemlock forest" (COSEWIC 2012)

The main feature in common among most descriptions is mesic or moist conditions and soil that is at least somewhat sandy, although there are a few reports that appear to be somewhat drier (Zhang et al. 1999). The exact range of moisture levels tolerated by Crooked-stem Aster is not known, but soil that is at least mesic for some part of the growing season appears to be a requirement.

The forested habitat was classified by COSEWIC (2012) in the Ecological Land Classification of Southern Ontario (ELC) (Lee et al. 1998), as Fresh-Moist Lowland Deciduous Forest (Ecosite FOD7) often with Black Maple (Acer saccharum ssp. nigrum), ash (Fraxinus spp.), and/or White Elm (Ulmus americana) in the canopy. This ecosite is associated with soils that usually have a component of finer silt or clay that slows drainage (Lee 2008). However, this ecosite applies only to some habitats or parts of habitats. For example, thickets, cedar groves, and other kinds of wetlands have other ELC types, which have not been documented for Crooked-stem Aster. In addition, the disturbed edge of a forest or along a roadside, where Crooked-stem Aster can occur are not well typed by the current ELC.

The habitat needs of Crooked-stem Aster may be better understood by looking at the tolerances of its associates. A large number of associate species (Appendix B) have been reported (Zhang et al. 1999; COSEWIC 2012). Only about a quarter of those associate species are found mainly in forests. About a third have weedy growth habits (meaning they are able to grow in disturbed places or to spread over large areas) and another third are usually found in wet places (Reznicek et al. 2011). Photos taken by Allan Harris during field work in 2011 (COSEWIC 2012; Harris pers. comm. 2015) show Crooked-stem Aster growing with a variety of Eurasian weeds and native species of weedy habit, including European Colt's Foot (Tussilago farfara), Ox-eye Daisy (Leucanthemum vulgare), Canada Goldenrod (Solidago canadensis) and Common Plantain (Plantago major). In general, the ground flora found with Crooked-stem Aster is most often a dense layer of graminoids (grasses, sedges and rushes), goldenrods, and other asters (COSEWIC 2012).

Based on the above information, within the broad range of habitat situations, suitable habitat for Crooked-stem Aster will generally be found within or in proximity to creeks or streams, floodplains, seeps, or lowland forest; with mesic to wet soil conditions; often with sandy soil and somewhat shady sites.

Habitat dynamics

It is possible that suitable habitat for Crooked-stem Aster may be dynamic or may be disturbance-based. Floodplains and creek banks are subject to periodic natural disturbance from inundation and fast currents during high water, which may clear off vegetation and expose soil for new establishment of this species. Forest openings may be the result of natural blow-down or human activities. Thickets may also be the result of disturbance in much wetter areas. Roadsides and forest edges are the result of human actions.

In floodplain forest, Ambrose and Aboud (1983) speculated that periodic openings in the forest may be needed for seedling establishment of mature trees that fruit infrequently, and that habitat dynamics that allow periodic creation of light gaps or prevent full canopy closure may be necessary to ensure tree seedling survival. If there is a natural cycle of disturbance occurring within lowland and floodplain forests, it is possible that other species in addition to trees are adapted to that cycle. However, field reports have not tied Crooked-stem Aster habitat to specific disturbance events, and populations remained extant between COSEWIC surveys of 1997 and 2010, and even between older records (e.g., 1985 to 1987) and 2010. Therefore, if habitat dynamics do play a role in creating or maintaining suitable habitat for Crooked-stem Aster, it is possible that the disturbance is needed only over long time periods, such as every 25 years or more.

4 Threats

Historically, loss of habitat was considered a major threat to Crooked-stem Aster and many other Carolinian species as most forest was converted to agricultural use. Present-day threats to the species may be compounded by the overall scarcity and fragmentation of forest habitat due to historical habitat loss. However, COSEWIC (2012) does not report limited habitat as a current threat to Crooked-stem Aster in Canada.

4.1 Threat assessment

The Crooked-stem Aster threat assessment (Table 3) is based on the unified threats classification system of the International Union for Conservation of Nature (IUCN) and the World Conservation Union- Conservation Measures Partnership (CMP) (Salafsky et al. 2008). Threats are defined as the proximate activities or processes that have caused, are causing, or may cause in the future the destruction, degradation, and/or impairment of the entity being assessed (population, species, community, or ecosystem) in the area of interest (global, national or subnational). Limiting factors are not considered during this assessment process. For purposes of threat assessment, only present and future threats are considered. Historical threats, indirect or cumulative effects of the threats, or any other relevant information that would help in understanding the nature of the threats are presented in section 4.2 Description of Threats.

The predominant threats to Crooked-stem Aster are residential and commercial development, recreational activities and invasive non-native/alien species.

^a Impact – The degree to which a species is observed, inferred, or suspected to be directly or indirectly threatened in the area of interest. The impact of each threat is based on Severity and Scope rating and considers only present and future threats. Threat impact reflects a reduction of a species population or decline/degradation of the area of an ecosystem. The median rate of population reduction or area decline for each combination of scope and severity corresponds to the following classes of threat impact: Very High (75% declines), High (40%), Medium (15%), and Low (3%). Unknown: used when impact cannot be determined (e.g., if values for either scope or severity are unknown); Not calculated: impact not calculated as threat is outside the assessment timeframe (e.g., timing is insignificant/negligible or low as threat is only considered to be in the past); Negligible: when scope or severity is negligible: Not a Threat: when severity is scored as neutral or potential benefit.

^b Scope – Proportion of the species that can reasonably be expected to be affected by the threat within 10 years. Usually measured as a proportion of the species’ population in the area of interest. (Pervasive = 71 to 100%; Large = 31 to 70%; Restricted = 11 to 30%; Small = 1 to 10%; Negligible <1%).

^c Severity – Within the scope, the level of damage to the species from the threat that can reasonably be expected to be affected by the threat within a 10-year or three-generation timeframe. Usually measured as the degree of reduction of the species’ population. (Extreme = 71 to 100%; Serious = 31 to 70%; Moderate = 11 to 30%; Slight = 1 to 10%; Negligible < 1%; Neutral or Potential Benefit ≥ 0%).

^d Timing – The time frame over which the threat may occur or is occurring. High = continuing; Moderate = only in the future (could happen in the short term [< 10 years or 3 generations]) or now suspended (could come back in the short term); Low = only in the future (could happen in the long term) or now suspended (could come back in the long term); Insignificant/Negligible = only in the past and unlikely to return, or no direct effect but limiting.

4.2 Description of threats

Threats to the Crooked-stem Aster are described below in the order in which they appear in Table 3. The most serious threats to Crooked-stem Aster are habitat loss from invasive species and roadside maintenance using herbicide to reduce vegetation or using large machinery for major road reconstruction or improvement. Trampling from recreational activities, such as inappropriate all-terrain vehicle (ATV) use or off-trail hiking, is also a serious concern. Other threats also occur with somewhat lower impact.

1 Residential and commercial development

1.1 Housing and urban areas

Habitat for Crooked-stem Aster may be degraded or lost due to development. Most floodplain habitat is not suitable for development. However, cottage development was still noted as being a current threat at one site not on a floodplain (COSEWIC 2012). Although this threat is not likely to have a population-level effect on the species as a whole, it may lead to a significant loss of individuals at local population locations. Development may cause a direct loss of habitat by covering the ground with structures, lawns, or roadways. Even if all substrate is not covered up, development may also cause a change in the moisture regime. Crooked-stem Aster tolerates moderate disturbance, so it may be possible for disturbance to occur without damaging the species. However, it can be presumed that development would cause a loss of available habitat overall.

2 Agriculture and aquaculture

2.3 Livestock farming and ranching

Livestock grazing has been noted as a potential threat although there have been no observations of this threat occurring (COSEWIC 2012). However, this threat is likely to occur mainly on sites on private land, most of which have not been surveyed. Thus, the current impact of grazing is unknown. Livestock grazing may threaten Crooked-stem Aster in the short term due to consumption of the plants. It may also cause degradation of habitat over the long-term, or if large numbers of animals are present. Livestock grazing may cause trampling of ground, soil disturbance or compaction, increased nutrient inputs from manure, and introduction of non-native or invasive plant seeds, which can promote the spread of species that compete with Crooked-stem Aster (Scasta et al. 2015).

4 Transportation and service corridors

4.1 Roads and railroads

Three populations of Crooked-stem Aster occur along roadsides. Vegetation on some roadsides is regularly maintained with mowers or herbicides, both of which could damage Crooked-stem Aster plants. However, one roadside population which was regularly mowed actually increased in numbers (COSEWIC 2012). As long as mowing does not cut Crooked-stem Aster plants, periodic mowing (frequency not determined but probably not more than once or twice in a summer) appears not to be a threat. Conversely, the use of herbicide may directly harm Crooked-stem Aster and associated species and may change the species composition of habitat. Road improvement and construction may be a threat if ditches and roadsides are altered, or drainage and moisture levels changed.

5 Biological resource use

5.3 Logging and wood harvesting

Logging may degrade or destroy habitat if it opens the canopy enough to change the light and moisture regimes. It may also cause a rebound in growth of tree seedlings (Reader and Bricker 1992), which may compete with Crooked-stem Aster or take over areas used by the species. However, Crooked-stem Aster may withstand moderate levels of disturbance, so there may be a threshold below which logging would not be a threat. Threshold levels are unknown, but it is possible that small scale-selective cutting of trees could provide a benefit from increased light (Reader and Bricker 1992). Nevertheless, there could still be a cumulative effect from smaller operations over a number of years. There are currently active logging operations on some conservation authority lands, but silvicultural areas are surveyed prior to work commencing, and buffers are established to protect any species at risk present (Holmes pers. comm. 2015). Crooked-stem Aster has not been surveyed on most private land sites, so it is unknown whether logging may be a threat there.

6 Human intrusions and disturbance

6.1 Recreational activities

The use of recreational vehicles (e.g., ATVs) occurs in some forests and along some roads and trails where Crooked-stem Aster is present (Harris pers. comm. 2015). Inappropriate ATV use is an on-going problem at many sites despite gates and other attempts to prevent access (Gagnon pers. comm. 2015; Holmes pers. comm. 2015). Inappropriate ATV use may damage plants and may degrade or destroy habitat if it causes rutting or compaction of soil, especially if it is moist. Despite this, a fairly large number of Crooked-stem Aster plants were observed along one forest ATV trail (Harris pers. comm. 2015), pointing to possible beneficial effects from light disturbance and a possible threshold for detrimental effects. Effects of trampling from foot traffic along hiking trails may be similar to recreational vehicle use but may have a higher threshold before effects become detrimental.

8 Invasive non-native/alien species

8.1 Invasive non-native/alien species

Invasive species were found at almost all sites surveyed for Crooked-stem Aster in 2010 (COSEWIC 2012). These include: invasive Phragmites (Phragmites australis australis), Garlic Mustard (Alliaria petiolata), Glossy Buckthorn (Frangula alnus), Dame's Rocket (Hesperis matronalis), Honeysuckle (Lonicera tatarica), Spotted knapweed (Centaurea stoebe ssp. micranthos), Smooth Brome (Bromus inermis), as well as Reed Canary Grass (Phalaris arundinacea) which is a native species. All of these species are able to colonize and take over disturbed places (moist or otherwise), forest understory, and open areas. The presence of invasive species is a serious threat to native biodiversity (Environment Canada 2004). However, Crooked-stem Aster is a large, vigorous species able to compete with other colonial plants such as Canada Goldenrod, so the effects of invasive species may be less harmful to Crooked-stem Aster than to other species. Nevertheless, there may be potential impacts, including allelopathic^{Footnote 7} effects (Garlic Mustard), shading (Glossy Buckthorn, Honeysuckle), and altered soil moisture (Common Reed, Reed Canary Grass) (COSEWIC 2012). Finally, if invasive species do not greatly affect growth of Crooked-stem Aster, they may potentially affect seedling establishment if they cover most of the available ground. Habitat degradation due to invasive species is also considered a threat to populations in the United States, particularly in Minnesota and Ohio (COSEWIC 2012).

The Emerald Ash Borer (Agrilus planipennis or EAB), a foreign, invasive beetle, has been documented as a threat to Carolinian forests that have a high component of ash trees (Environment Canada 2015). EAB is present in the Lake Erie region and is spreading throughout southern Ontario and Quebec (Canadian Food Inspection Agency 2015). In the Catfish Creek area, ash trees have been completely infested and all but the Blue Ash (Fraxinus quadrangulata) have died (Difazio pers. comm. 2015). Die-back of ash trees was not observed within Crooked-stem Aster habitat in 2010 (COSEWIC 2012), though die-back has occurred east and west of the species’ range. As the species tolerates a variety of open canopy conditions, potential effects on Crooked-stem Aster are unknown. However, the loss of ash trees constitutes a major change in forests and could cause direct habitat changes such as opening up the canopy causing drier soil conditions, and indirect effects such as increases in invasive plant species (COSEWIC 2012).

Other potential threats

A lack of pollinators may also be a potential threat. Crooked-stem Aster flowers from late August to early October and requires out-crossing^{Footnote 8} with pollen transfer by insects. Pollinators may be limited in the latest part of the bloom period. In addition, there may be a general decline in insect pollinators (bees especially) in Canada and globally, due to loss of habitat and food sources, diseases, pests, and pesticide exposure (Health Canada 2015). It is currently unknown what impact the decline in pollinator populations may have on Crooked-stem Aster. However, in the short-term, vegetative reproduction by rhizomes may compensate somewhat for reduced sexual reproduction.

Deer browse was not observed on Crooked-stem Aster during 2010 field work although deer were present (Harris pers. comm. 2015). Browse was not noted as a threat to this species by COSEWIC (2012), but other asters are often subject to browse. For example, monitoring in prairie restoration sites in Windsor found that deer preferentially ate Willowleaf Aster (Symphyotrichum praeltum), a threatened species, over other herbaceous plants (WEMG 2012; Jones 2013). Deer browse has also been noted as a threat to other species in Carolinian forests (Jones et al. 2013; Environment Canada 2015) but is currently not considered a threat to Crooked-stem Aster.

Any activity that changes the soil moisture regime or prevents flooding could pose a potential threat. Some examples might include construction of permanent structures to prevent high water levels, changes to agricultural drainages, replacing natural creek banks with cement or riprap, etc. However, no specific activities are observed as current threats to the species.

5 Management objective

The management objective for the Crooked-stem Aster in Canada is:

• maintain or increase (if determined to be biologically and technically feasible), the distribution and abundance of all populations in Ontario, including any newly discovered populations

Crooked-stem Aster has experienced historic declines mainly due to habitat loss; however, current numbers suggest that populations are fairly stable and no recent losses have occurred (COSEWIC 2012). The number of mature individuals is unknown, but likely in the thousands. There is an estimated total of 4562 to 4812 stems at 19 of the 22 extant populations. However, uncertainty about the abundance of total individual plants remains (COSEWIC 2012). This uncertainty, includes a lack of recent information about a number of populations with a historic-unknown status (Table 1), setting quantitative abundance objectives is not possible at this time. Efforts to increase the abundance and distribution of populations of Crooked-stem Aster in Canada will be carried out as opportunities arise (e.g., through ongoing and future restoration work by Conservation Authorities and stewardship groups, best management practices, and threat mitigation). The priority will be to focus on existing locations with small extant and historic populations or new locations within the native range where sufficiently large areas of suitable habitat (forest edges or in sunny openings within river floodplains or forests) are available or can be made available through restoration (e.g. to migitate threats of invasive species) to support long-term persistence of the population.

Maintaining and/or increasing current populations will likely require the reduction or elimination of threats, particularly the encroachment of invasive species. Habitat management and use of best management practices along with increased outreach and communication with landowners to inform and raise awareness of the species and its threats may assist in achieving these recovery objectives and allow for a natural increase of plants within extant and presumed extant populations. In addition to measuring progress towards the management objectives, a regular assessment of threats will be important in evaluating the management of this species.

6 Broad strategies and conservation measures

6.1 Actions already completed or currently underway

On lands owned by the Long Point Region Conservation Authority, Crooked-stem Aster is located in managed forested areas with active logging operations. These areas are surveyed prior to work commencing and BMP’s are followed (Holmes pers. comm. 2015). One such guidance document is the Forest Management Guide for Conserving Biodiversity at the Stand and Site Scales (OMNR 2010), which seeks to contribute to the conservation of biodiversity through sustainable forestry management practices.

Management and stewardship of woodland habitats, surveys and public engagement projects are supported and funded by the federal Habitat Stewardship Program (HSP). The Carolinian Canada Coalition undertook several projects from 2009 to 2013 which focused on ensuring that conservation efforts targeting species at risk in Carolinian Canada are well coordinated and collaborative. This led to the development of regional Conservation Action Plans. Crooked-stem Aster is included in Carolinian Canada Coalition's (CCC) Elgin Greenway Conservation Action Plan (Jalava et al. 2012), along with 64 other species at risk. The document lays out conservation targets for the habitat of each species and suggests actions for habitat protection, and applies to most of the extant and historic populations of Crooked-stem Aster because all but six are located in Elgin County.

6.2 Broad strategies

The broad strategies of this management plan are described below. They are not identified in order of priority. The priority is identified in relation to the conservation measures (see section 6.3 Conservation Measures).

1. conduct surveys to gather data on presence, abundance, and threats to guide future conservation efforts
2. manage and protect habitat to reduce threats
3. engage key stakeholders in Crooked-stem Aster conservation and stewardship
4. conduct outreach and education to promote awareness of Crooked-stem Aster and its habitats
5. address knowledge gaps on the biological and habitat requirements of Crooked-stem Aster

6.3. Conservation measures

^e “Priority” reflects the degree to which the measure contributes directly to the conservation of the species or is an essential precursor to a measure that contributes to the conservation of the species. High priority measures are considered those most likely to have an immediate and/or direct influence on attaining the management objective for the species. Medium priority measures may have a less immediate or less direct influence on reaching the management objective, but are still important for the management of the population.Low priority conservation measures will likely have an indirect or gradual influence on reaching the management objective, but are considered important contributions to the knowledge base and/or public involvement and acceptance of the species.

6.4 Narrative to support conservation measures and implementation schedule

In order to plan effective conservation measures, better information is needed on the current status of many populations. The development and establishment of long-term protocols is important in monitoring abundance at all Crooked-stem Aster populations. There are 12 populations on privately-owned land that have not been reconfirmed since the 1990's or earlier. Communication with private landowners where the species occurs would be beneficial to promote awareness,  encourage stewardship and reduce threats. In addition, other landscape-wide actions, such as supporting efforts to protect Carolinian habitats in the regions where Crooked-stem Aster occurs, will be beneficial. A long-term monitoring protocol would allow the status of populations to be tracked and would allow a timely response if threat levels increase.

Developing approaches to reduce destructive or inappropriate types of ATV will be important, as efforts to maintain gates and prevent unauthorized access have not been very successful at some sites (Holmes pers. comm. 2015), and enforcement may be difficult. Increased on-the-ground presence of land management staff or of conservation-minded local people may be beneficial in deterring this threat. A landscape-wide effort to encourage environmentally-responsible ATV riding would benefit Crooked-stem Aster as well as and many other species and habitats.

Controlling invasive species in the habitat of Crooked-stem Aster will likely require a long-term commitment if it is to be effective. At current levels, invasives may be only a moderate-level threat for Crooked-stem Aster because it may tolerate some competition from weedy species. However, controlling invasive species will be beneficial to the habitat as a whole, and may prevent more serious or future problems for Crooked-stem Aster.

7 Measuring progress

The performance indicators presented below provide a way to measure progress towards achieving the management objectives and monitoring the implementation of the management plan.

• the abundance and distribution of current and confirmed Crooked-stem Aster populations are maintained or increased

8 References

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Appendix A: conservation ranks of Crooked-stem Aster in Canada and the United States

Rank Definitions (Master et al. 2012)

S1: Critically Imperilled: At very high risk of extirpation in the jurisdiction due to very restricted range, very few populations or occurrences, very steep declines, severe threats, or other factors.

S2: Imperilled: At high risk of extirpation in the jurisdiction due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors.

N3/S3: Vulnerable: At moderate risk of extirpation in the jurisdiction due to a fairly restricted range, relatively few populations or occurrences, recent and widespread declines, threats, or other factors.

S4: Apparently Secure: At a fairly low risk of extirpation in the jurisdiction due to an extensive range and/or many populations or occurrences, but with possible cause for some concern as a result of local recent declines, threats, or other factors.

S5: Secure/Apparently Secure: At no risk to fairly low risk of extirpation in the jurisdiction due to an extensive to very extensive range, abundant populations or occurrences, with little to some concern as a result of local recent declines, threats or other factors.

G5/N5/S5: Secure: At very low risk of extinction or elimination due to a very extensive range, abundant populations or occurrences, and little to no concern from declines or threats.

SNR: Unranked: Conservation status not yes assessed.

U: Unrankable: Currently unrankable due to lack of information or due to substantially conflicting information about status or trends.

?: Inexact numeric rank: The addition of a ? qualifier to a 1 to 5 conservation status rank denotes that the assigned rank is imprecise.

Appendix B: plant species found in the habitat of Crooked‑stem Aster

Appendix C: effects on the environment and other species

A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision-making and to evaluate whether the outcomes of a recovery planning document could affect any component of the environment or any of the Federal Sustainable Development Strategy’s (FSDS) goals and targets.

Conservation planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that implementation of management plans may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts upon non-target species or habitats. The results of the SEA are incorporated directly into the management plan itself but are also summarized below in this statement.

Most conservation measures suggested for Crooked-stem Aster, such as controlling invasive species, preventing inappropriate ATV use, speaking with private landowners, sharing information with planning authorities, and working to protect Carolinian forest as a whole, will be beneficial for all species occurring in the same areas as Crooked-stem Aster. Surveys to fill knowledge gaps on population status, and research on the biological needs and limitations of Crooked-stem Aster are also not expected to have any negative effects. All of these actions are expected to have only beneficial effects on other species and the region. Crooked-stem Aster has some tolerance for disturbance, and may tolerate some human activities that might harm other species, for example moderate logging. However, disturbance is not considered a requirement for Crooked-stem Aster, so it is not necessary to create disturbance that might harm other species. Therefore, recovery of Crooked-stem Aster is not expected to have any negative environmental effects.