Pygmy pocket moss (Fissidens exilis) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

As Beever (1999) points out, species of Fissidens reflect the preference of many bryophytes for specific micro-environmental conditions. F. exilis is found largely on bare, moist, often clay soil. It usually occurs in woodlands but has also been collected on roadsides and floodplains where soil has been disturbed (Crum & Anderson 1981, herbarium records). It may be associated with ephemeral (extremely short-lived) mosses such as Ephemerum and Micromitrium (Crum & Anderson 1981), which are known to prefer temporary habitat patches.

In Montréal, F. exilis was reportedly collected from clay soil below a planted spruce-tamarack (Picea-Larix) canopy in the Morgan Arboretum of McGill University. In Essex County, F. exilis was found on the floodplain or banks of rivers, on clay in mature deciduous Carolinian forest (Appendix 1). In Kent County, the species was found on bare trailside mud in upland maple-beech forest. No habitat notes accompany the specimens from Gatineau Park, Waterloo County, or Haldimand-Norfolk County.

Trends

Mature, deciduous, Carolinian forest such as that characterizing the Essex and Kent County sites where F. exilis was found is increasingly rare in Canada, and many Canadian Carolinian species are endangered. However, the fact that F. exilis was also discovered in Gatineau Park and (reportedly) in a coniferous site in Montréal, and that the species has been found on roadsides and other anthropogenic habitats in the United States, indicates that F. exilis may not rely heavily on mature temperate forest, and that its habitat may therefore be more abundant. The species’ known distribution (Figure 2) suggests climatic limitation and may be susceptible to change concomitant with long-term climate change.

Protection/ownership

Bare clay soil may be found in many forested privately owned and public protected areas in southern Ontario and Quebec. The details of habitat preference in F. exilis are not well known; only an unknown subset of these sites would be likely to support populations of the species.

At one Essex County (Canard River) site where F. exilis has been recorded, the land is privately owned, but is adjacent to the Canard Valley Conservation Area (CVCA), where bare clay substrate is abundant. The CVCA has been listed as one of the top botanical sites in Essex County (Varga & Allen 1990). Although fifteen bryophyte collections made by J. Doubt in the CVCA in 2002 proved, upon laboratory inspection, not to represent F. exilis, more research should be conducted there. The other Essex County (Cedar Creek) site for F. exilis falls within the Cedar Creek Area of Natural and Scientific Interest (ANSI) and was recently purchased by the Nature Conservancy (Ron Gould, personal communication 2005), providing it some protection through stewardship and municipal zoning. The Cedar Creek ANSI is described by Eagles and Beechey (1985) as the most significant natural site in Essex County not under public ownership, due to its large size, its potential for beneficial research and education, and its high aesthetic and historical value. The national and provincial importance of the Cedar Creek ANSI is widely acknowledged among local and provincial authorities, who take close interest in activities at the site.

Kent and Haldimand-Norfolk County populations of F. exilis occur on land managed by local Conservation Authorities, and as such are protected from certain kinds of disturbance. Sinclair’s Bush, the Kent County site, houses seven rare plant species, and has special designation as a Carolinian Canada site. However, only four acres of the site is actually owned by the Conservation Authority (Valerie Towsley, personal communication 2002). Although voluntary conservation is encouraged by the municipality through incentive programs, the absence of a tree-cutting by-law and heavy development pressure has resulted in recent clearing and road building in privately owned sectors of the site. It should be noted that F. exilis was found on a trail, and its persistence may rely on disturbance by foot traffic. The Gatineau Park and Morgan Arboretum (Montréal) populations are presumably protected, but without knowing the location or conditions under which the species was found, protection cannot be assessed. The effect of infrastructure, management activities, or visitor activities on the populations cannot be determined.

Sudden Tract, where the Waterloo County population of F. exilis occurs, consists mainly of municipally owned regional forest (Chris Gosselin, personal communication 2003). The forest, and some adjacent privately owned land were designated in 1976 as an Environmentally Sensitive Policy Area (ESPA #52), giving it protection from development. The exceptional conservation value of Sudden Tract in terms of rare species (including plants, birds, and salamanders) is well-recognized and promoted. Human activities such as active management intervention to preserve natural species and processes and recreational hiking may influence local plant populations.

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