Rusty cord-moss (Entosthodon rubiginosus) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

In British Columbia, Entosthodon rubiginosus is restricted to seasonally damp and alkaline, usually silt or clay-rich soil at the edges of open ponds, lakes, and sloughs, and on seepage slopes in relatively dry environments. It grows amongst litter and vascular plants, in particular graminoids, in particular salt grass (Distichlis stricta) and field sedge (Carex praegracilis). Common moss associates are Desmatodon heimii, Drepanocladus sp., and Conardia compacta. It is most often found within a narrow band around the edges of the wetland where the topography is flat to very slightly sloping. It has not been found in alkaline sites where tall rushes and sedges dominate. The alkaline nature of these areas arises from evaporation of water during warmer months over many years, leaving minerals behind.

Alkaline wetlands are relatively common in the south-central portions of the province, along river valleys and adjacent lowlands. They are most common in a relatively large area south and west of Williams Lake, but are also fairly common in relatively narrow bands in the drier portions of the Fraser, Thompson, Nicola, Similkameen, and Okanagan Valleys. Scattered alkaline areas are also present in the Rocky Mountain Trench.

Although alkaline wetlands probably number in the hundreds in British Columbia relatively few appear to have suitable habitat for Entosthodon rubiginosus. Based on field experience, Terry McIntosh has defined 'potential habitat' for this taxon as:

  1. In seasonally wet alkaline areas where bare soil is available; these alkaline areas are either distinct ponds, pocket complexes comprised of small ponds and seepage areas, or seepage slopes. The species appears to be most common near ponds and least common on seepage slopes.
  2. On a flat to very gentle slope within a low-growing vegetation zone above, but not in, a zone defined by a complete alkaline-deposit crust; the low-growing vegetation is often defined by the presence of two graminoid species: Carex praegracilis and Distichlis stricta. The species has not been found where taller sedges and rushes predominate.
  3. In open areas (no shade) at relatively low elevations in sagebrush, grassland, and open forested (ponderosa pine/Douglas-fir/lodgepole pine, although less commonly with the latter two species)
  4. In areas where erect-growing moss species predominate; E. rubiginosus has not been found in sites where creeping moss species, and in particular where Drepanocladus (probably D. aduncus) are present.

Table 1 gives estimates of potential sites, by regions. Potential sites are defined as sites separated by at least 5 km. (but usually much more) and separated by landscapes that do not contain the potential habitats. Based on examinations of maps and through field work, between 93 and 111 distinct sites (geographically isolated ponds, lakes, seepage slopes, or complexes) may provide suitable habitat for this species in the province. Although more work needs to be completed, this species appears to be restricted to those alkaline areas in warmer locations (lower elevation/more southerly latitude). This is supported by the concentration of this species in the Okanagan and Kamloops areas. Alkaline wetlands are found in the Bunchgrass, Ponderosa Pine, and dry Interior Douglas-fir Biogeoclimatic Zones.

Over the past seven years and during his Ph.D. work, the report writer has investigated the edges of probably more than 75% of the alkaline wetlands that have potential habitat for this species in British Columbia (see Table 1). Despite this intensive survey effort, Entosthodon rubiginosus was found only three times. However, the edges of many of these ponds and the potential habitat for this species are extensive, covering hectares in some sites, and, because of collection time constraints, this species could have been overlooked at some of the sample locations. Moreover, in field surveys conducted by T. McIntosh in 2002-2003, 30 additional alkaline wetland sites were visited. Although the investigations during this survey were more intense than the earlier survey, and more time was spent at each site, only one new population was found (Riske Creek).

Table 1. Estimated numbers of 'potential habitat' alkaline areas in British Columbia, including visitation and collection information. Potential sites are defined as sites separated by at least 5 km., (but usually much more) and separated by landscapes that do not contain the potential habitats.
Region Number of Potential SitesFootnotea Approximate number of sites visited Numbers of Known Sites
Kootenay
8 - 10 7 0
Okanagan (from Osoyoos to the SE base of Richter Mountain westwards and to just north of Kaledon to the north)
20 - 25 18 - 20 2
Kamloops(from just east of the city to Spences Bridge/Cache Creek, and including the Pavilion and Clinton areas, although somewhat disjunct)
28 -32 22 - 25 1
Cariboo (mainly in areas along the Fraser and Chilcotin Valleys, but also north and east of Chasm north of Clinton)
37 - 44 28 -32 1

Trends

In 1997, T. McIntosh initiated a survey of provincial arid-land areas in order to complement his Ph.D. work (McIntosh 1986) in preparation for a research paper describing and providing keys for the bryophytes of these regions. From 1997 to 2001, some 45 alkaline wetlands of potential habitat for this species were visited at various locations throughout the semi-arid regions of south-central British Columbia (about 20 sites were visited in the Cariboo Region from north of Clinton to west of Williams Lake, and another 25 were visited in the Kamloops/Merritt/Okanagan areas; these sites were not documented with UTM information). The primary focus of these visits was to look for a number of rare bryophytes, including Entosthodon rubiginosus. No additional sites were found during this field work period.

Three extant populations of Entosthodon rubiginosus are currently known in Canada. The Riske Creek population was discovered during 2002-03 field work by T. McIntosh and the White Lake and Princeton populations were confirmed during that field work period also. The early collection from Princeton has probably been extirpated because of serious grazing activities around the pond where it was collected; however, more plants were found in a small seasonally wet pocket to the southeast of this pond, and probably represent the same population. The population found in 1981 near Kamloops was not relocated.

The White Lake and Riske Creek habitats appear to be stable, although there appears to be intermittent, but minor cattle activity at both sites. The Princeton site is regularly heavily disturbed by cattle and horses, and the pond where this moss was collected previously is now almost completely devoid of vegetation around its margins; however, other areas near this pond, including the small wet area where this species was relocated, show no signs of recent disturbance.

Protection/ownership

Ownership of the Kamloops and Princeton locations is undetermined. The Riske Creek site is on Crown land. It has also been collected at White Lake in the southern Okanagan Valley. In the past, cattle and horses utilized the area around the lake. However, The Nature Trust (J. Hope, pers. comm. 2002) recently signed a 99 year lease in order to establish a study area on federal lands at White Lake in accordance with their 2000 Biodiversity Ranch Management Plan. As part of this plan, White Lake and the surrounding riparian vegetation, including the known location for Entosthodon rubiginosus, are to have been permanently excluded from grazing and other potential large-scale disturbances through the construction and maintenance of a fence. It is expected that the habitat will improve in the riparian area, although data is lacking on how changes will affect the population of this species.

Page details

Date modified: