Smooth goosefoot (Chenopodium subglabrum) COSEWIC assessment and status report: chapter 5

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Habitat

Habitat requirements

Chenopodium subglabrum grows in the mixed grassland natural region south of the 52^nd parallel. The climate of this area is continental, with the mean annual temperature ranging from 6°C to 0°C. The growing season is short, with an average of 105 to 130 frost-free days. Precipitation ranges from 30-cm to 40-cm. About two-thirds of the annual precipitation is rain, the peak occurring in June. Late summer rains come mainly in the form of thundershowers. The rate of evaporation is high through the summer months (Wallis 1982; Acton et al. 1998).

Chenopodium subglabrum populations occur in the Aspen Parkland, Moist Mixed Grassland and Mixed Grassland Ecoregions of the Prairie Ecozone (Acton et al. 1998). Within this ecological area, C. subglabrum is found in mixed grasslands with sandy soils. The sand hills in Saskatchewan and Alberta are isolated from each other as the land in between them is largely cultivated. The Manitoba sites are particularly isolated, being approximately 100 km apart from each other, 500-600 km from the nearest C. subglabrum population in Saskatchewan and about 350-450 km from the nearest population in the United States (i.e. North Dakota). This fragmentation is natural since C. subglabrum does not generally grow on the silty and clayey soils that occur in between the various sand hills. The populations that occur along the South Saskatchewan River are less isolated than the ones growing in the sand hills to the south since the habitat along the river is largely undisturbed.

Chenopodium subglabrumis an early successional habitat specialist growing typically in the stabilizing sand at the edges of active dunes and blowouts, and along eroding, sandy river banks and coulees (Maher et al. 1979; White and Johnson 1980; Packer and Bradley 1984; Robson 1997a; Lamont and Gerry 1998). Chenopodium subglabrum is generally found on south- or west-facing actively eroding slopes, at the edge of stabilizing sand and sometimes in dune slacks. Populations are highest in areas of finer and more compacted sand. Rarely, this species grows in very active sand away from the stabilization zone. In some cases, C. subglabrum was collected from areas grazed by cattle in sand dune blowouts or along trails. Chenopodium subglabrum has also been found growing at the edge of a saline lake. In North Dakota, the plants were growing on sandstone cliffs, sandy terraces along rivers and sand bars (Schmoller 2002). Given that C. subglabrum was found historically along the South Saskatchewan River, it is possible that much of this species’ habitat disappeared when Gardiner Dam was built on the South Saskatchewan River in the late 1960s, flooding the sand bars and terraces.

More specifically, plants in the Dundurn Sand Hills occurred on stabilizing dune blowouts, and along an eroding portion of the South Saskatchewan River bank. At Patience Lake, plants occurred along the shore of a saline lake. At Bridgeford, C. subglabrum was found growing in a sandy heathland. At Broderick, C. subglabrum was found growing along the South Saskatchewan River in sand dunes on nearly bare sand. At Empress, C. subglabrum grew on a dry, hot south slope of a sand ridge on the north side of a ravine. At the Bigstick-Crane Lakes, Burstall, Cramersburg, Elbow, Great, Seward and Tunstall Sand Hills, C. subglabrum grew at the edges of stabililizing sand dunes and blowouts. Chenopodium subglabrum has also been found on Northern Pocket Gopher mounds in the Great, Seward and Cramersburg Sand Hills (Lamont and Gerry 1998). Although it grows on well-drained soils, C. subglabrum may benefit from heavy, late summer rains, which seem to stimulate germination. Dynamic factors such as grazing, erosion and fire may aid in destabilizing sand resulting in more habitat for C. subglabrum (Robson 1999).

Chenopodium subglabrum, as most members of the Chenopodiaceae, is tolerant of alkali-impregnated areas. Most other plants are unable to occupy such areas as they are so inhospitable. There is little other competition on such soils as well (Nelson 1902). Chenopodium subglabrum is shade intolerant but can handle some soil disturbance. In fact, C. subglabrum grew in disturbed soil surrounding oil wells in the Seward Sand Hills. This is not unusual as other early successional rare plants have also been observed colonizing human-disturbed areas within native vegetational communities (Robson 1997a, 1999).

In total, C. subglabrum was associated with six nationally rare and eight provincially rare plants (Table 1). Three of the nationally rare species in Table 1 are also at risk and protected under the federal Species at Risk Act (Dalea villosa, endangered; Tradescantia occidentalis, threatened; and Tripterocalyx micrantha, endangered).

¹ According to Argus and Pryer 1990
² According to provincial Conservation Data Centres

The grasses most typically found as associates with C. subglabrum are: Agropyron dasystachyum, Calamovilfa longifolia, Elymuscanadensis, Oryzopsis hymenoides and Sporobolus cryptandrus (Wallis and Wershcher 1988, Robson 1997a). In Manitoba, Andropogon hallii was also a common associated grass. The most common forbs (flowering herbs) found in C. subglabrum habitat are: Chenopodium pratericola, Helianthus petiolaris, Heterotheca villosa, Lygodesmia juncea and Psoralea lanceolata (Wallis and Wershcher 1988, Robson 1997a). Occasional associates include: Artemisia campestris, Cryptantha fendleri, Glycyrrhiza lepidota, Lappula squarrosa and Xanthium strumarium (Wallis and Wershcher 1988, Robson 1997a). The shrub species sometimes occurring in C. subglabrum habitat include: Arctostaphylos uva-ursi, Artemisia cana, Elaeagnus commutata, Juniperus horizontalis, Rosa spp. and Salix exigua (Wallis and Wershcher 1988, Robson 1997a).

Habitat trends

Surveys for C. subglabrum have been conducted in major sand hills in Alberta (Wallis and Wershler 1988) and Saskatchewan (Lamont and Gerry 1998, Robson 1997a). However, there may be habitat for C. subglabrum along some of the riparian areas and isolated sand dunes in Alberta and Saskatchewan. There are several areas in Manitoba that have not been thoroughly searched for C. subglabrum including the Lauder, Portage and Brandon Sand Hills.

Research indicates that over time there is a pattern of dune activity associated with major droughts, followed by moister periods during which stabilization occurs (David 1993, Epp 1980). Extensive dune activity occurs only during major droughts except in areas that contain very large dunes (Epp 1980). The stabilization rate of the dunes in Canada since 1970 ranges from 0.4 ha/year in the Elbow Sand Hills of Saskatchewan to 17.7 ha/year in the Brandon Sand Hills of Manitoba (Hugenholtz and Wolfe in press). As the sand hills and undifferentiated eolian deposits stabilize there is a reduction in the potential habitat for C. subglabrum (David 1993, Wallis 1988). Dune stabilization could reverse, however, with changes in climate and land use. Exotic species encroachment is another habitat trend occurring in the dunes that also results in the reduction of the area of occupancy for this species.

Habitat protection/ownership

Only three sites where C. subglabrum occurs are in parks set aside for conservation purposes: the Beaver Creek site in the Dundurn Sand Hills, the Elbow site in the Elbow Sand Hills, which is part of Douglas Provincial Park and the Spruce Woods site in the Brandon Sand Hills (Table 2). The remaining sites are on private land or publicly owned land being used for grazing (i.e. community pastures). The portion of Canadian Forces Base Dundurn where live fire exercises occur are not grazed but are subject to military training activities.