Lakeside daisy (Hymenoxys herbacea) COSEWIC assessment and update update status report: chapter 5

Habitat

Habitat Requirements

Hymenoxys herbacea is largely confined to the grassland and pavement alvars or lakeshores in the Great Lakes regions. These habitats are characteristically flat, thin-soiled areas with prevalent dolomite and limestone rocks, sand and gravel that are sparsely vegetated (De Mauro, 1993; Voss, 1996; Wunderlin, 1971). The habitats are open, with little tree cover, and receive large amounts of sunlight. The limestone pavement that is prevalent in the area allows for good drainage. The plants primarily grow in the cracks of the limestone pavements or on tufts of low-growing vegetation (i.e. mosses).  In localized areas of alvar and cliff habitats, H. herbacea can be a community dominant. Although in one alvar (population CH), which is thickly vegetated with grasses and sedges, H. herbacea is much less dense.

Specific Habitat

Hymenoxys herbacea occurs in one of three specific types of alvar habitat as defined by Reschke et al. (1999). A shortened description of each habitat type is given below; for a more detailed description see Reschke et al. (1999).

Grassland alvars have been classified by the Alvar Working Group of The Nature Conservancy (Reschke et al.,1999) as a ‘Little bluestem alvar grassland’.  This community has a global rank of G2 (imperiled globally with usually 6 to 20 global occurrences) and is recognized by: open canopy, few shrubs over 0.5 m tall, many dwarf shrubs under 0.5 m tall, less than 50% of the ground surface is exposed and is dominated by grasses and sedges, loam soils are shallow over flat limestone dolostone bedrock, soils are often seasonally wet (saturated) and very dry (Reschke et al., 1999).

Non-vascular pavement alvars have a global rank of G2 and are defined as having: open canopy, few shrubs, ground layer is primarily exposed limestone or dolostone bedrock covered with lichens and mosses, and the little soil present is restricted to rock crevices (grikes), or underneath a mossy mat (Reschke et al., 1999).

Great Lakes limestone alvars are sparsely vegetated lakeshores found along the Great Lakes shorelines of Ontario and have exposed flat limestone or dolostone bedrock (about 20% vegetative cover). The surface of the bedrock has numerous cracks and crevices where most of the plants are rooted (Reschke et al., 1999). 

Regional Climate

On average, the Bruce Peninsula/Manitoulin Region experiences temperatures between 0 C and +27°C during the flowering season (April to July) and between 0°C and –25°C during the winter (December to February) (Environment Canada Statistics). In the pavement and grassland alvars, there is an alternating wet and dry soil moisture regime. These locations tend to be wet in the spring and fall and very dry in midsummer. Often these locations are sheltered from the wind by surrounding forests (Reschke et al., 1999). On the lakeshore habitat, there is frequent fog and populations are exposed to the prevailing winds.

Regional Vegetation

The dominant species in grassland alvars are typically Sporobolus heterolepis, Schizachyrium scoparium or Carex scirpoidea. The characteristic species of the non-vascular pavement alvars are lichens and mosses (such as cup lichen, blackthread lichen, twisted moss, Saxifraga virginiensis, Penstemon hirsutus, Potentilla norvegica, and Trichostema brachiatum.  Typically, in the limestone lakeshores of the Great Lakes, Calamintha arkansana, Pentaphylloides floribunda, Potentilla anserina, Panicum lindheimeri, Thuja occidentalis, Deschampsia cespitosa, Viola nephrophylla, Primula mistassinica and Lobelia kalmii are present (Reschke et al., 1999).

Associated Species

Several species of plants are frequently found within ten meters of an H. herbacea individual in at least one of the habitat types. Those found include:

  • Allium schoenoprasum
  • Aquilegia canadensis
  • Arabis lyrata
  • Aster macrophyllus
  • Astragalus neglectus
  • Calamintha arkansana
  • Campanula rotundifolia
  • Carex scirpoidea
  • Castilleja coccinea
  • Cerastium arvense
  • Chrysanthemum leucanthemum
  • Cirsium hillii
  • Cirsium pitcheri
  • Cladina pixidata
  • Commandra umbellata
  • Coreopsis lanceolata
  • Cypripedium arietinum
  • Cypripedium calceolus var. pubescens
  • Danthonia spicata
  • Deschampsia cespitosa
  • Elymus lanceolatus ssp. psammophilus
  • Fragaria virginiana
  • Hieracium pilosella
  • Iris lacustris
  • Juniperus communis
  • Juniperus horizontalis
  • Liatris cylindracea
  • Lobelia kalmii
  • Lonicera hirsuta
  • Medicago lupulina
  • Minuartia michauxii
  • Pellaea atropurpurea
  • Pentaphylloides floribunda
  • Phalaris arundinacea
  • Plantago lanceolata
  • Polygala paucifolia
  • Polygala senega     
  • Potentilla anserina
  • Carex scirpoidea                                                     
  • Potentilla recta
  • Primula mistassinica
  • Prunella vulgaris
  • Prunus pumila
  • Prunus virginiana
  • Panicum lindheimeri
  • Rhamnus alnifolia
  • Saxifraga virginiana
  • Schizachyrium scoparium
  • Senecio obovatus
  • Senecio pauperculus
  • Sisyrinchium montanum
  • Smilacina stellata
  • Solidago houghtonii
  • Solidago juncea
  • Solidago simplex ssp. randii
  • Sporobolus heterolepis
  • Thuja occidentalis
  • Tortella tortuosa
  • Vaccinium angustifolium
  • Viola nephrophylla
  • Woodsia oregana var. cathcartiana
  • Zigadenus elegans

Other Rare Species found Associated with H. herbacea

Alvar communities share several key characteristics, one of which is that they contain many species that are rare elsewhere in the Great Lakes basin and some are endemic to the basin. Other rare species (i.e., they are included in the NHIC’s list of rare plants; Oldham 1999 and in Brownell and Riley, 2000) that were observed to be living in the same alvars as H. herbacea include Iris lacustris (G3, S3), Cypripedium arietinum (G3, S3), Solidago simplex ssp. randii (S3), Astragalus neglectus (G3G4, S3), Solidago houghtonii (G3, S2),Pellaea atropurpurea (S3), Senecio obovatus (S3), Woodsia oregana var. cathcartiana (S3), Cirsium hillii (G3, S3), Sporobolus heterolepis (S3), Liatris cylindracea (S3), Cirsium pitcheri (Endangered in Canada, G3, S2) and Elymus lanceolatus ssp. psammophilus (G5T3?, S3). See Oldham (1999) for definitions of global (G-ranks) and subnational (S-ranks) conservation status ranks. 

Trends

Some shoreline habitat is degrading rapidly, particularly where pedestrian traffic is high within Bruce Peninsula National Park. These areas have been trampled consistently for a number of years as the Bruce Trail and National Park trails make use of the open spaces typical of the lakeshore habitat of the plant. Likewise, alvar habitats, with their open spaces, are being converted into camping areas although at a much slower pace than the shoreline habitat.

Protection/Ownership

Sixteen of the 39 known populations of H. herbacea are found on privately owned land (Natural Heritage Information Centre Records; Brownell and Riley, 2000). The other 23 populations are on property owned at least in part by public agencies (e.g. Bruce Peninsula National Park, Ontario Parks) or organizations interested in the conservation of the plant and its habitat (Federation of Ontario Naturalists, Nature Conservancy of Canada, Cape Croker First Nations Band, Private Plant Reserve). Most of the privately owned properties occur on Manitoulin Island while most of the Bruce Peninsula populations exist on nature reserves. 

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