Barrens Willow (Salix jejuna Fernald) recovery strategy: chapter 2

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PART I. BACKGROUND

Species Information                                                                                    

2.         Distribution

The Barrens Willow is endemic to the Strait of Belle Isle on the northwestern part of the Great Northern Peninsula of Newfoundland. Its distribution spans approximately 30 km of coast from Watts Point to Cape Norman (Fig. 1). It is still present at all known historic locations. Although there are few data available, extent of distribution has probably been stable since the species was first discovered by Wiegand and Long in 1925.

Figure 1. Range of the Barrens Willow (Salix jejunaFernald) in Newfoundland.

3.         Population Size and Trend

Anions (2000) reported less than 50 known individuals. Fieldwork conducted since indicates that the population is much larger: probably totaling more than 10,000 individuals. Available data are not sufficient to determine trends in population size.

The laying of roads through the habitat of the Barrens Willow, particularly in the latter half of the 20^th century, may have adversely affected the population. Quarrying, mainly for road construction and maintenance, is another factor that possibly has had an adverse effect. On the other hand, the Barrens Willow is a pioneer species and now seems to thrive along disturbed roadsides throughout its range. It is possible that road building and maintenance might have had a neutral or positive effect in some areas. Since the 1980s, when the Northern Peninsula Highway was built, there appears to have been only a few, localized disturbances within the range of the species.

4.         Biological Limiting Factors

Habitat specificity is an important component of extinction risk (Rabinowitz 1981, as reported in Keith 1998). The Barrens Willow is endemic to a narrow band of coastal limestone barrens characterized primarily by arctic-like climatic conditions. Such harsh weather conditions, and natural processes like frost heave and abrasion by wind, typically limit plant growth. On the other hand, in more sheltered or shaded areas, competition from other plant species may limit the Barrens Willow’s survival. It is unknown whether, or how, climate change might impact the amount of habitat available. Ultimately, population size and distribution are bound by the restrictive nature of the species’ habitat.

Willow species generally hybridize readily. All willows, including hybrids, are vigorous pioneers that colonize disturbed habitats. In such habitats, hybrids can compete as well as pure individuals but they often display reduced viability and may die within a few years, or they may be infertile and survive only as vegetative plants (Argus 2003).

Herbivorous insects and pathogens have been observed and collected on the Barrens Willow. Their identities and impact on the willow population are unknown at this point.

5.         Threats

According to Anions (2000), the main threat to this species has been loss of habitat. Further quarrying and/or road construction within the range of the species would constitute a significant threat (Argus 2003). Other known threats include habitat degradation associated with vehicular traffic, trails, and the maintenance of roads and infrastructure (Anions 2000). Off- trail vehicle use has been observed repeatedly by field biologists during recent years. Other potential threats include garbage dumping and net drying which have been observed in nearby areas. Anions (2000) also considered moose browsing and invasive plants to be potential threats. However, the risk posed by these threats is probably largely insignificant, as dwarf willows do not provide the kind of browse preferred by moose, and currently few introduced weeds are well adapted to the specific limestone barren habitat where the Barrens Willow occurs (Argus 2003).

6.         Habitat Requirements

Currently, the Barrens Willow occupies exposed coastal limestone barren habitat where vegetation cover is sparse. It is found in dry to periodically wet conditions. The substrate is generally silt and/or sand accumulated in depressions and openings between rocks, or open silt, sand and gravel, sometimes sorted by frost. Given the small population size and restricted distribution of the Barrens Willow, all natural areas of occurrences are considered critical habitat, in other words habitat that is critical to the survival of the species.

7.         Ecological Role

The Barrens Willow is one of three, known, endemic plant species occurring in the coastal limestone barren of the Great Northern Peninsula. The other endemic species are Long’s Braya (Braya longii Fernald, Endangered) and Fernald’s Braya (Braya fernaldii Abbe, Threatened). All three occupy sites where the vegetation cover is usually sparse due to regular disturbance by frost and wind. They are edge species, adapted to a marginal habitat. Many other vascular plant species that are rare in Newfoundland share this niche, disjuncts of arctic-alpine affinity found here at the southern limit of their range (e.g. Bartsia alpina L., Pedicularis flammea L., Potentilla pulchella R. Br. ex Ross). The presence of these species makes the Strait of Belle Ecoregion the richest in Newfoundland in terms of rare and exclusive vascular plants (Bouchard et al. 1991).

The Barrens Willow appears to be morphologically closest toSalix ovalifolia Trautv. and S. stolonifera Cov. (Argus 1997). These species are found in northwestern America, ranging from the Bering Sea and the arctic coast of Alaska and Yukon, south in the cordillera to a few isolated populations in the Rocky Mountains of British Columbia and Alberta. The evolutionary relationship between these species suggests that the Barrens Willow in Newfoundland is probably of refugial origin (Argus 2003). This hypothesis correlates with the presence of a significant number of species of arctic-alpine affinity within the same ecosystem.

Finally, the Barrens Willow is one of the dominant species at some sites. It probably plays a significant role as food source or shelter to a number of invertebrate species. It is also a pioneer species colonizing a habitat characterized by disturbance. Its presence could contribute to the establishment and survival of other plant species.

8.         Importance to People

Botanists and natural history enthusiasts have long been attracted to the limestone barrens of the Great Northern Peninsula. One of the main points of interest is the unique limestone barrens flora. Endemic species like the Barrens Willow are an important component of this flora, and so contribute to the ecotourism potential of the area.

Residents of the Great Northern Peninsula have generally been supportive of and interested in plant conservation efforts within the region. For example, residents of Raleigh were instrumental the creation of a Provincial Botanical Ecological Reserve at Burnt Cape. They are now involved in the management of the reserve and development of activities around it. The Habitat Stewardship Program for the coastal limestone barrens of the Great Northern Peninsula, which is part of the recovery efforts for Long’s and Fernald’s Braya (Hermanutz et al. 2002), is another example. To date, the program has been very successful. Surveys of local residents have shown a strong interest in protecting the species at risk and their habitat. Three stewardship agreements have been signed in the area in 2002, including the first agreement with an elementary school in Canada.

Because of its unique features, the limestone barrens have also been, and continue to be, the subject of many scientific studies in the field of botany, zoology, ecology, and geology. Cape Norman, the type locality of the Barrens Willow, is of particular importance to science. The species itself, and its evolutionary relationships which suggest a refugial origin (see section 7 above), has the potential to provide interesting insight into the history of northern floras.

9.         Knowledge Gaps

Additional information is required on population size and distribution, life history, population genetics, habitat, threats and limiting factors.

9.1.      Survey Requirements:

Surveys to determine occurrence and population size need to be completed, in suitable habitat, within the known range of the species. Adjacent areas where similar habitat may also occur, notably Belle Isle, the southern Labrador coast, and Burnt Cape, should also be surveyed for occurrence of the species.

9.2.      Biological/Ecological Research Requirements:

Further information is required on species recognition, life history parameters (longevity, reproduction, growth), population genetics, and detailed habitat requirements. This information, along with information on threats and limiting factors, is necessary to carry out a population viability analysis, and important for refining the definition of critical habitat and for supporting ex-situ conservation efforts. Although not critical to recovery, a comparative genetic study could provide insights into the evolutionary relationships of the Barrens Willow and origin.

9.3.      Threat Clarification Research Requirements:

Natural and human-induced threats to the habitat are identified in the status report (Anions 2000). The importance of each of these threats and their prevalence on the landscape needs to be assessed. Pests and pathogens have been observed on the Barrens Willow. These still need to be identified and their potential impact assessed. The species may be sensitive to climate change, since its restricted habitat is apparently dependent upon narrow climatic parameters operating within a narrow coastal zone. Long term climatic data may be useful in determining trends. Surveys and research may identify other threats and limiting factors.