New Jersey rush (Juncus caesariensis) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Long-term trend information for Nova Scotia populations of Juncus caesariensis is not available as very little was known about Canadian populations of this species prior to the 1990s. Fieldwork was originally conducted by the writer over a 3 day period in 1993 following the designation of this species by COSEWIC and, as well, over 4 days by the writer and an assistant in late August and early September of 2002. This latest survey showed that there has been no significant decrease in population sizes at previously reported sites (Newell and Newell, 1992), over the past ten-years (Table 1). Some sites were in fact observed to have larger populations than when first surveyed. This may reflect a more efficient survey technique than an actual increase in plant numbers. Plants could not be relocated on one wetland (Site 17, St. Esprit/Ferguson Road). Original numbers for this location were very low (<10) and it would be easy to overlook the presence of this species at this particular location.

A number of new sites were discovered during the fieldwork conducted for this update status report in 2002. Additional sites were also located during a Species at Risk Survey conducted by Parks Canada in 2001 (pers. comm., J. Bridgland, 2002). A herbarium specimen of New Jersey Rush from a new site was discovered at the Herbarium at the University College of Cape Breton. This had been misidentified as Juncus canadensis, a similar appearing species.  Another location was discovered in the fall of 2002 (pers. comm., C. Sneddon, 2003). All currently known locations for New Jersey Rush in Nova Scotia are listed in Table 1.

In total, the number of known locations for New Jersey Rush now stands at 26. At Site 17 (St. Esprit/Ferguson Road), the small number of plants reported in 1992 could not be relocated in 2002 and are assumed to be extirpated. This represents an increase of 11 populations from the original status report. Gracieville Sites 4 and 5 (Newell and Newell, 1992) are combined here as one site (Site 4a and 4b) since they represent one wetland that was divided by a highway. 

There has been no significant change in the known geographic range of this species in Nova Scotia.

Population sizes range from <10 to 1000 mature individuals. From population estimates by the author and others, it is suggested in this update status report, that there are approximately 5000-10,000 mature individuals or clumps (each clump made up of 1-27 culms) of New Jersey Rush in the Canada (Table 1). There is no data available on number of vegetative individuals. There are still many wetlands within the known geographic range of this species in Nova Scotia that remain to be investigated for the presence of New Jersey Rush. Many of these are somewhat more difficult to access than the known sites.

The Canadian populations are effectively isolated from the populations in the United States by distance. The closest U. S. populations to those in Cape Breton would be in New Jersey. There would be little chance of colonization from the south if the Canadian populations should be extirpated.

Globally, this species is said to reach its greatest abundance in the Pine Barrens of New Jersey (S2). Beyond this area, it is restricted to isolated occurrences in Maryland (S1) and Virginia (S2) and has disjunct populations in Nova Scotia (S2) and North Carolina (S1) (NatureServe Explorer, 2003). In New Jersey, most sites are located in the Pine Barrens and appear secure (Schuyler, 1990). According to the New Jersey Natural Heritage Program (pers. comm., D. Snyder, 2003) a minimum of 62 out of 95 occurrences are believed to be extant with population sizes ranging from a few plants to several thousand. A few populations number 10,000 or more.

There are a number of historical records for this species in the United States suggesting that New Jersey Rush was more widely spread in the past than it is today (Schuyler, 1990).

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