In a paper titled "Early Mississippian lycopsid forests in a delta-plain setting at Norton, near Sussex,...", by H.J. Falcon-Lang,¹  Mr. Falcon-Lang came up with a similar figure that I myself came up with (i.e. only about 1 in 50 trees "appear" to be "in situ"). 

His paper discusses similar upright trees that were observed in road cuts in New Brunswick, Canada --  not far from Joggins, Nova Scotia.  And although he claims that these trees were "in growth position", I doubt that this is the case.  Below is a quote from his paper.

"More than 99% of the trees observed in growth position are lycopsids (n=672). These mostly consist of either rootstock compressions or mould-casts, or sandstone-cast upright trunks that lack a preserved rootstock. Only about 14 in situ lycopsid specimens at Norton showing both rootstock and trunk in organic connection are exposed."                                                                                Emphasis Added.

In other words, out of 672 upright trees observed "Only about 14" possessed "both rootstalk and trunk in... connection... exposed."  And even though this number would likely be somewhat higher if one were to dig down into (or chip away at) the strata that encloses these trees, if one were to do so, he or she would also very likely find that a great MANY (if not an overwhelming majority) of these trees are either missing their entire root-stalk, or that a great many of the roots that they possess are truncated (i.e. broken off).  Note also that the condition of these "soils" is also similar to those at Joggins, being  "very poorly developed."  Below is another quote from this article with regard to the "soils."

"All tree-bearing palaeosols were very poorly developed, composed of thin, medium grey mudstone–siltstone layers that showed either no alteration (apart from being pervasively rooted) or at most a weak horizonation defined by a light grey upper layer (interpreted as a leached epipedon). These palaeosols would be classified as entisols and inceptisols using modern soil taxonomy nomenclature (USDA Soil Survey Staff 1999), soils typical of very immature fluvial exposure surfaces (Retallack 1990)."

Entisols = Soils of slight and recent development; common along rivers and flood plains.
Inceptisol: A soil so young that horizons have just begun to form: esp. prevalent in tundra areas.

The fact that "all paleosols were very poorly developed" and that they were layered suggests that they were not growing surfaces at all, but rather simply the strata in which the upright floating trees were entombed. And the extreme paucity of trees exhibiting both roots with attached rootlets appear also to suggest the same. Therefore (as with the similar upright trees at Joggins) it appears highly doubtful that ANY of these trees as well are in their original growth position (i.e. in situ), but rather  have also likely been transported by the same flood or floods which both uprooted and entombed them.

1. Falcon-Lang, "Early Mississippian lycopsid forests in a delta-plain setting at Norton, near Sussex, New Brunswick, Canada," Journal of the Geological Society. 2004; vol. 161; pp. 969-981

This paper can also be purchased at: http://jgs.geoscienceworld.org/cgi/content/full/161/6/969 or http://www.ingentaconnect.com/content/geol/jgs/2004/00000161/00000006/art00009

It may also be obtained by visiting one's local University Library, or from one of the following Document Delivery Services: http://www.biodocuments.net/services/pricing.php
http://www.lindahall.org/services/document_delivery/index.shtml