Inland populations of Juncus balticus (Juncaceae) in Scotland

Abstract

Typically considered a coastal species in Great Britain, Juncus balticus Willd. also occurs inland as a native plant beside the Rivers Avon, Dulnain and Findhorn in NE Scotland (and beside the R. Lossie in the 19th Century). Here it is found at median altitude 290 m AOD (inter-quartile range, 249 - 341 m). It also occurs as a native at one inland loch-side, and was found beside another loch in the 19th Century. In total, J. balticus has been recorded beside inland rivers from 14 10 km grid squares. In its inland riverside habitat, J. balticus is overwhelmingly found within communities dominated by native plant taxa, primarily associated with infertile, moist to damp, weakly to moderately acid soils, with high levels of illumination. Few observers are familiar with seeing J. balticus at its inland sites, therefore it is possible that this species has been overlooked along other rivers and burns in NE Scotland, and perhaps elsewhere. The first record of J. balticus beside a road was in 1907, long before roads were widely treated with salt in the winter, but it was not until 1979 that a second roadside population was discovered. Roadside and trackside populations have now been found in 19 10 km grid squares. At most of these sites it is likely to be an accidental introduction. It is now more widespread on roadsides than along inland riversides. The isolated nature of the roadside populations indicates that there have been multiple independent colonisations. It is highly likely that additional roadside populations await discovery, and that further colonisation events will occur.