Effect of disturbance treatment and diaspore fragment type on establishment of Sphagnum angermanicum at Barvallhållen, central Sweden
Gunnarsson U. & Söderström L. (2008) Can artificial introductions of diaspore fragments work as a conservation tool for maintaining populations of the rare peatmoss Sphagnum angermanicum? Biological Conservation, 135, 450-458.
In Europe, the moss Sphagnum angermanicum is known from about 20 localities in Sweden where it is classified as near threatened. There is a single report from Iceland; elsewhere it occurs in coastal northeast USA and southeast Canada. S.angermanicum probably use the capitula as the main short distance dispersal unit, as a fragile part of the stem occurs just below the capitula, which is easily broken. At almost all Swedish S.angermanicum localities there were indications of small scale disturbances, usually moose Alces alces trampling or irregular ground water levels. An experiment was undertaken to assess the effects of disturbance treatments and diaspore fragment type on establishment of S.angermanicum at a fen within its Swedish range.
Study area: The experiment was undertaken in a fen at Barvallhållen (61°04′N13°26′E), central Sweden.
Experimental design: Whole shoots, capitula, stems and capitula fragments were 'planted' in 20 plots (0.5 × 0.5 m), with five replicates of each of three disturbances: living moss removed (bare peat); top 10 cm of peat mixed with a hoe (mixing); trampling the plot three times (trampling); plus untreated control plots. The plots were established in September 2001 in sites that appeared suitable (i.e. typical associated vegetation, pH 4.1–5.7 and distance to the ground water table ranging 5–23 cm) but not occupied by S.angermanicum.
Moss was cut into shoots (top 3 cm), capitula (top 0.3 cm), stems (3 cm section from 3 to 6 cm down from apex) and capitula fragments (10 capitula cut with a scalpel several times to create fragments of branches, stems and leaves a few mm long). The fragments were sown in four sub-plots (0.1 × 0.1 m) in the centre of the 0.5 × 0.5 m plot (10 shoots, capitula and stems; capitula fragments, average of 320 fragments/plot, were spread evenly over the surface).
Establishment success: Establishment was recorded at 9, 12, 24, 36 and 48 months. The number of capitula formed by the different fragment types was scored and transformed into establishment success. The length increment of the established Sphagnum community was measured with a ruler to the nearest mm at 9, 12 and 24 months.
Stem fragments: Establishment after 9 months was very low with only two plots developing two capitula each (total establishment frequency 0.02), but these were not relocated in the October 2002 survey.
Capitula fragments: Establishment success after 9 months was very low with 11 fragments establishing after 9 months; because of the high number sown, the total establishment frequency was very low (1.7 × 10−3). Only two of these established capitula fragments were recorded in October 2002, but 10 established capitula were found in 2005.
Shoots and capitula: Shoots and capitula had much higher success (total frequency in October 2002 of 0.61 and 0.19, respectively). There was a reduction in numbers of capitula and shoots after the first summer (as for stems and capitula fragments), with a slight recovery until the last survey in 2005. For capitula no treatment effects on establishment success were apparent; for shoots there was a high disappearance of shoots over the first summer in the bare peat and the mixing treatments.
The reasonably high establishment success of S.angermanicum shoots and capitula suggests that introductions to apparently suitable but unoccupied habitat could be considered if the number of occcupied localities continues to decrease.
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