Individual study: Artificial dispersal of the endangered epiphytic lichen Evernia divaricata within a boreal forest at Jokkmokk, Norrbottens, Sweden
Liden M., Petterson M., Bergsten U. & Lundmark T. (2004) Artificial dispersal of endangered epiphytic lichens: a tool for conservation in boreal forest landscapes. Biological Conservation, 118, 431-442
Deforestation has caused fragmentation of boreal forests, resulting in geographical and reproductive isolation of many species. Conservation in this habitat has focused primarily on the creation of nature reserves. However, reserves that are not very large often do not contain each successional stage, causing the loss of species. In the case of epiphytic lichens, some species are poor dispersers preventing re-colonisation of many areas due to fragmentation. For example, thalli fragments of fruticose filamentous lichens are dispersed a maximum of 100 m by wind and the possibility that vectors, such as Siberian jay Perisoreus infaustus, will move lichen fragments large distances between suitable fragments is rare. Of particular concern, therefore, are threatened lichen species which live in isolated populations. In this study, the success of transplanting the rare lichen Evernia divaricata within a site where it commonly occurs is assessed. (For other examples of lichen transplant experiments see Cases 298, 299, 301-303).
On 14 August 2001, E.divaricata material was collected from northern boreal forest at the confluence of the river Nautasätno with lake Padjeluoppal, near the town of Jokkmokk, Norrbotten. At this site E. divaricata occurs at one of its highest densities in Sweden. The habitat is a multi-layered Norway spruce Picea abies- dominated forest, with an open and old-growth humid environment. Within two hours of collection, the material was transplanted to trees on which the species was absent. In total, 40 fragments (30 mm in length) were transplanted on ten randomly selected trees.
On a tree, one north and one south facing branch was selected that were similar to branches on which E.divaricata was observed to live at the collection site. On both of these branches, two attachment points were randomly selected, and from these points all other lichens were removed to prevent competition. This gave four attachment points on each tree. E.divaricata fragments were fastened to each attachment point using nylon thread. To determine whether an artificial micro-environment might increase vitality, one of the two fragments on each branch was then covered with a sheltering cocoon made from cultivation fabric (HPJ Fiberduk 17 g/m², HP). It was considered that the cocoon might increase air humidity, protect from herbivores, competition and harsh weather.
Fragments were monitored on three occasions: 27-29 Mar 2002; 25 Jun-1 Jul 2002; and 19-23 Aug 2002. During transplanted fragment monitoring, each fragment was given a score from 5 to 0:
5) Fully Vital: no infection or decay, full level of green pigment
4) Vital: no infection or decay, moderate level of green pigment
3) Fragmented, but otherwise vital: pigmented like (4) and (5)
2) Chlorotic: lacking green pigment, signs of slight decay
1) Necrotic: infected or diseased, signs of decay
0) Dead: Absent or in advanced decay
Additionally, the new growth was recorded.
One year after transplanting, overall survival of E.divaricata (i.e. class 1-5) was 90%. The proportion of fragments in vitality class 3-5 was 82.5% (n=33), in class 5 was 67.5% (n=27) and in class 0 was 10% (n=4). The accumulated score (scores added for all lichens) of vitality declined minimally across the study from approx. 180 in March to 165 in August. Growth occurred on 27% (n=11) of the fragments. Combined, these results suggest that transplanting fragments worked well at this site. Also, artificially covering fragments caused increased vitality after one year than leaving transplanted fragments exposed. Finally, there was no difference in growth between north and south facing lichen.
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