Individual study: Artificial dispersal of the endangered epiphytic lichen Evernia divaricata to forest adjacent to clear-cut in Vindlen, Västerbotten, 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, causing 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 to fragments in which it had become extirpated and adjacent to clear-cut land was assessed. (For other examples of lichen transplant experiments see Cases 298-302).
On 14 August 2001, Evernia divaricata material was collected from northern boreal forest at the confluence of the river Nautasätno with Lake Padjeluoppal (66°48 N, 19°19 E), Jokkmokk, Norrbotten. At this site E.divaricata occurs at one of its highest densities in Sweden. For transportation to the transplant site, each lichen fragment was sprayed with water from the lake, stored within an air-filled plastic bag, which was placed in an insulated box. The box temperature was kept between 17 and 20.5 °C.
Forty fragments (30 mm in length) were transplanted on 10 randomly selected trees at Svartberget. Svartberget is an old stand (>160 years) of Norway spruce Picea abies-dominated forest. The forest is single layered, and exposed to the ENE where there is a clear-cut slope. Although relatively humid and shaded, the habitat is exposed to increased wind speeds from the clear-cut area. E.divaricata was transplanted to two sites 100 m apart and next to a 50 cm wide ditch.
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 microenvironment 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). 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, new growth was recorded.
One year after transplanting, overall survival of E.divaricata (i.e. class 1-5) was 87.5%, and the proportion of fragments in vitality class 3-5 was 67.5% (n=27), in class 5 was 32.5% (n=13), and in class 0 was 12.5% (n=5). The accumulated score (scores added for all lichens) of vitality declined across the study from approx. 175 in March to 130 in August. Growth occurred on 27.5% (n=11) of the fragments. These results suggest that transplanting fragments is at least partially successful at this site. Additionally, there is a nearly significant positive effect (p=0.057) of artificially covering fragments after one year compared to exposed fragments. Also, there was no difference in growth between north and south facing lichen.
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