Hotbild för ädellav Megalaria grossa i Uppland och på Gotland

Sammanfattning: Megalaria grossa is classified as Near treatened on the Swedish Red List. It is also a so called signals spieces, e. g. a spieces that function as an indicator, signalling a forest that is worthy of protection. The aim of this study was to clarify the status at selected localities in the province of Uppland and Gotland. 12 old localities, were visited in Uppland and 3 wooded meadow on Gotland. A wooded meadow is an open meadow with some segments of trees and bushes; it has a long term management with, for example, spring clearing, hay-making and grazing. The results showed that M. grossa had decreased in 2 out of the 3 wooded meadows compared to an inventory at 1989. In Tjängdarve, M. grossa decreased from 7 to 1 inventoried trees along a transect and in Lojsta from 8 to 1 trees between the years 1989 to 2007. In the wooded meadow of Laxare there were no changes. The average circumference of the trees in Lojsta and Laxare has increased with 30 % whereas the distance between the trees remains unchanged since 1989. In Laxare the average circumference of the trees has increase with 17 % and the distance between the trees has decreased. The decrease of the M. grossa population in the wooded meadows might depend on the fact that the wooded meadows have become denser and therefore darker. Another reason may be impact from e.g. air pollution. In the province of Uppland M. grossa was found in 7 out of 12 known localities. The forest in this area has become denser and the future for M. grossa at the localities is obscure. Moreover, Picea abies has increased rapidly at the localities. The old deciduous trees at the localities should be protected and forest clearance is one measure that could be carried out to ensure the continuous growth of M. grossa. If nothing is done the population of M. grossa is likely to continue decrease in Sweden which may lead to a change of categorization in the Swedish Red List from Near Threatened to Vulnerable. Finally, due to more dense forests, also other species occurring in the same habitat will certainly decrease as well.