A globally rare species on old Populus tremula. The deterioration of its habitat is caused by human activities. Proposed and data compiled by Göran Thor.
Suggested assessment by proposer: VU on the A criterium (A2bc; C1), population decrease has been 30 (15-40) % over 100 years and is expected to be 15 (10-25) % the coming 100 years.
Collema curtisporum has its largest population (probably >90 %) in North Sweden (c. 200 localities). Outside Sweden it is reported from a few localities in Norway (red-listed), Finland (red-listed), Italy and western North America.
The species has decreased rapidly in Sweden and is red-listed in at least Sweden, Norway and Finland.
Documentation and motivation needed.
Population Trend: Decreasing
The species is found on middle aged Populus tremula in semi-open, boreal, mixed forests in humid but open situations as near streams, mires and in north slopes. Very rarely also found on other tree species. Most forests where it occurs are established after forest fires.
Forestry is the major threat. In a long term perspective, the low number of forest fires is a threat as the regeneration of Populus tremula decrease.
All localities should be protected. The regeneration of Populus tremula trees should be supported on localities for the species.
The Information System on Italian Lichens. http://dbiodbs.univ.trieste.it/italic/italic03
Degelius, G. 1954. The lichen genus Collema in Europe. Symb. Bot. Ups. 13(2).