| Summary: | There are indications that lichen-rich areas in northern Sweden, commonly used for winter grazing by semi-domesticated reindeer (Rangifer tarandus), has declined by 30-50% since the 1950s. This is mainly believed to be because of a rise in clear-cutting activities during that time period. With fewer areas for the reindeer to conduct their winter grazing it is important to know how grazing activities potentially affect the ground lichen. This report investigates what variables, such as tree density and reindeer grazing intensity, affect the height of five ground lichens; four Cladonia and one Cetraria species. The research was conducted in Norrbotten and Västerbotten, with a total of 55 sample plots, during the month of July 2015. Previous National Forest Inventory plots with a ground cover of at least 25% reindeer lichen were used. The commonly found species were Cladonia rangiferina and Cladonia arbuscula/mitis. Grazing intensity from reindeer had a low explanatory power on the variation in the mat-forming lichen height in boreal forests if considered by itself (R2=0.05, p=0.06). Instead, reindeer grazing effects became more evident when considering an interaction with the tree density of the forest. Tree density and grazing pressure have an important role for lichen height, but there probably are more variables which, directly or indirectly, affect lichen height. Tree density also effects the amount of reindeer found in the area and seems to be of great importance when reindeer graze during the winter.
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