Field measurements of the growth rates of forage lichens, and the implications of grazing by Svalbard Reindeer

Mean relative growth rates of lichens on Broggerhalvoya, Svalbard, (78 degr ees 60 ' N, 12 degrees0 ' E, Norwegian High Arctic) ranged from 2.4 (Alecto ria nigricans) to 10.6 (Cladonia rangiferina) mg.g(-1) per week. This relat ed, to a seasonal increase of between 2.5% and 11.2% of original dry mass. The number of species and percentage cover of lichens were greater inside t han outside three long-term reindeer exclosures, suggesting that through th eir indiscriminate trampling and selective grazing Svalbard reindeer have t he ability to completely alter lichen community structure, in both the shor t and long term. The lichen communities are only likely to be able to reest ablish if there is a significant reduction in the reindeer population for a t least 20 years, such as could occur by a complete emigration of deer from the area. Reduced lichen forage availability has potentially serious impli cations for the reindeer population.