Effects of reindeer density on vascular plant diversity on North Scandinavian mountains

We studied the effects of reindeer grazing on species richness and diversity of vascular plants on dolomite influenced low alpine sites in the species rich northern part of the Scandes using 8 sites with different reindeer densities. Two sites were situated inside Malla Strict Nature Reserve, where reindeer grazing have been totally prohibited since 1981, and strongly restricted since 1950s. The six other sites were located in other species rich hotspot sites standardized to be as similar to the dolomite-influenced sites in Malla Strict Reserve as possible but varying in reindeer densities commonly found in the Fennoscandian mountain chain. Each site with a habitat complex especially rich in rare vascular plants (the Dryas heath – low herb meadow complex) was systematically sampled in four plots of 2 m x 10 m. The plots were divided to 20 squares of 1 m x 1 m, and complete species lists of vascular plants were compiled for each of the squares. The first DCA (detrended correspondence analysis) axis was strongly related to an index of reindeer grazing, indicating that grazing has a strong impact on the composition of the vegetation. None of the characteristics indices of biodiversity (species richness, evenness or Shannon-Wiener H’) was correlated with reindeer density. The local abundances of categories consisting of relatively rare plants (Ca favored plants and red listed plants of Finland) showed significant, positive correlation with the intensity of reindeer grazing. We conclude that even though the density of reindeer has no influence on the total species richness or diversity of vascular plants, reindeer may still be important for regional biodiversity as it seems to favour rare and threatened plants. Moreover, our results imply that standard diversity indices may have limited value in the context of conservation biology, as these indices are equally influenced by rarities and by trivial species. Abstract in Swedish / Sammandrag: Vi studerade hur renbete paverkar karlvaxtflorans artrikedom och diversitet pa dolomitpaverkade lagalpina lokaler i de artrikaste delarna av norra Fennoskandien. Vi inventerade 8 lokaler med olika rentatheter. Tva lokaler ligger inom Malla Nationalpark, dar renar har varit forbjudna sedan 1981 och starkt begransade sedan 1950-talet. De sex andra lokalerna ligger i andra artrika omraden med samma dolomitdominerade berggrund, men ar betade av renar. Rentatheterna vid de studerade lokalerna varierar fran helt obefintligt till bland de hogsta rentatheter man kan finna i Fennoskandien. Inventeringen utfordes genom att systematiskt undersoka fyra 2 m x 10 m stora ytor i varje lokal i en habitattyp som ar speciellt rik i ovanliga karlvaxter (fjallsippehed-lagortsang komplex). Varje yta delades upp i 20 smaytor (1 m x 1 m), och en total artlista upprattades for var och en av dessa smaytor. Den forsta axeln i DCA (detrended correspondence analyses) analysen korrelerade med rentatheten. Det visar att renar paverkar sammansattningen av vaxtsamhallet. Ingen av de vanliga matten pa biodiversitet (artrikedom eller Shannon-Wiener diversitetsindex) var korrelerade med rentatheten. Trots detta, var tatheterna av Ca-gynnade vaxter och arter rodlistade i Finland positivt korrelerade med rentatheten. Trots att renarna inte paverkade totala artrikedommen, kan de vara betydelsefulla for regionala biodiversiteten eftersom de gynnar ovanliga och hotade arter. De vanliga matten pa biodiversitet har begransat varde for bevarandebiologiska fragestallningar, eftersom de ar lika kansliga for ovanliga och vanliga arter.