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

摘要

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 p?verkar k?rlv?xtflorans artrikedom och diversitet p? dolomitp?verkade l?galpina lokaler i de artrikaste delarna av norra Fennoskandien. Vi inventerade 8 lokaler med olika rent?theter. Tv? lokaler ligger inom Malla Nationalpark, d?r renar har varit f?rbjudna sedan 1981 och starkt begr?nsade sedan 1950-talet. De sex andra lokalerna ligger i andra artrika omr?den med samma dolomitdominerade berggrund, men ?r betade av renar. Rent?theterna vid de studerade lokalerna varierar fr?n helt obefintligt till bland de h?gsta rent?theter man kan finna i Fennoskandien. Inventeringen utf?rdes genom att systematiskt unders?ka fyra 2 m x 10 m stora ytor i varje lokal i en habitattyp som ?r speciellt rik i ovanliga k?rlv?xter (fj?llsippehed-l?g?rts?ng komplex). Varje yta delades upp i 20 sm?ytor (1 m x 1 m), och en total artlista uppr?ttades f?r var och en av dessa sm?ytor. Den f?rsta axeln i DCA (detrended correspondence analyses) analysen korrelerade med rent?theten. Det visar att renar p?verkar sammans?ttningen av v?xtsamh?llet. Ingen av de vanliga m?tten p? biodiversitet (artrikedom eller Shannon-Wiener diversitetsindex) var korrelerade med rent?theten. Trots detta, var t?theterna av Ca-gynnade v?xter och arter r?dlistade i Finland positivt korrelerade med rent?theten. Trots att renarna inte p?verkade totala artrikedommen, kan de vara betydelsefulla f?r regionala biodiversiteten eftersom de gynnar ovanliga och hotade arter. De vanliga m?tten p? biodiversitet har begr?nsat v?rde f?r bevarandebiologiska fr?gest?llningar, eftersom de ?r lika k?nsliga f?r ovanliga och vanliga arter.