High species turnover and decreasing plant species richness on mountain summits in Sweden : reindeer grazing overrides climate change?

• We investigated changes in vascular plant species richness in nine summit floras in the central part of the Fennoscandian mountain range compared to historical data from 1950. We revisited the summits (defined as the top 50 altitudinal meters of each mountain) in 2002, and recorded all species. The changes in species richness were tested against both species and mountain characteristics. Species richness had declined on eight of the nine summits. Five of the species were new since the 1950s, while 17 species were lost from the summits. However, species turnover was even higher: 57 of our recorded species occurrences had established on at least one mountain since the 1950s, while we could not find 132 of the recorded occurrences in 1950 on one or more mountains. Temperature had increased since 1950 by about 1 oC and precipitation by 12%. The reindeer population has more than doubled. No correlations between plant responses, plant characteristics, and mountain characteristics were found, suggesting individualistic and mountain-specific responses. We conclude that climate changes may be responsible for an increased establishment and reindeer trampling for increased mortality of established individuals. However, the net result is a decline in species richness.

Ämnesord

LANTBRUKSVETENSKAPER  -- Annan lantbruksvetenskap -- Miljö- och naturvårdsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Other Agricultural Sciences -- Environmental Sciences related to Agriculture and Land-use (hsv//eng)

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