Effects of reindeer grazing and recovery after cessation of grazing on the ground-dwelling spider assemblage in Finnish Lapland
Vahtera Varpu; Saikkonen Teemu; Koponen Seppo; Suominen Otso
https://urn.fi/URN:NBN:fi-fe2021042823247
Tiivistelmä
The effect of reindeer Rangifer tarandus L. grazing on the ground-dwelling spider
assemblage in Northern Finland was studied. Changes in species richness, abundance
and evenness of spider assemblages were analyzed in relation to changes in vegetation
and environmental factors in long term grazed and ungrazed sites as well as sites that
had recently switched from grazed to ungrazed and vice versa. Grazing was found to
have a significant impact on height and biomass of lichens and other ground vegetation.
However, it seemed not to have an impact on the total abundance of spiders. This is
likely caused by opposing family and species level responses of spiders to the grazing
regime. Lycosid numbers were highest in grazed and linyphiid numbers in ungrazed
areas. Lycosidae species richness was highest in ungrazed areas whereas Linyphiidae
richness showed no response to grazing. Four Linyphiidae, one Thomisidae and one
Lycosidae species showed strong preference for specific treatments. Sites that had
recovered from grazing for nine years and the sites that were grazed for the last nine
years but were previously ungrazed resembled the long term grazed sites. The results
emphasize the importance of reindeer as a modifier of boreal forest ecosystems but
the impact of reindeer grazing on spiders seems to be family and species specific. The
sites with reversed grazing treatment demonstrate that recovery from strong grazing
pressure at these high latitudes is a slow process whereas reindeer can rapidly change the
conditions in previously ungrazed sites similar to long term heavily grazed conditions.
Kokoelmat
- Rinnakkaistallenteet [19207]