Abstract

Historical contingency is the impact of past events, like the timing and order of species arrival, on community assembly, and can sometimes result in alternative stable states of ecological communities. Large herbivores, wild and domestic, can cause profound changes in the structure and functioning of plant communities and therefore probably influence historical contingency; however, little empirical data on the stability of such shifts or subsequent drivers of stability are available. We studied the centennial legacy of reindeer (Rangifer tarandus) pressure on arctic tundra vegetation by considering historical milking grounds (HMGs): graminoid- and forb-dominated patches amid shrub-dominated tundra, formed by historical Sami reindeer herding practices that ended approximately 100years ago. Our results show that the core areas of all studied HMGs remained strikingly stable, being hardly invaded by surrounding shrubs. Soil nitrogen concentrations were comparable to heavily grazed areas. However, the HMGs are slowly being reinvaded by vegetative growth of shrubs at the edges, and the rate of ingrowth increased with higher mineral N availability. Furthermore, our data indicate that several biotic feedbacks contribute to the stability of the HMGs: increased nutrient turnover supporting herbaceous vegetation, strong interspecific competition preventing invasion and herbivore damage to invading shrubs. In particular, voles and lemmings appear to be important, selectively damaging shrubs in the HMGs. We concluded that HMGs provide clear evidence for historical contingency of herbivore effects in arctic ecosystems. We showed that several biotic feedbacks can contribute to subsequent vegetation stability, but their relative importance will vary in time and space.

Keywords

alternative stable states; plant-herbivore interactions; historical contingency; land use legacy; plant-soil interactions; Rangifer tarandus; soil nutrients; vegetation composition

Published in

Ecosystems
2018, Volume: 21, number: 8, pages: 1545-1563

SLU Authors

• Allard, Anna

  • Department of Forest Resource Management, Swedish University of Agricultural Sciences
    

• Åkerholm, Marianne

  • Department of Forest Resource Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences


Publication identifier

DOI: https://doi.org/10.1007/s10021-018-0239-z

Permanent link to this page (URI)

https://res.slu.se/id/publ/94359