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Long-lasting ecological legacies of reindeer on tundra vegetation [Elektronisk resurs] / Dagmar D. Egelkraut

Egelkraut, Dagmar D. 1989- (författare)
Olofsson, Johan (preses)
Forbes, Bruce (preses)
Tømmervik, Hans (preses)
van der Wal, René (opponent)
Umeå universitet. Institutionen för ekologi, miljö och geovetenskap (utgivare)
Alternativt namn: Institutionen för ekologi, miljö och geovetenskap, Umeå universitet
Alternativt namn: Institutionen för EMG
Alternativt namn: Engelska: Umeå University. Department of Ecology and Environmental Science
Umeå : Umeå University, 2017
Engelska 33 s.
Läs hela texten (Fritt tillgänglig via Umeå universitet)
Läs hela texten (Fritt tillgänglig via Umeå universitet)
  • E-bokAvhandling(Diss. (sammanfattning) Umeå : Umeå universitet, 2017)
Sammanfattning Ämnesord
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  • Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. Several studies suggest that the effect of reindeer on vegetation may follow predictable patterns and could induce an alternative stable vegetation state. However, little empirical data on the long-term stability of reindeer effects on vegetation exist, as it is inherently challenging to study these ecological processes experimentally on a sufficiently long timescale. The main objective of this thesis was therefore to gain a better understanding of the long-term ecological processes following reindeer-induced vegetation shifts. In order to gain a more mechanistic insight in what initially drives this transition, I used a field-based grazing simulation experiment in which I separated defoliation, trampling, moss removal and the addition of feces. This allowed me to test the relative contribution of reindeer-related activities to initiating the shift from moss and heath- dominated tundra towards a graminoid-dominated vegetation state. Additionally, I studied the long-term ecological stability following such a vegetation shift. I did this by addressing historical milking grounds (HMGs): sites where high reindeer concentrations associated with historical traditional reindeer herding practices induced a vegetation transition from shrubs towards graminoids several centuries earlier, but which were abandoned a century ago. Studying HMGs allowed me to address: 1. The potential stability of reindeer-induced vegetation shifts; 2. The ecological mechanisms contributing to the long-term stability of these vegetation shifts; and 3. How such long-lasting vegetation changes influence soil carbon- and nutrient cycling. I found that trampling by reindeer is an important mechanism by which reindeer cause vegetation change. Addressing HMGs further revealed that this vegetation change can be hightly persistent, as the studied HMGs showed only a low encroachment at the surrounding borders in the last 50 years. The vegetation in the core areas of all studied HMGs had remained strikingly stable, and were hardly invaded by surrounding shrubs. Interestingly, soil nutrient concentrations and microbial activities were still different from the surrounding area as well, and even comparable to actively grazed areas. Even after many centuries of changed vegetation composition and soil processes, there was no difference in total carbon sequestration. This suggests that the environmental conditions for microbial decomposition were more important than vegetation composition for the soil carbon stocks, in our study site. After studying the contemporary habitat use of HMGs by reindeer and other herbivores, investigating the potential plant-soil feedbacks mechanisms and detailed soil analyses, I concluded that several ecological mechanisms contribute to the long-term stability of HMGs: first, the altered soil biotic and abiotic conditions appear to have a stronger advantage for HMG vegetation than for the surrounding tundra vegetation. Furthermore, I found a clear browsing preference of small rodents on single shrubs proliferating in HMGs, causing a strong limitation on shrub expansion. Moreover, the dense established sward of graminoids likely poses a strong direct competition for space and nutrients, hindering seedling establishment. Finally, I conclude that HMGs are highly stable on relevant ecological timescales, and propose how the concepts of historical contingency and ASS can be applied to understand stability of these reindeer-induced vegetation transitions. 

Ämnesord

Natural Sciences  (hsv)
Biological Sciences  (hsv)
Ecology  (hsv)
Naturvetenskap  (hsv)
Biologiska vetenskaper  (hsv)
Ekologi  (hsv)
Ekologi  (sao)
Renar  (sao)
Renbete  (sao)
Växtätare  (sao)
Reindeer  (LCSH)
Ecology  (LCSH)
Herbivores  (LCSH)

Indexterm och SAB-rubrik

Alternative stable state
Herbivory
Historical contingency
Nutrient cycling
Plant-herbivore interactions
Plant-soil feedbacks
Rangifer tarandus
Reindeer herding
Traditional land use
Tundra vegetation

Klassifikation

577.586 (DDC)
Ue.056 (kssb/8 (machine generated))
Inställningar Hjälp

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