Reindeer keep shrubs in a browse trap

Publisert 22.11.2017

In a recently published paper in Ecological Applications, COAT researchers Bråthen & Ravolainen and colleagues show how reindeer management controls the climate-sensitive tundra state transition from open tundra grasslands to shrublands.

Reindeer, Photo: Geir Vie
Reindeer, Photo: Geir Vie

Palatable willows (Salix) are dominant tall shrubs and highly responsive to climate change. However, for the state transition to take place, small life stages of willow must become tall and abundant. Where reindeer are abundant, more specifically at densities above 5 reindeer per km2, the transition from small to tall life stages does not take place. The small life stages are kept in a browse trap by reindeer, and the shrubs are prevented from growing tall. However, where reindeer are at densities lower than 5 reindeer per km2, the shrubs are no longer in a browse trap and the shrubs grow taller and are more likely to reach their tall life stage with foliage beyond the reach of reindeer.

Our results were achieved through a large-scale quasi-experimental study design that included a range of reindeer management units across Finnmark with different reindeer densities, seasonal ranges and a gradient of 5°C in summer temperatures. We conducted ground-surveys in these management units during which we measured the abundance and height of the small shrub life stages. We also studied aerial photographs and assessed the shrubline, i.e. the elevation at which tall shrub life stages make up continuous shrublands.

As opposed to the small life stages, the tall life stages were responsive to increasing temperatures. In both migratory and summer seasonal ranges the shrubline increased 100 m per 1°C increment in temperature. However, we also found the shrubline to be at a 100 m lower elevation in the summer ranges as opposed to in the migratory ranges, where there is no browsing in summer. Because tall shrublands can be several decades old, we interpret this finding as indicative of that most management units have managed their reindeer at densities high enough to cause a browse trap during some time in the past.

In conclusion, reindeer management controls a climate-sensitive state transition in the tundra, and past management is visible in the landscape through reduced elevation of the shrubline.



More news

Nov06 Weather stations up and running!
Created by Eeva Soininen on 11/6/2018 2:22:28 PM

We proudly announce that the first three COAT weather stations at the Varanger peninsula are now in...
Read More..

Sep24 Rodent-plant interactions are temporally variable
Created by Ingrid Jensvoll on 9/24/2018 10:07:05 AM

Rodent abundance during population peaks in the tundra is highly variable. In a new study COAT re...
Read More..

Jun29 Moth outbreaks at Varanger peninsula have spread to salix shrub
Created by Ingrid Jensvoll on 6/29/2018 3:26:00 PM

In recent years there has been large moth outbreaks in the birch forest west of Vadsø, now the outb...
Read More..

Jun18 First recording of scarce umber moth in Northern-Finland
Created by Ingrid Jensvoll on 6/18/2018 11:14:41 AM

Every autumn since 1972, researchers from Kevo Subarctic Research Station (Univ. Turku), have bee...
Read More..

May24 New series: COAT CASE STORIES
Created by Ingrid Jensvoll on 5/24/2018 3:05:50 PM

COAT CASE STORIES are short popular handouts from COAT covering a variety of topics related to COAT...
Read More..

May24 Available position in COAT
Created by Ingrid Jensvoll on 5/24/2018 2:51:56 PM

COAT has a available position as Advisor. The position will mainly have the responsibility for to h...
Read More..

Mar20 Winter fieldwork in COAT
Created by Ingrid Jensvoll on 3/20/2018 4:52:48 PM

March and April are the months for winter fieldwork in COAT. The yearly monitoring of snow conditio...
Read More..

Feb15 A new management action implemented in COAT Varanger Arctic fox module
Created by Ingrid Jensvoll on 2/15/2018 9:49:20 AM

On February 13, twenty-seven captive bred arctic foxes were released on the Varanger Peninsula as a...
Read More..

Feb06 Goose density influences predation on ground-nesting birds in Svalbard
Created by Ingrid Jensvoll on 2/6/2018 11:26:40 AM

The number of geese that spend the summer in Svalbard has increased in recent years. Geese nest on ...
Read More..

Dec05 Salvage logging of mountain birch after moth outbreaks
Created by on 12/5/2017 11:06:01 AM

Outbreaks of defoliating geometrid moths have damaged thousands of square kilometres of mountain bi...
Read More..