Abstract
To better understand how various factors affect the establishment of forest and trees around the tree line-ecotone, this study was conducted in Troms County, Norway. The altitude of different forest and tree limits together with the surrounding vegetation type were collected during August 2011. Comparisons of the collected data were made with previously collected data from the same sites conducted 1914 and 1915. On average the forest limit has expanded with 26 meters in altitude, however, an expansion is not statistically significant for the whole area. The tree limit has significantly expanded in altitude. At all weather stations the temperature sum and length of the growing season have increased which is proposed to have positive effects on sapling establishment. There is no significant correlation between the change in sheep density in relation to the shift in forest and tree limit. The shift in reindeer density did not correspond to the shift of forest limit, but to the shift in tree limit. However the coefficient of determination was low which means that reindeer only accounts for a small part of the altitudinal shift. At many sites where the tree limit has expanded, reindeer density has declined which might have provided for new plants to establish and older to grow in size. The altitude of the forest and tree limits increases with increasing distance to the coast, most likely due to the degree of maritimity. It should also be noted that the magnitude of the shift in the limits, decrease with increasing distance to the coast. With reduced amount of reindeers and increased temperature vegetation changes have occurred. The amount of birch forest has increased, most likely, in expense of declined willow-thickets. Also abundance of alpine lichen/moss heath has increased, which might be a result of reduced grazing by reindeers.
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Claims 11
Claim · model-written summary
Forest limit rose by an average 26 meters in altitude, without statistical significance across the area.
Not reportedTaxon
Verbatim
e0“On average the forest limit has expanded with 26 meters in altitude, however, an expansion is not statistically significant for the whole area.”
Claim · model-written summary
Tree limit significantly expanded in altitude.
Not reportedTaxon
Verbatim
e0“The tree limit has significantly expanded in altitude.”
Claim · model-written summary
Temperature sum and growing season length increased at all weather stations.
Not reportedTaxon
Verbatim
e0“At all weather stations the temperature sum and length of the growing season have increased which is proposed to have positive effects on sapling establishment.”
Claim · model-written summary
Change in sheep density was not significantly correlated with shifts in forest and tree limits.
- Interactor
- sheep
Ovis ariese0herbivore - Outcome
- shift in forest and tree limite0
- Direction
- no significant correlatione0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There is no significant correlation between the change in sheep density in relation to the shift in forest and tree limit.”
Claim · model-written summary
Reindeer density shifts corresponded to tree limit shifts, with low explained variation.
- Interactor
- reindeer
Rangifer taranduse0herbivore - Outcome
- shift in tree limite0
- Qualifier
- coefficient of determination was lowe0
Not reportedTaxonDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The shift in reindeer density did not correspond to the shift of forest limit, but to the shift in tree limit. However the coefficient of determination was low”
Claim · model-written summary
Reindeer density shifts did not correspond to forest limit shifts.
- Interactor
- reindeerRangifer taranduse0herbivore
- Outcome
- shift of forest limite0
- Direction
- did not corresponde0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The shift in reindeer density did not correspond to the shift of forest limit, but to the shift in tree limit.”
Claim · model-written summary
Forest and tree limit altitude increases with distance from the coast.
Not reportedTaxon
Verbatim
e0“The altitude of the forest and tree limits increases with increasing distance to the coast”
Claim · model-written summary
Magnitude of limit shifts decreases with distance from the coast.
Not reportedTaxon
Verbatim
e0“the magnitude of the shift in the limits, decrease with increasing distance to the coast”
Claim · model-written summary
Birch forest increased.
Verbatim
e0“The amount of birch forest has increased, most likely, in expense of declined willow-thickets.”
Claim · model-written summary
Willow thickets declined.
SalixOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The amount of birch forest has increased, most likely, in expense of declined willow-thickets.”
Claim · model-written summary
Alpine lichen and moss heath abundance increased.
- Taxon
- lichen/mosse0
- Interactor
- reindeersRangifer taranduse0herbivore
- Outcome
- abundance of alpine lichen/moss heathe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Also abundance of alpine lichen/moss heath has increased, which might be a result of reduced grazing by reindeers.”