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Journal Article•DOI•

A century of tree line changes in sub-Arctic Sweden shows local and regional variability and only a minor influence of 20th century climate warming

Rik Van Bogaert1, Kristof Haneca1, Jan Hoogesteger2, Christer Jonasson3, Christer Jonasson4, Morgan De Dapper1, Terry V. Callaghan5, Terry V. Callaghan4 •
Ghent University1, University of Helsinki2, Uppsala University3, Royal Swedish Academy of Sciences4, University of Sheffield5
01 May 2011-Journal of Biogeography (Blackwell Publishing Ltd)-Vol. 38, Iss: 5, pp 907-921
TL;DR: In this article, the authors used repeat photography, dendrochronological analysis, field observations along elevational transects and historical documents to study tree line dynamics in a sub-Arctic model area at different temporal and spatial scales.
Abstract: Aim Models project that climate warming will cause the tree line to move to higher elevations in alpine areas and more northerly latitudes in Arctic environments. We aimed to document changes or stability of the tree line in a sub-Arctic model area at different temporal and spatial scales, and particularly to clarify the ambiguity that currently exists about tree line dynamics and their causes. Location The study was conducted in the Tornetrask area in northern Sweden where climate warmed by 2.5 degrees C between 1913 and 2006. Mountain birch (Betula pubescens ssp. czerepanovii) sets the alpine tree line. Methods We used repeat photography, dendrochronological analysis, field observations along elevational transects and historical documents to study tree line dynamics. Results Since 1912, only four out of eight tree line sites had advanced: on average the tree line had shifted 24 m upslope (+0.2 m year-1 assuming linear shifts). Maximum tree line advance was +145 m (+1.5 m year-1 in elevation and +2.7 m year-1 in actual distance), whereas maximum retreat was 120 m downslope. Counter-intuitively, tree line advance was most pronounced during the cooler late 1960s and 1970s. Tree establishment and tree line advance were significantly correlated with periods of low reindeer (Rangifer tarandus) population numbers. A decreased anthropozoogenic impact since the early 20th century was found to be the main factor shaping the current tree line ecotone and its dynamics. In addition, episodic disturbances by moth outbreaks and geomorphological processes resulted in descent and long-term stability of the tree line position, respectively. Main conclusions In contrast to what is generally stated in the literature, this study shows that in a period of climate warming, disturbance may not only determine when tree line advance will occur but if tree line advance will occur at all. In the case of non-climatic climax tree lines, such as those in our study area, both climate-driven model projections of future tree line positions and the use of the tree line position for bioclimatic monitoring should be used with caution.

Summary (1 min read)

Jump to: [A century of tree line changes in sub-Arctic Sweden shows local and regional] – [Tables] – [Figure legends] and [Figures]

A century of tree line changes in sub-Arctic Sweden shows local and regional

  • Twentieth century tree line changes in Swedish sub-Arctic Abstract 1 Models project that climate warming will cause the treeline to move to higher 2 elevations in alpine areas and more northerly latitudes in Arctic environments, also known as Running head.
  • The lack of 446 recent tree (>2 m) establishment and the browsing scars documented in the tree rings 447 indicated that, in addition to moth herbivory, reindeer browsing is still a controlling 448 factor at these sites (Fig. 5, Table 4).

Tables

  • Previous field studies on observed treeline shifts and their presumed causes in the Torneträsk area of sub-Arctic Sweden.
  • Browsing damage was classified visually and for five sites also by dendrochronological analysis (the values listed in brackets).
  • So as not to bias the results, Mount Nuolja (site S3), for which the two treeline sites were not randomly selected, was not included in the calculation of the mean elevational shift of the treeline in the Torneträsk area.
  • Pearson correlation coefficients and R2-values (the proportion of explained variance in documented treeline shifts) obtained by forward selection of the different variables are listed at the bottom of the table.

Figure legends

  • The Torneträsk study area in sub-Arctic Sweden.
  • The locations of the historical transects and photo points that have been revisited to study changes in the tree line ecotone are indicated.
  • The statistically-determined 30%-tree cover isoline is plotted in yellow.
  • Upper photo on the left: E. Persson, bottom left: B. Mesch; upper and bottom right: R. Van Bogaert.
  • Fig. 8. Tree (>2 m) establishment at the Torneträsk tree line versus summer (June- August) temperature and reindeer population numbers for the period 1800-2000.

Figures

  • Historical transects and photo points that have been revisited to study changes in the tree line ecotone are indicated.
  • The statistically-determined 30% tree-cover isoline is plotted in yellow.
  • Upper photo: E. Persson, lower photo: S. Johnsson.
  • Upper photo on the left: E. Persson, bottom left: B. Mesch; upper and bottom right: R. Van Bogaert. relation to disturbance (b) and summer temperature (c) for the period 1964-2006.
  • August) temperature and reindeer population numbers for the period 1800-2000.

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This item is the archived peer-reviewed author-version of:
A century of tree line changes in sub-Arctic Sweden shows local and regional variability and only a
minor influence of 20th century climate warming
Van Bogaert, R.; Haneca, K.; Hoogesteger, J.; Jonasson, C.; De Dapper, M.; Callaghan, T.V.
In: Journal of Biogeography, 38 (5), 907-921, 2011.
doi: 10.1111/j.1365-2699.2010.02453.x
To refer to or to cite this work, please use the citation to the published version:
Van Bogaert, R.; Haneca, K.; Hoogesteger, J.; Jonasson, C.; De Dapper, M.; Callaghan, T.V.
(2011). A century of tree line changes in sub-Arctic Sweden shows local and regional
variability and only a minor influence of 20th century climate warming. Journal of
Biogeography 38 (5), 907-921. doi: 10.1111/j.1365-2699.2010.02453.x
1
A century of tree line changes in sub-Arctic Sweden shows local and regional
variability and only a minor influence of 20
th
century climate warming
Rik Van Bogaert
1,2*
, Kristof Haneca
3
, Jan Hoogesteger
4
, Christer Jonasson
5,6
, Morgan
De Dapper
2
and Terry V Callaghan
5,7
1
Flanders Research Foundation (FWO); Egmontstraat 5, B-1000 Brussels, Belgium
2
Department of Geography, Ghent University, Krijgslaan 281 S8, B-9000 Ghent, Belgium
3
Flemish Heritage Institute, Koning Albert II-laan 19 bus 5, B-1210 Brussels, Belgium,
formerly Laboratory of Wood Technology, Ghent University Coupure Links 653, 9000
Ghent, Belgium
4
Department of Forest Sciences, University of Helsinki, PO Box 27, FI-00014 Helsinki,
Finland
5
Abisko Scientific Research Station, Royal Swedish Academy of Sciences, SE-98107
Abisko, Sweden
6
Department of Physical Geography, Uppsala University, S-75122 Uppsala, Sweden
7
Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield
S10 2TN, UK
*Corresponding author: Address: Yzerhand 85, B-9120 Beveren, Belgium.
rikvanbogaert@gmail.com
Running head: Twentieth century tree line changes in Swedish sub-Arctic
2
Abstract 1
Models project that climate warming will cause the treeline to move to higher 2
elevations in alpine areas and more northerly latitudes in Arctic environments. We 3
aimed to document changes or stability of the treeline in a sub-Arctic model area at 4
different temporal and spatial scales, and particularly to clarify the ambiguity that 5
currently exists about treeline dynamics and their causes. The study was conducted in 6
the Torneträsk area in northern Sweden where climate warmed by 2.5 ˚C between 7
1913 and 2006. Mountain birch (Betula pubescens ssp. czerepanovii) sets the alpine 8
treeline. We used repeat photography, dendrochronological analysis, field 9
observations along elevational transects and historical documents to study treeline 10
dynamics. Since 1912, only four out of eight treeline sites had advanced: on average 11
the treeline had shifted 24 m upslope (+0.2 m year
-1
assuming linear shifts). 12
Maximum treeline advance was +145 m (+1.5 m year
-1
in elevation and +2.7 m year
-1
13
in actual distance), whereas maximum retreat was 120 m downslope. Counter-14
intuitively, treeline advance was most pronounced during the cooler late 1960s and 15
1970s. Tree establishment and treeline advance were significantly correlated with 16
periods of low reindeer (Rangifer tarandus) population numbers. A decreased 17
anthropozoogenic impact since the early 20
th
century was found to be the main factor 18
shaping the current treeline ecotone and its dynamics. In addition, episodic 19
disturbances by moth outbreaks and geomorphological processes resulted in descent 20
and long-term stability of the treeline position, respectively. In contrast to what is 21
generally stated in the literature, this study shows that in a period of climate warming, 22
disturbance may not only determine when treeline advance will occur but if treeline 23
advance will occur at all. In the case of non-climatic climax treelines, such as those in 24
our study area, both climate-driven model projections of future treeline positions and 25
3
the use of the treeline position for bioclimatic monitoring should be used with caution.26
27
28
Key words: climate warming, dendrochronology, herbivory, human impact, mountain 29
birch, reindeer, sub-Arctic, Sweden, tree line, tree line causes 30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
4
Introduction 47
Mean annual temperatures have risen globally over the past century, with the most
48
pronounced and rapid changes at high elevations and latitudes (ACIA, 2005). As the
49
location of elevational and polar treelines is mainly caused by heat deficiency, in the
50
Northern Hemisphere climate warming is expected to cause treelines to advance to
51
higher elevations and more northerly latitudes (Harsch et al., 2009). Indeed, modern
52
evidence for such relocations exists and these have been explicitly or implicitly
53
related to recent climate warming (Shiyatov et al., 2007; Kullman and Öberg, 2009).
54
However, in many circumpolar and high-elevational areas the position of the treeline
55
has not changed (Masek, 2001; Holtmeier et al., 2003; Payette, 2007; Van Bogaert et
56
al., 2007) or has even retreated (Vlassova, 2002; Dalen and Hofgaard, 2005; Kullman,
57
2005; Cherosov et al., 2010).
58
Treeline heterogeneity increases from global to regional, to landscape and to local
59
scales of analysis (Callaghan et al., 2002). Moreover, the factors controlling the
60
position and structure of the treeline are highly scale-dependent and vary from place
61
to place (Sveinbjörnsson et al., 2002). Individual trees and the forest system may
62
respond differently to change; warming may increase tree growth, while at the same
63
time seedling survival may be reduced because of water stress brought about by
64
greater evapotranspiration and drying of the uppermost soil. Furthermore, the time-
65
scale of a study influences outcomes because it determines the processes and
66
responses that can be studied. There are short-term responses (defined as a year or
67
less and reflected in individual tree growth), medium-term responses (some years to a
68
few decades and reflected in changing survival rates of seedlings and altered tree
69
physiognomy) and long-term responses (several decades to centuries and reflected in
70
a general treeline advance or retreat) (Holtmeier and Broll, 2005).
71
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References
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Journal Article•DOI•
Epiphytic Lichens as Indicators of Snow Depth

[...]

Mats Sonesson1, Colin P. Osborne2, Gustaf Sandberg1•
Royal Swedish Academy of Sciences1, University of Manchester2
29 Jan 1994-Arctic and alpine research
TL;DR: The vertical distributions of Parmelia olivacea and a few other epiphytic lichens on trunks of deciduous trees were studied in relation to maximum snow depth along an oceanic-continental climate regime.
Abstract: The vertical distributions of Parmelia olivacea and a few other epiphytic lichens on trunks of deciduous trees were studied in relation to maximum snow depth along an oceanic-continental climate gr...

20 citations

"A century of tree line changes in s..." refers methods in this paper

  • ...on adult birch stems was used as a proxy for mean snow depth (Sonesson et al., 1994)....

    [...]

  • ...The mean height limit of the epiphytic lichen Melanelia olivacea (L.) Essl. on adult birch stems was used as a proxy for mean snow depth (Sonesson et al., 1994)....

    [...]

Book Chapter•
Recent changes in vegetation

[...]

Rik Van Bogaert, Donald A. Walker, Gensuo Jia, M Grau, Martin Hallinger, Morgan De Dapper, Christer Jonasson, Terry Callaghan 
01 Jan 2007
TL;DR: In this article, the authors present the results of a study at the Sheffield Centre for Arctic Ecology (SCE) at Sheffield University in the UK, where the authors used the Flanders Research Foundation and the Belgian Geography Department.
Abstract: FWO Flanders Research Foundation, Geography Department, Ghent University, Belgium Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK Institute of Atmospheric Physics, Chinese Academy of Science, Beijing, China Plant Biology Department, Unit of Botany, University of Barcelona, Catalonia, Spain Institute for Botany and Landscape Ecology, Ernst-Moritz-Arndt-University Greifswald, Greifswald, Germany Geography Department, Ghent University, Belgium Abisko Scientific Research Station, Abisko, Sweden Department of Physical Geography, Stockholm University, S-106 91 Stockholm, Sweden Sheffield Centre for Arctic Ecology, Department of Plant and Animal Sciences, University of Sheffield, UK

5 citations

"A century of tree line changes in s..." refers background in this paper

  • ...However, in many circumpolar and high-elevational areas the position of the tree line has not changed (Masek, 2001; Holtmeier et al., 2003; Payette, 2007; Van Bogaert et al., 2007) or has even retreated (Vlassova, 2002; Dalen & Hofgaard, 2005; Kullman, 2005; Cherosov et al., 2010)....

    [...]

  • ...Projecting future tree line dynamics The extreme discrepancy that exists between model projections of the tree line position and in situ observations is a world-wide phenomenon (Holtmeier & Broll, 2007; Van Bogaert et al., 2007)....

    [...]

Book Chapter•DOI•
Vegetation and Human Activity

[...]

M. M. Cherosov, A. P. Isaev, S. I. Mironova, L. P. Lytkina, L.D. Gavrilyeva, R.R. Sofronov, A.P. Arzhakova, N.V. Barashkova, I.A. Ivanov, I. F. Shurduk, A. P. Efimova, N. S. Karpov, P. A. Timofeyev, L. V. Kuznetsova 
01 Jan 2010
TL;DR: In this paper, the main causes, directions and principles of degradation and recovery of ecosystems after anthropogenic disturbance are discussed in South, North-East and West Yakutia regions.
Abstract: One of most significant factors that in various ways impacts the vegetation of South, North-East and West Yakutia is mining activity (extraction of diamonds, gold, coal, tin, etc.). Another important factor is forest fire of natural and anthropogenic origin. Their frequency and intensity are determined by the arid climate in most of the territory of Yakutia. The vegetation cover is also greatly influenced by timber felling, agricultural activity (hayfields and pastures), etc. In the chapter the main causes, directions and principles of degradation and recovery of ecosystems after anthropogenic disturbance are discussed.

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"A century of tree line changes in s..." refers background in this paper

  • ...However, in many circumpolar and high-elevational areas the position of the tree line has not changed (Masek, 2001; Holtmeier et al., 2003; Payette, 2007; Van Bogaert et al., 2007) or has even retreated (Vlassova, 2002; Dalen & Hofgaard, 2005; Kullman, 2005; Cherosov et al., 2010)....

    [...]

Nutida trädgränsförändringar i Abisko-området, norra Lappland.

[...]

M. Lundgren
01 Jan 1999

3 citations

Den pågående klimatförändringen.

[...]

G. Sandberg
01 Jan 1940

2 citations

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