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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the authors used repeat photography, dendrochronological analysis, field observations along elevational transects and historical documents to study tree line dynamics in a sub-Arctic model area at different temporal and spatial scales.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 Methods We used repeat photography, dendrochronological analysis, field observations along elevational transects and historical documents to study tree line dynamics.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.

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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
Citations
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Journal Article•DOI•
Sensitivity to environmental change of the treeline ecotone and its associated biodiversity in European mountains

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Frans Emil Wielgolaski, Annika Hofgaard, Friedrich-Karl Holtmeier
21 Aug 2017-Climate Research
TL;DR: In this paper, the authors discuss the biodiversity in various trophic levels in treeline ecotones throughout Europe, with particular focus on recent changes in land use and climate in northern and central mountains.
Abstract: Transition zones between mountain forests and treeless tundra, i.e. treeline ecotones, are characterized by great regional variety. In this paper, we discuss the biodiversity in various trophic levels in treeline ecotones throughout Europe, with particular focus on recent changes in land use and climate in northern and central mountains. In northernmost Europe, mountain birch prevails, while conifers (spruce, pine, larch) are the dominating species further south. While at continent-wide to global scales, the ecotone position is largely controlled by heat deficiency, it depends on a multitude of partly interacting abiotic and biotic factors other than climate at smaller scales. Climate change is a driving factor in treeline ecotone change, including physiognomic structure and biodiversity, although the effects of climate and other factors often overlap. Historical legacy plays an important role in this respect, and human impacts are particularly important. The recent decline in pastoral use of many European treeline areas often strongly influences plant diversity and re-growth of trees and other woody species. Climate change together with changing tree cover may influence snow cover, moisture regime, and nutrient conditions. Subsequently changed site conditions influence plant−plant interactions, favoring some species and disfavoring others, and plant−animal interactions. Native animals may cause widespread or local disturbances in treeline ecotone areas. Mass outbreaks of leaf-eating insects, for example, usually affect comparatively large forested areas whereas mammalian herbivores and birds have more local impact. However, high numbers of wild or domestic mammalian herbivores may challenge the carrying capacity of treeline ecotone areas at the same time as they preserve an open pasture character. This calls for cross-disciplinary study approaches, addressing the complexity of the ecotone regarding both causal background and biogeographic diversity.

36 citations

Cites background from "A century of tree line changes in s..."

  • ...Species richness across European treeline ecotones decreases with latitude, but depends on a large number of abiotic and biotic factors, such as human activities and soil conditions (Callaghan et al. 2004, Vittoz et al. 2010)....

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Persistent nitrogen limitation of stream biofilm communities along climate gradients in the Arctic

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Maria Myrstener1, Gerard Rocher-Ros1, Ryan M. Burrows2, Ann-Kristin Bergström1, Reiner Giesler1, Ryan A. Sponseller1 •
Umeå University1, Griffith University2
01 Aug 2018-Global Change Biology
TL;DR: It is suggested that in the absence of increased nutrient inputs, Arctic streams will be less sensitive to future changes in other habitat variables such as temperature and DOC loading.
Abstract: Climate change is rapidly reshaping Arctic landscapes through shifts in vegetation cover and productivity, soil resource mobilization, and hydrological regimes. The implications of these changes fo ...

34 citations

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  • ...…continuous, such declines in DIN concentration and export are consistent with increasing terrestrial nutrient demand and retention linked to greater plant productivity (Xu et al., 2013), tree line expansion (Van Bogaert et al., 2011) and/or increased shrub abundance (Sturm, Racine, & Tape, 2001)....

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No change without a cause – why climate change remains the most plausible reason for shrub growth dynamics in Scandinavia

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Martin Hallinger1, Martin Wilmking•
University of Greifswald1
01 Mar 2011-New Phytologist

34 citations

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Ecotonal dynamics of the altitudinal forest limit are affected by terrain and vegetation structure variables: an example from the Sudetes Mountains in Central Europe

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Václav Treml1, Tomáš Chuman1•
Charles University in Prague1
24 Feb 2015-Arctic, Antarctic, and Alpine Research
TL;DR: In this article, the authors examined the influence of topographic and vegetation-structure variables on spatial patterns of treeline ecotone shifts in the Sudetes Mountains (Czech Republic).
Abstract: At the landscape scale, the response of alpine treelines to increasing temperatures often varies due to second-order factors such as terrain properties, vegetation structure, and land use. In this study, we examined the influence of topographic and vegetation-structure variables on spatial patterns of treeline ecotone shifts in the Sudetes Mountains (Czech Republic). The changing positions of the alpine timberline and alpine treeline were determined from orthogonal aerial images allowing comparisons between 1936 and 2005. Our results showed that the alpine timberline advanced upward at an overall rate between 0.30 m yr-1 in the Hrubý Jesenik Mountains (eastern part of the Sudetes) and 0.43 m yr-1 in the Giant Mountains (western part of the Sudetes). Forest infilling was substantially greater than advances above original alpine treeline positions. Forest upward shifts occurred mostly on sites with already established, well-dispersed trees and low levels of prostrate dwarf pine cover. Topographic v...

34 citations

Cites background from "A century of tree line changes in s..."

  • ...In particular, the patterns of near-ground temperatures, snow distribution, wind abrasion, and mass movement are expected to be reflected in the patterns of treeline advance or retreat (Dalen and Hofgaard, 2005; Holtmeier and Broll, 2005; Van Bogaert et al., 2011; Sutinen et al., 2012)....

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Journal Article•DOI•
Plant and Vegetation Dynamics on Disko Island, West Greenland: Snapshots Separated by Over 40 Years

[...]

Terry V. Callaghan1, Terry V. Callaghan2, Torben R. Christensen3, Elin J. Jantze4•
University of Sheffield1, Royal Swedish Academy of Sciences2, Lund University3, Stockholm University4
24 Aug 2011-AMBIO: A Journal of the Human Environment
TL;DR: Re-sampling of the same clones of the grass Phleum alpinum after 39 years showed complete stability in biometrics but dramatic earlier onset of various phenological stages that were not related to changes in population density.
Abstract: We report on a revisit in 2009 to sites where vegetation was recorded in 1967 and 1970 on Disko Island, West Greenland. Re-sampling of the same clones of the grass Phleum alpinum after 39 years showed complete stability in biometrics but dramatic earlier onset of various phenological stages that were not related to changes in population density. In a fell-field community, there was a net species loss, but in a herb-slope community, species losses balanced those that were gained. The type of species establishing and increasing in frequency and/or cover abundance at the fell-field site, particularly prostrate dwarf shrubs, indicates a possible start of a shift towards a heath, rather than a fell-field community. At the herb-slope site, those species that established or increased markedly in frequency and/or cover abundance indicate a change to drier conditions. This is confirmed both by the decrease in abundance of Alchemilla glomerulans and Epilobium hornemanii, and the drying of a nearby pond. The causes of these changes are unknown, although mean annual temperature has risen since 1984.

34 citations

Cites background from "A century of tree line changes in s..."

  • ...Furthermore, some observations of ecosystem change, such as recent advances of shrubs into the tundra, assume implicitly or explicitly that the vegetation dynamics are related to climate warming (e.g. Sturm et al. 2001; Tape et al. 2006; Hallinger et al. 2010), but this assumption can sometimes be challenged because many other factors, such as herbivory (e.g. Cairns and Moen 2004; Olofsson et al. 2009; Van Bogaert et al. 2011), extreme winter warming events (Bokhorst et al. 2009), and methodological constraints (Büntgen and Schweingrubber 2010) often confound simple cause–response relationships....

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  • ...…but this assumption can sometimes be challenged because many other factors, such as herbivory (e.g. Cairns and Moen 2004; Olofsson et al. 2009; Van Bogaert et al. 2011), extreme winter warming events (Bokhorst et al. 2009), and methodological constraints (Büntgen and Schweingrubber 2010) often…...

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  • ...Exceptions to the general trend of range extension and increased plant performance are treeline and forest vegetation that have not responded to recent warming (Van Bogaert et al. 2009, 2011), low Arctic vegetation of southeast Greenland (Daniëls and de Molenaar 2011 [this issue]) and high Arctic vegetation on Svalbard (Prach et al. 2010)....

    [...]

  • ...…general trend of range extension and increased plant performance are treeline and forest vegetation that have not responded to recent warming (Van Bogaert et al. 2009, 2011), low Arctic vegetation of southeast Greenland (Daniëls and de Molenaar 2011 [this issue]) and high Arctic vegetation on…...

    [...]

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Journal Article•DOI•
Are treelines advancing? A global meta‐analysis of treeline response to climate warming

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Melanie A. Harsch1, Philip E. Hulme1, Matt S. McGlone2, Richard P. Duncan1, Richard P. Duncan2 •
Lincoln University (New Zealand)1, Landcare Research2
01 Oct 2009-Ecology Letters
TL;DR: Diffuse treelines may be more responsive to warming because they are more strongly growth limited, whereas other treeline forms may be subject to additional constraints.
Abstract: Treelines are temperature sensitive transition zones that are expected to respond to climate warming by advancing beyond their current position. Response to climate warming over the last century, however, has been mixed, with some treelines showing evidence of recruitment at higher altitudes and/or latitudes (advance) whereas others reveal no marked change in the upper limit of tree establishment. To explore this variation, we analysed a global dataset of 166 sites for which treeline dynamics had been recorded since 1900 AD. Advance was recorded at 52% of sites with only 1% reporting treeline recession. Treelines that experienced strong winter warming were more likely to have advanced, and treelines with a diffuse form were more likely to have advanced than those with an abrupt or krummholz form. Diffuse treelines may be more responsive to warming because they are more strongly growth limited, whereas other treeline forms may be subject to additional constraints.

1,003 citations

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

  • ...In contrast to Harsch et al. (2009) who concluded that the role of disturbance during recent climate warming is restricted to determining when tree line advance will occur, this study shows that disturbance and its after-effects may equally well determine ı́f tree line advance will occur at all....

    [...]

  • ...As the location of elevational and polar tree lines is mainly caused by heat deficiency, in the Northern Hemisphere climate warming is expected to cause tree lines to advance to higher elevations and more northerly latitudes (Harsch et al., 2009)....

    [...]

  • ...…widely held expectations of vegetation responses to warming, i.e. that Arctic tree lines will move northwards and elevational tree lines upslope (Harsch et al., 2009), this study documented highly varying tree line dynamics for the Torneträsk area in sub-Arctic Sweden during a period of…...

    [...]

  • ...A global study by Harsch et al. (2009) showed that only 52% of all 166 global tree line sites had advanced over the past 100 years despite documented amplified climate warming at high-elevation areas and northern latitudes (ACIA, 2005)....

    [...]

Journal Article•DOI•
Sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change at landscape and local scales

[...]

Friedrich-Karl Holtmeier1, Gabriele Broll2•
University of Münster1, University of Vechta2
01 Sep 2005-Global Ecology and Biogeography
TL;DR: The sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change are increasingly discussed in terms of climate change, often forgetting that climate is only one aspect of environmental variation as mentioned in this paper.
Abstract: The sensitivity and response of northern hemisphere altitudinal and polar treelines to environmental change are increasingly discussed in terms of climate change, often forgetting that climate is only one aspect of environmental variation. As treeline heterogeneity increases from global to regional and smaller scales, assessment of treeline sensitivity at the landscape and local scales requires a more complex approach than at the global scale. The time scale (short-, medium-, long-term) also plays an important role when considering treeline sensitivity. The sensitivity of the treeline to a changing environment varies among different types of treeline. Treelines controlled mainly by orographic influences are not very susceptible to the effects of warming climates. Greatest sensitivity can be expected in anthropogenic treelines after the cessation of human activity. However, tree invasion into former forested areas above the anthropogenic forest limit is controlled by site conditions, and in particular, by microclimates and soils. Apart from changes in tree physiognomy, the spontaneous advance of young growth of forest-forming tree species into present treeless areas within the treeline ecotone and beyond the tree limit is considered to be the best indicator of treeline sensitivity to environmental change. The sensitivity of climatic treelines to climate warming varies both in the local and regional topographical conditions. Furthermore, treeline history and its after-effects also play an important role. The sensitivity of treelines to changes in given factors (e.g. winter snow pack, soil moisture, temperature, evaporation, etc.) may vary among areas with differing climatic characteristics. In general, forest will not advance in a closed front but will follow sites that became more favourable to tree establishment under the changed climatic conditions.

518 citations

Journal Article•DOI•
Variability, contingency and rapid change in recent subarctic alpine tree line dynamics

[...]

Ryan K. Danby1, David S. Hik1•
University of Alberta1
01 Mar 2007-Journal of Ecology
TL;DR: In this article, the authors examined recent tree line dynamics at six topographically different, but climatically similar, sites in south-west Yukon, Canada and found that tree line elevation and stand density increased significantly during the early to mid 20th century.
Abstract: Summary 1 Boundaries between forest and tundra ecosystems, tree lines, are expected to advance in altitude and latitude in response to climate warming. However, varied responses to 20th century warming suggest that in addition to temperature, tree line dynamics are mediated by species-specific traits and environmental conditions at landscape and local scales. 2 We examined recent tree line dynamics at six topographically different, but climatically similar, sites in south-west Yukon, Canada. Dendroecological techniques were used to reconstruct changes in density of the dominant tree species, white spruce (Picea glauca), and to construct static age distributions of willow (Salix spp.), one of two dominant shrub genera. Data were analysed to identify periods and rates of establishment and mortality and to relate these to past climate. 3 Tree line elevation and stand density increased significantly during the early to mid 20th century. However, this change was not uniform across sites. Spruce advanced rapidly on south-facing slopes and tree line rose 65–85 m in elevation. Tree line did not advance on north-facing slopes, but stand density increased 40–65%. Differences observed between aspects were due primarily to the differential presence of permafrost. Additional variability among sites was related to slope and vegetation type. Results were less conclusive for willow, but evidence for an advance was found at two sites. 4 Increases in stand density were strongly correlated with summer temperatures. The period of rapid change coincided with a 30-year period of above average temperatures, beginning in 1920. The highest correlations were obtained using a forward average of 30–50 years, supporting the hypothesis that tree line dynamics are controlled more by conditions influencing recruitment than by establishment alone. 5 The changes observed at several sites are suggestive of a threshold response and challenge the notion that tree lines respond gradually to climate warming. Overall, the results provide further evidence to support the idea that the pattern and timing of change is contingent on local, landscape, and regional-scale factors, as well as species’ biology.

334 citations

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

  • ...In contrast to other studies (Danby & Hik, 2007; Kullman & Öberg, 2009), slope aspect and inclination were not correlated with elevational shifts of the tree line ecotone....

    [...]

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