Spatial patterns and structure of the mountain birch tree‐limit in the southern swedish scandes – a regional perspective

Kjällgren, Lena; Kullman, Leif

doi:10.1111/j.0435-3676.1998.00023.x

Cited by 26 publications

(20 citation statements)

References 26 publications

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“…The disadvantage on 'cold' slopes (Schönenberger & Frey 1988) could also be the result of slower forest regeneration, which results in an increasing probability that the forest be classified in the GIS as 'shrub' rather than 'forest'. A greater abundance of forests at western and southern exposures at the climatic tree line has also been found in Betula tree lines in northern Sweden in regions where the tree-line ecotone is regarded as natural (Kjällgren & Kullmann 1998).…”

Section: Discussionmentioning

confidence: 77%

GIS‐analysis of tree‐line elevation in the Swiss Alps suggests no exposure effect

Paulsen

Körner

2001

J Vegetation Science

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Abstract. Counter intuition, an analysis of tree‐line position across the Swiss Alps based on a geographical information system (GIS) with a spatial resolution of 100 m (2.5 million points) revealed no difference in climatic tree‐line altitude with slope exposure. Through step wise discrimination procedures our analysis accounts for anthropogenic tree‐line depression. Any land cover bias affects the frequency of GIS‐points corresponding to tree‐line forests rather than the mean elevation of such points, captured by our analysis. We explain this phenomenon (1) by the absence of significant drought effects in the Alps (no disadvantages for southwest slopes), (2) by the fact that tree tops, unlike low stature vegetation, do not profit from greater radiation warming on south slopes during the growing season but are thermally coupled to free air circulation, and (3) by preliminary data for root zone temperatures during the growing season, which do not differ between south and north slopes, as long as the soil is screened by a closed forest canopy. The overall difference in season length and snow cover, often seen between south and north slopes, does not seem to affect tree‐line position but explains greater natural forest fragmentation on north slopes. It is this greater fragmentation and patchiness (avalanche tracks, snow beds etc.) which seem to have nourished the idea of a generally lower limit of tree growth and tree lines at northern slopes. These results are in line with a recently developed theory, which suggests that tree‐line elevations in humid climates correspond to similar isotherms, irrespective of latitude and thus, season length.

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Section: Discussionmentioning

confidence: 77%

GIS‐analysis of tree‐line elevation in the Swiss Alps suggests no exposure effect

Paulsen

Körner

2001

J Vegetation Science

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“…Across seasons Innerebner (1933) had already documented the same air temperatures in shade, 2 m above ground, on N and S slopes in the central Alps. Slope contrasts come into play in low‐stature plant cover (see Introduction) and when oceanicity, snow pack or general moisture gradients are important, as was shown for subarctic birch treelines (Kjällgren & Kullmann, 1998) and as can be seen in some very dry parts of central Asia (Esper et al. , 1995) or northern Chile (Troll, 1968).…”

Section: Comparison With Regionally Available Datamentioning

confidence: 97%

A world‐wide study of high altitude treeline temperatures

Körner

Paulsen

2004

Journal of Biogeography

1,178

1,132

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Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts. Location We present the results of a data‐logging campaign at 46 treeline sites between 68° N and 42° S. Methods We measured root‐zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003. Results Disregarding taxon‐, landuse‐ or fire‐driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus‐specific boundaries rather than boundaries of the life‐form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical. Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.

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“…The general features of the tree line ecotone and its environmental correlates are provided by Kullman (1992b). More detailed accounts of the physiography, geology, climate, plant cover and human impacts are given by Kjällgren & Kullman (1998).…”

Section: Study Areamentioning

confidence: 99%

Ecological tree line history and palaeoclimate – review of megafossil evidence from the Swedish Scandes

Kullman

2013

Boreas

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The postglacial tree line and climate history in the Swedish Scandes have been inferred from megafossil tree remains. Investigated species are mountain birch (Betula pubescens ssp. czerepanovii), Scots pine (Pinus sylvestris) and grey alder (Alnus incana). Betula and Pinus first appeared on early deglaciated nunataks during the Lateglacial. Their tree lines peaked between 9600 and 9000 cal. a BP, almost 600 m higher than present‐day elevations. This implies (adjusted for land uplift) that early Holocene summer temperatures may have been 2.3°C above modern ones. Elevational tree line retreat characterized the Holocene tree line evolution. For short periods, excursions from this trend have occurred. Between c. 12 000 and 10 000 cal. a BP, a pine‐dominated subalpine belt prevailed. A first major episode of descent occurred c. 8200 cal. a BP, possibly forced by cooling and an associated shift to a deeper and more persistent snow pack. Thereafter, the subalpine birch forest belt gradually evolved at the expense of the prior pine‐dominated tree line ecotone. A second episode of pine descent took place c. 4800 cal. a BP. Historical tree line positions are viewed in relation to early 21st century equivalents, and indicate that tree line elevations attained during the past century and in association with modern climate warming are highly unusual, but not unique, phenomena from the perspective of the past 4800 years. Prior to that, the pine tree line (and summer temperatures) was consistently higher than present, as it was also during the Roman and Medieval periods, c. 1900 and 1000 cal. a BP, respectively.

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Spatial patterns and structure of the mountain birch tree‐limit in the southern swedish scandes – a regional perspective

Cited by 26 publications

References 26 publications

GIS‐analysis of tree‐line elevation in the Swiss Alps suggests no exposure effect

GIS‐analysis of tree‐line elevation in the Swiss Alps suggests no exposure effect

A world‐wide study of high altitude treeline temperatures

Ecological tree line history and palaeoclimate – review of megafossil evidence from the Swedish Scandes

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