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

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 - Download this document for free, or read online. Document in PDF available to download.

(2011)JOURNAL OF BIOGEOGRAPHY.38(5).p.907-921 Mark abstract AimModels 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.LocationThe 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.MethodsWe used repeat photography, dendrochronological analysis, field observations along elevational transects and historical documents to study tree line dynamics.ResultsSince 1912, only four out of eight tree line sites had advanced: on average the tree line had shifted 24 m upslope (+0.2 m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 conclusionsIn 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.

Please use this url to cite or link to this publication: http://hdl.handle.net/1854/LU-1221992

Author: Rik Van Bogaert , Kristof Haneca, Jan Hoogesteger, Christer Jonasson, Morgan De Dapper and Terry V Callaghan

Source: https://biblio.ugent.be/publication/1221992


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