Regional variability in the response of alpine treelines to climate change
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Regional variability in the response of alpine treelines to climate change Emma L. Davis 1 Ze’ev Gedalof 1
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& Robert Brown & Lori Daniels & Trudy Kavanagh &
Received: 30 October 2019 / Accepted: 14 May 2020/ # Springer Nature B.V. 2020
Abstract
The distributions of many high-elevation tree species have shifted as a result of recent climate change; however, there is substantial variability in the movement of alpine treelines at local to regional scales. In this study, we derive records of tree growth and establishment from nine alpine treeline ecotones in the Canadian Rocky Mountains, characterise the influence of seasonal climate variables on four tree species (Abies lasiocarpa, Larix lyallii, Picea engelmannii, Pinus albicaulis) and estimate the degree to which treeline movement in the twentieth century has lagged or exceeded the rate predicted by recent temperature warming. The growth and establishment records revealed a widespread increase in radial growth, establishment frequency and stand density beginning in the mid-twentieth century. Coinciding with a period of warming summer temperatures and favourable moisture availability, these changes appear to have supported upslope treeline advance at all sites (range, 0.23–2.00 m/year; mean, 0.83 + 0.67 m/ year). However, relationships with seasonal climate variables varied between species, and the rates of treeline movement lagged those of temperature warming in most cases. These results indicate that future climate change impacts on treelines in the region are likely to be moderated by species composition and to occur more slowly than anticipated based on temperature warming alone. Keywords Alpine treeline . Climate change . Dendrochronology . Subalpine forest . Tree establishment . Western Canada
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10584-02002743-0) contains supplementary material, which is available to authorized users.
* Emma L. Davis [email protected] Extended author information available on the last page of the article
Climatic Change
1 Introduction Many alpine treeline ecotones around the world have increased in density and elevation throughout the twentieth century as climates have become more amenable to tree recruitment at high elevations (see Harsch et al. (2009) for review). Throughout western North America, repeat photography (e.g. Roush et al. 2007; Trant et al. 2015) and historical reconstructions of tree establishment (e.g. Elliott and Petruccelli 2018; Laroque et al. 2000; Lloyd and Fastie 2003) have provided numerous examples of forest infilling and treeline advance in alpine environments. However, variability in treeline dynamics exists due to the important role of moderating factors at local to regional scales (HilleRisLambers et al. 2013; Holtmeier and Broll 2012; Kroiss and HilleResLambers 2015; Macias-Fauria and Johnson 2013), and there is evidence that the range shifts of some treeline species are already lagging behind the rapid pace of climate warming (Gray
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