Abstract
Woody vegetation at the upper limit of its growth is a sensitive indicator of climate change. The aim of this study is to provide an analysis of the centuries-old spatiotemporal dynamics of larch trees at the upper limit of their growth (mountain massif Rai-Iz, Polar Urals, Russia). We used a ground-based method of mapping the remnants of trees that grew in the study area and died during the Little Ice Age. Aerial photographs from the 1960s and high-spatial-resolution satellite images from 2015 were used as data sources to define the locations of trees. Maps of the forest–tundra phytocoenochoras (areas of the terrain that are relatively homogeneous for one or more components of vegetation and/or other indicators) were created using a modified method of boundary detection between forest parcels with different stand densities. The proposed method of boundary detection between the main types of phytocoenochoras allowed us to identify a 15% total increase in areas of closed and open forest and areas with sparse tree growth, as well as a decrease in areas of tundra with single trees over these last decades. Using our spatiotemporal analysis of forest–tundra demographics over the last 50 years, we found that the number of trees in the ecotone had doubled. However, modern trees have not yet reached the areas occupied by trees in the past.
Highlights
Peer-reviewed: April 2020 Accepted: May 2020. Plants located at their upper and/or northern range limits are sensitive to even small changes in climatic conditions; many highland and northern territories are used as monitoring sites to assess the early response of biota to climate change (Shiyatov 1993; Kullman 2002, 2007, 2016; Camarero and Gutierrez 2004; Dufour-Tremblay et al 2012; Hellmann et al 2016; Pellizzari et al 2017; Chhetri 2018)
The area of the terrain shown in these photos can be seen on the map in Figure 1 and Figure 3
A comparative analysis of the number of trees in the early 1960s and in 2015 suggests that regional climate warming, which is observed in the Polar Urals (Briffa et al 1995; Shalaumova et al 2010; Hagedorn et al 2014; Shiyatov and Mazepa 2015), was accompanied by significant changes in the ecotone of the upper boundary of woody vegetation
Summary
Plants located at their upper and/or northern range limits are sensitive to even small changes in climatic conditions; many highland and northern territories are used as monitoring sites to assess the early response of biota to climate change (Shiyatov 1993; Kullman 2002, 2007, 2016; Camarero and Gutierrez 2004; Dufour-Tremblay et al 2012; Hellmann et al 2016; Pellizzari et al 2017; Chhetri 2018). Comparative analyses of changes in the boundaries of woody vegetation and the speed of these changes show that these vary according to region, for various reasons. A search for past boundaries of woody vegetation cover is not an easy task, especially for time intervals from half a century to several centuries ago, because there is often no information about where trees have previously grown due to rapid wood decomposition.
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