Treeline advances along the Urals mountain range – driven by improved winter conditions?

• DOI: 10.1111/gcb.12613
• Publication Date: 2014-04-22T15:56:44Z
• Authors: Frank Hagedorn; Stepan G. Shiyatov; Valeriy S. Mazepa; Nadezhda M. Devi; Andrey A. Grigor'ev; Alexandr A. Bartysh; Valeriy V. Fomin; Denis S. Kapralov; Maxim Terent'ev; Harald Bugman; Andreas Rigling; Pavel A. Moiseev
• Keywords: Ecotone; Microclimate; Tree line; Alpine climate; Snow line

Abstract High‐altitude treelines are temperature‐limited vegetation boundaries, but little quantitative evidence exists about the impact of climate change on in untouched areas Russia. Here, we estimated how forest‐tundra ecotones have changed during last century along Ural mountains. In South, North, Sub‐Polar, and Polar Urals, compared 450 historical recent photographs determined ages 11 100 trees 16 altitudinal gradients. these four regions, boundaries open closed forests (crown covers above 20% 40%) expanded upwards by 4 to 8 m altitude per decade. Results strongly suggest that snow was an important driver for forest advances: (i) Winter precipitation has increased substantially throughout Urals (~7 mm decade −1 ), which corresponds almost a doubling while summer temperatures only slightly (~0.05 °C ). (ii) There positive correlation between canopy cover, height soil temperatures, suggesting increasing cover promotes accumulation and, hence, more favorable microclimate. (iii) Tree age analysis showed expansion mainly began around year 1900 concave wind‐sheltered slopes with thick covers, it started 1950s 1970s shallower covers. (iv) During 20th century, dominant growth forms from multistemmed trees, resulting harsh winter conditions, single‐stemmed trees. While 87%, 31%, 93% stems appearing before 1950 were North than 95% younger had single stem. Currently, there is high density seedlings saplings ecotone, indicating ongoing alpine tundra will disappear most mountains South where treeline already close highest peaks.