Struggle zone: alpine shrubs are limited in the Southern Urals by an advancing treeline and insufficient snow depth

Abstract

In recent decades, the rapid climate warming in polar and alpine regions has been accompanied by an expansion of shrub vegetation. However, little is known about how changes in shrub distribution will change as the distribution of tree species and snow cover changes as temperatures rise. In this work, we analyzed the main environmental factors influencing the distribution and structure of Juniperus sibirica, the most common shrub species in the Southern Ural Mountains. Using mapping and digital elevation models, we demonstrated that J. sibirica forms a well-defined vegetation belt mainly between 1100 and 1400 m a.s.l. Within this zone, the abundance and cover of J. sibirica are influenced by factors such as rockiness, slope steepness, water regime and tree (Picea obovata) cover. An analysis of data spanning the past 9 years revealed an upward shift in the distribution of J. sibirica with a decrease in its area. The primary limiting factors for the distribution of J. sibirica were the removal of snow cover by strong winter winds and competition with trees. As a consequence of climatic changes, the tree line and forest limit have shifted upward, further restricting the distribution of J. sibirica to higher elevations where competition for light with trees is reduced and snow cover is sufficiently deep.

Keywords

Juniperaceae / Juniperus sibirica / Snowpack cover / Shrubline / Shrub-tree competition / Southern Urals / Tree line

References

[1]	Baptist F, Yoccoz NG, Choler P (2010) Direct and indirect control by snow cover over decomposition in alpine tundra along a snowmelt gradient. Plant Soil 328:397–410. https://doi.org/10.1007/s11104-009-0119-6
[2]	Blok D, Sass-Klaassen U, Schaepman-Strub G, Heijmans MMPD, Sauren P, Berendse F (2011) What are the main climate drivers for shrub growth in Northeastern Siberian tundra? Biogeosciences 8:1169–1179. https://doi.org/10.5194/bg-8-1169-2011
[3]	Bokhorst S, Bjerke JW, Bowles FW, Melillo J, Callaghan PGK (2008) Impacts of extreme winter warming in the sub-Arctic: growing season responses of dwarf shrub heathland. Glob Chang Biol 14:2603–2612. https://doi.org/10.1111/j.1365-2486.2008.01689.x
[4]	Borisevich DV (1968) Relief and geological structure. Urals and Cis-Urals. Nauka, Moscow, pp 19–81
[5]	Boscutti F, Casolo V, Beraldo P, Braidot E, Zancani M, Rixen C (2018) Shrub growth and plant diversity along an elevation gradient: evidence of indirect effects of climate on alpine ecosystems. PLoS ONE 13:1–12. https://doi.org/10.1371/journal.pone.0196653
[6]	Bret-Harte MS, Shaver GR, Chapin FS (2002) Primary and secondary stem growth in arctic shrubs: implications for community response to environmental change. J Ecol 90:251–267. https://doi.org/10.1046/j.1365-2745.2001.00657.x
[7]	Büntgen U, Hellmann L, Tegel W, Normand S, Myers-Smith I, Kirdyanov AV, Nievergelt D, Schweingruber FH (2015) Temperature-induced recruitment pulses of arctic dwarf shrub communities. J Ecol 103:489–501. https://doi.org/10.1111/1365-2745.12361
[8]	Bürkner PC (2017) brms: An R package for Bayesian multilevel models using Stan. J Stat Softw 80(1):1–28. https://doi.org/10.18637/jss.v080.i01
[9]	Campioli M, Leblans N, Michelsen A (2012) Stem secondary growth of tundra shrubs: impact of environmental factors and relationships with apical growth. Arct Antarct Alp Res 44:16–25. https://doi.org/10.1657/1938-4246-44.1.16
[10]	Carpenter B, Gelman A, Hoffman MD, Lee D, Goodrich B, Betancourt M, Brubaker M, Guo J, Li P, Riddell A (2017) A probabilistic programming language. J Stat Softw 76(1):1–32. https://doi.org/10.18637/jss.v076.i01
[11]	Carrer M, Pellizzari E, Prendin AL, Pividori M, Brunetti M (2019) Winter precipitation—not summer temperature—is still the main driver for Alpine shrub growth. Sci Total Environ 682:171–179. https://doi.org/10.1016/j.scitotenv.2019.05.152
[12]	Chapin FS, Sturm M, Serreze MC, Mcfadden JP, Key JR, Lloyd AH, Mcguire AD, Rupp TS, Lynch AH, Schimel JP, Beringer J, Chapman WL, Epstein HE, Euskirchen ES, Hinzman LD, Jia G, Ping CL, Tape KD, Thompson CDC, Walker DA, Welker JM (2005) Role of land-surface changes in arctic summer warming. Science 310:657–660. https://doi.org/10.1126/science.1117368
[13]	Dial RJ, Berg EE, Timm K, McMahon A, Geck J (2007) Changes in the alpine forest-tundra ecotone commensurate with recent warming in southcentral Alaska: evidence from orthophotos and field plots. J Geophys Res 112:G04015. https://doi.org/10.1029/2007JG000453
[14]	Dial RJ, Scott Smeltz T, Sullivan PF, Rinas CL, Timm K, Geck JE, Tobin SC, Golden TS, Berg EC (2016) Shrubline but not treeline advance matches climate velocity in montane ecosystems of south-central Alaska. Glob Chang Biol 22:1841–1856. https://doi.org/10.1111/gcb.13207
[15]	Forbes BC, Fauria MM, Zetterberg P (2010) Russian Arctic warming and “greening” are closely tracked by tundra shrub willows. Glob Chang Biol 16:1542–1554. https://doi.org/10.1111/j.1365-2486.2009.02047.x
[16]	Formica A, Farrer EC, Ashton IW, Suding KN (2014) Shrub expansion over the past 62 years in Rocky mountain alpine tundra: possible causes and consequences. Arct Antarct Alp Res 46(3):616–631. https://doi.org/10.1657/1938-4246-46.3.616
[17]	Frost GV, Epstein HE (2014) Tall shrub and tree expansion in Siberian tundra ecotones since the 1960s. Glob Chang Biol 20(4):1264–1277. https://doi.org/10.1111/gcb.12406
[18]	Frost GV, Epstein HE, Walker DA, Matyshak G, Ermokhina K (2018) Seasonal and long-term changes to active-layer temperatures after tall shrubland expansion and succession in arctic tundra. Ecosystems 21:507–520. https://doi.org/10.1007/s10021-017-0165-5
[19]	Gelman A, Carlin J, Stern H, Dunson DB, Vehtari A, Rubin DB (2013) Bayesian data analysis. Chapman and Hall/CRC, New York, p 675
[20]	Gorchakovskiy PL, Shiyatov SG (1985) Phytoindication of environmental conditions and natural processes in high mountain regions. Nauka, Moscow, p 208
[21]	Grigoriev AA, Moiseev PA, Nagimov ZY (2013) Dynamics of the timberline in high mountain areas of the nether-polar Urals under the influence of current climate change. Russ J Ecol 44:312–323. https://doi.org/10.1134/S1067413613040061
[22]	Grigoriev AA, Shalaumova YV, Erokhina OV, Sokovnina SY, Vatolina EI, Wilmking M (2020) Expansion of Juniperus sibirica Burgsd. as a response to climate change and associated effect on mountain tundra vegetation in the Northern Urals. J Mt Sci 17:2339–2353. https://doi.org/10.1007/s11629-019-5925-6
[23]	Grigoriev AA, Shalaumova YV, Balakin DS, Erokhina OV, Abdulmanova SY, Moiseev PA, Camarero JJ (2022) Alpine shrubification: juniper encroachment into tundra in the Ural mountains. Forests 13(12):2106. https://doi.org/10.3390/f13122106
[24]	Gronau QF, Singmann H, Wagenmakers EJ (2020) bridgesampling: an R Package for estimating normalizing constants. J Stat Softw 92(10):1–29. https://doi.org/10.18637/jss.v092.i10
[25]	Hagedorn F, Shiyatov SG, Mazepa VS, Devi NM, Grigor’ev AA, Bartysh AA, Fomin VV, Kapralov DS, Terent’ev M, Bugman H, Rigling A, Moiseev PA (2014) Treeline advances along the Urals mountain range—driven by improved winter conditions? Glob Chang Biol 20:3530–3543. https://doi.org/10.1111/gcb.12613
[26]	Hallinger M, Manthey M, Wilmking M (2010) Establishing a missing link: warm summers and winter snow cover promote shrub expansion into alpine tundra in Scandinavia. New Phytol 186:890–899. https://doi.org/10.1111/j.1469-8137.2010.03223.x
[27]	Hantemirov RM, Shiyatov SG, Gorlanova LA (2011) Dendroclimatic study of Siberian juniper (Juniperus sibirica Burgsd.). Dendrochronologia 29(2):119–122. https://doi.org/10.1016/j.dendro.2010.05.001
[28]	Hollesen J, Buchwal A, Rachlewicz G, Hansen BU, Hansen MO, Stecher O, Elberling B (2015) Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century. Glob Chang Biol 21(6):2410–2423. https://doi.org/10.1111/gcb.12913
[29]	Holtmeier FK (2003) Mountain timberlines. Ecology. Patchiness, and dynamics. Kluwer, Dordrecht, p 369
[30]	Jia GJ, Epstein HE, Walker DA (2003) Greening of arctic Alaska, 1981–2001. Geophys Res Lett 30(20):1–4. https://doi.org/10.1029/2003GL018268
[31]	Makowski D, Ben-Shachar MS, Lüdecke D (2019) bayestestR: describing effects and their uncertainty, existence and significance within the Bayesian framework. J Open Source Softw 4(40):1541. https://doi.org/10.21105/joss.01541
[32]	Mod HK, Luoto M (2016) Arctic shrubification mediates the impacts of warming climate on changes to tundra vegetation. Environ Res Lett 11(12):124028. https://doi.org/10.1088/1748-9326/11/12/124028
[33]	Moiseev PA, Shiyatov SG, Grigoriev AA (2016) Climatogenic dynamics of woody vegetation at the upper limit of its distribution on the Bolshoy Taganay Ridge over the last century. Publishing house UMC UPI, Yekaterinburg, p 136
[34]	Moiseev PA (2011) Structure and dynamics of woody vegetation on the upper limit of its growth in the Urals. Dissertation, Institute of Plant and Animal Ecology, Ural Branch of Russian Academy of Sciences.
[35]	Myers-Smith IH, Hik DS (2018) Climate warming as a driver of tundra shrubline advance. J Ecol 106(2):547–560. https://doi.org/10.1111/1365-2745.12817
[36]	Myers-Smith IH, Elmendorf SC, Beck PSA, Wilmking M, Hallinger M, Blok D, Tape KD, Rayback SA, Macias-Fauria M, Forbes BC, Speed JDM, Boulanger-Lapointe N, Rixen C, Lévesque E, Schmidt NM, Baittinger C, Trant AJ, Hermanutz L, Collier LS, Dawes MA, Lantz TC, Weijers S, J?rgensen RH, Buchwal A, Buras A, Naito AT, Ravolainen V, Schaepman-Strub G, Wheeler JA, Wipf S, Guay KC, Hik DS, Vellend M (2015) Climate sensitivity of shrub growth across the tundra biome. Nat Clim Chang 5:887–891. https://doi.org/10.1038/nclimate2697
[37]	Pellizzari E, Pividori M, Carrer M (2014) Winter precipitation effect in a mid-latitude temperature-limited environment: the case of common juniper at high elevation in the Alps. Environ Res Lett 9:104021. https://doi.org/10.1088/1748-9326/9/10/104021
[38]	Pogodina GS, Rozov NN (1968) Soils. In: Komar IV, Chikishev AG (eds) Urals and the Suburals. Nauka, Moscow, pp 167–210
[39]	R Core Team (2022) A language and environment for statistical computing. R Foundation for Statistical Computing. https://www.R-project.org/ [accessed on 28.03.2023].
[40]	Rixen C, Schwoerer C, Wipf S (2010) Winter climate change at different temporal scales in Vaccinium myrtillus, an arctic and alpine dwarf shrub. Polar Res 29:85–94. https://doi.org/10.1111/j.1751-8369.2010.00155.x
[41]	Schimel JP, Bilbrough C, Welker JM (2004) Increased snow depth affects microbial activity and nitrogen mineralization in two arctic tundra communities. Soil Biol Biochem 36(2):217–227. https://doi.org/10.1016/j.soilbio.2003.09.008
[42]	Schmidt NM, Baittinger C, Forchhammer MC (2006) Reconstructing century-long snow regimes using estimates of high arctic Salix arctica radial growth. Arct Antarct Alp Res 38:257–262. https://doi.org/10.1657/1523-0430(2006)38[257:RCSRUE]2.0.CO;2
[43]	Shiyatov SG, Moiseev PA, Grigoriev AA (2020) Photomonitoring of tree and shrub vegetation in the highlands of the Southern Urals over the past 100 years. Publishing house UMC UPI, Yekaterinburg, p 191
[44]	Shiyatov SG, Vaganov EA, Kirdyanov AV, Kruglov VB, Mazepa VS, Naurzbaev MM, Khantemirov RM (2000) Dendrochronological methods. Part I: Fundamentals of dendrochronology. Collection and obtaining of tree ring information. Krasnoyarskij Gosudarstvennyj Universitet, Krasnoyarsk, p 80.
[45]	Sturm M, Schimel J, Michaelson G, Welker JM, Oberbauer SF, Liston GE, Fahnestock J, Romanovsky VE (2005) Winter biological processes could help convert arctic tundra to shrubland. Bioscience 55(1):17–26. https://doi.org/10.1641/0006-3568(2005)055[0017:WBPCHC]2.0.CO;2
[46]	Tape K, Sturm M, Racine C (2006) The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Glob Chang Biol 12:686–702. https://doi.org/10.1111/j.1365-2486.2006.01128.x
[47]	Tape KD, Hallinger M, Welker JM, Ruess RW (2012) Landscape heterogeneity of shrub expansion in arctic Alaska. Ecosystems 15:711–724. https://doi.org/10.1007/s10021-012-9540-4
[48]	Tukey JW (1977) Exploratory data analysis by John W. Tukey Biometrics 33:688
[49]	Wang YF, Liang EY, Lu XM, Camarero JJ, Babst F, Shen MG, Pe?uelas J (2021) Warming-induced shrubline advance stalled by moisture limitation on the Tibetan Plateau. Ecography 44:1631–1641. https://doi.org/10.1111/ecog.05845
[50]	Wang YL, Wang YF, Camarero JJ (2023) Inconsistent growth responses of alpine rhododendron shrubs to climate change at two sites on the eastern Tibetan Plateau. Forests 14:331. https://doi.org/10.3390/f14020331
[51]	Wipf S, Stoeckli V, Bebi P (2009) Winter climate change in alpine tundra: plant responses to changes in snow depth and snowmelt timing. Clim Change 94:105–121. https://doi.org/10.1007/s10584-009-9546-x
[52]	Wood S (2017) Generalized additive models: an introduction with R. CRC Press, Boca Raton, p 496