Editing IPCC:AR6/WGII/Chapter-10 (section)

===== 10.4.2.1.1 Biomes and mountain treeline =====

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Changes in biomes in Asia are compatible with a response to regional surface air temperature increase ( [[#Arias--2021|Arias et al., 2021]] ) ( ''medium agreement, medium evidence'' ). Expansion of the boreal forest and reduction of the tundra area is observed for about 60% of latitudinal and altitudinal sites in Siberia ( [[#Rees--2020|Rees et al., 2020]] ). In Central Siberia, the changes in climate and disturbance regimes are shifting the southern taiga ecotone northward ( [[#Brazhnik--2017|Brazhnik et al., 2017]] ). In Taimyr, no significant changes in the forest boundary have been observed during the past three decades ( [[#Pospelova--2017|Pospelova et al., 2017]] ). For the Japanese archipelago, it is suggested that the change in tree community composition along the temperature gradient is a response to past and/or current climate changes ( [[#Suzuki--2015|Suzuki et al., 2015]] ).

Alpine treeline position in Asian mountains in recent decades either moves upwards in North Asia or demonstrates multi-directional shifts in Himalaya ( ''high confidence'' ). Since AR5, in North Asia new evidence has appeared of tree expansion into mountain tundra and steppe, of intensive reproduction and increase in tree stands productivity in the past 30–100 years at the upper treeline in the Ural Mountains ( [[#Shiyatov--2015|Shiyatov and Mazepa, 2015]] ; [[#Zolotareva--2017|Zolotareva and Zolotarev, 2017]] ; [[#Moiseev--2018|Moiseev et al., 2018]] ; [[#Sannikov--2018|Sannikov et al., 2018]] ; [[#Fomin--2020|Fomin et al., 2020]] ; [[#Gaisin--2020|Gaisin et al., 2020]] ), in the Russian Altai Mountains ( [[#Kharuk--2017a|Kharuk et al., 2017a]] ; [[#Cazzolla%20Gatti--2019|Cazzolla Gatti et al., 2019]] ) and in the Putorana Mountains ( [[#Kirdyanov--2012|Kirdyanov et al., 2012]] ; [[#Pospelova--2017|Pospelova et al., 2017]] ; [[#Grigor’ev--2019|Grigor’ev et al., 2019]] ). Lower treelines in the southernmost ''Larix sibirica'' forests in the Saur Mountains, eastern Kazakhstan, have suffered from increased drought stress in recent decades causing forest regeneration and tree growth decrease, and tree mortality increase ( [[#Dulamsuren--2013|Dulamsuren et al., 2013]] ). In Jeju Island, Republic of Korea, recent warming has enhanced ''Quercus mongolica'' growth at its higher distribution and has led to ''Abies koreana'' (ABKO) growth reduction at all elevations, except the highest locality. Thus, the combination of warming, increasing competition and frequent tropical cyclone disturbances could lead to population decline or even extinction of ABKO at Jeju Island ( [[#Altman--2020|Altman et al., 2020]] ). In the Himalaya, the treeline over recent decades either moves upwards ( [[#Schickhoff--2015|Schickhoff et al., 2015]] ; [[#Suwal--2016|Suwal et al., 2016]] ; [[#Sigdel--2018|Sigdel et al., 2018]] ; [[#Tiwari--2018|Tiwari and Jha, 2018]] ) or does not show upslope advance ( [[#Schickhoff--2015|Schickhoff et al., 2015]] ; [[#Gaire--2017|Gaire et al., 2017]] ; [[#Singh--2018c|Singh et al., 2018c]] ), or moves downwards ( [[#Bhatta--2018|Bhatta et al., 2018]] ). In the Tibetan Plateau, the treeline either shifted upwards or showed no significant upwards shift ( [[#Wang--2019c|Wang et al., 2019c]] ). This can be explained by site-specific complex interaction of positive effect of warming on tree growth, and negative effects of drought stress, change in snow precipitation, inter- and intraspecific interactions of trees and shrubs, land-use change (especially grazing) and other factors ( [[#Liang--2014|Liang et al., 2014]] ; [[#Lenoir--2015|Lenoir and Svenning, 2015]] ; [[#Tiwari--2017|Tiwari et al., 2017]] ; [[#Sigdel--2018|Sigdel et al., 2018]] ; [[#Tiwari--2018|Tiwari and Jha, 2018]] ; [[#Sigdel--2020|Sigdel et al., 2020]] ). It is largely unknown how broader-scale climate inputs, such as pre-monsoon droughts, interact with local-scale factors to govern treeline response patterns ( [[#Schickhoff--2015|Schickhoff et al., 2015]] ; [[#Müller--2016|Müller et al., 2016]] ; [[#Bhatta--2018|Bhatta et al., 2018]] ; [[#Singh--2019b|Singh et al., 2019b]] ).

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