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

===== 10.4.2.2.1 Biomes and mountain treeline =====

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Across Asia, under a range of representative concentration pathways (RCPs) and other scenarios, rising temperatures are expected to contribute to a northward shift of biome boundaries and an upwards shift of mountain treeline ( ''medium confidence'' ). Northward shift and area change of bioclimatic zones in Siberia ( [[#Anisimov--2017|Anisimov et al., 2017]] ; [[#Torzhkov--2019|Torzhkov et al., 2019]] ) and northeast Asia ( [[#Choi--2019|Choi et al., 2019]] ) are projected. Projected changes in vegetation in China at the end of the 21st century reveal that the area covered by cold–dry potential vegetation decreases as the area covered by warm–humid potential vegetation increases ( [[#Zhao--2017a|Zhao et al., 2017a]] ). Forest expansion into mountain tundra of the northern Urals is expected ( [[#Sannikov--2018|Sannikov et al., 2018]] ). In Republic of Korea, projected under RCP4.5 and RCP8.5 in the 2070s, suitable area loss of six subalpine tree species, namely, Korean fir, Khingan fir, Sargent juniper, Yeddo spruce, Korean yew and Korean arborvitae, range from 17.7 ± 20.1% to 65.2 ± 34.7%, respectively ( [[#Lee--2021b|Lee et al., 2021b]] ). Korean fir forests would be replaced by temperate forests at lower elevations, while they would continuously persist at the highest elevations on Mt. Halla, Jeju Island and Republic of Korea ( [[#Lim--2018|Lim et al., 2018]] ). Himalayan birch at its upper distribution boundary either is projected to move upwards ( [[#Schickhoff--2015|Schickhoff et al., 2015]] ; [[#Bobrowski--2018|Bobrowski et al., 2018]] ) or considered to downslope as a response to global-change-type droughts ( [[#Liang--2014|Liang et al., 2014]] ). Upwards shift in elevation of bioclimatic zones, decreases in area of the highest elevation zones and large expansion of the lower tropical and sub-tropical zones can be expected by the year 2050 throughout the transboundary Kailash Sacred Landscape of China, India and Nepal, and ''likely'' within the Himalayan region more generally ( [[#Zomer--2014|Zomer et al., 2014]] ).

In North Asia, a shift is projected in the dominant biomes from conifers to deciduous species across Russia after 20 years of altered climate conditions ( [[#Shuman--2015|Shuman et al., 2015]] ). In South Siberia, [[#Brazhnik--2015|Brazhnik and Shugart (2015)]] projected a shift from the boreal forest to the steppe biome. [[#Rumiantsev--2013|Rumiantsev et al. (2013)]] also project a positive northward shift of vegetation boundaries for the greater part of West Siberia in line with warming; however, no shift for the north of West Siberia and negative shift for the southern Urals and northwest Kazakhstan are projected for 2046–2065. The replacement of forest–steppe with steppe at the lower treeline in South Siberia is projected ( [[#Brazhnik--2015|Brazhnik and Shugart, 2015]] ), and retreat of larch forests from the southernmost strongholds of boreal forest in eastern Kazakhstan is expected as part of a global process of forest dieback in semiarid regions ( [[#Dulamsuren--2013|Dulamsuren et al., 2013]] ). In North Asia, tree growth is intertwined with permafrost, snowpack, insect outbreaks, wildfires, seed dispersal and climate (e.g., [[#Klinge--2018|Klinge et al., 2018]] ). It is challenging to isolate the affects of individual factors, particularly since they can interact on one another in unanticipated ways because the underlying mechanisms are not well understood ( [[#Berner--2013|Berner et al., 2013]] ; [[#Brazhnik--2015|Brazhnik and Shugart, 2015]] ). The accuracy of treeline-shift projections is limited because projections are based on vegetation models which do not consider all the factors ( [[#Tishkov--2020|Tishkov et al., 2020]] ). The regional vegetation model structure and parameterisation can affect model performance, and the corresponding projections can differ significantly ( [[#Shuman--2015|Shuman et al., 2015]] ).

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