The effects of climate, permafrost and fire on vegetation change in Siberia in a changing climate

Abstract

Observations and general circulation model projections suggest significant temperature increases in Siberia this century that are expected to have profound effects on Siberian vegetation. Potential vegetation change across Siberia was modeled, coupling our Siberian BioClimatic Model with several Hadley Centre climate change scenarios for 2020, 2050 and 2080, with explicit consideration of permafrost and fire activity. In the warmer and drier climate projected by these scenarios, Siberian forests are predicted to decrease and shift northwards and forest-steppe and steppe ecosystems are predicted to dominate over half of Siberia due to the dryer climate by 2080. Despite the large predicted increases in warming, permafrost is not predicted to thaw deep enough to sustain dark (Pinus sibirica, Abies sibirica, and Picea obovata) taiga. Over eastern Siberia, larch (Larix dahurica) taiga is predicted to continue to be the dominant zonobiome because of its ability to withstand continuous permafrost. The model also predicts new temperate broadleaf forest and forest-steppe habitats by 2080. Potential fire danger evaluated with the annual number of high fire danger days (Nesterov index is 4000-10 000) is predicted to increase by 2080, especially in southern Siberia and central Yakutia. In a warming climate, fuel load accumulated due to replacement of forest by steppe together with frequent fire weather promotes high risks of large fires in southern Siberia and central Yakutia, where wild fires would create habitats for grasslands because the drier climate would no longer be suitable for forests.

Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka bp

“…Hence, climate is assumed to be the dominant control of modern biomes and forest distribution at a continental scale in northern and eastern Asia (e.g. Alpat'ev et al 1976;Fang et al 2005;Tchebakova et al 2009). …”

“…In permafrost areas, for example, the summer thaw-depth may influence the occurrence of a specific biome, particularly evergreen or deciduous needle-leaf forests (e.g. Tchebakova et al 2009;Helbig et al 2016;Herzschuh et al 2016). Biome distribution can also be impacted by changes in wildfire regime (Abaimov and Sofronov 1996;Abaimov et al 2002).…”

“…They argue that the vegetation-climate disequilibrium is related to the combined effects of permafrost persistence, distant glacial refugia, and fire . Accordingly, the spatial and temporal complexity of biome distributions may be strongly influenced by the interaction of the various driving forces and associated feedback mechanisms (Abaimov et al 2002;Tchebakova et al 2009;Rogers et al 2015). The vegetation responses to future climate changes are likely to be characterised by feedback mechanisms that result in vegetation-climate disequilibrium at both leading and trailing edges of those changes, as represented, for example, by lags in migration and delayed local extinctions, respectively (Svenning and Sandel 2013).…”

Lake Baikal isotope records of Holocene Central Asian precipitation

“…For example, 21 st Century climate change across Central Asia is likely to lead to a northward migration of the forest-steppe ecotone with remaining forest stand height highly dependent on rates of precipitation (Tchebakova et al, 2009;. At the same time reductions in soil moisture associated with climate change are expected to accelerated grassland degradation, negatively impacting nomadic pastoralism (Liu et al, 2013;Sugita et al, 2015), whilst issues of water security are likely to be exacerbated by plans for increased groundwater extraction and dam construction (Karthe et al, 2015).…”

“…The increased risk of fires across grasslands and boreal forest will impact vegetation regeneration (Tchebakova, 2009;IPCC, 2012;Tautenhahn et al, 2016) and lead to an immediate increase in atmospheric CO2 (Randerson et al, 2006).…”