Lecture 10: Consequences of climate change upon the southern boreal forest Flashcards
Lecture outline
The southern forest-steppe transition zone – transitional zone between forest in SE Russia and grasslands of northern siberia
Intermittent natural fires – what result? What does this mean for forest regeneration? Does it result in a changed state?
Climate change: what potential future scenarios?
Studies carried out in SE Russia
Earth’s boreal forests circle our planet’s far northern reaches, just south of the Arctic’s treeless tundra and north of the grasslands (steppe).
Satellite measurements show that plant growth widely increased along the cold northern margins of the boreal forest in recent decades, but it often decreased along the warm southern margins − potential early indicators that the boreal forest is beginning to migrate northward. Logan Berner, based on results from Berner and Goetz 2022., CC BY-ND
Greening – increased tree growth
Browning – areas where fires are switching forests to grassland
Forest of SE Russia transitions to grassy steppe of NE Mongolia and increased fire risk
Pine forests in southern Siberia:
Mostly made up of Scott’s Pine (Pinus sylvestris) on the Southern edge
Forest of SE Russia transitions to grassy steppe of NE Mongolia
In grassy areas fire is common
Quick burns punctuate succession burning the lower layer of the forest and often sparing the canopy whereas candling kills old growth trees and burn to the ground.
See in notes map coloured according to dominant tree species and map showing fire return interval is decreasing
See:
Boreal carbon loss due to poleward shift in low-carbon ecosystems Koven (2013)
&
Threshold for boreal biome transitions Scheffer et al (2012)
Key points
Wild fire is an increasing issue in Russia
*Russia’s 2024 wildfire season appeared to be off to an exceptionally fierce start, with a thick blanket of smoke stretching across much of the Far East by early July.
*The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a true-color image of the choking smoke on July 3.
*The gray haze was so thick, especially over Yakutia (Sakha Republic), that it was impossible to see the land beneath.
*Along the western edge of the thickest smoke, many dozens of red-hot spots mark actively burning fire.
*Officials say more than 2.3 million hectares of forest have burned in Russia since the start of 2024, the highest since 2020.”
Intervals getting shorter and fires getting fiercer
Enhanced fire activity in Siberia
increase in:
*Length of fire season
*Number of days for high risks of moderate to high severity fires
*Burn areas
*Fire frequency
Forest habitat recovery variations:
*Recruitment failure – when all trees and cones are burned – removing trees from the landscape
*Intermediate recruitment -pioneer species present
*Abundant recruitment – full compliment of tree species present – forest re-established
See Post-fire recruitment failure in scotts pine Barrett et al
Examples of forest recovery
in three different 2010 wildfire burn severity sites in the Middle Volga region.
see figures in notes from:
https://doi.org/10.3390/f15111919
Summary
*Recruitment failure sites in southern Siberia are associated with lower greenness and vegetation moisture levels, higher fire severity, and lower snow index than intermediate or abundantly recruiting sites.
*These differences become more pronounced over time, likely as a reflection of feedback mechanisms that reinforce recruitment trajectories post-fire.
*Shifts between Scots pine and grass-dominated vegetation in the region may be responsive to winter snow cover in the intermediate assessment period 3–4 years post-fire
