Tamm Review: Observed and projected climate change impacts on Russia’s forests and its carbon balance

Abstract

a b s t r a c tRussia's boreal forests provide numerous important ecosystem functions and services, but they are being increasingly affected by climate change. This review presents an overview of observed and potential future climate change impacts on those forests with an emphasis on their aggregate carbon balance and processes driving changes therein. We summarize recent findings highlighting that radiation increases, temperature-driven longer growing seasons and increasing atmospheric CO 2 concentrations generally enhance vegetation productivity, while heat waves and droughts tend to decrease it. Estimates of major carbon fluxes such as net biome production agree that the Russian forests as a whole currently act as a carbon sink, but these estimates differ in terms of the magnitude of the sink due to different methods and time periods used. Moreover, models project substantial distributional shifts of forest biomes, but they may overestimate the extent to which the boreal forest will shift poleward as past migration rates have been slow. While other impacts of current climate change are already substantial, and projected impacts could be both large-scale and disastrous, the likelihood for a tipping point behavior of Russia's boreal forest is still unquantified. Other substantial research gaps include the large-scale effect of (climate-driven) disturbances such as fires and insect outbreaks, which are expected to increase in the future. We conclude that the impacts of climate change on Russia's boreal forest are often superimposed by other environmental and societal changes in a complex way, and the interaction of these developments could exacerbate both existing and projected future challenges. Hence, development of adaptation and mitigation strategies for Russia's forests is strongly advised.

Effects of climate and fire on short-term vegetation recovery in the boreal larch forests of Northeastern China

“…As the frequency and severity of drought is expected to increase under a warmer and drier climate, elevated chances of postfire water stress may have a significant influence on ecosystem composition and function20. Recent climate warming has resulted in a rather uniform trend toward higher plant productivity and forest cover gain in the North, and a trend toward decreased productivity and forest cover loss in southern Siberian boreal forests66, similar to observations from Canada’s boreal forests70.…”

“…This analysis thus revealed that postfire recovery in boreal Larch forests of Northeastern China was collectively controlled by processes that controlled seed availability, site condition, and climate variability after fire. Anticipated increases in fire severity and moisture stress66, interacting with gradients of environmental conditions, will have significant influences on vegetation structure and function, and forest feedbacks to climate6768.…”

“…If an intensified fire regime unfolded as expected under warmer and drier climate conditions, accelerated changes in species composition or even biome boundaries may potentially hasten transitions to ‘no-analogue communities’ in the region74. If large-scale changes in biotic communities occur after disturbance, there will also be significant consequences for many ecosystem processes, such as carbon cycling and thawing of the permafrost66. Therefore, the potential interactions among climate, fire, and ecosystem change in Siberian Larch forests warrant further research.…”

Pinus taeda forest growth predictions in the 21st century vary with site mean annual temperature and site quality

“…Measurements taken at the stand level on different tree species in other regions have already detected a positive effect of warming and elevated atmospheric [CO 2 ] on forest productivity (Bosela et al., ; Charru et al., ; Schaphoff et al., ), but in areas where droughts have increased, forest productivity has decreased, despite increased temperature and atmospheric [CO 2 ] (Bonal, Burban, Stahl, Wagner, & Hérault, ; Sun et al., ).…”

Northeastern North America as a potential refugium for boreal forests in a warming climate

“…Over the current century, this ecosystem is expected to undergo one of the largest increases in temperatures (3). Low mean annual temperatures (MATs) are a major constraint on boreal forest productivity, and increases in temperature and growing season length in recent decades are reported to have benefited tree growth over large areas of Fennoscandia (4) and Russia (5). In central and western areas of North American boreal forests, however, anal-ysis of recent tree-ring width data (6,7), in combination with stable carbon isotope analysis (8,9) and satellite images (10), suggests that changes in soil water balance have canceled potential gains in forest growth from recent warming.…”