COS 131-5 - Extreme heat might threaten photosynthetic carbon assimilation by Siberian larch in the southern edge of the North Asian taiga

Wednesday, August 17, 2022

9:00 AM – 9:15 AM EDT

Location: 516E

Presenting Author(s)

MR

Mukund P. Rao

University Corporation for Atmospheric Reserach, United States

Coauthor(s)

ND

Nicole Davi

William Patterson University, United States
TM

Troy Magney

University of California Davis, United States
LA

Laia Andreu-Hayles

Lamont Doherty Earth Observatory, Columbia University, United States
NB

Nachin Baatarbileg

National University of Mongolia, Mongolia
BS

Byambagerel Suran

National University of Mongolia, Mongolia
AV

Arianna Varuolo-Clarke

Lamont Doherty Earth Observatory, Columbia University, United States
BC

Benjamin Cook

NASA GISS, United States
RD

Rosanne D'Arrigo

Lamont Doherty Earth Observatory, Columbia University, United States
NP

Neil Pederson

Harvard Forest, United States
LO

Lkhagvajargal Odrentsen

Food and Agricultural Organization, Mongolia
MR

Milagros Rodríguez-Catón

University of California Davis, United States
CL

Caroline Leland

William Patterson University, United States
KG

Kevin Griffin

Lamont Doherty Earth Observatory, Columbia University, United States

Background/Question/Methods

The circumpolar taiga or boreal forests represents the world’s most extensive terrestrial biome and accounts for nearly one third of global terrestrial carbon stocks. Boreal carbon primarily resides in three major pools, peatlands, soils, and forest biomass. All three carbon pools are sensitive to rising temperature from human-caused climate change due to direct impacts of warming and indirect impacts such as permafrost thaw, increased wildfire and insect activity. North Mongolia, defined here as a ~1 million km2 region between 95-114°E and 46-52°N, is located at the southern edge of the North Asian taiga. Summertime extreme heat events are becoming increasingly common in the taiga or boreal biome of North Asia. Since the 1990s summer mean June-July-August (JJA) temperature in North Mongolia have warmed at a rate thrice that of the global average. An often overlooked but important consequence of rising global mean temperatures is an increase in the frequency and intensity of extreme heat events such as the temperature of the hottest day (Txx) Better quantification of vegetation physiology and its thermal tolerance is needed to predict ecological change under a warming climate.

Results/Conclusions

Here we report that Siberian Larch (Larix sibirica), a keystone species of the North Asian taiga, has the highest photosynthetic capacity among co-located species in North Mongolia. However, despite its photosynthetic capacity, L. sibirica has a low thermal tolerance of photosynthesis (Tcrit), indicating susceptibility to irreversible damage from heat events and climate change. L. sibirica’s relatively low Tcrit is likely attributable to North Mongolia forming the southern range limit of its distribution. Projections
using Earth System Models (ESMs) participating in CMIP6 suggest that increases the temperature of the hottest days (Txx) might cause leaf temperatures to exceed L. sibirica’s Tcrit under high emission scenarios (SSP5-8.5 and SSP3-7.0) in the second half of this century. However, this likelihood will be considerably reduced under lower emissions trajectories (SSP2-4.5 and SSP1-2.6). This work
highlights the potential of crossing ecological tipping points in the taiga-steppe transition zone without emission reductions.