Temperature‐induced water stress in high‐latitude forests in response to natural and anthropogenic warming

• Published in: Global Change Biology
• Main Authors: Trahan, Matthew W., Schubert, Brian A.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Arctic; Climate change; Siberia
• Online Access: http://dx.doi.org/10.1111/gcb.13121; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.13121; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13121; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.13121; http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.1111%2Fgcb.13121

Abstract The Arctic is particularly sensitive to climate change, but the independent effects of increasing atmospheric CO 2 concentration ( p CO 2 ) and temperature on high‐latitude forests are poorly understood. Here, we present a new, annually resolved record of stable carbon isotope (δ 13 C) data determined from Larix cajanderi tree cores collected from far northeastern Siberia in order to investigate the physiological response of these trees to regional warming. The tree‐ring record, which extends from 1912 through 1961 (50 years), targets early twentieth‐century warming ( ETCW ), a natural warming event in the 1920s to 1940s that was limited to Northern hemisphere high latitudes. Our data show that net carbon isotope fractionation (Δ 13 C), decreased by 1.7‰ across the ETCW , which is consistent with increased water stress in response to climate warming and dryer soils. To investigate whether this signal is present across the northern boreal forest, we compiled published carbon isotope data from 14 high‐latitude sites within Europe, Asia, and North America. The resulting dataset covered the entire twentieth century and spanned both natural ETCW and anthropogenic Late Twentieth‐Century Warming (~0.7 °C per decade). After correcting for a ~1‰ increase in Δ 13 C in response to twentieth century p CO 2 rise, a significant negative relationship ( r = −0.53, P < 0.0001) between the average, annual Δ 13 C values and regional annual temperature anomalies is observed, suggesting a strong control of temperature on the Δ 13 C value of trees growing at high latitudes. We calculate a 17% increase in intrinsic water‐use efficiency within these forests across the twentieth century, of which approximately half is attributed to a decrease in stomatal conductance in order to conserve water in response to drying conditions, with the other half being attributed to increasing p CO 2 . We conclude that annual tree‐ring records from northern high‐latitude forests record the effects of climate warming and p CO 2 rise across the ...